Resistance of Schistosoma mansoni to praziquantel: is there a problem?

Abstract

Evidence for resistance to praziquantel (PZQ) in Schistosoma mansoni has been sought in parasites taken from treated, but uncured human patients, and in a laboratory isolate of S. mansoni subjected to successive passages under drug pressure. Patients from villages in Egypt and Senegal have yielded isolates that can tolerate higher dosages of PZQ than other ostensible control isolates when passaged and subjected to drug treatment in mice. In vitro tests on these and the laboratory-selected isolate support the conclusion that a degree of resistance to PZQ can occur in S. mansoni, but the levels of drug resistance found so far are low. Preliminary studies have begun on these isolates to identify genetic, physiological and morphological characteristics associated with PZQ resistance and some of these may find use as markers for monitoring whether or not resistance is developing in endemic areas where the drug is used. More intensive application of PZQ can be expected in future, particularly in other parts of Africa, and vigilance will be needed to ensure that it continues to be useful as a drug for treatment of schistosomiasis. Further work is needed to elucidate the mode of action of PZQ and there is already a need for alternative drugs to treat PZQ-resistant schistosomiasis, such as already exists in northern Senegal.

Large-scalein Vitro. Screening of Egyptian Native and Cultivated Plants for Schistosomicidal Activity

“…Praziquantel is the mainstay of schistosomiasis control programs worldwide, and thus an enormous investment in terms of money and training rests solely on the efficacy of a single compound. This extensive reliance on just one drug might represent a serious situation, due to the possible development of drug-resistant parasite (Ismail et al, 1999;Doenhoff et al, 2002). Therefore, there is now an urgent need for developing new antischistosomal drugs (Lambertucci et al, 1980;Souza et al, 1982).…”

Schistosome vaccines: a critical appraisal

“…Furthermore, chemotherapy cannot prevent re-infection. Low cure rates have been reported that may presage the appearance of drug resistance (Doenhoff et al 2002). Lastly, schistosome infections are potent immunomodulators, a process that appears related to worm burden (Silveira et al 2004), and may alter host responses to other infections in a deleterious manner.…”

Topical application of DEET for schistosomiasis

“…Another alternative to control schistosomiasis in endemic areas is mass chemotherapy with praziquantel, the only effective drug against schistosomiasis. Unfortunately, there are indications of potential drug resistance against praziquantel [6]. Added to this is the declining trend of reduced investment of pharmaceutical industries in drug research for tropical diseases mainly because of the high cost of drug development and registration [7].…”