While serological and virological evidence documents the exposure of bats to medically-important arboviruses, their role as reservoirs or amplifying hosts is less well-characterized. We describe a novel orbivirus (Reoviridae:Orbivirus) isolated from an Egyptian fruit bat (Rousettus aegyptiacus leachii) trapped in 2013 in Uganda and named Bukakata orbivirus. This is the fifth orbivirus isolated from a bat, however genetic information had previously only been available for one bat-associated orbivirus. We performed whole-genome sequencing on Bukakata orbivirus and three other bat-associated orbiviruses (Fomede, Ife, and Japanaut) to assess their phylogenetic relationship within the genus Orbivirus and develop hypotheses regarding potential arthropod vectors. Replication kinetics were assessed for Bukakata orbivirus in three different vertebrate cell lines. Lastly, qRT-PCR and nested PCR were used to determine the prevalence of Bukakata orbivirus RNA in archived samples from three populations of Egyptian fruit bats and one population of cave-associated soft ticks in Uganda. Complete coding sequences were obtained for all ten segments of Fomede, Ife, and Japanaut orbiviruses and for nine of the ten segments for Bukakata orbivirus. Phylogenetic analysis placed Bukakata and Fomede in the tick-borne orbivirus clade and Ife and Japanaut within the Culicoides/phlebotomine sandfly orbivirus clade. Further, Bukakata and Fomede appear to be serotypes of the Chobar Gorge virus species. Bukakata orbivirus replicated to high titers (10⁶–10⁷ PFU/mL) in Vero, BHK-21 [C-13], and R06E (Egyptian fruit bat) cells. Preliminary screening of archived bat and tick samples do not support Bukakata orbivirus presence in these collections, however additional testing is warranted given the phylogenetic associations observed. This study provided complete coding sequence for several bat-associated orbiviruses and in vitro characterization of a bat-associated orbivirus. Our results indicate that bats may play an important role in the epidemiology of viruses in the genus Orbivirus and further investigation is warranted into vector-host associations and ongoing surveillance efforts.

The reservoir for zoonotic o’nyong-nyong virus (ONNV) has remained unknown since this virus was first recognized in Uganda in 1959. Building on existing evidence for mosquito blood-feeding on various frugivorous bat species in Uganda, and seroprevalence for arboviruses among bats in Uganda, we sought to assess if serum samples collected from bats in Uganda demonstrated evidence of exposure to ONNV or the closely related zoonotic chikungunya virus (CHIKV). In total, 652 serum samples collected from six bat species were tested by plaque reduction neutralization test (PRNT) for neutralizing antibodies against ONNV and CHIKV. Forty out of 303 (13.2%) Egyptian rousettes from Maramagambo Forest and 1/13 (8%) little free-tailed bats from Banga Nakiwogo, Entebbe contained neutralizing antibodies against ONNV. In addition, 2/303 (0.7%) of these Egyptian rousettes contained neutralizing antibodies to CHIKV, and 8/303 (2.6%) contained neutralizing antibodies that were nonspecifically reactive to alphaviruses. These data support the interepidemic circulation of ONNV and CHIKV in Uganda, although Egyptian rousette bats are unlikely to serve as reservoirs for these viruses given the inconsistent occurrence of antibody-positive bats.

Uganda is home to a rich diversity of bats, which carry high ecological and socioeconomic value through the ecosystem services that they provide. However, critical bat habitats including caves are facing increasing anthropogenic pressures, and the types and frequencies of disturbances to cave-roosting bats are not well understood in Uganda. Therefore, we examined the role of anthropogenic disturbances in caves to assess the threats posed to bat populations. We used the Bat Cave Vulnerability Index (BCVI) framework to evaluate the likely effects of anthropogenic disturbance on the cave bats inhabiting 14 caves within the study region. We included qualitative surveys with human communities to better understand various aspects within the BCVI. All bat species recorded are of the IUCN category - “Least Concern”. The BCVI ranked 50% of the caves as “High” and “Moderate” priority for conservation interventions due to high bat diversity and anthropogenic disturbance and determined that most caves studied were highly vulnerable to anthropogenic disturbance. All the caves we studied (except two) are outside the protected area, and due to their imputed vulnerabilities, interventions ought to be implemented to balance cave conservation and human use in the Mt Elgon area. Such interventions should integrate human dimensions.

Uganda is home to a rich diversity of bats, which carry high ecological and socioeconomic value through the ecosystem services that they provide. However, critical bat habitats, including caves, are facing increasing anthropogenic pressures, and the types and frequencies of disturbances to cave-roosting bats are not well understood in Uganda. Therefore, we examined the role of anthropogenic disturbances in caves to assess the threats posed to bat populations. We used the Bat Cave Vulnerability Index (BCVI) framework to score 14 caves inhabited by bats within the study region. We included qualitative surveys with human communities to better understand various aspects within the BCVI. All bat species recorded were of the IUCN category “Least Concern”. The BCVI indicated 50% of the caves (with insectivorous and frugivorous bats) require urgent conservation interventions due to high bat diversity and anthropogenic disturbances (e.g., guano collection). Most of the caves studied were highly vulnerable to anthropogenic disturbances, as assessed in the study. All the caves we studied (except two) are outside the protected area, and due to their imputed vulnerabilities, interventions ought to be implemented to balance cave conservation and human use in the Mt. Elgon area. Such interventions should integrate human factors.