The behaviour of children with Attention-Deficit / Hyperactivity Disorder is often described as highly variable, in addition to being hyperactive, impulsive and inattentive. One reason might be that they do not acquire complete and functional sequences of behaviour. The dynamic developmental theory of ADHD proposes that reinforcement and extinction processes are inefficient because of hypofunctioning dopamine systems, resulting in a narrower time window for associating antecedent stimuli and behaviour with its consequences. One effect of this may be that the learning of behavioural sequences is delayed, and that only short behavioural sequences are acquired in ADHD. The present study investigated acquisition of response sequences in the behaviour of children with ADHD.Fifteen boys with ADHD and thirteen boys without, all aged between 6–9 yr, completed a computerized task presented as a game with two squares on the screen. One square was associated with reinforcement. The task required responses by the computer mouse under reinforcement contingencies of variable interval schedules. Reinforcers were cartoon pictures and small trinkets. Measures related to response location  and to response timing  were analyzed by autocorrelations of consecutive responses across five lags. Acquired response sequences were defined as predictable responding shown by high explained variance.Children with ADHD acquired shorter response sequences than comparison children on the measures related to response location. None of the groups showed any predictability in response timing. Response sequencing on the measure related to the discriminative stimulus was highly related to parent scores on a rating scale for ADHD symptoms.The findings suggest that children with ADHD have problems with learning long sequences of behaviour, particularly related to response location. Problems with learning long behavioural sequences may ultimately lead to deficient development of verbally governed behaviour and self control. The study represents a new approach to analyzing the moment-to-moment dynamics of behaviour, and provides support for the theory that reinforcement processes are altered in ADHD. Attention-Deficit/Hyperactivity Disorder (ADHD)  is a behThere is some support for the notion that ADHD behaviour may be characterized by hampered acquisition of complete and functional sequences of behaviour. First, children with ADHD did not perform sequences of arm movements as one functional unit, but were slower, showed greater variability in movement timing, and demonstrated longer inter-segment intervals than children without ADHD, who appeared to program the entire arm movements and executed the sequence as one functional unit that was temporally coordinated . The chiThe DDT suggests that dysfunctioning reinforcement and extinction processes can explain why symptomatic ADHD behaviour is acquired through dynamic interaction between the child and the environment throughout development ,3. ReinfOn a behavioural level, reinforcers select responses by increasing the probability of repeating responses that produce reinforcers. Reinforcement as a process operates within a limited time window from the occurrence of the behaviour to the perception of the consequences of this behaviour. Altered reinforcement processes in ADHD may be described as a narrower time window than normal for associating behaviour with its consequences. A narrow time window may theoretically be depicted as a shorter and steeper delay-of-reinforcement gradient  Figure . The delThere may be many behavioural consequences of a shorter delay gradient in ADHD  schedules, where responses result in a reinforcer after varying time intervals. With VI schedules a possible confusion of reinforcement effects with timing problems is avoided, as reinforcers are presented at unpredictable times . All mouThe present study analyzed response data from 28 boys in the age range of 6:2–9:0 (yr:mo), 15 of whom had an ADHD diagnosis and 13 were healthy controls. These boys represented the young age group from the previous study. The older children (aged 9.5–12 yr) from that study were not included, as the comparison group showed to be inadequate  [Participants in the ADHD group were referred from different clinical sources  and were included if they met the following criteria: 1) DSM-IV diagnosis of ADHD, of either three subcategories; 2) Full Scale IQ of at least 80; 3) no evidence of neurological disorder, psychosis, or pervasive developmental disorder; and 4) not taking any medication within the last 48 hours prior to testing. A diagnosis was confirmed after thorough clinical evaluation. Eight of the children had ADHD combined type, six had ADHD hyperactive / impulsive type, and one child had ADHD inattentive type. In addition, inclusion in the ADHD group warranted a score at or above the 95e (DBRS)  home or Comparison children were recruited from schools in urban and suburban areas of Oslo, the capital of Norway. Inclusion criteria were the same as for the ADHD group, except that no DSM-IV diagnosis should be present. In addition, they had to score below the sub-clinical range on the DBRS.Intellectual ability was assessed by screening all children with four subtests  of the WISC-R  demogra.The study was approved of by the Regional Medical Committee of Research Ethics. The parents of all the participants received written information about the study and gave written consent for their child to take part. All children were tested in quiet rooms, using the same tasks, apparatus, and test procedures . If you want to point, you can click with one of these buttons (experimenter points to the mouse buttons). You may talk while you are playing, but I will not answer any questions about the game. I will sit back here and write a little while you play. Do you understand your task? You may start now."The task was designed as a computer game, and was presented to the child with the following instruction (translated from Norwegian): The task was run on a Toshiba Pentium 300 CDT laptop connected to a colour monitor  schedules of reinforcement, where responses may produce reinforcers after the passage of varying time intervals , were usThere were two sessions, each of five segments. Each segment consisted of four short and four long intervals, and was terminated by a response and the delivery of a reinforcer. In the first session, the child would see a total of 40 reinforcers (cartoons). In the second session, the child received a small tangible reinforcer  in addition to the cartoon picture. This was done in order to maintain reinforcer value. The entire task, including instruction, break between sessions, and a final, short interview with the child, took less than 30 min to complete.Data were recorded by the laptop. Response side (left or right), response coordinates , and interresponse times (IRTs) were the recorded dependent measures. The individual IRT distributions were highly skewed with a long tail towards long IRTs. IRTs were therefore normalized by log transformations prior to analysis (logIRT = log10 (IRT/1000 + 0.001)).side response pattern, i.e., whether consecutive responses were on the left or right side of the screen. Highly predictable responding would probably be related to the side where the correct target was positioned, and would thus be a complementary measure of stimulus control. Likewise, low predictability implies that responses are equally distributed on the two sides and is thus also a measure of low stimulus control. Next, due to the fact that reinforcers affect more responses than the one that produces it .Data from the VI 20s condition was used to study response sequences, as the short schedule only allowed for one or a few responses before a reinforcer was delivered. Predictability of responses over long sequences could theoretically be found according to different aspects of the behaviour, and in order to explore the different possibilities we computed three measures related to the spatial dimension and one measure related to timing. The first measure was a general t Figure , predictThe ordering of responses spatially and temporally was assessed by autocorrelations. Autocorrelations  of each measure were correlations of consecutive values over five lags . The autocorrelations were computed for each individual over sessions and segments. We predicted that the behaviour of children with ADHD would be characterized by lower autocorrelations and that their autocorrelation curves across lags would be steeper compared to the behaviour of healthy comparison children.Data were analyzed by means of SPSS 11.0 for Windows (SPSS) and Statistica 6.1  program Demographic and diagnostic measures of the ADHD and the comparison group were tested with two-tailed t-tests for equality of means and are displayed in Table In general, acquisition of predictable response sequences was found in the spatial measures and not in the temporal measure. The ADHD group had significantly lower autocorrelations than the comparison group on two of the three spatial measures. Both groups had very low autocorrelations related to response timing. There was no Session effect on the three spatial measures, but the main effect of Lag was significant for all four measures. Results of the planned analyses with ANOVA and MANOVA are shown in Table 2 > 0.22, median R2 = 0.26), while it was in the upper range for the comparison group  . Highly predictable responding over lags would imply that behaviour was ordered in sequences related to side. Less variance was