Panmixia in the African fruit bat Eidolon helvum supports high diversity and prevalence of Bartonella infection

Background/Question/Methods

A central question in disease ecology is how pathogen diversity is generated and maintained in host populations and its influence on disease dynamics. We use Bartonella in African fruit bats to explore how host population structure supports high pathogen diversity and infection prevalence. Bartonella are facultative intracellular bacteria that infect a variety of mammals worldwide, showing particularly high prevalence and diversity in bats. Bartonella species are transmitted by hematophagous arthropods and it is hypothesized that ectoparasitic bat flies are vectors of the bacteria in bats. However, little is known about how bat and bat fly ecology contribute to Bartonella transmission dynamics. Recent studies show that the fruit bat Eidolon helvum is panmictic across its African range. We hypothesize that this level of connectivity allows for high transmission of Bartonella among distant populations, resulting in minimal population structure and high diversity in the bacteria. We characterize Bartonella diversity in blood samples collected from Eidolon helvum in Ghana, islands in the Gulf of Guinea, Nigeria, Uganda, Kenya, and Saudi Arabia using multi-locus sequence typing of five constitutive genes and one intergenic spacer region. A novel method using nested PCR was developed to identify infections and isolate unique genotypes without culturing.

Results/Conclusions

Preliminary results show that Eidolon helvum have high prevalence of Bartonella infection around 60% across their range. Sequence types from mainland bat populations show high genotypic diversity, but cluster very closely to strains previously described in E. helvum in Kenya and Cyclopodia bat flies in Ghana and islands in the Gulf of Guinea. These results support our expectations based on continent-wide panmixia in E. helvum, however we find cryptic diversity in Bartonella that may result from non-random migration or roosting behavior in the host. Populations on the islands in the Gulf of Guinea and in Saudi Arabia showed lower diversity and higher numbers of orphan Bartonella genotypes as a result of their isolation from the mainland population. Future work will develop this system as a model for other vector-borne diseases to explore the roles of host-vector interactions and pathogen diversity in disease dynamics. The nested PCR method we developed may be beneficial for other researchers studying pathogens that are difficult to culture or in environments where culturing is unfeasible.