Variety of diseases transmitted by ticks
There are a variety of diseases transmitted by ticks in Minnesota. The most well-known is Lyme disease. Lyme disease is caused by bacteria that are transmitted from deer ticks to humans. In 2011, there were 1,201 confirmed cases in Minnesota according to the Minnesota Department of Health.
Human anaplasmosis is also caused by bacteria that are transmitted from deer ticks to humans. This bacterium was formerly known as human granulocytic ehrlichiosis. This is not as common in Minnesota as Lyme disease, but has been more prevalent since the early 1990s. There were 782 confirmed cases in 2011.
Babesiosis is a protozoan infection that is transmitted by deer ticks. Babesiosis is not very common in Minnesota. Most humans infected do not have symptoms. Those with symptoms often have babesiosis as a co-infection with Lyme disease. People without a spleen are more likely to get babesiosis. There were 56 confirmed cases in Minnesota in 2010 and 72 in 2011.
Ehrlichiosis is the general name used to describe several bacterial diseases that affect humans from an infected tick. The bacteria include Ehrlichia chaffeensis, Ehrlichia ewingii, and a potential third species called Ehrlichia muris-like (EML). Ehrlichiosis is commonly confused with human anaplasmosis. Human ehrlichiosis caused by the first three bacteria is endemic to the southern states and is carried by the Lone Star tick. Epidemiologists believe the Ehrlichia murin-like agent can be transmitted by deer ticks, hence making its way to Minnesota. Ehrlichiosis was first reported in Minnesota in 2009. There have been few cases reported in Minnesota of ehrlichiosis.
Powassan virus is a virus that is transmitted from deer ticks to humans. The virus transmits very quickly from the tick to a human — once the tick is attached, it generally affects the central nervous system (causing inflammation in the brain, spinal cords and surrounding membranes). There have been about 15 cases of Powassan virus in Minnesota from 2008-11. Although the risk in Minnesota is very low, the virus is very serious.
Two very uncommon diseases from ticks in Minnesota include Rocky Mountain Spotted Fever and Southern Tick-Associated Rash Illness (STARI). Both are extremely rare in Minnesota, but a few isolated cases have been reported, all cases of RMSF were confirmed in southern Minnesota, all cases of STARI were confirmed from patients who had traveled to south central states.
One disease we often do not think of coming from ticks, but rather, infected water supply, is tularemia. Tularemia is a bacteria that is transmitted from ticks that are infected with the bacteria after feeding on animals (especially rodents, rabbits, hares, beavers) that are also infected with the bacteria. You can also contract tularemia from coming into contact with infected animals, waste, water or soil. The bacteria can live several weeks in soil, water or carcasses. Although tularemia is easy to catch, and very little of the bacteria are needed to make a human sick, it is not very common in Minnesota.
Symptoms and testing
Patients with a tick disease have fever and chills, headaches, muscle and/or joint pain and fatigue. Sometimes patients will also present with additional symptoms of decreased appetite, nausea, vomiting and a rash. In general, as health care professionals, we start thinking about tick-borne illness in late spring through mid-fall.
Tests that help in the diagnosis of a tick disease include looking at the patient’s complete blood count and liver tests. We will often see a low white blood cell count, low platelet count, and elevated liver enzymes. Specifically in babesiosis, often the kidneys are not functioning properly, and there will be low platelets and low hemoglobin.
Confirmatory testing for some of the tick diseases are available in a clinic or hospital setting. There are some tests not commercially available, which means if the health care provider is suspicious of Powassan virus, blood or cerebral spinal fluid would be sent directly to the Minnesota Department of Health for examination.
Some hospitals and clinics are capable of completing all of the tick disease testing in their own facility. There are other clinics and hospitals that send the blood sample to an outsource lab for testing. Regardless, results generally take a few days to complete.
Some patients will ask about testing the tick itself. Although this is commercially available, most experts do not recommend testing of the ticks since the results do not affect how a provider would choose to manage the patient.
Test results can vary depending on when the patient is tested. For example, the antibodies found in Lyme disease typically appear within one to two weeks following the appearance of signs and symptoms; other antibodies appear two to six weeks following the onset of the erythema migrans rash. Therefore, it is not recommended to test the patient at the time of the bite. Often patients have a “false negative test,” simply because the test was drawn too soon after the bite. This is why often patients start treatment based on signs and symptoms (clinical presentation) and immediate changes we see in labs (low white blood cell count, low platelets, increased liver enzymes). It is important to get lab tests to confirm the infection if your provider recommends treatment. And your provider may recommend extended treatment based on your results.
For patients presenting with symptoms, confirmed laboratory testing or high suspicion of disease are treated with antibiotics generally for 14 to 30 days, depending on the severity of symptoms. Most are treated with doxycycline. There are alternative antibiotic choices for patients with antibiotic allergies or for children under the age of 8, due to the side effect of doxycycline potentially staining (darkening) the adult teeth that have not come in yet. For patients suspicious of babesiosis or Rocky Mountain Spotted Fever, the provider generally will discuss treatment with an infectious disease physician first.
There is efficacy in treating a tick bite with preventative antibiotics in patients that meet a specific set of criteria. This includes presence of rash (erythema migrans), the deer tick was attached to the human for greater than 36 hours and the patient presents within 72 hours, the tick was engorged (meaning full of human blood) and the patient is in an area of high incidence. The patient must meet all of the criteria for prophylaxis to be given. The recommended treatment is doxycycline 200 milligrams once for adults and weight dosed for children over the age of 8. If there is an allergy to doxycycline, there are no recommendations for prophylaxis.
There is much debate on this topic. The first approach for the patient that feels they have recurrent symptoms or incomplete resolve of the disease should be for the provider to determine: does the patient have a co-infection, was the initial treatment adequate, was the initial diagnosis correct, was the original test a false-positive and the patient has developed a new problem? Patients with persistent or recurrent symptoms but without objective (confirmed testing) findings may have a post-infectious process, meaning other mechanisms may be involved. The Minnesota Department of Health recommends treating the symptoms with other medications, considering failed antibiotic therapy is also reasonable and accepted, but this is often determined by an infectious disease specialist.
According to the Centers for Disease Control and Prevention (CDC), approximately 10 to 20 percent of patients treated for Lyme disease with a recommended two to four week course of antibiotics will have lingering symptoms of fatigue, pain, joint and muscle aches. Some patients experience symptoms for up to six months. Although this is often referred to as “chronic Lyme disease,” this condition is properly known as “Post-treatment Lyme Disease Syndrome.”
The exact cause is not yet known. Most medical experts believe the lingering symptoms are the result of residual damage to the tissues and immune system that occurred during the infection. For example, this is known to occur in patients that are treated for Streptococcal pharyngitis (strep throat) and develop rheumatic heart disease.
Regardless of the cause of the lingering symptoms, to date, studies have not shown patients improve with long-term antibiotics versus patients given a placebo (not antibiotics). This doesn’t mean providers are dismissing the patient’s symptoms or disease process, it simply means long-term antibiotic treatment doesn’t help any more than a placebo (sugar pill). The CDC recommends patients journal their symptoms, sleep patterns, diet, activity to help their provider determine a diagnosis and the best course of treatment. For those who want to research on their own as well, be well-informed; consider the source when researching information available on the Internet.
The National Institute of Health has trials currently in progress, as well as trials for which they are actively recruiting patients who have been diagnosed with Lyme disease. Information is available at http://clinicaltrials.gov/ and search for Lyme disease in the search tool bar.