Understanding lyssavirus dynamics in an African fruit bat population

Background/Question/Methods . Rabies is an acute viral infection that is invariably fatal in humans, and globally causes over 55000 human deaths per annum. Models of rabies virus (RABV) dynamics have concentrated on terrestrial mammal systems (e.g., dogs, raccoons and foxes). However, the vast majority of lyssaviruses, of which RABV is only one, have bats as their reservoir hosts and phylogenetic analyses suggest RABV originated from bats.  Additionally, lyssaviruses such as Lagos bat virus (LBV), which circulates in African bats, are phenotypically divergent enough from RABV that current vaccines are not protective. Given the potential for spillover and infection emergence of such viruses, and that bats are reservoirs for numerous emerging zoonotic viruses, understanding mechanisms which allow these infections to be maintained within bat populations is important to understand spillover and infection emergence into new populations. A study of RABV in big brown bats (Eptesicus fuscus) in Colorado used a mathematical model to determine that life history patterns, such as seasonally variable mortality rates including reduced mortality during hibernation, allow for rabies virus maintenance in temperate zone bats. This, therefore, poses the question as to what mechanisms allow for lyssavirus infection persistence in bat populations in tropical regions that do not hibernate. 

Results/Conclusions . Data collected from a 5 year study of a migratory African fruit bat species, Eidolon helvum, and its associated lyssavirus, LBV, will be presented. These data on host demographic and infection related parameters for the E. helvum-LBV system suggest the species is a long-lived K-selected species (annual survival probability 0.83, 95% CI 0.73-0.93), with a seasonal birth pulse. Infection with LBV is endemic with a high proportion of individuals become immune following infection, and probability of being seropositive increases with age. Using these data in a stochastic mechanistic model that incorporates seasonal births and transmission, different mechanisms of persistence for LBV within an E. helvum colony are tested and compared to those in the temperate E. fuscus-RABV system to determine which aspects of host ecology allow persistence in this system.