The tick you can't see or feel is more dangerous than the one you can.

The tick you can't see or feel is more dangerous than the one you can.

Spring is prime tick season in Southern Oregon. It's also the time that tick nymphs — tiny creatures no larger than a poppy seed — are waiting in the woods for some passing victim to feed on. Some of them carry the bacterium that causes Lyme disease, which can cause chronic medical problems if it isn't treated.

Nymphs are so small that people may not feel them on their skin or when they bite. That means they may stay attached long enough to infect their host with Lyme disease. Many people who have been diagnosed with Lyme were apparently infected by nymphs, because they have no recollection of a tick bite.

"I don't know where or when I was infected," says Judi Johnston, an Ashland nurse who came down with Lyme about two years ago. "I never did see the tick."

Johnston organized a local Lyme disease support group last fall with Sharon Lee, an Eagle Point nurse who was infected some 30 years ago in California. Now they're working with a retired Applegate entomologist on a project designed to determine just how widespread the bacterium that causes Lyme may be among tick nymphs.

They also want to expand awareness of Lyme disease in Southern Oregon. As nurses, they're especially concerned that some members of the local medical community apparently still don't recognize Lyme exists here. Johnston said she spoke with someone who expressed concern about Lyme disease during a recent hospital visit, only to be told "our ticks don't carry Lyme."

Besides establishing the presence of Lyme in tick nymphs, their project could confirm a strange phenomenon that California scientists discovered when they analyzed adult and nymph ticks: significantly fewer adults carried Lyme disease than nymphal ticks. Researchers eventually determined that Lyme-infected tick nymphs that fed on the blood of lizards were no longer infected with the Lyme bacterium when they became adults.

"West Coast lizards are killing the infection in the ticks," said the entomologist, Jim Clover, who worked on Lyme disease when he was an entomologist for the state of California.

Clover thinks the California findings are likely to be true here, too, because Southern Oregon has the same ticks and the same lizards.

"I'd love to confirm that," he said.

Ticks have a complex life cycle, and at each stage of their development, they need a meal of blood. Clover said all tick larvae are uninfected when they hatch from eggs. They acquire the Lyme bacterium if they feed on a mouse or other small animal that's already been infected. When they feed again to transform from nymph to adult, more may become infected adults if they take blood from an infected animal.

Clover said he studied adult ticks in Southern Oregon years ago and found the Lyme infection rate was 4 percent, the same rate that was confirmed in the California study. That means just one adult tick in 25 carries Lyme — pretty good odds, especially since researchers now believe a tick needs to be attached for at least 24 hours to pass the Lyme bacterium to a human.

"You can presume your chances of getting Lyme are pretty small," Clover says.

Nymphs are a different story. The California study found 14 percent of nymphs carried Lyme, or about one in seven.

"That's a little different," he says, because a biting nymph is far less likely to be seen or felt, and far more likely to be a Lyme carrier.

While those numbers may sound frightening Clover isn't telling people to stay indoors. He says avoiding the nymphs "is not rocket science. It's paying attention.

"Lyme is pretty much an avoidable disease," he says, because the nymphs are most often found in leaf litter on the forest floor. The nymphs creep along on eight little legs, but they can only go so far, and they can only bite what they can catch up with. He says leaf litter from hardwoods, especially oaks, seems pretty necessary for nymph habitat.

"You've got to stop and sit down in the woods" long enough for a nymph to crawl on you, Clover says, "or put an article of clothing down for a while, and then throw it over your shoulder."

To get started on the project, Clover wants to collect tick nymphs from several sites across Jackson and Josephine counties, most likely in woodland areas where people spend time on trails. Johnston and Lee are recruiting volunteers to help collect the ticks, and donations to pay for lab analysis.

"The more we can collect, the more we can send (for analysis)," Lee said.

They hope the research will expand awareness of Lyme disease in Southern Oregon and encourage physicians to test for it and treat it aggressively.

"This is really a preventable disease," Johnston said, "if people are educated."

Reach reporter Bill Kettler at 541-776-4492, or e-mail