Bats are reservoir hosts for a wide variety of viruses, several with the potential to cause human disease. The Indian Flying Fox (Pteropus medius, formerly P. giganteus) is a large, colonial fruit bat species that lives in close association with humans in Bangladesh and are a known source of Nipah virus (NiV), which can cause fatal encephalitis in humans.
Here we examine the dynamics co-circulation of multiple viruses with spillover potential in a population of P. mediusin Bangladesh. In addition to NiV, we report on circulation of Ebola virus (EBOV) antibodies present in the same population.
As part of a broader study, we sampled bats from a population in Fardipur, Bangladesh quarterly over six-year period. We used a Luminex assay to measure levels of both NiV and EBOV IgG antibodies in bat blood samples. Using hierarchical general additive models, we examine longitudinal trends and seasonal patterns in antibody levels. We infer periods of peak infection and the role of seasonal reproduction in driving disease dynamics using age-structured SIR models.
Results/Conclusions
Both NiV and EBOV infections exhibit seasonal dynamics driven in part by pulsed introduction of susceptible newborn bats into the population. Seasonal outbreaks vary year-to-year, with some years lacking a distinct period of infection. Exposure to EBOV infection occurs more quickly than NiV, with most bats exhibiting signs of first exposure during their first year. By contrast, exposure to NiV occurs later in life. This implies more efficient transmissiion of EBOV than NiV during the same contact events in this population.
We measure the loss of antibodies to NiV and EBOV in wild in recaptured individuals, finding that NiV IgG antibodies declined faster than EBOV IgG antibodies, suggesting shorter-lived immunity against EBOV. Differences in transmission dynamics and other virological properties may explain these differences in the dynamics of naturally infected bat populations and may have implications for spillover into other animals or human populations.
Slides and other related materials will be made available at http://doi.org/bcr9 prior to the presentation.