Host-parasite diplomacy

Abstract

Benzimidazole (BZ) resistance was also addressed in a number of reports. Roger Prichard (McGill University, Montreal, Canada) described a decrease in the extent of high-affinity binding, without a change in binding constant, in BZ resistant H. contortus and the evidence for a change in ~-tubulin in resistant nematodes. Two ~-tubulin gene families have been described in H. contortus and B. pahangi. Benzimidazole resistance was associated with a reduction in the number of alleles in each of these [}-tubulin gene families, with only one allele appearing to be present in one of the ~-tubulin gene families in BZ resistant nematodes. Leo Le Jambre (CSIRO, Armidale, New South Wales, Australia) showed a similar loss of 13-tubulin diversity in BZ-resistant Trichostrongylus colubnformis. Marleen Roos and Marcel Kwa (University of Utrecht, The Netherlands) presented evidence that intensive selection for BZ resistance in H. contortus may result in the selection for the complete loss of one of the J3-tubulin gene families as identified by restriction fragment length polymorphism (RFLP) analysis with a specific probe. However, there is still the possibility that other ~-tubulin genes/alleles not detected with the probe used may exist.