J. Patrick W. Cusaac, Ph.D.

I am broadly interested in environmental drivers of wildlife health, particularly in the physiological and behavioral changes that wildlife experience in response to selective pressures in the environment.  My research focuses on characterizing environmentally realistic risk from selective pressures like emerging pathogens, environmental pollutants, and declining habitat quality. Here are a few of my recent projects:

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Amphibian Disease Ecology

Disease is one of the leading hypothesized causes of amphibian declines worldwide, and indeed several pathogens (e.g., ranaviruses) have caused die-offs in amphibian populations both in the wild and in captivity.  The salamander chytrid fungus, Batrachochytrium salamandrivorans ('Bsal'), is an emerging fungal pathogen in the same genus as the frog chytrid fungus (B. dendrobatidis), which has caused declines of anuran populations worldwide.  Bsal has been detected in both wild and captive populations of salamanders, including in the international pet trade, and has caused die-offs of wild salamander species across Europe.  Despite recent bans on importation of salamander species, it is only a matter of time before Bsal reaches North America.  Unfortunately, preliminary risk models only scratch the surface of the possible areas at risk in North America.  My recent projects build on our knowledge of the pathogen’s potential host range and aspects of the host-pathogen and host-environment relationships.  Together, these data are used to build realistic epidemiology models and develop mitigation strategies for the pathogen.

 

Effects of Land Use Change in Amphibians

Amphibians have unique physiological characteristics that make them very sensitive to environmental change.  This is troubling given high incidence of land use conversion for urban landscape and agriculture. Agricultural land use presents a suite of unique selective pressures to aquatic systems, including increased sedimentation rates, impaired water quality (e.g., low dissolved oxygen), and pollution. I and my collaborators are interested in how these complex changes in habitat quality affect amphibian species of conservation concern, particularly species who are dependent on water quality.

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Maternal Transfer of Mercury in Snakes

Early in my career, I examined the maternal transfer of methylmercury from mother to prenatal offspring in Northern Water snakes (Nerodia sipedon).  This species possesses a primitive placenta, which is used to help supplement prenatal offspring during gestation.  The maternal transfer of organic mercury has been observed in other placental species, thus suggesting that N. sipedon may do the same.  However, little was known about to what degree mercury is transferred late in gestation, and what effects any exposure may have on the neonates.  I found that tissue concentrations in both adults and neonates followed a dose-dependent pattern of increase, although the mechanism behind the transfer was unclear.  I also found that neonatal N. sipedon are able to mount a hormonal stress response (via corticosterone), though mercury did not affect the change in corticosterone.  Lastly, there was a non-significant dose-dependent decrease in biomarkers of liver lipid oxidation.

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