Ticking time bomb of Lyme disease; increase might have a coyote connection

Posted July 18, 2012, at 4:05 p.m.

DETROIT — It was a picture-perfect afternoon catching butterflies and frogs with his children in a stream in Michigan’s Upper Peninsula — long, flowing grass along the sandy creek sides, warm sun and chilly waters.

But years later, Don Granchi is still paying the price — he is among a growing number of folks who have been diagnosed with Lyme disease.

It took years to understand it, he said.

“The whole time, I’m tired and I hurt and I’m just looking for answers. I started to think I’m crazy, that it was all in my head,” said the former phone company technician from Dearborn Heights, Mich.

New research now may offer insight into the rise in Lyme disease cases in recent years across the U.S. and in Michigan, where the number jumped 51 percent — from 68 in 2007 to 103 in 2011.

Increases in the deer population have been blamed for the explosion of Lyme disease cases, but changes in the numbers of foxes and coyotes — and what they eat — actually might be responsible, according to a study published late last month.

The study could have implications for how wildlife is managed and shed light on the complex ecosystems underlying the rise of Lyme and other tick-borne diseases.

But what do small predators such as foxes and coyotes have to do with a disease spread by the deer tick?

The answer lies not only in the life cycle of the Lyme bacterium, Borrelia burgdorferi, but also in the ecological changes of all the animals with which it comes in contact. Normally, small mammals get infected by the bacteria, ticks get infected by feeding on the mammals, and then ticks feed and lay their eggs on deer. Foxes disrupt the chain by feeding on the small mammals.

“It was thought that deer were the only game in town for ticks,” said Taal Levi, lead author of the new study and a research fellow at the Cary Institute of Ecosystem Studies in New York.

Foxes have hunting habits that are different from those of coyotes: They will kill many small mammals at once, stashing the kill for later. Coyotes, on the other hand, especially those that have crossbred with wolves, will eat deer, rabbits, or even foxes, and are not efficient predators of small mammals the way foxes are. As coyotes have expanded in numbers and range, the new study suggests, they interfere with the important role served by foxes: to suppress rodent hosts of Lyme disease, especially around human habitation.

The chain of events that leads to Lyme disease starts small, with a larval tick biting, say, a white-footed mouse that carries Borrelia bacteria. The tick matures into a nymph that can infect other animals each time it feeds. The life cycle of the tick typically ends with deer, on which they prefer to feed and lay their eggs. The unlucky outdoorsman or hunter may intrude at any stage and be bitten. Hunting, it turns out, was key to understanding the spread of Lyme.

Using harvest records from 1982 to the present, the researchers tracked the number of deer, coyotes and foxes in Wisconsin, Minnesota, Pennsylvania and Virginia. In all four states, coyote hunter harvests were up over the 30-year period, while fox harvests decreased.

Incidence of Lyme disease over the same period mirrored the rise of coyotes and the decline of foxes. Deer abundance and Lyme cases were not related in Wisconsin, debunking the common belief that more deer equals more Lyme, according to the study, which was published in the Proceedings of the National Academy of Sciences.

There also was no consistent increase in Lyme with deer numbers in the other states. In fact, an area with a high fox population in western New York was notably devoid of Lyme.

As researchers learn more about the disease and how it spreads, public awareness has become crucial in the fight against it.

In Michigan, the Department of Community Health has created signs to be posted at state and local parks, especially those in at-risk counties along the western edge of the state, warning outdoors enthusiasts — hikers and campers, for example — to watch for ticks.

Officials also have been monitoring tick numbers throughout the state, and they worry about another upswing in Lyme cases this year, in part because of the mild winter that might have allowed more ticks than usual to survive, said Erik Foster, a medical entomologist for the state.

Still, Foster noted, disease transmission takes the right mix of animals and their life cycles, the right weather and environment, and the right circumstances to connect people with bacteria-carrying ticks.

“It’s very complicated,” he noted, adding that it will take months for local Lyme disease cases to show up in surveillance data at the state level.

So far, disease-carrying ticks have not been detected around metro Detroit, he said.

Dr. Martin Lerner, a doctor affiliated with Beaumont Hospital, Royal Oak who specializes in chronic fatigue syndrome and Lyme disease, says he believes the number of Lyme disease cases is much higher than what’s reported. Lyme is often misdiagnosed, he said.

Most patients return to health quickly after a bite by an infected tick, especially if they’re treated with antibiotics right away, Lerner said.

But if the infection goes undetected, especially if the tell-tale bulls-eye bite mark doesn’t develop or lab tests are wrong, the absence or delay of antibiotics can mean years of “all varieties of severity” of aches, pains and fatigue, Lerner said.

Tick prevention tips

• Use bug repellents containing DEET.

• Wear long pants tucked into socks and long-sleeved shirts when walking in the woods or grassy areas.

• Check skin and clothes for ticks after being in the woods.

• Remove a tick by grasping it as close to the skin as possible with tweezers and gently pulling until it releases its grip.

• Clean a bite with antiseptic.

• If you live near woods, remove brush and litter and put wood chips or a gravel path between your yard and the woods as a buffer zone to minimize tick exposure.

Sources: CDC, Wisconsin Department of Health Services

The Milwaukee Journal Sentinel contributed to this report.

© 2012 Detroit Free Press

 

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