The β-tubulin genes of two Strongyloides species

The World Health Organization is sponsoring major treatment programs with the aim of controlling helminth infection throughout the tropical world. Prominent among the anthelmintics recommended for use in these programs are drugs in the benzimidazole (BZ) class. Resistance to these drugs has been associated with polymorphisms in the β-tubulin gene. We have cloned and sequenced the β-tubulin genes of Strongyloides stercoralis and Strongyloides ratti and have proceeded to develop a protocol for genotyping single worms for polymorphisms in β-tubulin. Our findings indicate that S. ratti has a single β-tubulin gene, making DNA sequence analysis of a single larva PCR product a feasible means of studying BZ resistance in these species. Our genotyping test allows the identification of polymorphisms at codons 167, 198, and 200 in the Strongyloides β-tubulin gene, thus enabling survey for BZ resistant genotypes.