Turnover of Village Chickens Undermines Vaccine Coverage to Control HPAI H5N1.
Highly pathogenic avian influenza (HPAI) subtype H5N1 remains an enzootic disease of village chickens in Indonesia, posing ongoing risk at the animal-human interface. Previous modelling showed that the fast natural turnover of chicken populations might undermine herd immunity after vaccination, although actual details of how this effect applies to Indonesia's village chicken population have not been determined. We explored the turnover effect in Indonesia's scavenging and mixed populations of village chickens using an extended Leslie matrix model parameterized with data collected from village chicken flocks in Java region, Indonesia. Population dynamics were simulated for 208 weeks; the turnover effect was simulated for 16 weeks after vaccination in two 'best case' scenarios, where the whole population (scenario 1), or birds aged over 14 days (scenario 2), were vaccinated. We found that the scavenging and mixed populations have different productive traits. When steady-state dynamics are reached, both populations are dominated by females (54.5%), and 'growers' and 'chicks' represent the most abundant age stages with 39% and 38% in the scavenging, and 60% and 25% in the mixed population, respectively. Simulations showed that the population turnover might reduce the herd immunity below the critical threshold that prevents the re-emergence of HPAI H5N1 4-8 weeks (scavenging) and 6-9 weeks (mixed population) after vaccination in scenario 1, and 2-6 weeks (scavenging) and 4-7 weeks (mixed population) after vaccination in scenario 2. In conclusion, we found that Indonesia's village chicken population does not have a unique underlying population dynamic and therefore, different turnover effects on herd immunity may be expected after vaccination; nonetheless, our simulations carried out in best case scenarios highlight the limitations of current vaccine technologies to control HPAI H5N1. This suggests that the improvements and complementary strategies are necessary and must be explored.
['Villanueva-Cabezas|J P|JP|', 'Campbell|P T|PT|', 'McCaw|J M|JM|', 'Durr|P A|PA|0000-0003-0851-5300', 'McVernon|J|J|']
D000822:Animal Husbandry D000818:Animals D002645:Chickens D003198:Computer Simulation D005260:Female D006801:Humans D007214:Indonesia D053124:Influenza A Virus, H5N1 Subtype D007252:Influenza Vaccines D005585:Influenza in Birds D008297:Male D008954:Models, Biological D011157:Population Dynamics D014611:Vaccination
Avian influenza population dynamics mathematical modelling poultry