What is babesiosis? The parasitic infection that 'eats' your red blood cells

Disease name: Babesiosis

Affected populations: Babesiosis is a rare and potentially fatal parasitic disease that destroys red blood cells, the cells that supply tissues with oxygen from the lungs. The disease, which is spread by ticks, occurs worldwide, including in the United States and Europe.

Fewer than 3,000 cases of babesiosis are reported annually in the U.S., and they most commonly occur between May and September in the upper Midwest and Northeast, including in Minnesota, Wisconsin, Connecticut and New York. Cases tend to rise in the spring and summer as this is when people are most likely to be in contact with the ticks that spread the disease.

Causes: Babesiosis is caused by microscopic parasites that belong to the genus Babesia. These parasites usually infect cattle and are spread between animals by ticks that eat the blood of different hosts.

Related: Tick-borne parasite is spreading in the Northeast, CDC says

Once inside the body, Babesia parasites invade and destroy red blood cells. This severely limits the ability of these cells to supply tissues with oxygen.

While more than 100 species of Babesia parasites have been identified, overall, only a few species are known to infect humans.

In the U.S., most babesiosis infections are caused by a parasite species called Babesia microti and are spread by blacklegged ticks (Ixodes scapularis), also known as deer ticks. These ticks are typically found in wooded, brushy or grassy areas.

In rarer instances, Babesia parasites can be spread from one person to another via contaminated blood transfusions, and they can also spread from mother to fetus across the placenta.

Symptoms: Most people exposed to Babesia parasites don't have any symptoms of babesiosis; this is especially true for young, healthy people.

However, in individuals who have weakened immune systems or who are over the age of 50, the parasites can trigger severe disease. People who have had their spleen removed are also more vulnerable to serious infections than the average person, because the spleen normally helps remove infected red blood cells from the body.

Typical symptoms of babesiosis include fever, chills, sweating, muscle aches and pains, as well as swelling of the liver and spleen and having a low level of red blood cells in the body. Symptoms usually emerge within one to four weeks of a person being infected with Babesia parasites, and they can last for several days after onset.

Serious cases of babesiosis can cause multiorgan failure and death, as tissues are starved of oxygen.

Estimates for death rates from babesiosis vary considerably between studies. However, surveillance data gathered in 2019 by the Centers for Disease Control and Prevention (CDC) found a 0.57% death rate among patients in the U.S.

Death rates may be closer to 20% in patients who belong to high-risk groups, even when they receive treatment.

Treatments: Patients who don't have symptoms of babesiosis usually don't require treatment, as the immune system will typically clear the parasites away within one to two weeks.

In symptomatic patients, the main treatment for babesiosis is a combination of antiparasitic drugs and antibiotics. The latter drugs are primarily used to treat bacterial infections, rather than parasitic infections, but certain kinds of antibiotics, such as clindamycin, can also be effective against parasites.

Patients who are very sick may also require a blood transfusion to replace their damaged and infected red blood cells.

The best way to prevent babesiosis is to avoid areas where ticks live, according to the CDC. If you are in those areas, there are precautions you can take to avoid tick bites.