Assessing the efficacy of anthelminthic drugs against schistosomiasis and soil-transmitted helminthiases
Overview
Background
Schistosomiasis caused by Schistosoma haematobium, S. mansoni, S. japonicum and S. mekongi and soil-transmitted helminthiases caused by Ascaris lumbricoides, Necator americanus/Ancylostoma duodenale (the hookworms) and Trichuris trichiura
are among the most prevalent neglected tropical diseases (Berthony et
al., 2006; Hall et al., 2008; Brooker, 2010). The main strategy for
controlling the morbidity caused by these diseases is preventive
chemotherapy with periodic administration of single-dose anthelminthics:
praziquantel at 40 mg/kg for schistosomes, and albendazole at 400 mg or
mebendazole at 500 mg for soil-transmitted helminthiases (WHO, 2006;
Gabrielli et al., 2011).
Significant progress has been made in the control of both schistosomiasis and soil-transmitted helminthiases over the past few decades, and WHO has drawn up a roadmap to guide implementation of the policies and strategies set out in Accelerating work to overcome the global impact of neglected tropical diseases (WHO, 2012a), and more than 70 governments, NGOs and pharmaceutical companies committed themselves to support implementation of this roadmap in the London Declaration on Neglected Tropical Diseases on 31 January 2012.
A considerable increase in the number of individuals treated with preventive chemotherapy is expected in the next few years (WHO, 2012b, 2012c); this may result in the development of anthelminthic resistance in the parasites targeted. The limited number of studies in the public domain that have reported reduced efficacy of anthelminthic drugs were confounded by methodological flaws (De Clercq et al., 1997; Reynoldson et al., 1997; Sacko et al., 1999; Flohr et al., 2007; Humpries et al., 2011; Soukhathammavong et al., 2012) and do not yet provide conclusive evidence of anthelminthic resistance among helminths that infect humans. The most important confounding factors in studies of anthelminthic drug efficacy are listed in Annex 1.
Guidelines on monitoring anthelminthic drug efficacy were issued by WHO (WHO, 1999). Since the publication of those guidelines, studies have provided new insight into: indicators of drug efficacy (Montresor, 2011), thresholds for reduced efficacy (Vercruysse et al., 2011; Levecke et al., 2012a), sample size (Levecke et al. 2011a, 2012b), length of follow-up (Scherrer et al., 2009) and statistical analysis of data on drug efficacy (Dobson et al., 2009; Vercruysse et al., 2011; Levecke et al., 2011b), indicating that revision of the current guidelines is warranted.
Objective
The objective of the present
document is to provide national control programmes with up-to-date
guidelines on monitoring the efficacy of anthelminthic drugs
administered in preventive chemotherapy programmes against
schistosomiasis and soil-transmitted helminthiases. Guidance is provided
on when and how to assess the efficacy of anthelminthics, including
detailed recommendations on indicators of efficacy, sample size,
follow-up period, laboratory methods, statistical analysis and final
interpretation of data collected, and also on how to respond when drug
efficacy is reduced. In addition, examples are provided of an
information letter for schools, an informed consent form, standard
operating procedures for all recommended laboratory methods and a form
for data collection.
The method described here is for evaluating the efficacy of a single anthelminthic drug against a group of parasites. It is not recommended for drug combinations (e.g. albendazole + praziquantel or albendazole + ivermectin).
ASSOCIATED DOCUMENTS:
- Évaluation de l’efficacité des anthelminthiques contre la schistosomiase et les géohelminthiases
- Оценка эффективности антигельминтных препаратов против шитосомоза и геогельминтозов
- Evaluación de la eficacia de los medicamentos antihelmínticos contra la esquistosomiasis y las geohelmintiasis
- Avaliação da eficácia de medicamentos anti-helmínticos contra a esquistossomose e as geohelmintíases