CAUSED BY A GROUP of hemoprotozoan parasites called Babesia, babesiosis is an infectious malaria-like disease transmitted by infected deer ticks. While more than 100 species of these parasites have been reported, only one (Babesia microti) has been identified as causing babesiosis in humans in the United States.1

Babesiosis isn't as common as Lyme disease, which is also transmitted by the deer tick. The actual prevalence of babesiosis is unknown because most infected patients are asymptomatic, but in the United States, only about 200 cases of babesiosis have been reported since 1968.2 Lyme disease is much more common, with 27,444 cases reported in 2007.3

Babesiosis is most prevalent in the Northeast and upper Midwest. Most cases occur during the summer along the coast and offshore islands of the Northeast.2

A tick infested with Babesia transfers the parasites through its saliva when it feeds on a human host's blood. The parasites infect the host's red blood cells (RBCs). Babesiosis can be transmitted through blood transfusions; the Babesia protozoan can survive blood-banking procedures, including freezing, and blood banks don't test for Babesia.4 Babesiosis can also be transmitted from an infected mother to the fetus during pregnancy.5

Signs and symptoms

Babesiosis is usually an asymptomatic infection in healthy individuals.5 Beginning about a week after a tick bite, common signs and symptoms of babesiosis include a gradual onset of malaise, anorexia, and fatigue. Several days later, myalgia, fever, drenching sweats, and headache may occur; these can continue over a long period, abate, then recur. Most cases of babesiosis resolve with treatment, but patients who've undergone splenectomy, have immune system compromise, or are older than age 65 are at the greatest risk for complications such as acute renal failure, acute respiratory distress syndrome, multisystem organ failure, and possibly death.

Babesiosis is diagnosed by visual exam of peripheral blood smears along with patient history. Possible exposure to deer ticks or travel to an area where malaria is endemic is important for differential diagnosis. Babesiosis has been misdiagnosed as malaria because Babesia-infected RBCs appear similar to malaria-infected RBCs to an inexperienced eye.

A diagnosis of babesiosis may also be missed in patients with Lyme disease, who may have babesiosis concurrently.6

Treatment guidelines

A patient with babesiosis doesn't require isolation. The infection is treated with a combination of quinine (Qualaquin) and clindamycin (Cleocin) for 7 to 10 days. An alternative regimen may include atovaquone (Mepron) and azithromycin (Zithromax) for 7 to 10 days. Notify the healthcare provider immediately if the patient experiences adverse reactions to quinine: hearing loss, tinnitus, stomach upset, diarrhea, or dizziness.

Doxycycline isn't effective for babesiosis. If a patient has concurrent Lyme disease and babesiosis, he'll require doxycycline as well as clindamycin and quinine or atovaquone and azithromycin.

Patient education

Teach your patient to guard against possible infection when hiking or camping in wooded areas by:

* applying insect repellant that contains DEET and reapplying it every few hours (use DEET with caution on children)

* tucking pant legs into socks and wearing light-colored clothing (ticks are attracted to dark colors)

* performing a visual body check after being in wooded areas. Adults should check children for ticks, especially in hair and skin folds.

If you see a tick embedded in your patient's skin, put on gloves and grasp it as close as possible to the insertion site with tweezers. Pull straight up to extract the tick. Don't twist, crush, or squeeze the tick as you remove it, as this may cause the tick to regurgitate or leave parts of the tick in the skin. Carefully examine the tick to ensure that all of the tick has been removed. Thoroughly cleanse the site with soap and water.

Teach your patient how to remove a tick properly and to avoid home remedies, such as touching the tick with a hot match or applying petroleum jelly, toothpaste, or vegetable oil. These don't work and may stimulate the tick to release more infectious fluid into the skin.

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