accounted for in the ADHD group than in the comparison group. For the ADHD group, explained variance in the first lag across segments was low , indicating that there was rather low predictability from one response to the next. For the comparison group, explained variance in the first lag was higher .This measure assessed to what degree the children tended to respond in any predictable pattern in terms of the distance between responses, anchored to the centre of the square that responses were placed within (whether it was the correct response target or not). Highly predictable responding would imply that behaviour was ordered in sequences of similar distances between responses. Again, the explained variance for the ADHD group was lower than for the comparison group Figure . ExplainThere were significant main effects of Group and Lag, but not of Session and Segment Table . A signi2 > 0.27; median R2 = 0.40), and slightly higher for the comparison group  . The significant main effect of Session showed that explained variance was lower in the second session than in the first, particularly for the comparison group. The main effect of Lag was significant, while the main effect of Segment was not. There was a significant interaction effect between Group and Session, showing that while the ADHD group had lower explained variance than the comparison group in the first session, the comparison group had lower explained variance than the ADHD group in the second session. The significant interaction between Group, Session, and Lag in the ANOVA was not confirmed by the MANOVA.The development of patterns in response timing was investigated by means of consecutive interresponse times (IRTs). Explained variance of the first lag was generally very low and not significantly different between the groups  argues that a shortened delay gradient probably relates more to the hyperactive / impulsive and the combined subtypes of ADHD than to the inattentive subtype . The preside response pattern and square response pattern, but not according to target response pattern or timing response pattern. This was supported by the high correlations between variance accounted for in consecutive response lags of these two spatial measures and the scores on both hyperactive/impulsive and inattentive clinical dimensions  of the screen, irrespective of on which side the correct target was displayed. The significant group difference implied a highly predictable pattern in the comparison group, indicating that these children varied their responding between sides almost only to the extent that the correct target square switched sides on the screen. This was supported by their mean percent correct responding at 87% during stable state [The le state , demonstle state . The comHowever, there was a drop in explained variance in the comparison group at the end of each session  in the first lag of the two groups indicates high predictability from response n to n+1 when in the correct square, while the ADHD group varied more on consecutive responses as indicated by the significant interaction between group and lag.The  the DDT , predictside response pattern. Therefore, it might be argued that the reduced predictability found in both square response pattern and target response pattern is a consequence of larger arm movements in the ADHD group because of more varied responding from side to side, rather than an effect of inefficient reinforcement of response placement within a square. The present analysis did not allow identifying predictability of response placements when consecutive responding was within the same square, which involves smaller movements. However, disentangling the variability related to larger arm movements and the variability related to decreased stimulus control  may not be feasible. Further, it may be speculated that, since the striatum, which is involved in the planning and execution of motor actions, and the nucleus accumbens, which is involved in learning and reinforcement, both receive important dopaminergic afferents, these functional processes may both be impaired in an individual with ADHD [Increased variability is a consequence of reduced stimulus control. This is seen in the ADHD group in terms of the ith ADHD .Acquisition of functional behavioural sequences may be related to processes involved in habit learning. Habit learning is characterized by a transition from response-consequence associations that are flexible and sensitive to reinforcement devaluation, to stimulus-response associations that are less flexible and sensitive (e.g. ). Thus, timing response pattern. Speculatively, this lack of a predictable timing pattern could be related to the visuo-spatial nature of the task, both in terms of response alternatives  and in terms of the reinforcer. There is some evidence that striatal neurons involved in sequential habit learning may encode visuo-spatial information rather than temporal [Explained variance of first lag (and following lags) was too low to conclude that there was any predictability in IRTs. Thus, there was no temporal .The present findings suggest that the learning of coherent and predictable behavioural sequences will be difficult in children with ADHD, probably because the time window available for reinforcers to work is narrower in ADHD compared to normal. Skilled performance is characterized by responses emitted with brief interresponse intervals, smooth transitions between responses, and efficient coordination of consecutive movements so that a whole sequence is conducted in a predictable manner (e.g. ). ReinfoOther interpretations are possible, however. It has been suggested that the length of delay gradients may be dependent on working memory (WM) capacity because the ability to relate sensory information to responses and reinforcing stimuli seems to correlate with ongoing neuronal activity in prefrontal cortex . BehavioThere might be alternative motivational explanations (than a shorter delay gradient) for the behaviour observed in the ADHD group. Rather than a reduced effect of positive reinforcement , the behaviour may be a result of reduced negative control . However, non-compliance would have involved refusal to complete the task, which none of the children did, and most of them even reported that the task was fun. In addition, the instruction was non-directive, excluding the possibility of non-compliance to any instructed response pattern. A group of children aged 9–12 yr also participated in the original study, but the results of the comparison group indicated that their responding was mainly compliant and not controlled by reinforcers, as shown by lack of schedule control . The behThe present study provides new insights into the recently started discussion of intra-individual ADHD-related variability . CastelSome limitations of the present study could be improved in future studies. First, the findings need to be replicated in a larger sample of children. New samples, including girls and children of other ages, need to be analyzed in order to verify if this behavioural style is general to ADHD, whether it may be identified at an earlier age, and whether it continues to constitute an important factor in the behaviour of older children. Children with other psychopathologies should be added in order to establish the specificity of this learning style. Second, the present task may be criticized for its lack of ecological validity. On the other hand, the present task may have been optimal for studying ordering and sequencing of responses, as no earlier experience or learning history would interfere. In the future, a wide range of serial or sequential tasks should be investigated because the dynamic developmental theory of ADHD predicts that the presently-observed learning style should be found in the behaviour of people with ADHD across tasks and activities. Finally, various serial tasks could be conducted during brain imaging in order to investigate the brain areas involved.The present findings provide support for the dynamic developmental theory of ADHD predicting that a short and steep delay-of-reinforcement gradient will result in fewer responses in a predictable sequence than when the delay gradient is normal . The hypThe present study represents a new approach to analyzing the micro-dynamics of consecutive responses in a moment-to-moment manner. A majority of the responses were emitted with IRT < 1s. The study of behavioural processes and their environmental correlates may thus approach the time-scale of brain processes and we may get closer to directly measure brain-behavioural interactions. In this perspective, concepts like working memory, inhibition, and even timing problems may be too wide concepts to identify the underlying learning style, because a learning style characterized by inefficient chunking or development of entire behavioural sequences may be manifest in different domains in different individuals. One might speculate that sequencing of motor action and sequencing of speech and thought may be of the same functional origin . Thus, The author(s) declare that they have no competing interests.HA participated in the development of the study design, development of the reinforcement task used, carried out the data collection, prepared the data, performed the statistical analyses, and wrote the manuscript. TS participated in the development of the study design, development of the reinforcement task, wrote the programs for statistical analyses, participated in data analyses, read the manuscript and approved the final draft.


