African fruit bats as potential reservoir for zoonotic pathogens

Emerging infectious diseases (EIDs) play an increasingly important role for human health. Although most research is focused on the detection of new viral pathogens, 54% of EID’s are of bacterial origin, including a large number of drug-resistant types. Tropical regions, especially sub-Saharan Africa, represent ‘hotspots’ for zoonotic EIDs, as the species richness is particularly high in those areas. Several features of physiology and ecology make bats unique in their role as reservoir and distributors for pathogens. In the present study, I combine a histopathological approach with micro- and molecular biological techniques in order to investigate the health state of and potential bacterial pathogens carried by asymptomatic free-living fruit bats (Eidolon helvum, Myonycteris torquata, Rousettus aegyptiacus, Megaloglossus woermanii, Hypsignathus monstrosus) from central and western Africa. Histopathological analyses of 131 bats revealed lesions mainly in lungs and livers. Almost one fourth of the bats (24.8%) showed granulomatous liver lesions of different developmental stages. The main lesion of the lungs was lobular interstitial infiltration in 26.9% (n=35) of the animals. Fifty-five animals were randomly chosen for a broad 16S rDNA screening, which gave hints for the presence of extra intestinal pathogenic Escherichia coli (ExPEC). Thirtyseven E. coli sequence types (STs) were identified including unknown as well as STs frequently linked to infectious diseases. Only few of the STs isolated showed intermediate resistance to certain antimicrobial substances tested. This, together with the mainly arboreal lifestyle of the fruit bats, points towards a rather “naïve” population of E. coli in those fruit bats investigated. A full genome analysis of a strain of ST131 revealed that the strain belongs to an older clade, usually not linked to antimicrobial resistance. Given the high number of new STs, further studies are needed to describe the E. coli diversity circulating in wildlife, especially in the understudied tropical setting. Even if not very likely, transmission of ExPEC to humans or domestic animals should be considered, as larger fruit bats, including those species investigated here, are frequently hunted as bushmeat. This results in ample opportunities for transmission, e. g. through preparation and consumption. In addition, several fruit bat species have adapted to human settlements, where they exist in large quantities and contaminate the environment, including food markets, with potentially pathogenic bacterial types.