A Desmodus rotundus (common vampire bat) leaving a cave in Belize. Photo taken by Price Sewell.
Research unlocks new disease ecology perspectives
Bats, much like humans, are exposed to the risks of cohabitation when it comes to sharing germs. In tight quarters, it can be increasingly difficult to prevent disease transmission. For bats, the added layer of small, communal dwelling spaces makes for an even trickier situation.
A highly important member of the animal kingdom, bats help provide free pest control, pollinate flowering plant species and mitigate disease spread from insects such as mosquitos. Due to the myriad of benefits they provide society, bat conservation has become a calling for one Auburn scientist.
Molly Simonis, an Auburn University assistant professor of disease ecology and avid bat researcher in the College of Forestry, Wildlife and Environment (CFWE) and the College of Veterinary Medicine, has been working to identify the major factors contributing to zoonotic disease transmission across different species, with a special focus on bats.
In a recent study published in Ecology, a premier resource for research by the Ecological Society of America, Simonis and a partner university reveal advancements in modeling frameworks for cross-species disease transmission using these flying mammals.
Bats are known biological reservoirs of several pathogens. Zoonotic diseases, or infectious diseases that naturally transmit from animals to people, can be a threat to human health. As the world witnessed recently with the COVID-19 pandemic, zoonotic disease types have the capability to cripple economies, industriesand global health, furthering the importance of disease ecology research
Simonis claims that one of the important factors for pathogen transmission between host species is how closely related those species are to one another. Further, when different species are in close contact, like multiple bat species roosting together, close relatedness between species could facilitate infections jumping to different hosts.
“When multiple species share a roost, or co-roost, their frequent contact can facilitate cross-species transmission of pathogens,” Simonis said. “Cross-species transmission can also be driven by phylogenetic, or evolutionary, relatedness between hosts, such that species that are more closely related share similar pathogens. However, we don’t yet fully understand what role phylogenetic relatedness plays in cross-species transmission when hosts co-roost with one another.”
A northern long-eared bat (top) and a tricolor bat (bottom) share a dwelling in a culvert in Lee County, Alabama.
Creating a Framework
By utilizing mathematic equations, Simonis and her colleage are able to create a modeling framework to better understand how disease transmission between bat species is affected by their relatedness. Daniel Becker, co-principal investigator and assistant professor at the University of Oklahoma, helped Simonis craft models that categorizes epidemiological structures into two systems: susceptible–infected–recovered–susceptible (SIRS) and a susceptible–infected–latent–infected (SILI).Both the SIRS and SILI models allow the research team to simulate infections among co-roosting bat species, and measure resulting infections within the shared roost over time.
With this new tool at the disposal of the research community, disease ecologists are now able to incorporate the ‘family tree’ into disease transmission models, which Simonis states will provide, “a better understanding ecological and evolutionary barriers to cross-species transmission and its risks to public health.”“Using Neotropical bat species to parameterize our models, we found that infection prevalence within co-roosting communities was greatest when hosts were more closely related, but we also found instances when infection prevalence increased when hosts were distantly related,” Simonis said. “Therefore, our approach to building this generalized cross-species transmission framework can provide realistic outcomes for how co-roosting species may contribute to spillover risks.”
Research Impact
Simonis and Becker were supported by a host of funding sources from Oak Ridge Institute for Science and Education, National Science Foundation and the Edward Mallinckrodt, Jr. Foundation. Investments of this magnitude reinforce the critical nature of disease ecology research and its potential impacts to human health.
The study recently published by the team in Ecology, “A general framework for modeling pathogen transmission in co-roosting host communities,” illustrates the potential for this ecological modeling framework as endless. By creating a generalized epidemiological framework that can be used for studying the pathogens of today and tomorrow, Simonis and Becker are eager to see how their hard work will help the overall understanding of cross-species transmission, and in particular, zoonotic pathogen transmission from bats to other hosts .
“We hope that other researchers will build off our modeling framework for incorporating phylogenetic relatedness between host species in the context of close species interactions,” Simonis said. “With coevolutionary relationships between hosts and their pathogens being a crucial aspect to understanding cross-species transmission, adjustments to this framework can provide greater insights to spillover risks in other multi-species disease systems in the future.”
As a whole, this research serves as a prime example of the CFWE’s commitment to quality, impactful research. Janaki Alavalapati, CFWE Emmett F. Thomspon Dean, reinforces the accomplishments of Simonis and her team.
“This work exemplifies the kind of bold, innovative science that defines our college,” Alavalapati said. “Dr. Simonis and her team are not only advancing our understanding of disease ecology, but also building tools that will shape how future generations protect wildlife, safeguard public health and respond to emerging global challenges. Their commitment to discovery reflects the very best of Auburn’s mission and the transformative impact our research can have far beyond campus.”