There are few studies that have investigated uncertainties surrounding the scientific community's knowledge of the geographical distribution of major animal diseases. This is particularly relevant to Rift Valley fever (RVF), a zoonotic disease causing destructive outbreaks in livestock and man, as the geographical range of the disease is widening to involve previously unaffected regions. In the current study we investigate the application of methods developed in the decision sciences: multiple criteria decision making using weighted linear combination and ordered weighted averages, and Dempster-Shafer theory, implemented within the geographical information system IDRISI, to obtain a greater understanding of uncertainty related to the geographical distribution of RVF. The focus is on presenting alternate methods where extensive field data are not available and traditional, model-based approaches to disease mapping are impossible to conduct.Using a compensatory multiple criteria decision making model based on weighted linear combination, most of sub-Saharan Africa was suitable for endemic circulation of RVF. In contrast, areas where rivers and lakes traversed semi-arid regions, such as those bordering the Sahara, were highly suitable for RVF epidemics and wet, tropical areas of central Africa had low suitability. Using a moderately non-compensatory model based on ordered weighted averages, the areas considered suitable for endemic and epidemic RVF were more restricted. Varying the relative weights of the different factors in the models did not affect suitability estimates to a large degree, but variations in model structure had a large impact on our suitability estimates. Our Dempster-Shafer analysis supported the belief that a range of semi-arid areas were suitable for RVF epidemics and the plausibility that many other areas of the continent were suitable. Areas where high levels of uncertainty were highlighted included the Ethiopian Highlands, southwest Kenya and parts of West Africa.We have demonstrated the potential of methods developed in the decision sciences to improve our understanding of uncertainties surrounding the geographical distribution of animal diseases, particularly where information is sparse, and encourage wider application of the decision science methodology in the field of animal health. Uncertainty is a major feature of human and animal health decision-making and increasing attention is being paid to methods that detect, measure and reduce uncertainty in a range of settings. Uncertainty can be any error, ambiguity or variation in a decision process or the data on which the decision process is based . UncertaRecent advances in geographical information system and remote-sensing (GIS/RS) technologies have been applied in a wide range of studies of the spatial distribution of tropical diseases and the factors that influence disease patterns. To a lesser extent, geographical studies have also had the objective of improving resource allocation to disease control and surveillance activities . HoweverIn the current study we explicitly considered decision rule uncertainty, which refers to uncertainty in the way parameters are specified and combined in the decision process. In our analysis, the decision frames were whether geographical units (pixels) were suitable or not suitable for the occurrence of endemic RVF or RVF epidemics according to specific criteria. Criteria refer to factors that influence the suitability of a given location. Fuzzy logic can be applied to model decision rule uncertainty, where the possibility of a criterion being satisfied is defined on a continuous scale by a membership function, which can take any shape .As RVF distributions are multifactorial, a method needed to be adopted within the context of multiple criteria decision making (MCDM) to combine membership functions for different criteria – one such method is weighted linear combination (WLC). With WLC, the criteria are standardised for comparison on a common scale, weights are applied so that more important criteria are able to exert a greater influence on the outcome, and a weighted average across criteria is calculated for each pixel, giving the final suitability estimates.MCDM models using WLC to construct the decision rule are fully compensatory models – a low score for a given factor may be compensated by a high score for another factor. We also considered the application of ordered weighted averages (OWA) analysis, which allows manipulation of the degree to which a high score for a criterion can compensate for a low score in another. With OWA, criteria are weighted for a given pixel according to the rank of their suitability scores within that pixel. For a less compensatory model, the lower ranked factors are given a higher relative weight .Many of the factors that are known to influence RVF suitability do so indirectly, via their relationships with vector and host populations. In this study we also considered methods for making inference from indirect evidence. The method of choice was Dempster-Shafer theory (DST) ,5, a genSuitability maps are presented on a graduated green-yellow-orange-red scale, with delineations between green/yellow, yellow/orange and orange/red occurring at scores of 140, 150 and 200 (range 0 to 255). For descriptive purposes we interpreted model outputs in the green scale to indicate unsuitability, outputs in the yellow scale to indicate low suitability, outputs in the orange scale to indicate moderate suitability and outputs in the red scale to indicate high suitability.With the exception of the coasts of Liberia, Sierra Leone and Cameroon and the arid areas of South Africa, Botswana, Namibia, Kenya, Somalia, Ethiopia, Eritrea and Djibouti, most of Sub-Saharan Africa (SSA) was suitable for the presence of endemic RVF according to our WLC model Figure . The whoThe endemic suitability map derived from our moderately non-compensatory OWA model is presented in Figure High-suitability areas for RVF epidemics Figure  occurredThe epidemic suitability map derived from our OWA model is presented in Figure Changing the weights of the lower-weighted factors had little impact on the WLC suitability maps Table , whereasOverlays of serological prevalence for RVF in ruminant livestock in Senegal and estimated suitability for endemic and epidemic RVF based on our WLC models are presented in Figures Comparison of the epidemic suitability map with the map of known RVF epidemics in Africa Figure  showed tThe three outputs of the DST model: belief, plausibility and belief interval are presented in Figure Fuzzy logic, implemented with a WLC framework, has been applied to assist spatial MCDM in a wide range of settings, as divergent as determining the desirability of houses in the real estate industry  and prioA number of common pitfalls in the application of WLC were presented and discussed by Malczewski , who staCorrelation between attributes was also highlighted as an important issue – Malczewski  stated tWe acknowledge that our approach to validation of the maps was qualitative in nature and further work is required for quantitative validation across the African continent. Another major issue with the methods applied in this study is subjectivity, particularly with regards to defining the weights in the WLC models, and the basic probability assignments in the DST analysis. A number of sources of information may be utilised for these purposes, including expert opinion , statistThere are an increasing number of reports of DST applications in engineering and climatology, such as analyses of water quality  and climIn the current study, we investigated the suitability of the environment, defined by a number of key parameters, for the occurrence of endemic and epidemic RVF. Environmental suitability for the disease is only one possible consideration when planning allocation of resources to disease surveillance and control activities. Other factors such as the proximity of testing laboratories or other important infrastructure, the distribution of the population at risk, the quality of roads and topography, amongst a wide range of other possible factors, may also be important in determining the cost-effectiveness of disease interventions and surveillance systems. An important area of further research is investigating the applicability of decision sciences to spatially-explicit cost-effectiveness analyses of different resource allocation strategies.Finally, the question arises as to which of the approaches is best for mapping RVF: WLC, OWA or DST. Each of the approaches is based on different assumptions regarding the epidemiology of RVF. Eastman  states tThe current study has demonstrated the potential of methods from the decision sciences, such as MCDM using WLC and OWA, and DST, for enhancing the use of available information in health-related decision making and resource allocation. We believe this is one of the key benefits of these methods: that existing published knowledge as well as expert opinion, accrued over a long period of time and by many individual workers, may be integrated to address the issues of geographical uncertainty with respect to different health problems in sub-optimal environments where field data are not available or too expensive to collect. The outputs from such analyses may be particularly useful for development of control strategies, as they can become available relatively quickly in emergency situations and express suitability as well as its uncertainty. We do, however, urge caution in the interpretation of such maps as estimates may be affected by the necessarily subjective nature of the approach, publication bias and the personal perspectives of the experts from which knowledge was obtained and the analyst who integrates the information to produce the maps, and validation may be difficult or impossible in the absence of supporting data.We stress that we do not see our mapping efforts as definitive for the geographical distribution of RVF in Africa, but as a valuable step towards the integration of epidemiological knowledge in the context of spatially-defining endemic and epidemic areas of the disease. Refinement of the maps will continue to be an ongoing process as new sources of information arise.MCDM involves a sequence of analytical steps. This includes: 1) defining the objective(s), 2) defining the factors (continuous) and constraints (Boolean), 3) defining the relationship between each factor and suitability, 4) standardising the factors so they can be compared, 5) defining the relative importance of each factor in relation to suitability and 6) combining each of the factors and constraints to produce a final weighted estimate of suitability for each location in the study area. We identified two additional steps as being important for determining the credibility of the resultant maps: 7) sensitivity analysis and 8) validation.The overall analytical objective was to use available published information to better describe the spatial distribution and associated uncertainties of Rift Valley fever at the continental scale. Two specific objectives were identified: 1) to produce estimates of suitability for the presence of endemic RVF activity and 2) to produce estimates of suitability for the occurrence of epidemics of RVF, at all locations in mainland continental Africa. Here, we