Ecology of infectious diseases in wild bats : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Sciences at Massey University, New Zealand
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Date
2019
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Massey University
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Abstract
Emerging infectious diseases present significant threats to the health of humans and wildlife. The
ecology of emerging infectious diseases is a data hungry field in a world of rare events. Bats are
both the source of human pathogens globally and the victims of a novel fungal pathogen causing
continent-wide population declines in North America. By using the principals of iterative model
design and model guided field work I leverage the mechanistic relationships between seasonally
limiting biotic and abiotic factors of wild bats to understand spatio-temporal disease emergence
dynamics from and within bat populations.
I first use a novel ecological niche modeling technique to relate the seasonal availability of
resources to predict African bat birthing events. I then use these model results to test hypotheses that
Ebola virus disease (EVD) transmission to humans and non-reservoir animal hosts are related to the
birthing events of bats through the use of a spatiotemporal Poisson point process model. The results
suggest EVD emergence in Africa may be driven in part by the pattern of births among bats, especially
fruit bats. Further, the identified temporal lag terms between bat birthing terms and EVD emergence
are consistent with hypothesized viral dynamics in bat populations. Out of sample testing on the two
most recent EVD outbreaks in the Democratic Republic of the Congo reveal a high predictive model
performance and suggest the existence of both strong regional seasonality and locations persistently
at risk of EVD outbreaks in humans and susceptible wildlife.
Finally, I model North American winter duration and incorporate spatial variation in host traits
related to body mass and composition to update survival estimates for hibernating Myotis lucifugus
infected with Pseudogymnoascus destructans, the causative agent of the emerging disease white-
nose syndrome (WNS) killing bats in Eastern North American populations. Results indicate that
hibernating M. lucifugus in the West are likely to suffer populations declines similar to those observed in the East. All my findings will require further ground-truthing to validate the results, yet demonstrate
the predictive power of identified mechanistic relationships on complex infectious disease systems.
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Figures are re-used with permission or under a Creative Commons licence.
Keywords
Bats, Diseases, Bats as carriers of disease, Communicable diseases, Pteropodidae, Africa, Reproduction, Ebola virus disease, Congo (Democratic Republic), Little brown bat, Hibernation, White-nose syndrome, North America, Mathematical models