Toxoplasma gondiiandTrypanosoma lewisiinfection in urban small mammals from Cotonou, Benin, with special emphasis on co-infection patterns

Abstract

ABSTRACTA growing number of studies has highlighted the importance of co-infections in eco-evolutionary processes underlying host-parasite interactions and the resulting epidemiology of zoonotic agents. Small mammals, and particularly rodents, are known to be important reservoirs of many zoonotic pathogens, such asToxoplasma gondiiandTrypanosoma lewisithat are responsible for toxoplasmosis and atypical trypanosomiasis in human, respectively. Laboratory experiments on rodent models have shown that primary infection withT. lewisiincreases the host susceptibility to other co-infectious parasites, includingT. gondii, following an alteration of the immune system. However, data on potential interactions between these parasites in wild small mammals remain scarce. In this study, we estimate theT. lewisiprevalence in 553 small mammals from four localities of Cotonou city, Benin. They were then combined withT. gondiidata previously collected on the same individuals in order to investigate the influence ofT. lewisionT. gondiiinfection, andvice-versa, using cooccurrence tests and Generalized Linear Mixed Models. Despite quite high overall prevalence (32.5% and 15.2% forT. gondiiandT. lewisi, respectively), we observed a clear and significant segregation between the two parasites. This may be explained by (i) differences in the species-specific susceptibility of small mammal host species to infection by these two parasites, withR. rattusandM. natalensisbeing the main reservoirs ofT. lewisiwhileC. olivieriandM. m. domesticusare the main hosts forT. gondii; and/or by (ii) a possibly high mortality in co-infected animal in the wild. Although dedicated experimental studies are required to confirm this pattern, as they stand, our data fail to support that infection of small mammals by one of these two parasites favours widespread infection by the second one in nature.