define an epidemic as a large increase in the number of cases of RVF in animals or animals and man (note: we do not distinguish between epizootics and epidemics), over a large but defined geographical area and a short, defined period of time. We do not consider small, localised outbreaks that may occur in endemic areas, but focus on the massive, devastating epidemics that have caused extensive morbidity, mortality and economic losses in past decades. We define endemic occurrence as stable transmission of RVF as viewed from a large geographical scale, which could occur at a low or a moderately high level, and which could possibly be characterised by small, localised epidemics, but not large-scale epidemics as defined above.In order to define the factors and constraints, the relationship between the factors and suitability and the relative importance of each factor, a systematic review of the published scientific literature was conducted. A wide search was conducted of three on-line databases: CAB abstracts , PubMed In total, 65 publications with information relating to RVF epidemics and endemic activity were obtained. An electronic database was created in Microsoft Access, for recording information obtained from the selected publications. A list of all factors and constraints that were referred to in the publications was created in the database and queries were run to determine the number of publications that referred to each factor/constraint. The factors were presented in the publications either as observations, expressed opinions or statistical associations. In many cases, observations on the epidemiology of RVF were reported in multiple publications written by the same author or groups of authors or they were made in relation to the same epidemic or serological survey. To prevent multiple inclusion of the same information, only a single entry was made in the database for any observation relating to the same study or made by the same group of authors.In total, observations were recorded from 47 separate studies/author groups, six studies from North Africa, 10 from East Africa, 10 from Southern Africa & Madagascar, two from Central Africa, 14 from West Africa, two from the Arabian Peninsula and three not specific to a region. Of the 47 separate reports, 25 were epidemic investigations, 19 were serological surveys and three were vector studies. The factors were categorised into those that influenced the distribution of the vector, including rainfall, other climatic factors, topographic and land-cover factors and hydrological factors and those that were related to host suitability, including livestock density, human factors and animal movement , for the spatial factors and constraints identified in the literature search. The following data were obtained: satellite-derived mean land surface temperature (LST) for 1982–1998, obtained from the National Oceanographic and Atmospheric Administration's (NOAA) Advanced Very High Radiometer (AVHRR), elevation, obtained from an interpolated digital elevation model from the Global Land Information System (GLIS) of the United States Geological Survey , annual The data were imported into the GIS software IDRISI 32 . Surfaces for distance to the nearest major river and distance to the nearest minor river were created in IDRISI. All surfaces were raster-based, with pixel dimensions of 0.05 square decimal degrees , covering an area extending from -17.55 to 51.4 degrees of longitude and -34.85 to 37.35 degrees of latitude, corresponding to the geographical limits of the African continent.2 for epidemic suitability as no epidemics were considered possible where livestock were absent. This constraint was not imposed on the endemic suitability map due to the possibility of a sylvatic component in the endemic cycle.The "decision wizard" in the "decision support" menu of IDRISI was used to conduct the WLC analysis (See Eastman ). The onThe shapes of the fuzzy set membership functions for the non-Boolean factors are presented in Table For temperature, we input a symmetrical relationship with endemic suitability because the vectors were assumed to have an optimal temperature range, with vector survival being limited by low temperatures and vector life-spans shortened by excessively high temperatures . IntermeFor elevation, distance to major rivers and distance to minor rivers, we input monotonically decreasing relationships with endemic and epidemic suitability as higher elevations and greater distances from water sources were assumed to be non-conducive to either suitability type. For livestock density, we input a monotonically increasing relationship with endemic and epidemic suitability as there would be greater opportunity for host/vector interactions and virus transmission with higher livestock densities.Table Our temperature data was LST, which is usually higher than air temperatures measured above the ground-surface level. As published experimental data involved measurements in temperature-controlled environments, the selection of thresholds based on published literature was not straightforward. We elected to increase the published thresholds by approximately 10 degrees and also widened the optimal temperature range for endemic suitability to allow for multiple vector species with varying temperature requirements.2).Unfortunately, no information was available to guide selection of thresholds for the other factors, other than vague observations . For these variables, the thresholds were necessarily defined according to subjective theoretical reasoning , or were set to encompass the whole range of values for that variable, but excluding extreme outliers  and the original weights of temperature and elevation were decreased to account for collinearity. The weights, which were normalised to have an additive value of one, are presented in Table Sensitivity analysis involved varying the structure and weighting values of the MCDM model parameters and measuring the average change in suitability scores at 10,000 randomly selected locations on the map. In terms of structure, the relationships between rainfall and temperature and suitability were input as monotonic increasing in the endemic suitability map, in contrast to the symmetrical relationships in the original model. In terms of weights, the weight of each factor was increased and decreased while the relative weights of the other factors were kept constant, giving a total of twelve subsequent weighted estimates for each location. In the absence of any statistical basis for choosing the amount to increase or decrease the weights, we decided to select 25% of the initial value, as it provided for a wide range of uncertainty while ensuring that the underlying model structure was maintained.th century, in addition to the observed serological data in Senegal.Validation of the endemic suitability map was undertaken by comparing the suitability estimates to observed serological data in Senegal. The methods of serological data collection are published in detail elsewhere . ValidatWe hypothesised that the biology of the vectors of RVF may not support a fully compensatory model . However, RVF virus is known to exist in different ecological systems in South Africa where it has different vector species . TherefoLike Bayesian theory, DST represents knowledge and associated uncertainty using probability distributions; in DST definition of the distributions is termed basic probability assignment (BPA). However, DST differs from the Bayesian approach in a number of key aspects: 1) in DST, probabilities may be assigned to intervals of values (subsets) that may be overlapping, whereas Bayesian probability assignments can only be made to mutually exclusive point values or non-overlapping intervals; 2) belief in a hypothesis in DST is not necessarily the compliment of belief in its negation and 3) ignorance is explicitly accommodated in DST.A) and not suitable (B). In DST, BPA can relate to belief in A, which is the actual support for A and plausibility of A, which represents the degree to which A cannot be disbelieved. The difference between the belief estimate and the plausibility estimate is the belief interval, which represents uncertainty in the acceptance or rejection of A.In this analysis we considered a single hypothesis with a binary outcome: that a given pixel is suitable for RVF epidemics. Therefore, the "frame of discernement"  contained two elements: suitable  declare that they have no competing interests.ACAC conducted the systematic literature review, collated the data, conducted the analysis and drafted the paper. DUP supervised ACAC and contributed the original concept of conducting spatial MCDM and DST analyses, which was further developed by ACAC. DUP also revised the manuscript and made many valuable suggestions for changes and improvements. VM provided essential guidance on the epidemiology and control of RVF in Africa and revised the manuscript.


On December 3 1984, more than 40 tons of methyl isocyanate gas leaked from a pesticide plant in Bhopal, India, immediately killing at least 3,800 people and causing significant morbidity and premature death for many thousands more. The company involved in what became the worst industrial accident in history immediately tried to dissociate itself from legal responsibility. Eventually it reached a settlement with the Indian Government through mediation of that country's Supreme Court and accepted moral responsibility. It paid $470 million in compensation, a relatively small amount of based on significant underestimations of the long-term health consequences of exposure and the number of people exposed. The disaster indicated a need for enforceable international standards for environmental safety, preventative strategies to avoid similar accidents and industrial disaster preparedness.Since the disaster, India has experienced rapid industrialization. While some positive changes in government policy and behavior of a few industries have taken place, major threats to the environment from rapid and poorly regulated industrial growth remain. Widespread environmental degradation with significant adverse human health consequences continues to occur throughout India. December 2004 marked the twentieth anniversary of the massive toxic gas leak from Union Carbide Corporation's chemical plant in Bhopal in the state of Madhya Pradesh, India that killed more than 3,800 people. This review examines the health effects of exposure to the disaster, the legal response, the lessons learned and whether or not these are put into practice in India in terms of industrial development, environmental management and public health.In the 1970s, the Indian government initiated policies to encourage foreign companies to invest in local industry. Union Carbide Corporation (UCC) was asked to build a plant for the manufacture of Sevin, a pesticide commonly used throughout Asia. As part of the deal, India's government insisted that a significant percentage of the investment come from local shareholders. The government itself had a 22% stake in the company's subsidiary, Union Carbide India Limited (UCIL) [In 1984, the plant was manufacturing Sevin at one quarter of its production capacity due to decreased demand for pesticides. Widespread crop failures and famine on the subcontinent in the 1980s led to increased