CORVALLIS, Ore. - An ailment plaguing Oregon and Washington blacktail deer for nearly a decade appears to be taking a heavy toll on fawns while it spreads within the two states.
Hair-loss syndrome was first detected among black-tailed deer in western Oregon and Washington in 1996, wildlife experts said, but has not been detected in other species in the wild.
The syndrome could be spreading along major highway corridors in the region, adding to a number of chronic issues already affecting herd health and fawn survival rates, said researchers from Oregon State University and Oregon Department of Fish and Wildlife.
"Hair-loss syndrome is probably a multi-factorial disease," said Rob Bildfell, a pathologist with the Veterinary Diagnostic Laboratory at OSU's College of Veterinary Medicine. Important factors may include lice, internal parasites, habitat, feed and overpopulation.
Characterized by missing patches of hair from the chests, flanks and hindquarters of blacktail deer, hair-loss syndrome usually occurs in late fall, just as cold weather begins to filter into the Pacific Northwest, said Doug Cottam, Department of Fish and Wildlife Mid-Coast District wildlife biologist.
While studying blacktail deer sent to the OSU diagnostic lab for necropsy examination, Bildfell and colleagues have found the animals are in generally poor overall health, in addition to the loss of hair.
"We found that deer with hair-loss syndrome often have high levels of internal parasites such as lung worms or intestinal worms," he said. "We're finding pneumonia and the animals are thin with very little fat."
Perhaps most telling, Bildfell said, the animals are generally infested with thousands of chewing lice, initially identified from samples collected at the OSU Veterinary Diagnostic Laboratory as a species previously unknown in the Pacific Northwest.
In the field, ODFW biologist Cottam said the syndrome is still very much in evidence throughout the region, but varies from severe to non-existent in the space of a few miles.
"There's no question about it - hair-loss syndrome is still a problem," Cottam said from his office at OSU's Hatfield Marine Science Center in Newport.
It was in 2004 that the disease was confirmed from northern Washington to southern Oregon, west of the Cascade Range.
"The striking thing about this is that hair-loss syndrome is just not consistent from one valley to the next," Cottam said. "There are places where it is much more severe and other locations where it really doesn't seem to be much of a problem. Regionally there seems to be more affected animals in Linn, Benton and Lincoln counties with low fawn-to-adult deer ratios in the spring."
Since hair-loss syndrome began taking its toll, the fawn-to-adult ratio has dropped up to 75 percent from an already low ratio in some areas, Cottam said.
For example, until 1996 - when hair-loss syndrome first surfaced - the lowest fawn-to-adult numbers in the Alsea unit stood at 42 fawns to every 100 adult black-tailed deer. In the last four years, the low point hit 12 fawns to every 100 adults.
"Three of the last four seasons we had lots of calls about dead fawns in December and January," Cottam said. "That's unusual since most natural over-the-winter mortality occurs in March and April. Deer with hair loss syndrome chew, bite and scratch their fur off, and then they get cold and use up body fat to maintain their body temperature. That makes them very susceptible to other conditions knocking them off, especially fawns as they have a weaker immune system than adults.
"It's a serious problem when there is low recruitment of young deer into the adult population. The percentage of yearlings and adults that survive through the winter is unknown. But with the mild winter we had this past year, it appears more of the adult and yearling deer have survived than in the previous three years."
Eventually, a more effective immune response to the lice should develop in the herds, Bildfell said, and prevalence of hair-loss syndrome should drop. The role of other factors such as the amount of available food, climatic conditions, and internal parasite loads will likely also influence how many deer develop hair-loss syndrome in any given year.
Informal analysis indicates the syndrome is more prevalent along transportation corridors.
"It almost looks like this may have traveled down the highway corridors," Cottam said. "The roads go through little valleys and there are quite a few deer that go down into the farm fields in the winter for better food. The hypothesis is that the syndrome seems to have traveled down the highway corridors, where the deer population is concentrated, to the coast."
More isolated areas, notably the San Juan Islands off the Washington coast, are showing little or no evidence of hair-loss syndrome.
Disease in native game animals in Oregon seldom represents a significant threat to humans, but the Veterinary Diagnostic Laboratory continues disease monitoring efforts throughout the state and people are encouraged to be cautious, Bildfell said. Hunters or landowners who encounter deer or other game that appear unhealthy should call their local office of the Oregon Department of Fish and Wildlife.
An OSU publication outlining safe handling of game is also available. "Big Game from Hunt to Home," publication number PNW 517, is available for $2.50 from OSU Extension and Experiment Station Communications.
The complete publication can also be accessed free of charge at the Extension Web site: http://eesc.orst.edu/agcomwebfile/edmat/PNW517.pdf. For information, contact OSU Extension and Experiment Station Communications at 800-561-6719.