Differences in microfilarial infection patterns in sympatric mouse lemur species

Population growth, shifting demographics and deforestation may enhance transmission of vectorborne pathogens at the human-livestock-wildlife interface. Endemic species play a key role in this context as potential reservoirs for emerging infectious diseases, but at the same time get exposed to newly introduced pathogens that may result in high morbidity and endanger wildlife populations. In this study, we investigated microfilarial infections in two sympatric mouse lemur species (Microcebus murinus and M. ravelobensis) in Northwestern Madagascar. Giemsa stained blood smears of captured individuals were screened for microfilaria over the course of an 11month study period. M. murinus had a significantly higher risk of infection (prevalence 30.43%) and showed higher microfilaremia than M. ravelobensis (prevalence 6.59%), which may be explained by species differences in vector exposure and/or a lower immune competence of M. murinus, that may be the result of a shorter period of host-parasite coevolution. Genetic analyses of the Onchocercidae sp. found in this study revealed more than 99% identity with microfilariae isolated from a blood sample of a larger lemur species (Lepilemur edwardsi) from the same forest area, indicating low host specificity of this nematode. Neither body mass, taken as a proxy for individual fitness, nor sex influenced parasite prevalence or intensity significantly. Our findings suggest a long-term co-evolutionary adaptation of lemur hosts and parasitic nematodes, resulting in persistent infection and low morbidity and a potential influence of sleeping site ecology on vector exposure and thereby risk of infection with vector-borne pathogens.