indebtedness and decreased capital for farmers to invest in pesticides. Local managers were directed to close the plant and prepare it for sale in July 1984 due to decreased profitability . When noAt 11.00 PM on December 2 1984, while most of the one million residents of Bhopal slept, an operator at the plant noticed a small leak of methyl isocyanate (MIC) gas and increasing pressure inside a storage tank. The vent-gas scrubber, a safety device designer to neutralize toxic discharge from the MIC system, had been turned off three weeks prior . ApparenEstimates of the number of people killed in the first few days by the plume from the UCC plant run as high as 10,000, with 15,000 to 20,000 premature deaths reportedly occurring in the subsequent two decades . The IndImmediately after the disaster, UCC began attempts to dissociate itself from responsibility for the gas leak. Its principal tactic was to shift culpability to UCIL, stating the plant was wholly built and operated by the Indian subsidiary. It also fabricated scenarios involving sabotage by previously unknown Sikh extremist groups and disgruntled employees but this theory was impugned by numerous independent sources .The toxic plume had barely cleared when, on December 7, the first multi-billion dollar lawsuit was filed by an American attorney in a U.S. court. This was the beginning of years of legal machinations in which the ethical implications of the tragedy and its affect on Bhopal's people were largely ignored. In March 1985, the Indian government enacted the Bhopal Gas Leak Disaster Act as a way of ensuring that claims arising from the accident would be dealt with speedily and equitably. The Act made the government the sole representative of the victims in legal proceedings both within and outside India. Eventually all cases were taken out of the U.S. legal system under the ruling of the presiding American judge and placed entirely under Indian jurisdiction much to the detriment of the injured parties.In a settlement mediated by the Indian Supreme Court, UCC accepted moral responsibility and agreed to pay $470 million to the Indian government to be distributed to claimants as a full and final settlement. The figure was partly based on the disputed claim that only 3000 people died and 102,000 suffered permanent disabilities . Upon anAt every turn, UCC has attempted to manipulate, obfuscate and withhold scientific data to the detriment of victims. Even to this date, the company has not stated exactly what was in the toxic cloud that enveloped the city on that December night . When MIAs further insult, UCC discontinued operation at its Bhopal plant following the disaster but failed to clean up the industrial site completely. The plant continues to leak several toxic chemicals and heavy metals that have found their way into local aquifers. Dangerously contaminated water has now been added to the legacy left by the company for the people of Bhopal ,14.The events in Bhopal revealed that expanding industrialization in developing countries without concurrent evolution in safety regulations could have catastrophic consequences . The disLocal governments clearly cannot allow industrial facilities to be situated within urban areas, regardless of the evolution of land use over time. Industry and government need to bring proper financial support to local communities so they can provide medical and other necessary services to reduce morbidity, mortality and material loss in the case of industrial accidents.Public health infrastructure was very weak in Bhopal in 1984. Tap water was available for only a few hours a day and was of very poor quality. With no functioning sewage system, untreated human waste was dumped into two nearby lakes, one a source of drinking water. The city had four major hospitals but there was a shortage of physicians and hospital beds. There was also no mass casualty emergency response system in place in the city . ExistinFollowing the events of December 3 1984 environmental awareness and activism in India increased significantly. The Environment Protection Act was passed in 1986, creating the Ministry of Environment and Forests (MoEF) and strengthening India's commitment to the environment. Under the new act, the MoEF was given overall responsibility for administering and enforcing environmental laws and policies. It established the importance of integrating environmental strategies into all industrial development plans for the country. However, despite greater government commitment to protect public health, forests, and wildlife, policies geared to developing the country's economy have taken precedence in the last 20 years [India has undergone tremendous economic growth in the two decades since the Bhopal disaster. Gross domestic product (GDP) per capita has increased from $1,000 in 1984 to $2,900 in 2004 and it continues to grow at a rate of over 8% per year [With the industrial growth since 1984, there has been an increase in small scale industries (SSIs) that are clustered about major urban areas in India. There are generally less stringent rules for the treatment of waste produced by SSIs due to less waste generation within each individual industry. This has allowed SSIs to dispose of untreated wastewater into drainage systems that flow directly into rivers. New Delhi's Yamuna River is illustrative. Dangerously high levels of heavy metals such as lead, cobalt, cadmium, chrome, nickel and zinc have been detected in this river which is a major supply of potable water to India's capital thus posing a potential health risk to the people living there and areas downstream .Land pollution due to uncontrolled disposal of industrial solid and hazardous waste is also a problem throughout India. With rapid industrialization, the generation of industrial solid and hazardous waste has increased appreciably and the environmental impact is significant .India relaxed its controls on foreign investment in order to accede to WTO rules and thereby attract an increasing flow of capital. In the process, a number of environmental regulations are being rolled back as growing foreign investments continue to roll in. The Indian experience is comparable to that of a number of developing countries that are experiencing the environmental impacts of structural adjustment. Exploitation and export of natural resources has accelerated on the subcontinent. Prohibitions against locating industrial facilities in ecologically sensitive zones have been eliminated while conservation zones are being stripped of their status so that pesticide, cement and bauxite mines can be built . Heavy rIn March 2001, residents of Kodaikanal in southern India caught the Anglo-Dutch company, Unilever, red-handed when they discovered a dumpsite with toxic mercury laced waste from a thermometer factory run by the company's Indian subsidiary, Hindustan Lever. The 7.4 ton stockpile of mercury-laden glass was found in torn stacks spilling onto the ground in a scrap metal yard located near a school. In the fall of 2001, steel from the ruins of the World Trade Center was exported to India apparently without first being tested for contamination from asbestos and heavy metals present in the twin tower debris. Other examples of poor environmental stewardship and economic considerations taking precedence over public health concerns abound .The Bhopal disaster could have changed the nature of the chemical industry and caused a reexamination of the necessity to produce such potentially harmful products in the first place. However the lessons of acute and chronic effects of exposure to pesticides and their precursors in Bhopal has not changed agricultural practice patterns. An estimated 3 million people per year suffer the consequences of pesticide poisoning with most exposure occurring in the agricultural developing world. It is reported to be the cause of at least 22,000 deaths in India each year. In the state of Kerala, significant mortality and morbidity have been reported following exposure to Endosulfan, a toxic pesticide whose use continued for 15 years after the events of Bhopal .Aggressive marketing of asbestos continues in developing countries as a result of restrictions being placed on its use in developed nations due to the well-established link between asbestos products and respiratory diseases. India has become a major consumer, using around 100,000 tons of asbestos per year, 80% of which is imported with Canada being the largest overseas supplier. Mining, production and use of asbestos in India is very loosely regulated despite the health hazards. Reports have shown morbidity and mortality from asbestos related disease will continue in India without enforcement of a ban or significantly tighter controls ,27.UCC has shrunk to one sixth of its size since the Bhopal disaster in an effort to restructure and divest itself. By doing so, the company avoided a hostile takeover, placed a significant portion of UCC's assets out of legal reach of the victims and gave its shareholder and top executives bountiful profits . The comSome positive changes were seen following the Bhopal disaster. The British chemical company, ICI, whose Indian subsidiary manufactured pesticides, increased attention to health, safety and environmental issues following the events of December 1984. The subsidiary now spends 30–40% of their capital expenditures on environmental-related projects. However, they still do not adhere to standards as strict as their parent company in the UK. .The US chemical giant DuPont learned its lesson of Bhopal in a different way. The company attempted for a decade to export a nylon plant from Richmond, VA to Goa, India. In its early negotiations with the Indian government, DuPont had sought and won a remarkable clause in its investment agreement that absolved it from all liabilities in case of an accident. But the people of Goa were not willing to acquiesce while an important ecological site was cleared for a heavy polluting industry. After nearly a decade of protesting by Goa's residents, DuPont was forced to scuttle plans there. Chennai was the next proposed site for the plastics plant. The state government there made significantly greater demand on DuPont for concessions on public health and environmental protection. Eventually, these plans were also aborted due to what the company called "financial concerns". .The tragedy of Bhopal continues to be a warning sign at once ignored and heeded. Bhopal and its aftermath were a warning that the path to industrialization, for developing countries in general and India in particular, is fraught with human, environmental and economic perils. Some moves by the Indian government, including the formation of the MoEF, have served to offer some protection of the public's health from the harmful practices of local and multinational heavy industry and grassroots organizations that have also played a part in opposing rampant development. The Indian economy is growing at a tremendous rate but at significant cost in environmental health and public safety as large and small companies throughout the subcontinent continue to pollute. Far more remains to be done for public health in the context of industrialization to show that the lessons of the countless thousands dead in Bhopal have truly been heeded.The author(s) declare that they have no competing interests.


