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Exotic Louse found on mule deer near Saratoga

From the Wyoming Game and Fish Department 

-- An adult mule deer buck collected from hunt area 80 near Saratoga was found to have a heavy infestation of the exotic louse Bovicola tibialis. This is the first time this nonnative external parasite has been documented in Wyoming.

According to Dr. Terry Kreeger, supervisor of Wyoming Game and Fish Department veterinary services, the exotic louse is another threat to mule deer populations. "Although it appears that this current case is a rare finding, we expect the louse to spread slowly over time," Kreeger said.

The deer was collected for necropsy on Apr. 3, 2009, by Saratoga Wildlife Biologist Will Schultz and was necropsied by WGFD veterinarian, Dr. Cynthia Tate, the same day.  Dr. Tate noted severe hair loss, skin inflammation and a heavy infestation of chewing lice.

Since it is difficult to distinguish native deer lice (Tricholipeurus lipeuroides) from exotic ones, Dr. Todd Cornish, associate professor/veterinary pathologist for the University of Wyoming sent several specimens to Dr. James Mertins, veterinary entomologist at the National Veterinary Services Laboratories in Ames, Iowa, who is an expert on the taxonomy of these species. On May 5, Dr. Tate was advised that both the exotic and native species of lice were identified from this deer.

The normal host of this species of louse is fallow deer, which is native to Europe and the Middle East. This introduced louse was first identified on native free-ranging black-tailed deer in Washington State in 2005. According to Cornish it is likely this exotic parasite came to North America from a fallow deer imported quite some time ago.

Jay Lawson, chief game warden for the department said that finding an exotic louse on our native mule deer once again reaffirms the wisdom of the Wyoming Game and Fish Commission in their decision to deny an application to import several species of exotic wildlife and open a game farm nearly 20 years ago.  "Based on the best information available to us at the time, this type of unintended introduction was one of many negative impacts possible if the Commission decided to allow game farming in Wyoming," Lawson said.

According to Lawson, mule deer are a high priority species in Wyoming.  "Through the Mule Deer Initiative we have placed increased emphasis on addressing the issues surrounding this wildlife icon of our state," Lawson said.  "The fact that we found this louse is disappointing and yet another blow to mule deer in Wyoming."

"This exotic louse has not been reported in elk, moose, pronghorn or bighorn sheep, but we do not know if they are susceptible or not at the present time," Cornish said. "There is some concern that this new disease may impact mule deer populations, particularly fawn winter survival."

Dr. Rob Bildfell, veterinary pathologist at Oregon State University Veterinary Diagnostic Laboratory in Corvallis, said that experience with other nonnative lice suggests that this species will have a greater impact on deer with other factors already affecting their overall condition. "These factors could include heavy loads of other internal or external parasites, poor nutrition resulting from poor habitat condition, injury, advanced or very young age and severe winter conditions," Bildfell said.  

According to the Washington Department of Fish and Wildlife Web site, this exotic louse was thought to be one factor in a large mule deer decline in eastern Washington.

"If it affects Wyoming mule deer similarly to how it has affected Washington state mule deer, then we would expect this parasite to be a source of additional mortality in our herds, disproportionately affecting fawns. Although treatable in captive deer, there is no effective treatment for free-ranging deer,” Kreeger said.

Deer infected with exotic lice tend to develop severe skin irritation, leading to excessive grooming by the animal and eventual patchy hair loss and loss of body condition. Lice infestations are heaviest during winter and early spring. Normal seasonal hair loss or molting can usually be distinguished from disease related hair loss because the coat under the molt appears normal and healthy. According to the Washington state site this exotic louse does not affect humans or domestic livestock.

Anyone observing wildlife that appears sick is encouraged to contact their local game warden or wildlife biologist or call their regional Game and Fish office.

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