Babesiosis is an infection of the red blood cells caused by the protozoa Babesia.
Babesiosis is transmitted by deer ticks.
Babesiosis may cause fever, headache, body aches, and fatigue.
To diagnose babesiosis, doctors examine a sample of blood under a microscope and look for the protozoa in red blood cells or do other blood tests.
Most otherwise healthy people do not need to be treated, but, if symptoms develop, people are usually given a combination of medications.
Preventing tick bites helps prevent babesiosis.
Protozoa are a type of parasite. They make up a diverse group of microscopic, one-celled organisms. Some protozoa need a human or animal host to live. There are many different kinds of protozoa.
Babesia are extraintestinal protozoa, which means they cause infections only in areas outside of a person's intestines such as the blood. Babesia protozoa infect red blood cells and eventually destroy them.
Babesiosis is common among animals, especially rodents, but is relatively uncommon among people. In 2020, there were 1,827 reported cases of babesiosis in the United States.
Babesia microti is the species of protozoa that most commonly infects people in the United States. Infections in people occur in the offshore islands or coastal regions of Massachusetts, Rhode Island, coastal Connecticut, eastern Long Island, Vermont, and New Jersey. Infections also occur in Wisconsin and Minnesota. Different Babesia species infect people in Missouri, Washington, and California and in other areas of the world.
Babesiosis is transmitted by the same ticks that transmit Lyme disease (Ixodes ticks or deer ticks). Ticks are vectors, which means they carry and transmit parasites that cause diseases in people. Ticks can become infected after feeding on infected animals, such as rodents. The infection spreads when an infected tick bites a human or an animal. Rarely, babesiosis can be transmitted through a blood transfusion or can pass from pregnant person to fetus.
Ticks may be infected with both Babesia and Ixodes, which means a person can have both Lyme disease and babesiosis at the same time. Ticks can cause other infections such as anaplasmosis, relapsing fever, and encephalitis.
(See also Overview of Parasitic Infections.)
Symptoms of Babesiosis
Some people with babesiosis, especially healthy people younger than 40, do not have noticeable symptoms. Newborns may have fever, low numbers of red blood cells (anemia), and low numbers of platelets (thrombocytopenia).
Symptoms of babesiosis usually start about 1 to 2 weeks after people are bitten. People may have fever, headache, muscle and joint aches, chills, and fatigue. In healthy people, symptoms usually go away after a week. In other people, the breakdown of red blood cells (hemolysis) may cause hemolytic anemia and the skin and the whites of the eyes to turn yellow (jaundice). The liver and spleen often enlarge.
The risk of severe disease and death is highest for people who are older, whose spleen has been removed, or who take medications or have disorders that weaken the immune system (particularly advanced HIV infection [also called AIDS]). In these people, symptoms include high fever, anemia, dark urine, jaundice, and kidney failure.
Diagnosis of Babesiosis
Examination of a sample of blood under a microscope
Other blood tests
Doctors may suspect babesiosis in people who have typical symptoms and hemolytic anemia and who live in or have traveled to an area where the infection is common. Often, people do not remember a tick bite.
To diagnose babesiosis, a doctor usually examines a blood sample under a microscope to look for Babesia in the red blood cells. To help identify the protozoa, a blood sample may be tested for Babesia's genetic material (DNA) or for antibodies to Babesia. (Antibodies are proteins produced by the immune system to help defend the body against a particular attack, including that by parasites.)
Treatment of Babesiosis
When treatment is needed, atovaquone plus azithromycin or quinine plus clindamycinWhen treatment is needed, atovaquone plus azithromycin or quinine plus clindamycin
Exchange transfusion
People with no symptoms usually do not need treatment because babesiosis typically goes away on its own.
All people with babesiosis are usually treated with atovaquone (a medication typically used to treat protozoa infections) plus azithromycin (an antibiotic). All people with babesiosis are usually treated with atovaquone (a medication typically used to treat protozoa infections) plus azithromycin (an antibiotic).Atovaquone plus azithromycin is the preferred treatment because it has fewer side effects and is as effective as quinine (used to treat malaria) plus clindamycin (an antibiotic) in people with babesiosis. is the preferred treatment because it has fewer side effects and is as effective as quinine (used to treat malaria) plus clindamycin (an antibiotic) in people with babesiosis.
People with severe symptoms may alternatively be treated with quinine plus clindamycin.
In severely ill people, an exchange transfusion (where a person's blood is replaced with donor blood) may be done to reduce the amount of parasites circulating in the bloodstream.
Prevention of Babesiosis
In areas where deer ticks are common, people can reduce the risk of getting babesiosis by taking precautions against ticks.
People can reduce their chances of picking up or being bitten by a tick by doing the following:
Staying on paths and trails when walking in wooded areas
Walking in the center of trails to avoid brushing up against bushes and weeds
Not sitting on the ground or on stone walls
Wearing long-sleeved shirts
Wearing long pants and tucking them into boots or socks
Wearing light-colored clothing, which makes ticks easier to see
Applying an insect repellent containing diethyltoluamide (DEET) to the skin
Applying an insect repellent containing permethrin to clothing or wearing clothing commercially pretreated with Applying an insect repellent containing permethrin to clothing or wearing clothing commercially pretreated withpermethrin
Frequently searching children and hairy areas of the body for ticks
To remove a tick, people should use fine-pointed tweezers to grasp the tick by the head and mouthparts right where it enters the skin and should gradually pull the tick straight off. The tick's body should not be grasped or squeezed. Once the tick is removed, the area of skin should be swabbed with alcohol. Petroleum jelly, alcohol, lit matches, or any other irritants are not effective ways to remove ticks and should not be used. (See also Treatment of Tick Bites.)
Did You Know...
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People who have had babesiosis can prevent transmitting the infection by not donating blood or probably organs until they have completed treatment and parasites cannot be found in their blood. In the United States, blood and organ donors are screened in areas where the incidence of infection is relatively high.
Ticks
More Information
The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.
Centers for Disease Control and Prevention (CDC): About Babesiosis
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