What would you do if your child became ill? How would you find a doctor? When you find one, will the doctor speak your native language or understand your culture? In a state of approximately 22 million people, many Texas residents, marginalized by poverty and cultural traditions, find themselves in this situation. To help them, some communities across Texas offer the services of promotores and the impact of this program on the lay health education workforce in Texas.In 1999, Texas became the first state in the nation to recognize these workers and their contributions to keeping Texans healthy. This paper examines a state health promotion policy that culminated in a training and certification program for Promotor(a) Program Development Committee to study issues involved in developing a statewide training and certification program. During its 2-year term, the committee met all six of its objectives toward establishing and maintaining a promotor(a) certification program.In 1999, the Texas legislature established the 15-member promotores in Texas. State certification brings community health workers into the public health mainstream as never before.By the end of December 2005, it is estimated that there will be more than 700 certified Promotores, a community health safety net and a natural extension of the health and human services agencies, improve health at the neighborhood level. Certification brings renewed commitment to serving others and a distinction to those who have been the unsung heroes of public health for decades. The term promotores refers to lay health educators who provide services in particular along the Texas–Mexico border; the term community health worker (CHW) refers to lay health educators who practice anywhere in Texas. Promotores or CHWs are often vital in linking underserved and disenfranchised clients with essential health and human services. The uniqueness of their service lies in their ability to relate to clients through shared experiences drawn from living in the same communities. Firsthand knowledge of the barriers that affect the health of a community gives CHWs a stake in eliminating those barriers (promotor(a) or CHW as a person who, with or without compensation, provides cultural mediation between communities and health and human services systems, informal counseling and social support, and culturally and linguistically appropriate health education; advocates for individual and community health needs; ensures that people get the health services they need; builds individual and community capacity; or provides referral and follow-up services  or CHW differs widely from community to community depending on the needs each community identifies. For example, CHWs may serve as interpreters for clients during physician visits, help clients identify benefits for which they are eligible, and assist them to complete applications to receive benefits and services. As community leaders, they may empower their neighbors by organizing and motivating them to become actively involved in improving living conditions within their neighborhood. In the role of health educators, CHWs may inform their clients of ways to prevent illness and disease and teach them how to manage chronic diseases. Experience has shown that CHWs are a valuable resource for informing their neighbors and recruiting them to participate in social programs for which they qualify.The role of a promotor(a)or CHW training and certification program. As part of that legislation, the state established a committee under the direction of the Texas Department of Health (TDH) to study the feasibility and elements of such a program and make recommendations for its implementation. This paper describes the work of this committee and the resulting certification program for promotores and CHWs in Texas.In 1999, Texas became the first state in the nation to legislate a statewide voluntary promotores and CHWs involved three groups. First, in the mid-1990s, a series of meetings was held that brought together promotores or CHWs, a CHW alliance, community leaders, health professionals, and others interested in this public health work force from several southwestern border states. Second and also important were the promotor(a) organizations, formed to provide communication and sharing networks among promotora programs. One example is the South Texas Promotora Association, a loose federation of promotores from 11 programs in the Lower Rio Grande Valley. One role of these organizations was to advocate locally, regionally, and statewide for recognition of their work. Third and finally, a group of state legislators, all representing districts that form the border with Mexico, became catalysts for creating a formal means through which to recognize and legitimize promotores' work. All three of these groups helped to provide the context for the initial legislation  Program Development Committee (PPDC) was formed. The PPDC was composed of 15 members, as provided for by the legislation: two promotores, two members of the general public, two employees of the TDH, seven representatives of designated colleges and universities in Texas, one representative of the Texas Workforce Commission, and one representative of the Texas–Mexico Border Health Services Delivery Project  or CHW programs currently in operation around the state;Review and assess promotores or CHWs;Study the feasibility of establishing a standardized curriculum for promotores or CHWs and the settings in which certification may be appropriate;Study the options for certification of promotor(a) or CHW programs;Assess available methods to evaluate the success of Create, oversee, and advise local pilot projects established under this article, subject to the availability of appropriations;promotor(a) or CHW services may be included as a reimbursable service provided under the state Medicaid program  or CHW programs currently in operation around Texas, required the PPDC members to identify programs that train and employ promotores or CHWs within their organizational networks. Using a Promotor(a) or CHW Workforce and Training Questionnaire, the PPDC found approximately 30 existing programs using some 300 promotores or CHWs as paid or unpaid, full-time or part-time staff. Promotores or CHWs were serving in neighborhood clinics, local health departments, community-based organizations, faith-based agencies, and university-sponsored activities.The first charge, to review and assess promotores and CHWs. PPDC members found that each existing training program uses its own curriculum, which tends to focus on health specialties, organizational standards, and other issues shaped by the needs of the community the program serves. These curricula are as diverse in content and number of course hours as the programs themselves. Consequently, a promotor(a) or CHW may be well trained to work with the agency where training occurred but lack the skills required by a different agency. Moreover, the differences in training can lead to uncertainty as to what basic competencies potential employers can expect.The second charge asked PPDC members to study the feasibility of establishing a standardized curriculum for The PPDC reviewed state and national curricula and decided that implementation of standard curriculum guidelines, which instill portable skills, would ensure a common base of knowledge and guarantee certain basic skills. This standardized curriculum focused on eight core areas of competence :AdvocacyInterpersonal relationsCapacity buildingCommunicationKnowledgeOrganizationTeachingService coordinationThese competencies are critical to accomplishing community health improvement goals, including chronic disease prevention.promotor(a) or CHW daily activities. With this the state is better able to ensure uniformity and transferability of basic knowledge and skills regardless of where the promotor(a) or CHW practices  or CHW services not fewer than 1000 cumulative hours from July 1997 to January 2004. This certification process was based loosely on the professional certification process for health educators known as the Certified Health Education Specialist and administered by The National Commission for Health Education Credentialing, Inc.Among other qualifications, a minimum of 160 course hours must be offered for a curriculum to qualify for certification. To be grandfathered into certification, individuals must submit an application and must have performed promotores or CHWs and the settings in which certification may be appropriate. The committee, with stakeholder feedback, chose to certify promotores or CHWs, their instructors, and sponsoring institutions or training programs. The rules specify qualifications and special provisions for those who have historically been a part of the CHW movement. Settings that are safe and comfortable and where learners feel valued and respected were given primary consideration to support the special needs of these adult learners.The third charge required the PPDC to study the options for certification of promotor(a) or CHW programs. Findings indicated that programs use evaluation tools differently. Some programs evaluate processes and others focus on outcomes. Some programs have used a combination of methods, and some programs do not gather data at all or use data to evaluate their efforts. The PPDC agreed that as an overriding principle, programs should at least be able to integrate an evaluation component that is adaptable for the varied promotor(a) or CHW functions, including health, social services, education, or instruction. Likewise, the ongoing evaluation of the program for practical purposes should include the ability to assess curriculum, certification, training, and programmatic implementation. In response to theses findings, the PPDC initially recommended the use of a comprehensive, thoroughly field-tested evaluation package known as the Community Health Worker Evaluation Tool Kit, developed by the University of Arizona Rural Health Office and the College of Public Health. The TDH  is in the initial phase of designing a tool to evaluate program processes and outcomes.The fourth charge to the PPDC was to assess available methods to evaluate the success of The fifth charge to the PPDC was to create, oversee, and advise local pilot projects established under this article, subject to the availability of appropriations that may be used for this purpose. Five pilot sites were selected by the TDH and Health and Human Services Commission (HHSC) committee through a competitive process. However, because of shortfalls in general revenue, the pilot sites were unfunded, which precluded the development of neighborhood projects to test the feasibility of training, certifying, and employing CHWs. However, in late 2002, HHSC assisted the TDH with funding a neighborhood project by seeking foundation resources to obtain additional federal Children's Health Insurance Program (CHIP) matching funds. In November 2002, Rockwell Fund, Inc awarded $25,000 to Harris County Hospital District, Gateway to Care in Houston, and this contract was executed in June 2003. The purpose of the pilot is to test the effectiveness of CHWs in increasing access to primary and preventive health care and reducing overall health care costs to the state. This project received an additional award of $173,000 from the Houston Endowment for a 3-year period.promotores or CHWs and one instructor were certified by the TDH to work with Gateway to Care families. In addition, Gateway to Care was approved by the TDH as a certified training program.During the first 14 months of implementation of the Harris County pilot project, 1017 CHIP and Medicaid families were served by receiving information on and assistance with using health