Many Virginians make it through tick bites just fine, but cases of tick-borne diseases have jumped.

By Duncan Adams

Reported cases of two tick-borne diseases, Lyme disease and Rocky Mountain spotted fever, have jumped in Virginia in recent years.

David Gaines, entomologist for the Virginia Department of Health, said he doesn't have a solid theory to explain the increase.

And there's a reason to be on guard: Tick season 2008 has arrived.

Reported cases of Lyme disease in Virginia jumped 165 percent from 2006 to 2007, up to 945.

Most cases occur in Northern Virginia and regions in eastern Virginia. So far, cases of Lyme disease in the Roanoke region have been comparatively few.

Meanwhile, the number of statewide cases of Rocky Mountain spotted fever has quadrupled in recent years.

Between 1995 and 2004, reported cases of the disease averaged about 30. In 2005, there were 121 cases, and "we have averaged about 126 cases per year over the last two years," Gaines said.

He emphasized that these numbers reflect reported cases.

"We're probably just measuring the tip of the iceberg," he said. "Not all physicians report cases."

Although cases are up, there is no need to panic.

Many, many Virginians are bitten by ticks each year and don't contract a tick-borne disease. Quick removal of attached ticks can help prevent transmission.

"Typically, only a small percentage of ticks from a species are infected with the disease agent associated with that species," Gaines said.

"For example, less than 3 percent of American dog ticks will test positive for the RMSF agent, even in a locality where an outbreak of RMSF is under way," he added.

But getting local information about tick populations can be difficult.

Unlike mosquitoes and some agricultural pests, the lowly tick doesn't rate a surveillance team. Federal grants have funded mosquito surveys because of West Nile virus, and small groups of farmers sometimes track pest numbers, Gaines said.

Like street gangs, ticks localize. Populations of the blood-feeding arachnids might be thick in one neighborhood and thin in another.

Meanwhile, it's tick time, said Eric Day, manager of Virginia Tech's Insect Identification Lab.

"They're attacking now," he said. "You'll see them questing on weeds and tall grasses."

Questing?

Yes. Lurking, thirsting for a blood donor. The unwitting victims could include mice, squirrels, voles, dogs, cats, bigger mammals such as deer or humans, and other animals.

Some anecdotal reports suggest regional tick numbers this spring are unusually high. However, one veterinarian, Gerald Buckland at the Vinton Veterinary Hospital, does not believe this spring is atypical.

Some people believe the absence of a "hard freeze" during winter can increase tick populations.

Gaines said effects of such a freeze on ticks probably would be limited to those without good winter cover.

"Most of them over-winter down in the duff or leaf litter," he said. "These critters have been around for eons, and they've coped with cold weather and evolved to survive."

Good acorn crops seem to be associated with increased tick populations, Gaines said.

"Immature phases of ticks feed on rodents," he said. "During a year when the production of acorns is particularly heavy, there can be an increase in rodent survival through the winter. That makes the ticks very happy."

In fact, crops in 2006 and 2007 of acorns from the white oak tree were better than the crop in 2005, said Julia Dixon, a spokeswoman for the Virginia Department of Game and Inland Fisheries.

Gaines said 15 tick species have been found in Virginia, but only three commonly bite humans.

Two of those tick species have dominated the human biting scene in Virginia -- the Lone Star tick and the American dog tick.

But blacklegged ticks, once called deer ticks, appear to have become more common in the state over the past several years.

The blacklegged tick is the only human-biting species in the Eastern United States to transmit Lyme disease, which was first detected in Lyme, Conn.

Gaines said that although he is an avid outdoorsman and has been identifying the ticks he finds for more than 20 years, he encountered his first blacklegged tick in Virginia in the winter of 2005. It was found on a dog at a family farm in Albemarle County. He and family members have found a few dozen more since.

The American dog tick is known to transmit Rocky Mountain spotted fever, which can be fatal.

Lone Star ticks could possibly transmit the disease but are not considered to be a primary culprit.

However, Gaines said, they can transmit human monocytic ehrlichiosis "and are thought to be the vector [carrier] of a Lyme diseaselike illness called Southern tick associated rash illness."

Pliny the Elder, a Roman naturalist of the first century, is said to have observed that ticks "are the foulest and nastiest creatures that be." Some ancients, however, apparently believed mashed ticks could be an aphrodisiac.

But really, what good are they?

"I get asked that question a lot, especially about mosquitoes," Gaines said. "Ticks are part of a food cycle, although they are probably not an important source of food.

"They probably help regulate animal populations by making their lives miserable."