The louse that roared?

Byline: Mike Stahlberg The Register-Guard

ADAIR VILLAGE - Minutes after being inoculated in its rump with a sedative, a limp mule deer was rolled onto a field stretcher and its eyes covered with a red mechanic's rag to provide calming darkness. An electronic device clipped to its tongue monitored the deer's vital signs while researchers weighed, measured and poked the deer with a thermometer.

Then Jason Robison leaned close, peering intently as he parted patches of hair with a fine-toothed flea comb and looked for lice on the deer's hide.

Such intense scrutiny is something that 32 deer being held in pens at the E.E. Wilson Wildlife Area go through every three weeks as part of Robison's graduate research project into how "Deer Hair-Loss Syndrome" is transmitted from one animal to another.

A louse not previously seen in the Northwest is suspected of being `the driving force' for hair-loss syndrome, Robison said.

Deer infected with a species of Damalina Cervicola, a family of louse native to Asia, are driven to self-mutilation - biting, chewing and scratching themselves so much that they scrape the hair from large patches of their hides.

"You can imagine having, say, 200 lice per square inch crawling all over your body, all moving and biting," Robison said. "And you've got nymphs that are biting so deeply into the skin that they're drawing blood."

Deer Hair-Loss Syndrome, first noted in Washington state in 1996, is believed to be a major contributor to the decline of blacktail populations in Oregon and Washington during the past decade.

Data collected in the spring of 2003 `suggests that DHLS is affecting approximately 33 percent of the blacktail population,' he said.

The spread of DHLS has coincided with a steady decline in hunter success rates, although wildlife biologists say other factors are putting pressure on blacktail deer. Those factors include reduced forage resulting from changes in logging practices, increased numbers of predators, other diseases, and increased numbers of elk (which compete for forage).

"In the McDonald Forest, we used to count 100 deer per linear mile," said Nancy Taylor, an ODFW district wildlife biologist who helped Robison during last week's "work-up" on the research herd. "Now we're lucky if we see 8 or 10."

While there's not yet conclusive evidence that Damalina Cervicola causes DHLS, many biologists hypothesize that biting lice trigger a "severe hypersensitivity reaction" which "results in excessive licking and biting by the host animal," leading to removal of large patches of hair.

Some of the deer are so busy scratching they don't even eat enough.

All this unusual behavior "can result in decreases in thermal insulation, decreased energy reserves, hypothermia, and a weakened immune system," Robison's research proposal said.

How a species of Damalina Cervicola made its way to the Pacific Northwest is not known. Some biologists suspect it is an exotic louse that could have accompanied the influx of large numbers of exotic deer in the 1980s.

"We're slowly narrowing down the possible native host," Robison said. "We don't know for sure yet, but believe it could be Sika deer."

On the other hand, what Northwest blacktail are dealing with could be a variety of native louse that simply hadn't previously come to the attention of scientists.

The thrust of Robison's research is to learn as much as possible about how these lice - and possibly hair-loss syndrome itself - is transferred from one animal to another.

"The main point of the study is to determine whether hair loss can be transferred to mule deer," Robison said. The majority of deer held at E.E. Wilson are Rocky Mountain mule deer from east of the Cascades.

And Robison already has an answer to that question.

"Our test results came back positive in the mule deer that yes, indeed, we did have an exotic lice transferring from blacktail to mule deer, just on a contact basis," he said.

But it's too early to tell whether the mule deer will develop clinical symptoms of the disease.

`We did see some extreme grooming behavior last year, but we got the two groups (of infected and uninfected deer) mixed a little late in the season to really get the full-blown hair loss we thought we'd get,' Robison said.

The maximum hair-loss usually occurs between December and April, which roughly coincides with the period during which the lice are in the nymph stage. Their life cycle, Robison said, takes about 30 days to complete.

`One theory is that the greatest irritation occurs when the nymphs are at their greatest numbers,' he said. `We also believe this is the most probable time for transmission.'

Meanwhile, Robison said there is no evidence yet of lice moving from infected deer to uninfected deer kept in separate pens just 32 feet apart.

That's consistent with the scientific literature on lice, which indicates they generally spread as a result of close "nose-to-nose" contact between individual animals.

But most lice cannot survive more than 24 hours off their host animal, Robison said, whereas "one of our studies has proven that these lice (Damalina Cervicola) will last up to seven days off the host animal, which is a long period of time."

That information suggests the lice could also be spread via the environment.

"We think it's possible bedding areas could be a major source of spreading," he said.

Robison cautions hunters about becoming too alarmed over the fact that the Asian variety of louse has also been found on Roosevelt elk. That means "there may be some `hitchhiking' on other species and spreading throughout the environment that way."

However, there has been no confirmed case of hair-loss syndrome in elk, and Robison tells hunters that "most lice are species-specific. ... While it may jump to another species, the chances of it jumping are pretty rare."

DHLS has also spread unevenly throughout the blacktail deer population.

"We're noticing that animals that live at lower elevations, like less than a couple thousand feet, have more prevalent hair loss than animals at the higher elevations where it is colder," Taylor said.

"There's speculation the lice could be killed off by the cold."

So the fact the louse survives on mule deer in captivity doesn't mean it could survive in the colder climes of Eastern Oregon.

Deer Hair-Loss Syndrome is not always fatal, and Robison hopes to learn more about the progression of the disease in captive deer.

"Fawns are more likely to suffer fatality than adults," Robison said.

Another aspect of Robison's study will look at whether deer who survived DHLS last winter exhibit any immunity to the disease.

Some of Robison's research subjects lost so much hair last winter that they wound up getting scarred by severe sunburn during the summer.

Five blacktail deer in the research herd died from complications due to hair-loss, Robison said. There were no fatalities among the mule deer.

The researchers also draw blood from the deer every two months to have it tested in a laboratory for "immune functions."

The 20-month study has a budget of $230,000. In addition, more than 1,500 hours of labor has been donated by volunteers who helped build pens and observation buildings, helped capture deer (some were caught in net traps baited with apples or alfalfa; others were shot with tranquilizer darts); and help with the periodic examinations of the animals.

Primary sponsors of the research include the Oregon Department of Fish and Wildlife, the Oregon Hunters' Association, the Blacktail Deer Foundation, the Traditional Archers of Oregon, the Oregon Wildlife Heritage Foundation, the Izaak Walton League and the Chuck Woosley family.

While Robison's research may help wildlife managers better understand what they are dealing with - and perhaps manage future hunting opportunities accordingly, don't expect it to lead to a "cure" for the problem.

`There's no amount of money that we can spend and go out and cure an entire population of deer,' Robison said.

So Deer Hair-Loss Syndrome will run its course. But biologists and hunters may soon have a better idea of what the course is likely to be.

CAPTION(S):

Jason Robison, an Oregon State graduate student, examines a deer for signs of lice at the E.E. Wilson area, with help from Suzanne Knapp. Upper left: A microscopic view of Damalina Cervicola, the suspected culprit in Deer Hair-Loss Syndrome. Chris Pietsch / The Register-Guard Jason Robison gives one of his test deer a shot.