resources. Eight promotor(a) or CHW services would be included as reimbursable services provided under the state Medicaid program. The PPDC recommended that all practical sources of funding within the state be considered in supporting CHW services. The sixth charge to the PPDC was to evaluate the feasibility of seeking a federal waiver so that The PPDC recommended the following changes within the Medicaid system and "right steps" for appropriate health and human services commission agencies to take:promotores or CHWs to assist recipients in accessing Medicaid services, simplifying Medicaid eligibility policies and procedures, reducing documentation required by the application process, and requiring customer service and cultural competency standards;Apply best practice models to eliminate barriers to care. These included employing or empowering Enable community residents to collaborate with health and human services systems to build or tailor the Medicaid infrastructure to the unique conditions of their environment;Promote independence and local control among community residents and sustain commitment among health and human services agencies to improve quality of life and eliminate health disparities.Recent legislationpromotor(a) training and certification program. In that same year, the Texas legislature passed two pieces of legislation related to promotor(a) certification. Senate Bill 1051 mandated that all promotores or CHWs who receive compensation for their services be certified. Previously, the certification process was voluntary for all promotores or CHWs. The second piece of legislation, Senate Bill 751, required that state health and human services agencies use certified promotores to the extent possible for recipients of medical assistance. Together, these mandates increased the immediate need for approved training programs and a standardized certification process.The PPDC accomplished its objectives in 2001 of preparing for a Promotor(a) or CHW Training and Certification Advisory CommitteePromotor(a) or CHW Training and Certification Advisory Committee was established in 2001. This committee, reporting to the TDH, determines the eligibility of and recommends certification for promotores or CHWs, instructors, and sponsoring institutions or training programs.To oversee the certification process, the Texas Promotor(a) or CHW Training and Certification Advisory Committee is composed of nine members approved by the Texas Health and Human Services Commission.  The committee includes four certified promotores, CHWs, or the equivalent; two members of the public; one member from the Texas Higher Education Coordinating Board or a higher education faculty member who has teaching experience in community health, public health, or adult education and has trained promotores or CHWs; and two professionals who work with promotores or CHWs in a community setting . By December 2003, a database for tracking the review and disposition of applications for all three forms of certification and recertification was implemented; 224 certifications for promotores or CHWs were conferred; certification IDs were accepted as proof of qualifications by all organizations in Texas; certification renewal forms were created; and a Web site for the Texas Promotor(a) or CHW Training and Certification Advisory Committee was launched. By December 2004, the committee had certified 337 promotores or CHWs, 24 instructors, and 3 training programs. By the end of December 2005, it is estimated that there will be more than 700 certified promotores or CHWs in Texas.By December 2002, the committee had developed, field tested, and finalized the certification application form for The impact of the training and certification program on CHWs is deeply personal. CHWs provide a number of reasons for seeking certification: self-development, recognition by others of their position and work, professional enhancement, new incentives to work, and the possibility for career development . In addiCounterarguments are made by CHWs who wish to function on a volunteer basis or by individuals who are concerned that certification of CHWs will erode the professional base of another regulated, licensed, or certified professional group. There are many people who feel that professionalizing CHWs will result in a loss of the indigenous qualities that contribute to their success. However, CHWs may continue to volunteer their services without penalty; CHWs who provide services without compensation are not required to be certified.CHWs in Texas, for the most part, work in an integrated fashion within the health and human services system and seldom work with a specific "carve-out" or solely funded CHW program. Therefore, sustainability of CHW programs may not be a major issue for Texas. As with all federally funded or state or locally funded programs, sustainability is an issue regardless of the types of individuals providing services to their communities. Institutions are at a greater legal risk if their CHWs are not certified, because many of these workers visit clients in their homes and are at greater personal risk if they cannot visibly and legitimately identify themselves with an organization. CHWs in Texas are just beginning to receive compensation for their services through various sources. For example, certified CHWs have been employed by Maximus, Texas' Medicaid enrollment broker, to conduct the outreach necessary to inform Medicaid enrollees of their benefits.There is no application fee associated with certification. Costs, if any, are borne by the employer or the CHW for training or recertification, which may include a cost for continuing education. To date, cost has not been an issue. The greater issue in the future is anticipated to be access to and availability of continuing education for CHWs. The time needed for training has not proven to be a barrier to certification, either. CHWs who wish to improve their skills and knowledge, regardless of certification status, will have the opportunity to do so through certified training programs.The greatest challenge to implementing the CHW training and certification program was working with a diverse, vocal, and broad-based committee that represented academic systems, state agencies, the general public, and CHWs in creating a shared vision and a unified set of recommendations on how this training and certification program should function. Staff worked diligently to ensure that the voice of the CHW was heard throughout the process and established a public comment period as a standard procedure for each official meeting and hearing conducted by the TDH.promotores or CHWs in December 2002, there has been much interest in the certification program statewide. Program staff respond to approximately 120 inquiries per month about certification policies and procedures. As of May 2005, the Texas Department of State Health Services had certified 500 promotores, 24 instructors, and 6 sponsoring institutions or training programs in Texas. Two additional training programs were certified in June 2005 (Table). A map showing the number of certified promotores in each Texas county is available from www.tdh.state.tx.us/ophp/chw/pubs/promotorasmay05.pdf*.Since the rollout of the certification application for For the first time, Texas has recognized the power and the value of this community health safety net by giving long overdue recognition to the health education workforce that has worked silently and tirelessly to keep their communities healthy and fit.


Contraceptive prevalence is relatively high in Brazil (55% among women of reproductive age). However, reversible methods account for less than half of the method mix and widespread differences persist across regions and social groups. This draws attention to the need for monitoring family planning service-related outcomes that might be linked with quality of care. The present study examines the factors associated with method discontinuation, failure and switching among current contraceptive users, with a focus on sub-national assessment.Data for the analysis are drawn from the Brazil Demographic and Health Survey, notably the calendar module of reproductive events. Multilevel discrete-time competing risks hazard models are used to estimate the random- and fixed-effects on the probability of a woman making a specific transition after a given duration of contraceptive use.Contraceptive continuation was found to be highest for the contraceptive pill, the most popular reversible method. Probabilities of abandonment while in need of family planning and of switching to another method were highest for injections. Failure, abandonment and switching were each higher among users in the Northeast region compared to the more prosperous Southeast and South.Findings point to seemingly important disparities in the availability and quality of family planning and reproductive health care services across regions of the country. Expanding access to a range of contraceptive methods, improving knowledge among health agents of contraceptive technologies and increasing medical supervision of contraceptive practice may be considered key to expanding quality reproductive health care services for all. Strengthening of reproductive health and family planning services in developing countries is repeatedly highlighted as a priority for reducing maternal mortality and improving maternal and child health. Effective implementation of appropriate services requires an understanding of the factors affecting reproductive outcomes among women at risk and their patterns of behaviour. In Brazil, despite relatively high levels of contraceptive use, there appears to remain a large unmet need for family planning, particularly in the poorer areas of the country. Evidence from the Demographic and Health Survey (DHS) suggests that if all Brazilian women who wanted to limit their fertility were protected by effective contraception, the total fertility rate (TFR) in 1996 would have stood at 1.8 children per woman – one-third lower than the observed rate [Differences in availability, accessibility, and acceptability of the range of contraceptive technologies may mean that not all methods are favoured at the same time. Evidence from a number of developing countries reveals that the method mix tends to continuously evolve. It has been estimated that at least half of the women using contraceptives switch methods within a five-year period . A studyIn Brazil, reversible methods account for less than half of the method mix . Oral coIn order to fully understand women's family planning choices, it is imperative to investigate the components of contraceptive dynamics such as contraceptive discontinuation, failure and switching. Contraceptive failure, resulting in unintended pregnancy, may be due to method failure, user error or provider failure . The impAt the same time, Brazilian society has been marked by sharp regional inequalities that have characterised the country since the colonial period . Much atThe objective of this paper is to analyze the factors associated with contraceptive discontinuation, failure and switching across regions of Brazil, drawing on data from the 1996 DHS. We examine the demographic and socio-cultural influences of contraceptive use dynamics across reversible methods, focusing special attention on the reported reasons for method discontinuation. Identifying the predictors of method failure and discontinuation in the context of rapid and profound changes in reproductive behaviours could draw the attention of policymakers on regional disparities and the difference in quality of reproductive health care provision and eventually assist in improving services.Pesquisa Nacional sobre Demografia e Saúde, collected information