UM Lyme expert studies ecology of the disease near his Ogema vacation home
Ogema, MN
A University of Minnesota microbiologist who has a vacation home near Ogema has come to some interesting conclusions about the local ecology of Lyme disease. His story might persuade Price County residents to think somewhat differently about two common visitors to Northwoods campsites and backyards.
Professor Russell Johnson's work has centered on the Twin Cities and Camp Ripley areas, where white-footed mice are the primary reservoir for the disease.
In a comparative study, Johnson live-trapped 39 animals near his Ogema home - including mice, squirrels, chipmunks and voles - and transported them to the university lab for analysis. The findings raised his eyebrows.
"I found the results to be very interesting and different from the data we have generated in Minnesota," he wrote in an e-mail to THE-BEE last month. Specifically, he found that red squirrels and chipmunks are major carriers for the disease on the Ogema property (Johnson is originally from Wausau and received his doctorate from the University of Wisconsin-Madison, and the Ogema home has been in his family for decades).
Moreover, several of the chipmunk and red squirrel specimens carried another lesser-known emergent disease known as human anaplasmosis, which, like Lyme disease, is caused by a bacteria and is transmitted by the deer tick.
Human anaplasmosis is marked by fever, aches and pains, and is less common than Lyme disease, but both are on the rise in Wisconsin.
Johnson, who has studied Lyme disease for 20 years and has appeared on Twin Cities television to talk about it, first decided to test the Ogema area to see how different habitat influences Lyme's pathways. He said the highly variable habitats of glacial moraines - which are prevalent in southern Price County - harbor different small-mammal species than the Twin Cities area.
He lured the critters on his 40-acre spread with peanut butter, oats and apples.
Chipmunks had the highest percentage of positive Lyme disease tests. Of nine chipmunks caught on his property, Johnson's team found that seven were infected with Lyme disease.
"That distribution is unusual and very high," he said.
Johnson admitted that his sample size is smaller than he would like, but he said the numbers were strong enough to suggest that Lyme disease in Price County and similar habitats follows a different path than has been documented elsewhere in the upper Midwest. One reason is simply that chipmunks and red squirrels are more plentiful here, he said.
The history of the disease
Nobody knows where Lyme disease lurked before cases started to become widespread in the 1970s and 1980s. One of the first cases was discovered in Lyme, Connecticut, which is how the disease was named.
Johnson said the two essential elements for deer ticks - forest cover and deer - were not as prevalent around the turn of the century and into the 1930s, when crosscut saws and unregulated hunting ruled the upper Midwest. But as deer populations grew and forest lands regenerated, deer tick habitat improved. As more and more humans came to the North seeking farmland or recreation, the potential for tick-borne diseases increased dramatically. Lyme disease cases have increased nearly every year since it was first discovered.
Tick life cycle
Deer tick larvae hatch disease-free, Johnson said. They then seek a blood meal from any animal that they can latch on to, which are often small mammals. If the mammal harbors Lyme disease, the tick is likely to pick it up. Then, during the nymph stage, the tick seeks another meal. If the host happens to be a human, transmission may occur.
Adult deer ticks prefer - you guessed it - deer.
"Deer blood is very nutritious," Johnson said, adding that deer do not harbor the disease. He said deer are also the "romantic site" for deer ticks at the end of their short life cycle, meaning the mating site.
Prevention and treatment
It takes approximately 36 hours for a tick to transmit Lyme disease, so tick checks are essential for people who spend time in the woods. Johnson said tick checks "are the most important preventive measure." He also recommends other common-sense steps, like bug-repellent application, tucking pant legs into boots and staying on cleared trails whenever possible.
An infected person will typically have a red bull's-eye around the bite area, but that's not always the case. The symptoms range from stiffness and swelling of joints to rashes, fever, lethargy, incoherence and loss of appetite. Anyone who suspects he or she might have Lyme disease should contact a physician right away.
Johnson said Lyme disease treatments for humans have come a long way since the disease was discovered. Although there is no human vaccine available, the disease can be effectively controlled and cured with antibiotics - especially if it's caught early enough.
"The earlier the better," Johnson said. "It's very few people who don't respond to treatment."
A human vaccine was on the market briefly but was pulled after authorities concluded the protection levels were insufficient in relation to the costs.
"It became too much of a headache," Johnson said.
One man's case
Ironically, Johnson's neighbor in Ogema fell ill with Lyme disease last summer. Ed Rhody didn't discover he had the disease until a rash had covered his body and he was sacked with aches and pains. He never saw a bull's-eye.
"He thought he had a bad flu," said Ed's wife Anne from their home last week. "Fortunately, his wife is a physician's assistant. (I) knew what to look for."
Even though his case was advanced, Rhody was cured with two courses of antibiotics over six weeks.
In light of his neighbor's case and his findings in the field, Johnson urged people to be aware of the risks.
"It's definitely around the area," he said. "The ticks in this area are active."