Rise of the Parasites

June 5, 2015

Northern Michigan is home to thousands of species, but this year’s crop is predicted to be a whopper, particularly among the tiny, pesky ones – the ticks, flatworm parasites and mosquitoes. Water loving and blood sucking, they mass breed in the moist months of May and June.

Ticks 

Rich Keith, director of the Kalamazoo Valley Bird Observatory, has been studying tick populations in Michigan for more than 10 years. In that time, Keith said there has been a well-documented increase in the three dominant tick populations and an expansion of western and eastern black-legged ticks.

Only black-legged ticks spread the Borrelia burgdorferi bacteria, which causes Lyme disease. The Companion Animal Parasite Council (CAPC) lists Manistee, Benzie, Leelanau and Charlevoix counties as high risk Lyme disease areas; Antrim, Grand Traverse and Otsego counties as moderate; while Emmett, Cheboygan, Kalkaska and Missaukee counties pose near zero risk.

"Ticks breed, and flourish, in the nests of small rodents. They’ll feed on baby rodents and then hitch a ride on a mouse to get to a larger animal like a dog or a person," said Dale Litney, owner of Mosquito Squad of Northern Michigan. "So, though they are in the woods, they can also be anywhere there are small rodents. With the warmer temperatures beginning earlier in the spring, rodents that play host to ticks are active earlier as well."

CAPC parasitologists forecast a 2.5 to 5 percent prevalence of Lyme disease among dogs in the area this year. So far in 2015, reported cases are at 1.42 percent prevalence or one out of every 81 dogs tested.

Although breeding explodes in the spring, CAPC member Dr. Susan Little cautioned that peak occurrences happen in the fall and adult black-legged ticks are still active in the cooler months.

The lonestar tick and dog tick have also been widely successful in our region. Though these ticks tend to be disease-free, they can carry ehrlichiosis, a term that encompasses multiple varieties of the potentially life threatening bacterial disease. Like Lyme disease, ehrlichisosis primarily affects humans and canines, but can also infect cats.

Experts agree that the best prevention is to check regularly for ticks.

"You should really check everyone over each time they come inside," said Litney.

Pharmacist Eric Reinhold has practiced in northwest Michigan for more than 15 years and he recommends washing an area where a tick has embedded with soap and water.

"The most important thing is to watch out for anything that looks like an infection, such as redness in the area, especially redness that begins branching out from the bite site," said Reinhold.]

Swimmer’s Itch

Flatworm parasites exist all over the world, but in North America their concentration is highest in the northern Lower Peninsula due to an abundance of clean lakes and presence of both water fowl and snails who each play host to the worms at different stages of development.

Once a lake becomes infested with these parasites that cause swimmer’s itch, outbreaks can last anywhere from one week to an entire season with few indications to predict the length of risk.

Of Michigan’s thousands of lakes, only about 1 percent have been overrun with the parasite, though incidences tend to be in large, popular recreational lakes such as Green Lake in Interlochen and Higgins Lake.

Attempts to eradicate the parasite have included mass relocating of mergansers and other native ducks and dumping copper sulfate into lakes to kill larva hosting snails. Relocation efforts require organizational support and cost thousands of dollars, while the copper sulfate compound is a nonspecific poison that can devastate lake habitat. Both methods have proven relatively ineffective in preventing the spread of the parasite.

With little recourse to stem its growth, Michiganders are stuck trying to avoid and tolerate the parasite.

The microscopic worms are sensitive to winds and water current and tend to congregate in alcoves and shorelines commonly used for swimming areas and docks. Swimmers should avoid lakes with incidences particularly on days with onshore winds, which blow the parasite into the shallows along the shore line.

"If the water is moving around, it’s generally safer because they [parasites] like calm, stagnant water," said Reinhold.

Since humans aren’t suitable hosts, the parasite typically dies within one week of encountering a person. In the meantime, there are no surefire methods for killing the worms more quickly.

"There are no good answers for treating swimmer’s itch," said Reinhold. "Some people use Rid or other lice treatments to eliminate the bugs, but generally you can use antihistamines like Benadryl and creams like hydrocortisone to help reduce the itching."

Mosquitoes 

Although 2015 has seen less precipitation than last year, the 50 species of mosquitoes native to Michigan will still be a formidable presence this spring and summer. The forecast is good news for fish and fishermen, and bad news for pretty much everyone else.

"Last year saw a large and very healthy spring hatch, and this year should be another quite ferocious season," said Dale Litney.

"Eggs can lay dormant for up to seven years waiting for water to reach them. Mosquitoes are a well-adapted species. Hundreds of mosquitoes can hatch from only a capful of water."

So long as the rain continues, mosquitoes will continue to hatch.

According to the Michigan Mosquito Control Association, the region is vulnerable to three main diseases spread from mosquitos to humans: West Nile virus, St. Louis encephalitis and Eastern Equine encephalitis. West Nile cases have been relatively low in the northern Lower Peninsula and 85 percent of all cases in Michigan occurred in Kent County. Both St. Louis and Eastern Equine encephalitis are rare. Though of the 17 states who reported incidences in the last ten years, Michigan had the highest occurrences outside of the south.

Mosquitoes may not pose a high disease threat to the region, but they are an irritant.

The Mosquito Squad recommends a proactive approach, by reducing yard and lawn waste and being vigilant about standing water.

"Tip over toys in the yard, shake out any tarps or other surfaces that could be holding water, and toss yard clippings and waste," recommended Litney.

In addition to traditional bite treatments, Reinhold said, "taking an antihistamine can help with the inflammation response. They also make mosquito bite sticks that work immediately on the bite and are easy to keep around in cars, boats or bags to use right away."