Last year’s decline in ticks doesn’t mean anything for this year
An unusually warm, dry spring and summer may have contributed to a substantial drop in cases of disease caused by ticks in 2012 in Minnesota, but the decline doesn’t mean the risk of illness from tick bites in 2013 will be any less than in most previous years, state health officials reported.
The three main tick-borne diseases carried by blacklegged ticks (also called deer ticks) in Minnesota — Lyme disease, human anaplasmosis and babesiosis — were all down in 2012. There were 911 confirmed cases of Lyme disease, down from 1,201 in 2011 and the lowest since 2003.
There were 503 cases of human anaplasmosis in 2012, down from 782 in 2011 and 40 cases of babesiosis in 2012, down from 72 in 2011.
Pinpointing a cause for decline in case numbers is difficult, said David Neitzel, tick-borne disease specialist with the Minnesota Department of Health.
“It’s possible that the decline may be due in part to more people taking steps to prevent tick bites, but it’s much more likely that extremely dry weather conditions last year were the main reason for reduced disease numbers,” he said.
Despite an early warm-up in spring that led to an earlier than normal start to tick activity, continued hot, dry weather may have reduced blacklegged tick feeding activity, thus lowering disease risk.
Blacklegged ticks do thrive in humid conditions, however.
“Based on what we’re seeing, we expect the highest risk period for tick-borne diseases to occur over the next few weeks in Minnesota,” Neitzel said. “We expect that risk will be high again this year, especially in those places that historically are high risk for tick-borne diseases.”
Those areas include wooded or brushy areas in southeastern, central and north central Minnesota.
Besides the three commonly reported diseases, blacklegged ticks carry the agents for Powassan disease and a new form of human ehrlichiosis. American dog ticks (wood ticks), which are very common in spring and early summer throughout Minnesota, can carry Rocky Mountain spotted fever (RMSF). While RMSF is most common in the southern United States, a small number of RMSF cases have occurred in Minnesotans who did not travel outside the state.
The best way to prevent tick bites is to avoid tick habitat during warm weather months:
- Wooded or brushy areas for the blacklegged tick.
- Grassy or wooded areas for the American dog tick.
If you can’t avoid tick habitat, use repellent to reduce the risk of disease:
- DEET-based repellents (up to 30 percent DEET), which can be applied to clothing or skin for temporary protection.
- Permethrin-based repellents, which are used to pre-treat fabric and can protect against tick bites for at least two weeks without reapplication.
To make your yard less attractive to ticks:
- Keep lawns mowed short.
- Remove leaves and brush.
- Create a landscape barrier of wood chips or rocks between mowed lawns and woods.
More information is available at http://www.health.state.mn.us or by calling 651-201-5414.