When his annual health report revealed that President George W. Bush had been treated for Lyme disease last year, it was enough to spark the usual media follow-ups telling people what the disease is and where it's most common. What those stories didn't mention was what has happened here in Wisconsin that puts people in this corner of the state at greater risk.

During the last several years, pockets of Lyme-infected ticks have sprung up in parts of the state, including southeastern Wisconsin. This is not the usual pattern.

Usually the disease has spread from area of the state to an adjacent part as deer and ticks have migrated naturally. But one pockets popped up about a decade ago in Marinette County, probably an incursion by some ticks from Michigan's Upper Peninsula, said Jim Kazmierczak, public health veterinarian with the state Division of Health. And last year, some infected deer ticks were collected from plants around Lake Geneva. "Obviously that's a big resort area so there's some public health significance."

In 2005 or '06, some ticks were found in Kohler-Andrae State Park in Sheboygan County. For several years there has also been a pocket known around Palmyra and the Kettle Moraine State Forest.

"The odd thing," Kazmierczak said, "is that these pockets are pretty isolated. As you look at the tick encroachment over the years, it's been incremental. You don't see these jumps, little islands, little pockets of ticks surrounded by areas of no ticks."

"And whether they were brought in on a deer carcass, or dropped off of a bird, or on someone's dog that had traveled up north, I don't think anybody knows, but I think that's the most plausible explanation is that they were hitchhikers."

"And I'm sure that happens all the time, that these areas might get seeded with one or two ticks." But over a wide geographic area, he said, the odds aren't great that a male and female will meet and start a new population.

Different risks

The existence of ticks doesn't imply that your risk of acquiring the disease in Lake Geneva or Palmyra is the same as it in western or central Wisconsin, Kazmierczak said. "Probably the easiest way of thinking of it is if you think of the Wisconsin River forming an east-west dividing line, it's the counties that are west of the Wisconsin River and the ones that immediately border the river to the east that are the highest incidence counties."

A state report on Lyme disease from 2002 to 2006 shows that the counties with the most cases, more than 100 for every 100,000 people, are still generally in the north and west, from Burnett east to Lincoln and Oneida. Farther south, Portage, Trempeleau, and Richland have similarly high instances of Lyme disease.

In June the U.S. Centers for Disease Control and Prevention published a report on Lyme disease from 2003-05. During that time, 46 states and the District of Columbia reported 64,382 cases of Lyme disease.

The number of cases in Wisconsin has reached a rough plateau, Kazmierczak said, yet it has been steadily increasing. "We're hoping that with the dry conditions we've seen for most of the summer - at least until his week - its result will be lower case numbers because ticks don't like dry conditions."

More pockets

That same pattern of spread to adjacent areas is seen elsewhere, said Joseph Piesman, chief of tick-borne disease activity for the CDC. Lyme disease has spread up the Hudson River Valley and since the 1980s has even reached into the area of Albany. Birds and deer are the two major ways by which ticks move, he said, and wherever they drop off it's like sparks and tinder; at some point there may be enough to start a fire.

An isolated pocket of ticks has been found on Long Point, Ontario, and from there has spread to adjacent areas, too, he said. Like the Wisconsin case, there's no clear explanation of how the ticks got there.

At present there's a project underway by Yale University, and funded by CDC, to map the likelihood of contracting Lyme disease in the eastern United States, Piesman said. Researchers are selecting sample areas and will collect ticks from them. In this case, eastern means east of the 100th meridian, the line of longitude which runs through about the center of the Dakotas and Nebraska.

"That's really where the Great Plains start and the deciduous forest ends. These ticks are really forest ticks. They like that leaf litter and high moisture protection."

That distaste for dryness is one of the keys with which people can help protect themselves from ticks, but researchers are also experimenting with methods which may work over larger areas.

Population control

When he spoke to The Journal Times last week, Piesman was on his annual tick tour, visiting researchers in eastern states to see how their work is coming. Scientists at the University of Rhode Island developed a method to control ticks by setting up rollers near deer feeders. As the deer approach to feed, they rub against the rollers which apply permethrin, a synthetic insecticide. A trial over four years showed that the method could control about 70 percent of the tick population in a core area.

Of course, Piesman said, there are issues with that method, notably the objections which wildlife agencies have to feeding deer.

A similar idea uses a bait box to attract and then coat rodents with the same insecticide used on dogs and cats. In the wild, immature ticks pick up the Lyme disease organism from mice. A combination of this and other methods used by a group in New Jersey controlled about 95 percent of ticks, Piesman said.

There was a human Lyme disease vaccine on the market for a while, but it was withdrawn in 2002 for reasons not entirely clear but apparently related to a mild public response and the need for multiple doses in order to achieve protection.

Molecular biologists have jumped on the problem, too, and are busy trying to find special tick proteins which could become targets for a human vaccine. Reseachers are busy trying to find a vaccine for mice, too, based on an old clue. In 1939 a scientist noticed that guinea pigs repeatedly infested with ticks developed a skin immune reaction which tended to stop ticks from feeding and increased the number of tick deaths.

Not magic yet

While that is all interesting, Piesman said, there are some overall problems. First, for a human vaccine you preferably want a substance which works right away because you don't want the tick to stay attached long enough to transmit the Lyme disease organism. And then, he said, a vaccine which works on guinea pigs may not work on mice or rabbits, and humans are different from all of those.

The CDC is working on some natural products, he said, and has found in the laboratory that an extract from Alaska yellow cedar kills ticks and mosquitoes.

And that's why preventing Lyme disease very much becomes an individual act.

"You can't really stress the personal protection enough," he said. Once a tick attaches itself to a human, it takes about two days to transmit the Lyme organism. "If you get them off before that two-day period, then your risk of infection is little or none."