Chemotherapeutic effects on larval stages of Schistosoma mansoni during infection and re-infection of mice

Abstract

The sensitivity of the larval stages of Schistosoma mansoni to chemotherapy with praziquantel and oxamniquine was tested in mice during primary and secondary infections and after different intervals from cercarial exposure. Worm recovery by perfusion of the porto-mesenteric system, followed by counting and a morphometric study of the parasite, allowed the conclusion that the relative resistance of the larval stages of S. mansoni to schistosomicide drugs, demonstrated in primary infections, also persists when the host is already infected. This indicates that a therapeutic failure may result when an infected host is treated some time after being re-infected, because of the presence of migrating, drug-resistant, immature forms of the parasite. Key-words: Schistosoma mansoni. Larval stages. Praziquantel. Oxamniquine.Resumo A susceptibilidade dos estágios larvais do Schistosoma mansoni aos esquistossomicidas praziquantel e oxamniquine foi testada em camundongos durante infecção primária ou secundária, e após diferentes intervalos de tempo após a exposição cercariana. A avaliação foi feita pela contagem dos vermes após recuperação destes por perfusão do sistema porto-mesentérico e pelo estudo morfométrico dos mesmos. O estudo revelou que a relativa resistência das formas larvais aos esquistossomicidas, já demonstrada em infecção primária, persiste no caso de hospedeiros já infectados. Este fato indica que uma falha terapêutica pode resultar quando o tratamento é feito em hospedeiros re-infectados recentemente, em virtude dos mesmos apresentarem formas migrantes e imaturas do parasita, as quais são particularmente resistentes aos esquistossomicidas. Palavras-chaves: Schistosoma mansoni. Estágio Larval. Praziquantel. Oxamniquine.

Efficacy and side effects of praziquantel in the treatment of Schistosomiasis mansoni in schoolchildren in Shesha Kekele Elementary School, Wondo Genet, Southern Ethiopia

“…In areas with heavy transmission of schistosomiasis, it has been suggested that people might have been infected in the previous 3-5 weeks. Hence, such patients would harbor immature schistosomes that are less susceptible to PZQ [7,[39][40][41] . These immature stages have the high chance to survive a single treatment and mature to deposit eggs in the subsequent weeks.…”

Evaluation of the in vivo activity of different concentrations of <i>Clerodendrum umbellatum</i> poir against <i>Schistosoma mansoni</i> infection in mice

“…For schistosomiasis, vaccine is nonexistent and drugs remain the mainstay of disease control. However, the current drug index is limited and/or inadequate, and the problem is being further exacerbated by the emergence of drug resistance (Ismail et al, 2002;Silva et al, 2003). This raises a need for complementary and alternative drugs that are both effective and safe.…”

Biomphalaria alexandrina snails as immunogens against Schistosoma mansoni infection in mice

“…Currently, control of the disease by chemotherapeutic agents is impractical because of the common occurrence of reinfection after treatment (Silva et al 2003). In addition, control through molluscicides is costly and creates the problem of distributing and accumulating the applied chemical agents (Hamed 2010).…”