through personal interviews with 12,612 women aged 15–49, selected through a two-stage random sampling process designed to represent 95% of the country's population at the national and sub-regional levels  [The DHS is one of the largest programs collecting quantitative data on reproductive health knowledge, attitudes and practices in the developing world. Surveys are carried out using standardized instruments, methods of training, data collection and data processing . The mosIn addition to core questions for measuring basic indicators for population and health program monitoring and evaluation, some DHS surveys include additional modules designed to obtain specialized information on specific topics. The present analysis takes advantage of the "calendar" module of reproductive events. The calendar records detailed information (i.e. month-by-month) about the timing of a number of events–including marital unions, residential mobility, births, and contraceptive use (including method or reason for discontinuation)–occurring in the five calendar years preceding the survey. This retrospective method of measurement makes heavy demands on the memory of respondents, but recall is aided by timing events in relation to one another. Overall, the quality of information obtained through this approach has been evaluated as superior to alternative retrospective data collection techniques for longitudinal information ,14. A reFor this study, a discrete-time competing risks hazard model is used to estimate the probability of a woman making a specific transition at a given duration of use. A discrete-time competing risks model is a multinomial logistic model in which the observations are repeated according to the duration of use until the event occurs or is censored. This approach allows incorporation of time-varying covariates as compiled in the calendar . Our main objective is to describe the patterns and explain the independent determinants of contraceptive discontinuation, failure and switching among women at risk across the main regions of the country.Included in the model are all women who were ever sexually active and who initiated use of a reversible method of contraception over the period covered by the calendar. The units of analysis are the episodes of contraceptive use . Observations in the three-month period immediately before the survey are excluded, to reduce bias in the estimation of use-failure rates, given that some women may have been unaware of their very early pregnancy . LikewisWe consider episodes of use of oral contraceptives, injections, condoms, and traditional or natural family planning methods . Uses of other modern reversible methods  are excluded, due to the small number of episodes observed in the survey and since it was not considered appropriate to aggregate these methods into a single category as discontinuation and failure rates can vary substantially across methods. Sterilization is also excluded given that discontinuation of this method occurs infrequently.In examining the patterns of contraceptive use dynamics, four categories were created for the response variable: (i) failure; (ii) abandonment of the method while still in need of family planning; (iii) switching to another reversible method; and (iv) continuing use of the method. Contraceptive failures include any  occurrence of a pregnancy while using the method. Episodes where the woman reported having discontinued use for non-method-related reasons–such as a desire to get pregnant, marital separation, or infrequent sexual intercourse–were included under the fourth category, as they were not considered to have ended while in need of family planning. Note that these categories should be interpreted as approximate, given that self-reported reasons for contraceptive discontinuation may be somewhat unreliable .A number of episode-specific and woman-specific variables were included in the model as potential confounding factors, including contraceptive intention and duration of use as well as woman's age, marital status, number of living children, education, ethnicity, place of residence , and mass media exposure (as assessed through television viewing habits). These covariates have been previously considered relevant to assess mechanisms that influence contraceptive use, method choice and/or discontinuation in Brazil and other developing countries -4,15-17.Of further substantive and methodological interest, our study uses a multilevel approach. Standard regression models assume that observations are independent. However, given the hierarchically nested structure of the data being used here, multilevel modeling becomes necessary to allow for controlling for any unobserved correlation between observations within hierarchical levels. At the first level, in modeling women's episodes of contraceptive use, an individual may contribute more than one segment of use to the sample. At the second level, the DHS sampling scheme entails selection of households and individuals within enumeration clusters . IndividThe multilevel discrete-time competing risks model is used to assess regional disparities in contraceptive failure, abandonment and switching, conditioned for the set of fixed- and random-effects. The formulation of the model is as follows:λrtijk is referred to as the hazard of a transition of type r at time t for the use interval i of woman j from cluster k. The baseline hazard is represented by αrt, a function of time. βr is the vector of parameters for transition r, with xtijk the associated set of covariates (the same for each of the three types of contrasts against continuation of method use). The estimators urjk and vrk measure the random variations at the woman and cluster levels respectively. They are assumed to be mutually independent and normally distributed with mean zero and variances where MLwiN statistical software program [The final sample for the study consisted of 6,027 episodes of contraceptive use. The analysis was carried out using the  program . In orde program . First, As seen in Table At the time of the survey, 55% of all women of reproductive age, and 77% of married women, were currently using some method of contraception. Of these, over half were relying on either female or male sterilization Table . Among uContraceptive discontinuation rates among the most common reversible methods by self-reported reason for discontinuation are presented for the national level in Table The estimated coefficients from the risks hazard model for the influences of selected episode- and woman-level variables on contraceptive use dynamics are presented in Table The cumulative probability of failure was highest for episodes of use of traditional methods (0.23). Probabilities of abandonment (presumably while in need of family planning) and of method switching were highest for injections. In contrast, the probability of continuation was highest for the contraceptive pill (0.64), the most widely used reversible method overall. Continuation was also high for condoms, albeit at a lower measure than for the pill.After controlling for the method type and other potentially confounding factors, the probabilities of failure, abandonment and switching were higher in the Northeast region compared to the Southeast and the South, a pattern that was statistically significant (p < 0.05).The probability of failure was essentially inversely associated with the woman's age at the start of the episode of use, as well as with her educational attainment. Abandonment was more likely among adolescents (19 years and under) as well as older users (30 years and over) compared to users in their twenties. Abandonment was positively correlated with the number of living children at the start of the episode, and inversely associated with educational attainment. Method switching was more common among married users than their unmarried counterparts.No discernible differences were found according to urban/rural residence Table , a resulOver 90% of governments around the world provide either direct or indirect support for contraceptive methods, including that of Brazil . While BThis paper examined regional patterns of contraceptive discontinuation, failure and switching for reversible methods in Brazil, drawing on data from the DHS calendar. Given both the larger size of the Brazilian survey sample , as well as the relatively high overall contraceptive prevalence rate, the study offered a valuable opportunity for monitoring of patterns in discontinuation and switching at the sub-national level. In the analysis of discontinuation, particular attention was paid to the reasons for stopping use and differentiating method failure from abandonment while in need for family planning. Multilevel competing risks hazard models served to assess the random- and fixed-effects on contraceptive dynamics.In summary, the probability of continuation was found to be highest for oral contraceptives. Encouragingly in the face of the HIV/AIDS epidemic, continuation was also high for condoms. As could be expected, the probability of failure was highest with respect to traditional methods. Greater likelihoods of abandonment and switching were found for injections compared to other modern and traditional methods, echoing research results from a number of Latin American countries and reinforcing suggestions that family planning service managers examine more closely the delivery of injectables .After controlling for episode- and individual-specific factors, the probabilities of contraceptive failure, abandonment and switching were each found to be significantly higher in the Northeast compared to the more developed Southeast and South, pointing to seemingly important disparities in the availability and quality of family planning and reproductive health care services across regions of the country.Moreover, failure for all methods combined was highest among adolescent and less educated users, likely related to higher rates of user error. Research in Brazil and other Latin American countries has reported that women of lower educational attainment, a characteristic considered as proxy for socio-economic status, were less likely to adopt sterilization for contraceptive purposes . Such paAn important venue for further research would thus be to examine, for example, effects of the proximity and quality of local service delivery points. As such, one potential future approach could be to merge independently collected data on municipal-level variables for availability and accessibility of health care resources with the DHS individual data.Many previous studies of contraceptive discontinuation and/or switching have focused only on reports from married women ,8,9,16. A limitation to this analysis may have been a failure to adequately investigate possible biases due to correlation between the observed variables and errors in the model. A recent study in Indonesia using multiprocess models showed that the contraceptive continuation rate is dependent on the contraceptive choice itself, when applied to the effect of choice for IUD and implants . The potLastly, the data used here were obtained during the course of fieldwork conducted in 1996, the last survey conducted in Brazil under the auspices of the DHS program. The availability of updated information drawing on results from a more recent survey, with a calendar module to allow for comparative analysis, would be essential to assess any changes in trends over the last decade.The authors declare that they have no competing interests.Both authors contributed to the study design. IC Leite performed the data manipulation and statistical programming. Both authors contributed to the data analysis as well as drafting of the manuscript, and have read and approved the final version.