Current opinion
Monitoring drug efficacy and early detection of drug resistance in human soil-transmitted nematodes: a pressing public health agenda for helminth control

https://doi.org/10.1016/j.ijpara.2004.08.001Get rights and content

Abstract

Control of soil-transmitted helminth infection and elimination of lymphatic filariasis by periodic chemotherapy increase drug pressure for possible occurrence of resistance against single dose anthelminthics. In veterinary practice, frequent treatment of closed populations has led to a serious problem of anthelminthic drug resistance which is now largely irreversible. Reduced efficacy of single dose drugs against nematodes of humans should be taken as early warnings to tackle the issue in due time. Research and development of sensitive tools for monitoring and early detection of drug resistance is urgently needed to sustain the benefits of helminth control programs gained so far. A concerted action with international partners and the creation of a network of scientists to address this issue is the next pressing public health issue for helminth control.

Section snippets

Control of soil-transmitted helminthiasis and elimination of lymphatic filariasis by periodic chemotherapy: the challenge for the worms

Rather than to achieve elimination of the helminth infection, current helminth control programs are focused on reducing infection load (worm burden) and transmission potential in order to reduce morbidity and avoid mortality associated with the disease (WHO, 2002). There is a vast body of evidence that periodic treatment against soil-transmitted helminths reduces chronic and subtle morbidity in high risk groups such as children and women of child bearing age, despite continuous transmission and

Lessons from livestock

Widespread treatment of farm animals with anthelminthics has been practised for many years to prevent disease and death and increase productivity. However, as a result veterinary medicine is facing an important and increasing problem of drug resistance (i.e. infections persist in the presence of previously curative doses of the drugs) to all the major groups of anthelminthics. It has become a serious problem in sheep and goats in many countries, but appears to be less common in cattle and pigs (

Available evidence for emerging resistance in nematodes of man

There have been two small scale studies reporting failure in the treatment of human hookworm infections following common usage (not mass or targeted treatment) of mebendazole in Mali (De Clercq et al., 1997) and of pyrantel in North West Australia (Reynoldson et al., 1997). Though these studies report reduced efficacy of anthelminthic drugs, their suggestion of emerging drug resistance should be interpreted with caution, since poor efficacy could have other causes. No treatment efficacy data

The concern from public health planners

On the basis of this information and the veterinary experience, there is a growing concern in International Agencies that frequent treatments with the same drug will increase drug pressure on the parasite population resulting in a selection of worms carrying resistant genes. The most worrying scenario would be to see the benefits of periodic chemotherapy hampered by generalised treatment failures. Furthermore, there are only a few anthelminthic drugs on the market and almost none under

Available tools to monitor drug efficacy/resistance in human nematodes

Based on the veterinary experience, laboratory methods to determine the presence of drug resistance have the advantage of being relatively cheap to perform and relatively quick to yield information although there may be problems in extrapolating these results to the field situation since parasite populations studied in the laboratory will have a small gene pool, often representing only a small fraction of the genetic repertoire of the field population (Waller, 1990). Field studies, on the other

Future perspectives for development more efficient and sensitive field tools

At present, only assessment of reductions in efficacy (ERR) following treatment as compared to previous efficacies (before drug exposure) provide data which would suggest the appearance of anthelminthic drug resistance in humans. There is therefore, a need to develop standardised protocols and to investigate reliable and valid in vivo and in vitro tests to confirm suspected drug resistance in humans under the conditions occurring in developing countries. A standard protocol for testing of drug

Conclusions and way forward

Although reduced efficacy of BZ against hookworms has been reported from a few studies, evidence of resistance has not been demonstrated by further tests and genomic analysis. However, due to the experience from the veterinary field, careful attention must be given to the monitoring of anthelminthic drug efficacy, and sensitive and practical tools should be developed for an early detection of increasing frequency of resistant strains. In conclusion, anthelminthic resistance does not yet seem to

References (31)

  • M. Albonico et al.

    Efficacy of mebendazole and levamisole alone or in combination against intestinal nematode infections after repeated targeted mebendazole treatment in Zanzibar

    Bulletin of the World Health Organization

    (2003)
  • M. Albonico et al.

    Molecular analysis of the β-tubulin gene of human hookworms as a basis for possible benzimidazole resistance on Pemba Island

    Molecular and Biochemical Parasitology

    (2004)
  • I. Beveridge et al.

    Prevalence of resistance in sheep nematodes populations to benzimidazole and levamisole anthelmintics in the high rainfall areas of South Australia

    Australian Veterinary Journal

    (1990)
  • F.H.M. Borgsteede et al.

    Increase in anthelminthic resistance in sheep in the Netherlands Veterinary Records

    (1991)
  • G.C. Coles

    Anthelmintic resistance and the control of worms

    Journal of Medical Microbiology

    (1999)
  • Cited by (0)

    View full text