Studies on concomitant
schistosomiasis and
human and experimental
malaria have shown a variation in the immunospecific response, as well as an increase in the severity of both parasitoses. In the present study, a murine
co-infection model was used to determine the effects of a
co-infection with
Schistosoma mansoni and
Plasmodium berghei on the protective
immunity acquired by repeated malarial
infections and subsequent curative
treatment with
chloroquine. Our results have demonstrated that, compared to an
infection with P. berghei only, the
co-infection increases the malarial parasitaemia and decreases the
survival rate. Indeed,
mice that were immunized by
infection and
treatment with
drug displayed no
mortality whereas co-infected
mice showed a reduced protective
efficacy of
immunization against P. berghei (
mortality > 60 percent). Interestingly, this high mortality rate was not associated with high levels of parasitaemia. Our findings support the idea of a suppressive effect of a
Schistosoma co-infection on the
anti-malarial protection by
immunization. This result reveals a possible drawback of the development of
anti-malarial vaccines, especially considering the wide endemic areas for both parasitoses.