Toxoplasma gondii and Trypanosoma lewisi Infection in Urban Small Mammals From Cotonou, Benin, With Special Emphasis on Coinfection Patterns

This study was conducted under the research agreement between the Republic of Benin and the French Institute for Substainable Development (IRD; renewed on April 6th, 2017) as well as between IRD and Abomey-Calavi University (signed on September 30th, 2010 and renewed on July 3rd, 2019). Field investigations were conducted after a written and/or oral authorization of local authorities (i.e., local heads of urban districts, authorities, and staffs of Cotonou Autonomous Seaport) as well as the systematic consent of residents when trapping was conducted inside private settings. Note that no animal research ethical committee is available in Benin and no ethical committee agreement is required in Benin to conduct research on pest animals such as those described in the present study. However, rodents were treated in a human manner according to the American Society of Mammalogy recommendations [71]. None of the species captured in the frame of the current study has IUCN protection status (see CITES list, https://checklist.cites.org). In line with the Nagoya protocol, authorization for access and equitable sharing of knowledge and data was issued by the competent national authorities of Benin (file 608/DGEFC/DCPRN/PF-APA/SA).

International audience

anglais. A growing number of studies has highlighted the importance of coinfections 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 as Toxoplasma gondii and Trypanosoma lewisi, that are responsible for toxoplasmosis and atypical trypanosomiasis in humans, respectively. Laboratory experiments on rodent models have shown that primary infection with T. lewisi increases the host sensitivity to other parasites, including T. gondii, following an alteration in the immune response. However, data on potential interactions between these parasites in wild small mammals remain scarce. In this study, we determined the T. lewisi prevalence in 553 small mammals from four localities of Cotonou city, Benin. The results were then combined with T. gondii data previously collected for the same individuals in order to investigate the influence of T. lewisi on T. gondii infection, and vice versa, using co-occurrence tests and generalized linear mixed models (GLMMs). Despite quite high overall prevalence (32.5% and 15.2% for T. lewisi and T. gondii, respectively), we observed a clear and significant segregation between the two parasites. This may be explained by (i) differences in the species-specific receptivity and/or sensitivity of small mammal host species to infection by these two parasites, with Rattus rattus (Rra), Rattus norvegicus (Rno), and Mastomys natalensis (Mna) being the main hosts of T. lewisi, while Crocidura olivieri (Cro) and Mus musculus domesticus (Mus) were the main hosts for T. gondii; and/or (ii) a possibly high mortality in coinfected animals in the wild. Although dedicated experimental studies are required to confirm this pattern, as they stand, our data fail to support that in nature, the infection of small mammals by one of these two parasites favors widespread infection by the second one.