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LETTER TO THE EDITOR

Dear Sir:

Recent studies have reported significant toxicity of artemisinin and its derivatives for schistosomula in various Schistosoma species.^1,2 These drugs have been suggested to reduce the incidence of infection in endemic regions and prevent complications of schistosomiasis. Following the recent paper by N’Goran and others² that deals with the efficacy of artemether against S. haematobium and proposes a new control strategy, we want to draw attention to some important issues.

First, we were surprised that these trials were performed in regions endemic for malaria, where such trials are inappropriate, as stated by the investigators themselves. Recommended doses of artemisinin derivatives for prevention of schistosomiasis are insufficient for treating malaria and able to induce drug resistance in Plasmodium falciparum. The World Health Organization has recommended restricting the use of these drugs, which at the present time are among the most effective drugs for treatment of malaria, to prevent or delay the appearance of drug-resistant parasites.³ Moreover, these studies, which trivialize the use of artemisinin derivatives, pose another ethical problem. The consequences of repeated use of artemether have never been evaluated.

The short duration of action of artemisinin derivatives on schistosomula requires a monthly or possibly shorter period of administration. The recommended strategy of schistosomiasis control in most endemic countries is based on annual distribution of praziquantel to the population at risk. Confirmed efficiency of this method is already hampered by financial and logistic constraints. It does not seem acceptable to propose a strategy that would be affected by these two serious limitations. Although the long-term objective is to effectively interrupt the transmission of schistosomiasis, health education and improvements in hygiene and sanitation, rather than chemotherapy, will be a more effective and long-lasting method of prevention.

Finally, we do not believe that the results presented by the investigators are relevant on two points. First, it is unlikely that a treatment that shows a protective efficacy of only 0.25 will be able to interrupt parasite transmission. Second, contrary to the assertions of the investigators, we assume that a decrease in the ovular load of less than 50% does not prevent clinical complications. Therefore, it seems inappropriate to draw such positive conclusions from such studies.

Studies of this type are of debatable interest because of their weak operational applicability. However, although this strategy could be restricted to the northern Africa, as suggested by the investigators, it does not seem appropriate to propose low efficiency and expensive control methods in countries where difficulties in implementing control strategies are considerable, especially if they represent a risk of establishing parasite drug resistance to one of the last effective treatments for malaria.

1. Utzinger J, Xiao SH, N’Goran EK, Bergquist R, Tanner M, 2001. The potential of artemether for the control of schistosomiasis. Int J Parasitol 31: 1549–1562.[ISI][Medline]
2. N’Goran EK, Utzinger J, Gnaka HN, Yapi A, N’Guessan NA, Kigbafori SD, Lengeler C, Chollet J, Xiao SH, Tanner M, 2003. Randomized, double-blind, placebo-controlled trial of oral artemether for the prevention of patent Schistosoma haematobium infections. Am J Trop Med Hyg 68: 24–32.[Abstract/Free Full Text]
3. WHO, 1998. The Use of Artemisinin and Its Derivatives as Anti-Malarial Drugs. Geneva: World Health Organization. WHO/ MAL/98.1086, 1998.

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