Marburgviruses and ebolaviruses (Filoviridae) cause sporadic outbreaks of hemorrhagic fever in humans and nonhuman primates. Filoviruses are significant because of rapid spread, high fatality rate, and a lack of specific treatment or vaccine. Though the definitive identity of natural animal reservoir(s) for filoviruses remained elusive for decades, bats have been implicated as potential sources of infection. Several lines of evidence have shown that Egyptian rousette bats (Rousettus aegyptiacus) are natural hosts of marburgviruses and consistent sources of virus spillover. Cumulative evidence suggests various fruit bat species may also play a role in transmission of ebolaviruses. The goal of this research was to investigate the pathology and pathogenesis of filovirus infection in Egyptian rousette bats through a series of experimental infection and susceptibility studies. In the first set of studies, we investigated the clinical and pathologic effects of experimental Marburg virus infection in Egyptian rousettes through a serial euthanasia study. Captive-born, juvenile rousettes were inoculated with a low-passage, wild-type Marburg virus originally isolated from a naturally-infected bat. Results showed very mild liver lesions associated with viral antigen. Findings were consistent with patterns of Marburg virus infection in wild bats, showing that our experimental model replicates closely the natural Marburg virus-reservoir host relationship. This establishes the model as a useful tool for exploring the molecular and immunologic determinants of filovirusnatural host dynamics. In the second set of experiments, we investigated the susceptibility of Egyptian rousettes to each of the five known ebolaviruses (Sudan virus, Ebola virus, Bundibugyo virus, Taï Forest virus, and Reston virus), and compared findings with Marburg virus. For four ebolaviruses, results showed that rousettes are generally refractory to infection. Sudan viral RNA was more disseminated, but tissue viral loads were low. In contrast, Marburg virus RNA was widely disseminated, with evidence of viremia, viral shedding, and antigen in spleen and liver. These results suggest that Egyptian rousettes are unlikely sources for ebolaviruses in nature. Cumulatively, our results lend support to a possible single filovirus – single bat host relationship. A better understanding of virus-host dynamics will help guide public health efforts toward prevention and mitigation of filoviral disease outbreaks.