Rabies remains an important public health concern in the United States, with most human cases associated with bat rabies virus variants. Cases of rabies virus (RV) infection in bats are widely distributed across the continental United States and elsewhere in the Americas. In this retrospective study, data on bats submitted to state laboratories for RV diagnosis between 2001 and 2009 were analyzed to investigate epidemiological trends in the United States. Season, region, and roosting habits were the primary risk factors of interest. During the study interval, more than 205,439 bats were submitted for RV diagnosis, and 6.7% of these bats were rabid. Increased odds of a submitted bat being rabid were associated with species that exhibit inconspicuous roosting habits, bats originating in the Southwest, and bats submitted for diagnosis during the fall. Periodic analysis of zoonotic disease surveillance is recommended to detect changes in trends regarding geographic distribution, seasonal fluctuations, and host associations; this is particularly necessary, as existing trends may be influenced by climate change or other emerging factors.

Influenza A virus reservoirs in animals have provided novel genetic elements leading to the emergence of global pandemics in humans. Most influenza A viruses circulate in waterfowl, but those that infect mammalian hosts are thought to pose the greatest risk for zoonotic spread to humans and the generation of pandemic or panzootic viruses. We have identified an influenza A virus from little yellow-shouldered bats captured at two locations in Guatemala. It is significantly divergent from known influenza A viruses. The HA of the bat virus was estimated to have diverged at roughly the same time as the known subtypes of HA and was designated as H17. The neuraminidase (NA) gene is highly divergent from all known influenza NAs, and the internal genes from the bat virus diverged from those of known influenza A viruses before the estimated divergence of the known influenza A internal gene lineages. Attempts to propagate this virus in cell cultures and chicken embryos were unsuccessful, suggesting distinct requirements compared with known influenza viruses. Despite its divergence from known influenza A viruses, the bat virus is compatible for genetic exchange with human influenza viruses in human cells, suggesting the potential capability for reassortment and contributions to new pandemic or panzootic influenza A viruses.

In this study we attempted to identify whether Commerson's leaf-nosed bat (Hipposideros commersoni) is the reservoir of Shimoni bat virus (SHIBV), which was isolated from a bat of this species in 2009. An alternative explanation is that the isolation of SHIBV from H. commersoni was a result of spill-over infection from other species, particularly from the Egyptian fruit bats (Rousettus aegyptiacus), which frequently sympatrically roost with H. commersoni and are known as the reservoir of the phylogenetically related Lagos bat virus (LBV). To evaluate these hypotheses, 769 bats of at least 17 species were sampled from 18 locations across Kenya during 2009-2010. Serum samples were subjected to virus neutralization tests against SHIBV and LBV. A limited amount of cross-neutralization between LBV and SHIBV was detected. However, H. commersoni bats demonstrated greater seroprevalence to SHIBV than to LBV, and greater virus-neutralizing titers to SHIBV than to LBV, with a mean difference of 1.16 log(10) (95% confidence intervals [CI]: 0.94-1.40; p<0.001). The opposite pattern was observed for sera of R. aegyptiacus bats, with a mean titer difference of 1.06 log(10) (95% CI: 0.83-1.30; p<0.001). Moreover, the seroprevalence in H. commersoni to SHIBV in the cave where these bats sympatrically roosted with R. aegyptiacus (and where SHIBV was isolated in 2009) was similar to their seroprevalence to SHIBV in a distant cave where no R. aegyptiacus were present (18.9% and 25.0%, respectively). These findings suggest that H. commersoni is the host species of SHIBV. Additional surveillance is needed to better understand the ecology of this virus and the potential risks of infection to humans and other mammalian species.

To better understand the role of bats as reservoirs of Bartonella spp., we estimated Bartonella spp. prevalence and genetic diversity in bats in Guatemala during 2009. We found prevalence of 33% and identified 21 genetic variants of 13 phylogroups. Vampire bat-associated Bartonella spp. may cause undiagnosed illnesses in humans.

For RNA viruses, rapid viral evolution and the biological similarity of closely related host species have been proposed as key determinants of the occurrence and long-term outcome of cross-species transmission. Using a data set of hundreds of rabies viruses sampled from 23 North American bat species, we present a general framework to quantify per capita rates of cross-species transmission and reconstruct historical patterns of viral establishment in new host species using molecular sequence data. These estimates demonstrate diminishing frequencies of both cross-species transmission and host shifts with increasing phylogenetic distance between bat species. Evolutionary constraints on viral host range indicate that host species barriers may trump the intrinsic mutability of RNA viruses in determining the fate of emerging host-virus interactions.

Bats are natural reservoirs for the majority of lyssaviruses globally, and are unique among mammals in having exceptional sociality and longevity. Given these facets, and the recognized status of bats as reservoirs for rabies viruses (RABV) in the Americas, individual bats experience repeated exposure to RABV during their lifetime. Nevertheless, little information exists with regard to within host infection dynamics and the role of immunological memory that may result from subclinical RABV infection in bats. In this study, a cohort of big brown bats (Eptesicus fuscus) was infected intramuscularly in the left and right masseter muscles with varying doses (10(-0.1)-10(4.9) median mouse intracerebral lethal doses-MICLD(50)) of an E. fuscus RABV variant isolated from a naturally infected big brown bat. Surviving bats were infected a second time at 175 days post-[primary] infection with a dose (10(3.9)-10(4.9) MICLD(50)) of the same RABV variant. Surviving bats were infected a third time at either 175 or 305 days post-[secondary] infection with a dose (10(4.9) MICLD(50)) of the same RABV variant. When correcting for dose, similar mortality was observed following primary and secondary infection, but reduced mortality was observed following the third and last RABV challenge, despite infection with a high viral dose. Inducible RABV neutralizing antibody titers post-infection were ephemeral among infected individuals, and dropped below levels of detection in several bats between subsequent infections. These results suggest that long-term repeated infection of bats may confer significant immunological memory and reduced susceptibility to RABV infection.