New study shows trends of Lymphoproliferative disease among Maine wild turkeys

ORONO — The potentially lethal Lymphoproliferative virus is becoming more prevalent among wild turkeys in the Northeast. With wild turkey populations growing, the risk of disease transmission between them, their domesticated counterparts and chickens may increase.

In a new University of Maine-led study, researchers identified the prevalence of LPDV in wild turkey populations statewide and the factors that can influence their chance of infection. Their research can help inform management strategies, such as harvest and translocation regulation, and support any future investigations into the possibility of disease transmission between wild turkeys and other fauna. 

Some turkeys that become infected with LPDV exhibit lymphoid tumors and other lesions, ataxia and lethargy, but not all show signs of the disease that are visible to the naked eye. There is no evidence disease can harm humans, and turkeys infected with it are still considered edible. 

The team of scientists led by Stephanie Shea, who conducted the study when she was a Ph.D. student in ecology and environmental sciences, collected tissue samples from 699 Maine turkeys from 2017–20. The group found that 59 percent tested positive for LPDV. 

Researchers also examined how seasonality, location, age and sex influenced the risk of infection among wild turkeys. They found that females, adults and individuals sampled in the spring had LPDV more often than males, juveniles and individuals sampled in the winter. The group also discovered that more juvenile turkeys that lived near forested areas had LPDV than those that lived near farms. 

The higher infection rate among female turkeys in Maine may result from differences in physiology and foraging behavior that make them more susceptible to disease, according to researchers. Adults are more likely than juveniles to have higher levels of exposure to the virus, possibly resulting in chronic infections. 

In the spring, turkeys move around more to forage and mate, which results in an increased possibility for LPDV exposure. Turkeys that reside near farmland have access to more bountiful, widespread food options than those that live in forested areas, which researchers say may affect how they interact and, therefore, influence the disparity in LPDV infections.  

“Our findings highlight patterns of LPDV infection in Maine’s wild turkey population, which can help us to predict location, timing and individuals affected and is useful for monitoring wild turkey health,” says Shea, now an assistant diagnostician with University of Maine Cooperative Extension’s Plant Disease Diagnostic Lab.

In addition to examining the prevalence of LPDV in Maine, the research team tested for reticuloendotheliosis virus infection, which can cause immunosuppression, tumors and runting disease; Mycoplasma gallisepticum, a lesion-causing disease that can inhibit reproduction and egg hatchability; and Salmonella pullorum, which can be lethal for chicks.

Of the 699 wild turkeys researchers sampled, 3.4 percent tested positive for Salmonella pullorum, 16 percent were infected with REV; and 74 percent tested positive for Mycoplasma gallisepticum. Co-infection rates for LPDV and Salmonella pullorum, REV and Mycoplasma gallisepticum were 2.6 percent, 10 percent, and 51 percent, respectively. 

“This study provides valuable information on the prevalence and co-occurrence of multiple pathogens of concern in wild turkeys, data that are important for understanding how pathogens affect turkey population dynamics and for assessing potential risks to Maine’s poultry industry,” says Pauline Kamath, Shea’s adviser at the time and an assistant professor of animal health. 

Other researchers involved in the project include Kamath; Erik Blomberg, associate professor of wildlife population ecology; Kelsey Sullivan, biologist with the Maine Department of Inland Fisheries and Wildlife; Matthew Gonnerman, a former UMaine Ph.D. student who is now a postdoctoral researcher at the University of Maryland; and Peter Milligan, an associate professor of biology at the the University of Maine at Augusta. Their findings were published in the Journal of Wildlife Diseases. 

Over the years, several UMaine researchers provided deeper insight into Maine wild turkey populations, their habits and the forces that threaten them. Earlier this year, a group led by Gonnerman produced a study which found that turkeys adjust their movements — for example, the locations where they roost at night — in order to increase their chances of surviving the tough Maine winters.