Diseases that can be Transmitted by Ticks
In Minnesota, there are about a dozen different types of ticks. Not all of them spread disease but it is always best to protect yourself against tick bites. The most common ticks that people come across in Minnesota are the American dog tick (commonly known as the wood tick) and the blacklegged tick (commonly known as the deer tick). The blacklegged tick causes by far the most tickborne diseases in Minnesota. The diseases spread by ticks in Minnesota include:
- Lyme Disease
Lyme disease, caused by Borrelia burgdorferi, is a potentially serious bacterial infection affecting both humans and animals. It is the most common tickborne disease reported in Minnesota and in the United States. The incidence of Lyme disease in Minnesota has been increasing in recent years. In 2013, a closely related bacteria, Borrelia mayonii, was found to cause an illness similar to Lyme disease (see below for more information on Borrelia mayonii disease).
Anaplasmosis, formerly known as human granulocytic ehrlichiosis (HGE) is a bacterial disease that was first recognized in Minnesota in the early 1990s. It is transmitted to people by blacklegged ticks (deer ticks), the same ticks that transmit Lyme disease. Anaplasmosis is less common than Lyme disease, however.
Babesiosis is a protozoan infection that occurs infrequently in Minnesota. Up to 20 percent of patients diagnosed with Babesiosis also have Lyme disease.
Ehrlichiosis caused by Ehrlichia chaffeensis is found throughout much of south-eastern and south-central United States and is not a common disease in Minnesota at this time, although a small number of cases have been reported. Ehrlichiosis due to Ehrlichia muris subspecies eauclairensis was first reported in 2009. Since then, low numbers of cases have been reported in Minnesota and Wisconsin.
- Powassan Virus Disease
Powassan virus is a tickborne flavivirus that has been reported in patients from the Upper Midwest and Northeastern states. It was first reported in a Minnesota resident in 2008 with low numbers of cases reported in the state since then.
- Borrelia miyamotoi Disease
Borrelia miyamotoi was recently identified in 2011 to cause an illness in humans similar to tickborne relapsing fever. It is distantly related to the bacteria that cause Lyme disease. Small numbers of human cases have been reported to date from the Upper Midwest and Northeastern states.
- Borrelia mayonii Disease
Borrelia mayonii was recently identified in 2013 to cause an illness similar to Lyme disease. To date, this organism has only been found in patients with exposures to blacklegged ticks in Minnesota and Wisconsin.
- Rocky Mountain Spotted Fever (RMSF)
Rocky Mountain spotted fever is extremely rare in Minnesota, but isolated cases have been reported within the state. This disease is transmitted by the American dog tick.
Tularemia is a potentially serious illness that occurs naturally in the United States. It is caused by the bacterium Francisella tularensis and can be transmitted by American dog ticks as well biting flies or infected animals. Human cases of tularemia are rarely reported in Minnesota.
Tickborne Diseases Affecting Travelers
Minnesota residents who travel to other countries or certain areas of the United States may become sick with one of the tickborne diseases listed above or other tickborne diseases. Avoidance of tick bites and use of tick repellent are recommended when traveling to potential tick habitat within affected areas. For more information on international travel, visit International Travel & Infectious Disease.