Current opinionMonitoring drug efficacy and early detection of drug resistance in human soil-transmitted nematodes: a pressing public health agenda 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)
- et al.
A randomised controlled trial comparing Mebendazole and Albendazole against Ascaris, Trichuris, and the hookworms
Transactions of the Royal Society of Tropical Medicine and Hygiene
(1994) - et al.
World Association for the Advancement of Veterinary Parasitology (WAAVP) methods for the detection of anthelmintic resistance in nematodes of veterinary importance
Veterinary Parasitology
(1992) - et al.
Benzimidazole resistance in Haemoncus contortus is correlated with a conserved mutation at aminoacid 200 in β tubulin isotype 1
Molecular and Biochemical Parasitology
(1994) - et al.
An international initiative on Praziquantel use
Parasitology Today
(1998) - et al.
Failure of pyrantel in treatment of human hookworm infections (Ancylostoma duodenale) in the Kimberly region of North West Australia
Acta Tropica
(1997) - et al.
Comparison of the efficacy of mebendazole, albendazole and pyrantel in treatment of human hookworm infections in the Southern Region of Mali, West Africa
Transactions of the Royal Society of Tropical Medicine and Hygiene
(1999) - et al.
Schistosomiasis and soil-transmitted helminth infections: forging control efforts
Transactions of the Royal Society of Tropical Medicine and Hygiene
(2002) A larval development test for the detection of anthelminthic resistance in nematodes of sheeps
Research in Veterinary Science
(1990)Resistance in nematode parasites of livestock to the benzimidazole anthlemintics
Parasitology Today
(1990)- et al.
Development and evaluation of the egg hatch assay (EHA) for detection of anthelminthic drug resistance by human hookworms. 14–19 June, Torino, XXII National Congress of Parasitology
Parassitologia
(2002)