Ecology of Fruit Bats in Ghana, With Special Focus on Epomophorus Gambianus, And the Role of Fruit Bats in Zoonotic Disease Transmission

Abstract

Bats are a unique order of mammals that are known to play vital roles in ecosystems and are also an important source of emerging zoonotic diseases of significant health importance. Knowledge of the ecology for several species, particularly fruit bats (Pteropodidae) is lacking and this limits our understanding of the role bats play in ecosystem functioning, disease transmission and hinders their management and conservation. The overall aim of this study was to describe the ecology of fruit bats in Ghana with particular reference to Epomophorus gambianus, and the role fruit bats play in possible emergence and transmission of zoonotic diseases. Specifically, this study sought to document the distribution of fruit bats in Ghana, determine demographic parameters and reproductive characteristics and describe aspects of the roosting and feeding ecology of E. gambianus. The study also focused on providing further serological evidence for prevalence of zoonotic viruses in fruit bats in Ghana and identifies human bat interactions that can serve as potential routes for zoonotic disease transmission. The study used direct field observations involving roost searches and mapping, mist netting, radio-tagging, faecal collection and plant phenological studies, as well as an innovative citizen science approach and questionnaire administration to collect empirical and biological data to address the aims of the study. Ten of the 13 species of fruit bats reported for the West African sub-region were recorded in this study. These were Epomophorus gambianus, Eidolon helvum, Nanonycteris veldkampii, Epomops franqueti, Epomops buettikoferi, Hypsignathus monstrosus, Lissonycteris angolensis, Megaloglossus woermanni, Rousettus aegyptiacus and Micropteropus pusillus. Roosts belonging to five species of fruit bats were identified in 74 different locations across the country. This is the first study that has attempted the nationwide description of the distribution of roost sites for fruit bats in Ghana. Most of the colonies identified occurred in close proximity to humans and in densely populated places. Majority of the roosts identified belonged to E. helvum and E. gambianus and several roosts were identified for the first time, although they had been occupied or used intermittently by bats for ten or more years. Trapping of bats at eleven different sites showed that E. gambianus and E. helvum were the most common fruit bat species in Ghana. Out of the 6,132 bats captured the two species accounted for 75%. By analyzing faecal and ejecta pellets collected under day roosts and from captured bats over a two year period, E. gambianus was found to utilise fruits and flowers from 35 plant species, including some economically important ones. Monthly monitoring of plants for fruit and flower abundance indicated that fruits were relatively available throughout the year but in varying quantities, with peaks during the rainy seasons. Flowers were mostly abundant during the dry season and potentially contributed up to 79% of the diet of bats during this season. Roost selection analysis showed that E. gambianus was more likely to select trees species such as Magnifera indica, Ficus sp., Azadirachta indica, and Polyalthia longifolia trees for roosting, and showed preference for bigger, taller trees. Roosting sites were also more likely to be closer to buildings and less likely to occur in areas with high tree densities. Roosts with higher number of bats, and were more frequently occupied by bats were more likely to be utilised as maternal roosts. Radio-tracking of 60 bats suggested a fission-fusion roosting system in E. gambianus. Female bats used a relatively smaller roosting area compared to males. Based on the proportion of adult females detected to be pregnant and lactating for each month, the reproductive rate of E. gambianus was estimated to vary between 0.56-1.0 offspring per female per reproductive season, while that for M. pusillus varied between 0.80 to 1.0 offspring per female per reproductive season. This study confirmed the reported reproductive chronology of E. gambianus and M. pusillus as continuous bimodal polyoestry, with post partum oestrus in Ghana. There was strong synchrony in parturition among most of the fruit bat species that were assessed in this study. The overall sex ratio for E. gambianus was male biased but varied for each age class and over different years. Capture-recapture analysis gave an estimated monthly survival of 0.81 (95% CI-0.74-0.86) for E. gambianus with slight variation between sexes and age groups. Monthly survival for M. pusillus varied between 0.92 (95% CI-0.62-0.99) for adult males to 0.77 (95% CI-0.65-0.86) for immature females. This is the first study to provide estimates of these important demographic parameters for a colony of E. gambianus and M. pusillus in Africa. Females of E. gambianus attained sexual maturity at 6 months, while males matured after about 11 months. Juveniles that were born and grew through the rainy seasons were significantly bigger (forearm length: 77±4 mm vs. 74±4 mm; p<0.0001) and heavier (weight: 67±12 g vs. 59±12 g; p<0.0001) than those that were born and grew through the dry seasons. A cross-sectional sero-survey conducted for 1,047 blood samples from six species of fruit bats that were sampled during this study indicated the presence of antibodies to Hendra virus, Nipah virus and Cedar virus in several of these species of fruit bats. Seroprevalence of henipaviruses were highest in E. Helvum, with evidence of sex and age effect on seroprevalence rates. Hunting of bats, fruit collection, contact with bat urine and faeces under roosts were identified as some of the common potential human-bat interaction pathways that could facilitate spillover of zoonotic pathogens from bats. The findings of this study are important in bridging the knowledge gap about the ecology of fruit bats and provide important estimates which can be incorporated in future analysis of infection and spillover dynamics in bats and how bat ecology can influence and drive disease dynamics.