Monkeys of the rainforest in French Guiana are natural reservoirs for P-brasilianum/P-malariae malaria

Monkey blood samples were collected from 214 monkeys relocated as part of t he wildlife rescue organized in French Guiana during the filling of the Pet it Saut Dam on the Sinnamary River. These samples were rested for malaria p arasites by microscopy of thick blood films and by nested PCR for small sub unit rRNA genes (SSUrRNA). Parasitic blood forms similar to Plasmodium bras ilianum were detected in 4 monkey species: Alouatta seniculus macconnelli, Saguinus midas midas, Pithecia pithecia and Ateles paniscus paniscus, with the highest prevalence in Alouatta monkeys. PCR was more sensitive than the conventional method for detecting low-grade parasitaemia in positive monke ys. The examination of blood films indicated that 5.6% of the animals carri ed parasites whereas the nested PCR for ribosomal DNA indicated a prevalenc e of 11.3%. The P. brasilianum SSUrRNA gene sequence was analysed and align ed with those from P. malariae, P. falciparum and P. vivax. This suggested that P. brasilianum and P. malariae are very closely related. Similar resul ts were obtained from analysis of the sequences in P. malariae and P. brasi lianum isolates of a polymorphic gene fragment analogous to the merozoite s urface protein-1 (MSP-1) gene of P. falciparum. The P. brasilianum/P. malar iae sequences were more similar to those of P. vivax than to those of P. fa lciparum, at least in the gene region examined. The high degree of DNA homo logy in the sequences of the SSUrRNA and msp1-like genes is consistent with other characterizations demonstrating a taxonomic relationship between P. brasilianum and P. malariae species. Our results provide further evidence t hat P. brasilianum and P. malariae are virtually identical and should proba bly be considered to be a single malaria species. This raises the question as to whether monkeys living in the rainforest are natural reservoirs for b oth simian and human malaria. These results have implications for the inter pretation of the current epidemiological situation in French Guiana.