Lunn, T. J. | Search bioRxiv

bioRxiv2026

Bartonella and hemotropic Mycoplasma species in synanthropic bats in Kenya

Identifying and characterizing zoonotic pathogens in wildlife is essential for understanding disease risk to humans. In Sub-Saharan Africa, many people live with bats in their houses and are exposed to their pathogens, yet little is known about the bacterial pathogens in Afrotropical bat species. Globally, Bartonella spp. (bartonellae) and hemotropic Mycoplasma spp. (hemoplasmas) are common bacterial pathogens in bats, and some lineages are known to spill over and cause infections in humans. To evaluate this disease risk, we screened three common synanthropic bat species in Kenya, and their ectoparasites, for hemoplasmas and bartonellae and assessed their relatedness to known human pathogens. Of 767 bats across 21 sites, 17.9% of bats were Bartonella spp. positive and 19.3% were hemoplasma positive. Bat ectoparasites had similar Bartonella prevalence (13.5-25.0%) and, for most bat species, ectoparasite loads were not associated with increased likelihood of Bartonella infection. We found that Bartonella lineages displayed phylogenetic overlap between different bat species and ectoparasites, suggesting pathogen sharing between species, while hemoplasma lineages corresponded strictly to host taxonomy. Finally, we found that 16S rRNA sequences from one heart-nosed bat (Cardioderma cor) were 97.85% similar to a human-associated hemoplasma found previously in Schreibers bats (Miniopterus schreibersii) in Spain. We show that synanthropic bats host bacteria of potential public health concern, highlighting the need to investigate the emerging impacts of these pathogens on human health in Kenya and elsewhere in Sub-Saharan Africa.

ecology↗

bioRxiv2024

Black flying foxes in Australia harbor novel Borrelia lineages adjacent to zoonotic clades

We explore the role of Australian black flying foxes (Pteropus alecto) as reservoir hosts of potentially zoonotic Borrelia bacteria. Across six sites, 2% of 840 bats were infected with one of two novel Borrelia haplotypes. Phylogenetic reconstruction indicated these infections are distinct from Lyme or relapsing fever clades.

evolutionary biology↗

bioRxiv2023

Periodic shifts in viral load increase risk of spillover from bats

Prediction and management of zoonotic pathogen spillover requires an understanding of infection dynamics within reservoir host populations. Transmission risk is often assessed using prevalence of infected hosts, with infection status based on the presence of genomic material. However, detection of viral genomic material alone does not necessarily indicate the presence of infectious virus, which could decouple prevalence from transmission risk. We undertook a multi-faceted investigation of Hendra virus shedding in Pteropus bats, combining insights from virus isolation, viral load proxies, viral prevalence, and longitudinal patterns of shedding, from 6,151 samples. In addition to seasonal and interannual fluctuation in prevalence, we found evidence for periodic shifts in the distribution of viral loads. The proportion of bats shedding high viral loads was higher during peak prevalence periods during which spillover events were observed, and lower during non-peak periods when there were no spillovers. We suggest that prolonged periods of low viral load and low prevalence reflect prolonged shedding of non-infectious RNA, or viral loads that are insufficient or unlikely to overcome dose barriers to spillover infection. These findings show that incorporating viral load (or proxies of viral load) into longitudinal studies of virus excretion will better inform predictions of spillover risk than prevalence alone. Significance statementWe present a comprehensive analysis of a high-profile bat-virus system (Hendra virus in Australian flying-foxes) to demonstrate that both prevalence and viral loads can shift systematically over time, resulting in concentrated periods of increased spillover risk when prevalence and viral loads are high. We further suggest that prolonged periods of low-prevalence, low-load shedding may not reflect excretion of infectious virus, resolving the outstanding puzzle of why spillovers have not been observed during periods of low off-season prevalence in subtropical Australia, or more frequently in tropical Australia despite consistent low-prevalence shedding. The consideration of viral loads (or proxies of viral load) along with prevalence may improve risk inference from longitudinal surveys of zoonotic viruses across wildlife reservoir hosts.

ecology↗