Sequence variation in the @entity13857 beta-tubulin locus: implications for the development of XXXX resistance.

@entity1 @entity2199 @entity535 @entity9158 @entity377 @entity177 @entity5167 @entity9124 @entity13857
@entity9158 resistance has evolved in a variety of organisms and typically results from mutations in the beta-tubulin locus at specific @entity535 sites. Despite widespread treatment of @entity1 intestinal @entity2199 with @entity9158 drugs, there have been no unambiguous reports of resistance. However, since beta-tubulin mutations conferring resistance are generally recessive, frequencies of resistance alleles less than 30% would be difficult to detect on the basis of @entity177 . Here we investigate sequence variation in a 1079 bp segment of the beta-tubulin locus in the @entity13857 @entity13857 from 72 individual @entity2199 from seven countries. We did not observe any alleles with @entity535 mutations indicative of resistance, and of 40 point mutations there were only four non-synonymous mutations all of which were singletons. Estimated effective population sizes are an order of magnitude lower than those from another @entity2199 species in which @entity9158 resistance has developed ( @entity5167 ). Both the lower diversity and reduced population sizes suggest that @entity9158 resistance is likely to evolve less rapidly in Trichuris than in trichostrongyle parasites of livestock. We observed moderate levels of population subdivision (Phi(ST)=0.26) comparable with that previously observed in @entity9124 , and identical alleles were frequently found in parasites from different continents, suggestive of recent admixture. A particularly interesting feature of the data is the high @entity377 diversities observed in @entity2199 from the Caribbean. This genetic complexity may be a direct result of extensive admixture and complex history of @entity1 populations in this region of the world. These data should encourage (but not make complacent) those involved in large-scale @entity9158 treatment of @entity1 intestinal @entity2199 .
