Researchers at Penn State have received $2.35 million from the National Science Foundation to study disease transmission among animals with a goal of better predicting outbreaks of infectious diseases within humans.
Specifically, the researchers are investigating the collection of viruses -- known as the virome -- that live within the white-footed mouse, Peromyscus leucopus, and the black-legged tick, Ixodes scapularis, both of which are common throughout the Eastern and Midwestern United States.
"The rodents that live in our homes and garages are the primary reservoirs for several of the emerging infectious viruses that we've seen in humans so far, including babesiosis, Lyme disease and Rocky Mountain spotted fever," said Kurt Vandegrift, research associate in the Department of Biology and the grant's principal investigator. "And we are frequently discovering new viruses in these rodents, and in the ticks that feed upon these rodents and then upon us.
For example, we have found that both white-footed mice and black-legged ticks harbor many previously undescribed microbes, including close relatives of human pathogens such as hepatitis C viruses and hantaviruses. Our work may allow us to identify new infectious viruses in these animals before they spill over into humans."According to Vandegrift, emerging infectious diseases threaten global health and security, but little is known about where or when we should expect these outbreaks.
"This may be because pathogens are virtually always considered in isolation," he said. "In reality, these pathogens are members of an ecological community of interacting microbes, and their behavior and success may be influenced by each other."
To investigate the viromes of white-footed mice, Vandegrift and his colleagues have, for 15 years, monitored thousands of individuals per year. Upon capture, the scientists collect various data, such as body length and mass and reproductive status. They also count and identify the ticks and other parasites the mice contain. Finally, the team takes a blood and fecal sample from each mouse, marks the animal with a transponder and releases it for eventual recapture.
"We recapture these mice many times, sometimes up to 36 times," said Vandegrift. "This gives us a sort of 'movie' showing how parasites move through individual mice within populations, and from both mouse to tick and tick to mouse." The team also is examining the viromes of ticks during their various life stages, as well as comparing the viromes of ticks that have fed on mice with those that have not.
In addition, the research team is addressing whether human-caused disturbances such as urbanization, as well as natural fluctuations in mouse and tick abundances, affect mouse and tick viromes and pathogen transmission patterns.
"Anthropogenic disturbance, particularly forest fragmentation and degradation, can affect abundances of mice and ticks," said Vandegrift. "Similarly, long-term studies show that mouse abundance can be predicted many months in advance based on acorn production, and that human contact rates with the pathogens harbored by mice and ticks are generally more frequent during acorn-driven mouse outbreaks. As a result, we seek to determine whether virome composition and transmission dynamics differ between habitat types and between years of high and low mouse abundance."
Ultimately, the scientists will use "machine learning," a type of artificial intelligence in which computers learn without being explicitly programmed, to pull together all of their data and make predictions about the future."Despite the staggering diversity of viruses and their prominence in causing many of the most virulent human emerging infectious diseases, very little is known about viral communities," said Vandegrift. "We hope that our research will shed light on these important communities and how they spread through animal hosts, including humans."
Other investigators on the grant include Barbara Han and Richard Ostfeld, Cary Institute of Ecosystem Studies; Peter Hudson, Penn State; Laura Kramer, New York State Department of Health; Felicia Keesing, Bard University; and Amit Kapoor, The Research Institute at Nationwide Children's Hospital.