Host immunity to repeated rabies virus infection in big brown bats.

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 (RABVs) in the Americas, individual bats may 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 abortive 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 titres 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.

Communal nursing in mexican free-tailed bat maternity colonies.

Examination of genotypes of female-pup nursing pairs taken from large maternity colonies of the Mexican free-tailed bat in Texas demonstrates that nursing is nonrandom and selective along genetic (kinship) lines. This is contrary to previous reports that nursing in these colonies is indiscriminate. Although nursing is nonrandom, an estimated 17 percent of the females sampled were nursing pups that could not be their offspring. This "nonparental" nursing is an apparent result of the difficulties females face in consistently relocating and selectively nursing their own pups within these enormous colonies.

Paternity and Genetic Heterogeneity in the Polygynous Bat, Phyllostomus hastatus.

Wild colonies of greater spearnose bats were marked, censused regularly, and genotyped at three polymorphic allozyme loci. While adult composition of social units is very stable and strong polygyny results in marked changes in gene frequencies between generations, dispersal of offspring is sufficient to prevent significant genetic heterogeneities between social units. Kin selection cannot explain social cohesiveness in these highly social mammals.

Ecology of zoonotic infectious diseases in bats: current knowledge and future directions.

Bats are hosts to a range of zoonotic and potentially zoonotic pathogens. Human activities that increase exposure to bats will likely increase the opportunity for infections to spill over in the future. Ecological drivers of pathogen spillover and emergence in novel hosts, including humans, involve a complex mixture of processes, and understanding these complexities may aid in predicting spillover. In particular, only once the pathogen and host ecologies are known can the impacts of anthropogenic changes be fully appreciated. Cross-disciplinary approaches are required to understand how host and pathogen ecology interact. Bats differ from other sylvatic disease reservoirs because of their unique and diverse lifestyles, including their ability to fly, often highly gregarious social structures, long lifespans and low fecundity rates. We highlight how these traits may affect infection dynamics and how both host and pathogen traits may interact to affect infection dynamics. We identify key questions relating to the ecology of infectious diseases in bats and propose that a combination of field and laboratory studies are needed to create data-driven mechanistic models to elucidate those aspects of bat ecology that are most critical to the dynamics of emerging bat viruses. If commonalities can be found, then predicting the dynamics of newly emerging diseases may be possible. This modelling approach will be particularly important in scenarios when population surveillance data are unavailable and when it is unclear which aspects of host ecology are driving infection dynamics.

Genetic variation and migration in the Mexican free-tailed bat (Tadarida brasiliensis mexicana).

Incomplete lineage sorting can genetically link populations long after they have diverged, and will exert a more powerful influence on larger populations. The effects of this stochastic process can easily be confounded with those of gene flow, potentially leading to inaccurate estimates of dispersal capabilities or erroneous designation of evolutionarily significant units (ESUs). We have used phylogenetic, population genetic, and coalescent methods to examine genetic structuring in large populations of a widely dispersing bat species and to test hypotheses concerning the influences of coalescent stochasticity vs. gene flow. The Mexican free-tailed bat, Tadarida brasiliensis mexicana, exhibits variation in both migratory tendency and route over its range. Observations of the species' migratory behaviour have led to the description of behaviourally and geographically defined migratory groups, with the prediction that these groups compose structured gene pools. Here, we used mtDNA sequence analyses coupled with existing information from allozyme, banding, and natural history studies to evaluate hypotheses regarding the relationship between migration and genetic structure. Analyses of molecular variance revealed no significant genetic structuring of behaviourally distinct migratory groups. Demographic analyses were consistent with population growth, although the timing of population expansion events differs between migratory and nonmigratory populations. Hypotheses concerning the role of gene flow vs. incomplete lineage sorting on these data are explored using coalescent simulations. Our study demonstrates the importance of accounting for coalescent stochasticity in formulating phylogeographical hypotheses, and indicates that analyses that do not take such processes into account can lead to false conclusions regarding a species' phylogeographical history.

Self-fertilization and monogenic strains in natural populations of terrestrial slugs.

Electrophoretic studies of genetic variation in 14 species of terrestrial slugs of the families Arionidae, Philomycidae, and Limacidae in the eastern United States indicate that self-fertilization, either facultative or obligatory, is the normal breeding system in six of the species. Three of these six species are single monogenic strains; one consists of three monogenic strains; one includes a highly heterozygous form and two monogenic strains; and one has a moderate amount of polymorphism but little heterozygosity and strong linkage disequilibrium. Eight species are outcrossers, being highly polymorphic and panmictic within local populations. Niche breadth, assessed in terms of extent of geographic distribution and variety of habitats occupied and measured on an experimental plot of woodland, is greater in some monogenic strains than in highly heterozygous, outcrossing species. Colonizing success apparently is independent of the amount of genetic variation carried by a species.