Oct. 31, 2019
Often maligned and largely misunderstood throughout history, bats have more recently been recognized for the important role they play in ecosystems throughout the world, pollinating flowers, dispersing seeds and controlling pests by eating insects.
But many North American species are now threatened by white-nose syndrome (WNS), a deadly fungal disease affecting millions of bats, primarily in the eastern US. The Ecology and Evolution of Infectious Diseases program of the National Science Foundation (NSF) is funding two major research projects investigating the disease in hopes of preventing the potential extinction of some species in the region.
One such project, led by infectious disease ecologists Kate Langwig and Joseph Hoyt from Virginia Tech, is funded through a $2.9 million joint award from the NSF and the National Natural Science Foundation of China to understand the long-term host and pathogen dynamics of WNS in bats.
Northern Arizona University wildlife disease ecologist Jeff Foster received a $563,000 subaward to collaborate with Langwig, Hoyt and several other scientists on the five-year project. Other collaborators are Beth Shapiro and A. Marm Kilpatrick from the University of California Santa Cruz and Jiang Feng and Keping Sun from Northeast Normal University in China. At NAU, Foster’s team includes lab manager Katy Parise and a graduate student Foster will hire to assist on the project.
Foster, an associate professor of biology in the Pathogen and Microbiome Institute, will focus on the fungal genetics aspects of the project. WNS is caused by the Pseudogymnoascus destructans (Pd) fungus, which colonizes the bat’s skin, eating away at its wing membranes during hibernation. As a result, the fungus completely disrupts the physiology of a hibernating bat, depleting its fat reserves, causing electrolyte imbalance and increased exposure to harsh winters.
Although bats across Asia and Europe have survived with WNS for thousands of years, many bat species in North America are susceptible to this disease, which has caused an unprecedented decline in bat populations in the Northeast since its first detection in 2006. The fungus thrives in the cold, damp caves of the region, spreading easily among the bats that cluster there in congregations of up to tens of thousands, hibernating for several months at a time. The project, titled “Lessons from the past: Synthesizing drivers of host persistence across a pathogen invasion gradient,” seeks to understand past and present disease patterns to find out how some hosts and pathogens can coexist and identify the mechanisms that bats use to survive with this deadly disease.
NAU a key partner
“NAU is a key partner on the project, responsible for quantitative polymerase chain reaction (qPCR) testing of samples, which involves molecular detection and quantification as well as sequencing and comparative genomics of Pd,” Foster said.
By using a qPCR diagnostic assay, a lab technique for detecting the fungus, Foster and his team will confirm infection status and measure the amount of Pd on more than 24,000 swab, tissue and fecal samples of individual bats to better understand the pathogen and the key environmental factors that affect its growth, including temperature and humidity. Foster will assess potential changes in the virulence of Pd by comparing these samples with those collected over time and across geographic regions and continents—comparing samples of the fungus in bats from Europe and Asia to samples of the fungus in bats from North America.
Foster has received a previous grant from the NSF to study WNS in bats. This current project builds on that earlier work, which found the fungus came from Europe; that Eurasian bats were infected but did not die from the disease; and that the fungus has adapted to living on the bats.
“White-nose syndrome is among the most devastating wildlife diseases ever recorded,” Foster said. “In the past 13 years, this fungal disease has killed millions, perhaps tens of millions, of bats in the U.S. and Canada.
“One of the key goals of the NSF program is to understand how diseases spread, so we’re interested in dispersal and transmission, interactions between pathogens and their hosts as well as the role of the environment.”
With the loss of the bats, ecologists believe the bats’ ecosystem services—which include eating mosquitoes as well as crop and forest pests—also may decline.
WNS in western bat populations
Although this NSF-funded project is not targeted at western bats, Foster and other scientists are studying WNS that recently arrived in the western U.S., which is different in climate and is home to different species of bats that typically roost alone in caves and abandoned mines. The next steps for studying WNS in the West include identifying the species affected, the likely routes of invasion, determining numbers and distributions of western bats, assessing hibernation physiology and behavior, understanding the ecology of infection and assessing the effects of the disease.
Early work in the West indicates lower amounts of the fungus on bats, which may be due to it being during the early stages of invasion or a feature of how WNS progresses in this different climate or different bat behaviors. Foster thinks that because the climate in the West is generally drier and warmer—and because hibernation periods are shorter—the fungus may not be able to grow as effectively.
Foster, who came to NAU in 2007 as a post-doctoral scholar, joined research faculty, left briefly for a tenure-track position with the University of New Hampshire, and then returned in 2017. His ongoing research focuses on WNS in bats, malaria in Hawaiian birds and pathogens in other animals, including livestock and waterfowl.
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