UF researchers embark on major multidisciplinary project to shed light on spread of respiratory disease in tortoises

Building on 10 years of research into an upper respiratory tract disease that has devastated endangered tortoises across the United States, University of Florida scientists hope a new $2.2 million federal grant will help them better grasp how various chronic diseases spread in animals and people.

Funded by the National Science Foundation, the Florida-based project is one of the largest of its kind ever awarded for this type of disease research, where wild animal disease is used as a model for understanding not just the impact on humans, but also on the entire ecosystem.

“The tortoise is unique, as it has about the same life span as a human and reaches reproductive age at about the same time,” said Mary Brown, Ph.D., a professor of pathobiology at UF’s College of Veterinary Medicine and a principal investigator. “Lots of changes have occurred in the tortoise’s habitat, many of which are human-induced. We are interested in learning more about how natural factors combine with human-induced ones, such as relocation and fire exclusion, and how those relationships interact with biological and microbial factors to determine the incidence and spread of disease.”

Brown and her colleague, Paul Klein, Ph.D., a professor and comparative immunologist at UF’s College of Medicine with a joint appointment in the veterinary college’s department of pathobiology, are collaborating with experts in reptile medicine and biology, habitat assessment, population dynamics and modeling. Their group includes pathologists and veterinarians, ecologists from the University of South Florida, biologists from UF’s Institute of Food and Agricultural Sciences, a UF population ecologist and a biologist from the state Fish and Wildlife Conservation Commission.

In the first year of the new project, the team plans to survey more than 700 tortoises at 30 distinct sites in Florida to determine population characteristics, habitat quality and upper respiratory tract disease status at each location. The sites include state parks, water management areas, military reserves, state mitigation parks and private holdings. In subsequent years, they will focus on 12 of these sites using ecological, molecular and other tools to determine the influence of anthropogenic, or human-induced, factors in disease spread and virulence. These multidisciplinary approaches should shed light on how the disease in its various stages affects gopher tortoise populations. Finally, they hope to develop mathematical models in order to predict the effect of these multiple, complex factors on disease spread.

“Infectious diseases are an ever-present risk to wildlife, particularly during situations in which animals are removed from their natural habitat for captive breeding programs, or during conditions of stress, such as release into new habitats or encroachment into their habitats by urbanization,” Brown said. “This is even more important when the species concerned is a keystone species, such as the Florida gopher tortoise, that is critical to ecosystem health.”

As many as 360 animal species depend on the gopher tortoise for survival, including other threatened species such as the indigo snake. “Without the gopher tortoise, the biological diversity of upland habitats would be greatly diminished,” Klein said. “Furthermore, in a long-lived species that does not attain reproductive maturity for 10-20 years, a single catastrophic event such as a disease epidemic could reduce a population to the point that recovery would be extremely difficult.”

Such an event has happened to the threatened desert tortoise of the American Southwest, said Kristin Berry, Ph.D., a biologist with the U.S. Geological Survey who first brought the disease to the attention of the UF group 10 years ago.

“We have experienced catastrophic declines,” Berry said. “We have lost at least 90 percent of our breeding tortoises in some populations, and in some of these groups, mycoplasmosis (an upper respiratory tract disease) has played a role. It’s going to take decades, if not centuries, for us to see recovery.”

Brown, Klein and others at UF, who have studied this disease in both the gopher tortoise and the desert tortoise, were first to identify the mycoplasma bacteria as the disease-causing agent. With a $750,000 grant from the Walt Disney Co., their group amassed data on several key populations of the gopher tortoise in Florida.

“That work was an important foundation for what we are doing now,” Brown said.

Jim Yawn, project manager for Walt Disney Imagineering, the business unit responsible for developing theme parks and other real estate development projects on company property, was involved in the earlier collaborative effort.

"Sometimes research is criticized for not being as valuable for folks in the field, but this research definitely provided value to those who develop and implement best management practices for tortoises," Yawn said.

Brown said receiving word the grant had been funded was gratifying, not just because of the amount of money involved, but also because its funding through a federal agency was an important acknowledgment of the role wildlife ecology plays in overall human and environmental health.

“We think it is exciting that the National Science Foundation is realizing the role of disease in the ecology of wildlife,” Brown said. “They are recognizing that in general, microbial infections in wildlife populations could have an impact on human populations, and that understanding how the disease spreads and what factors affect microbial virulence is very important.”

She added that the UF team’s overall goal is to provide better information to state and federal wildlife management agencies in order to assist them in making decision.

“If we can provide better answers regarding the impacts of tortoise relocation, for example, these agencies might be able to make better management decisions,” Brown said.