Characterization of beta-tubulin genes in hookworms and investigation of resistance-associated mutations using real-time PCR

Sampling strategies to detect anthelmintic resistance: the perspective of human onchocerciasis

The large-scale use of mass drug administration in human helminthiases control has raised awareness that anthelmintic resistance could develop. This has motivated an increasing number of studies to investigate changes in genetic structure of parasite populations undergoing treatment. For these studies to reflect accurately the current situation, parasitologists need to consider the sampling schemes they employ. In this article, we use mathematical models to discuss issues such as which hosts to examine, on which parasite life stage(s) to focus, and when after treatment to sample to quantify the presence and frequency of genetic markers of treatment-induced selection or drug resistance.

Intestinal nematodes: disease burden, deworming and the potential importance of co-infection

PURPOSE OF REVIEW

Intestinal nematodes affect the world's poorest communities through clinical morbidity associated with heavy infection and the economic consequences of reduced productivity.

RECENT FINDINGS

There has been a significant increase in funding and global support for mass treatment programmes. Local epidemiology is necessary if these programmes are to target the most affected communities, and new mapping tools and mathematical modeling methodologies are identifying the high degree of spatial heterogeneity and the relevance of polyparasitism in estimating attributable morbidity. Recent meta-analyses have highlighted the limited evidence base for many of the claims for treatment benefit. Programme evaluations are beginning to demonstrate good outcomes, but further work is required to assess public health benefit and sustainability of these campaigns. New drugs have been identified which may be necessary to counteract resistance; vaccine studies show early promise as a potentially sustainable approach in the longer term. Research on the impact of helminths and treatment on other diseases continues, with reassuring evidence that mass treatment does not increase prevalence of allergy, and potential treatment benefit for patients with HIV. The relationship with malaria is of particular concern, and further studies are needed to assess how best to integrate control of these diseases.

SUMMARY

There has been a major scale-up of mass treatment in recent years. In this climate, it is vital that such programmes are appropriately evaluated, and that well designed controlled trials assess the role of deworming in other groups.

Absence of three known benzimidazole resistance mutations in Trichostrongylus tenuis, a nematode parasite of avian hosts

Benzimidazole (BZ) resistance is widespread in nematode parasites of livestock, but very little is known about the levels of BZ resistance in parasites with avian hosts. We investigated BZ resistance in Trichostrongylus tenuis, a nematode parasite of red grouse, Lagopus lagopus scotica. BZ anthelmintics had been in use in this system for up to 15 years, yet existing phenotypic evidence for resistance was inconclusive. We screened 1530 individuals from 14 populations at the principal beta-tubulin locus for BZ resistance (isotype 1, residue 200) and 940 of these at two further resistance sites (isotype 1, residue 167; isotype 2, residue 200). No BZ resistant genotypes were found. Alternative mechanisms may be responsible for BZ resistance in this system, or the method and timing of treatments may reduce selection pressure for BZ resistance by creating substantial refugia for susceptible genotypes.