Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at April 30, 2016

Ehrlichiosis, a bacterial infection, is transmitted to humans by ticks. Ehrlichiosis results in flu-like symptoms. It is both treatable and preventable.


Definition & Facts

There are two types of ehrlichiosis; human monocytic and human granulocytic. Monocytic ehrlichiosis is spread by the Amblyomma americanum, which is also known as the lone star tick, and the bacteria that is transmitted is the Ehrlichia chaffeensis. It is more often seen in the southeastern United States, and is the more common form of ehrlichiosis.

Ehrlichia phagocytophila is the bacteria that causes granulocytic ehrlichiosis. This is likely spread by the same tick that causes Lyme disease, the blacklegged Ixodes scapularis. It is seen more often in the following states: Connecticut, New York, Wisconsin, and Minnesota.

Symptoms & Complaints

Flu-like symptoms of ehrlichiosis include fever, chills, a headache, nausea, muscle aches, vomiting, fatigue, diarrhea, loss of appetite, confusion, rash, joint pain, and cough.

Some people who are infected with ehrlichiosis may experience very mild symptoms, to the point that they do not go to a doctor and the body ends up healing itself. However, if erlichiosis is left untreated and symptoms persist, it may result in a serious illness requiring hospitalization. Severe clinical presentations of ehrlichiosis may result in coma, encephalopathy, and kidney failure.


Ehrlichiosis is the result of ehrlichia bacteria entering the body via transmission from a tick. Ticks nourish themselves by drinking blood. Ticks latch onto a host and feed until they are full, oftentimes swelling up to several times their own size. While feeding, disease-carrying ticks are able to transmit their infected bacteria back to their host. Alternatively, ticks can contract diseases from their hosts.

When bitten, the tick's bacteria enters the host through the skin, making its way to the bloodstream. This takes about 24 hours, so the tick must have been latched on for this amount of time; this is why one way to prevent erlichiosis is to remove ticks as soon as they are spotted. Ehrlichiosis can also be transmitted to a fetus by a pregnant mother, through blood transfusions, and by touching an infected animal that has been slaughtered.

Diagnosis & Tests

Tick-borne diseases are hard to diagnose, due to how common their symptoms are. Flu-like symptoms are the basis of many diseases, so it is not an obvious diagnosis. Blood tests can be taken to test for abnormalities, as well as a medical history of exposure to ehrlichia.

If infected with ehrlichiosis, a blood test will result in abnormal findings such as a low white blood cell count, a low platelet count, and abnormal liver function. If these blood tests are not sufficient, deeper tests can be looked into such as a polymerase chain reaction test to help find the genes that are specific to ehrlichiosis.

An indirect fluorescent antibody test can also be performed to measure the amount of antibodies in the blood to the ehrlichiosis-causing bacteria. If ticks are common in the patient's area, doctors may tend to begin a round of antibiotics before getting the results from the blood test, since it is best to start treatment as early as possibly with tick-related diseases.

Treatment & Therapy

Ehrlichiosis is a potentially serious disease. Just under 2% of people who are infected with ehrlichiosis end up dying from it. The earlier a patient is treated, the quicker the recovery. People who experience a very severe case of ehrlichiosis might require intravenous antibiotics and intensive care in a prolonged hospitalization setting.

Doxycycline is the first treatment given to people who have contracted this disease and it should be initiated immediately after ehrlichiosis is suspected. Doxycycline is the most effective tetracycline in treating ehrlichiosis in its early stages and it most often prevents severe complications. If a patient is treated in the first week after being infected, the symptoms typically subside within a couple days.

Failure to respond to a round of doxycycline may show that the patient does not indeed have ehrlichiosis. Doxycycline should be taken every 12 hours, and patients should continue their dose of antibiotics for a minimum of three days after the symptoms have gone away. This typically takes one to two weeks. Some people with severe infections may experience their symptoms for longer.

Prevention & Prophylaxis

The best way to avoid ehrlichiosis is to prevent tick bites. Ticks tend to attach themselves to the lower area of the legs and feet when walking in grassy or wooded areas. After attaching, a tick crawls to find a spot to burrow. Removing a tick in the first 24 hours after it attaches to the body reduces the risk of infection.

If one needs to go into a location where ticks are present, some steps can be taken to help avoid them. Wearing light colored clothes can make it easier to spot dark ticks. It is not recommended to wear open-toed shoes in grassy areas or fields, because wearing these can increase the risk of a tick latching onto bare skin and crawling under the clothes.

Using insect repellent containing DEET or permethrin may help. One should avoid exposing skin by wearing long sleeves and long pants. Tucking one's clothing so ticks can not crawl over pants and onto skin that is exposed is also wise. Finally, it is good to check one's clothing throughout the day to make sure there are no ticks.