Bureau of Communicable Disease

Babesiosis

What is babesiosis?

Babesiosis is a rare, sometimes severe or fatal tick-borne disease caused by Babesia microti, a parasite that infects red blood cells. Babesiosis occurs most frequently in elderly or immunocompromised individuals. In 2007, there were 25 cases reported among New York City residents (rate of 3 cases per 1,000,000 persons).

Who gets babesiosis?

Anyone can get babesiosis. Cases of this disease have been reported throughout the year, but peak in late spring or early summer.

How is babesiosis spread?

Babesia is transmitted by the bite of an infected blacklegged tick, Ixodes scapularis. Larval and nymphal ticks become infected by feeding on infected mice or meadow voles. The nymph and adult stages of this tick may feed on humans. Transmission occurs rarely through blood transfusion.

When and where does transmission of babesiosis occur?

The blacklegged tick is only rarely found in New York City, however it is present in nearly all areas surrounding the City. Highly endemic areas for Babesia microti in the greater New York City region include Suffolk County (especially Fire Island and Shelter Island), portions of Connecticut and New Jersey, and Nantucket Island off the Massachusetts shore. Transmission risk is greatest during the spring and summer, when nymphal ticks are in greatest abundance. Adult ticks occasionally feed on humans, so infection can occur in fall and winter when adult Ixodes ticks are abundant.

What are the symptoms of babesiosis?

The disease can cause fever, fatigue, jaundice, and anemia lasting from several days to several months. Many infections can occur without producing symptoms.

How soon after infection do symptoms appear?

Clinical illness usually occurs 1-4 weeks after infection. Rarely, it may take up to 12 months for symptoms to appear.

Does past infection with babesiosis make a person immune?

It is not known whether past infection with babesiosis can make a person immune.

How is babesiosis diagnosed?

The diagnosis is made by microscopic examination for the parasite on a blood smear, or by blood tests for antibody to the parasite.

What is the treatment for babesiosis?

Most people have mild illnesses, and recover without specific treatment. Combination therapy is usually recommended, typically with clindamycin and quinine or azithromycin and quinine or atovaqoune.

How can babesiosis be prevented?

When in tick infested areas (i.e., tall grass, overgrown brush, etc.), special precautions should be taken. Wear light-colored clothing, tuck pant legs into socks, and wear closed toe shoes. Use commercial insect repellent with no more than 20% - 30% DEET. Use repellents sparingly and with care, as they may cause side effects, especially in young children. Avoid application to damaged skin. Check for ticks every two to three hours and upon returning from outdoors on yourself, your children and your pets. Look for ticks in all joint areas, the navel, behind ears, in the hairline, and in other skin folds. Wash all skin treated with insect repellent thoroughly. Keep your lawn mowed, cut overgrown brush, and remove leaf litter to reduce tick populations.

For more information about preventing tick bites, see How to Prevent Tick Bites Brochure
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For more information on insect repellent safety see Insect Repellent Use and Safety

How should a tick be removed?

• Remove attached ticks as soon as possible.
• Use tweezers to grasp the tick as close to the skin surface as possible.
• Pull up on the tick with slow, even pressure to gradually ease out the mouth parts.
• If tweezers are not available, use fingers shielded with tissue paper or rubber gloves.
• Do not handle ticks with bare hands.
• Do not use petroleum jelly, nail polish remover, or heat to remove the tick, since these methods may increase the risk of infection with a tick-borne disease.
• Do not squash or squeeze the tick during removal.
• Wash the area of the tick bite and your hands with soap and water after the tick is removed.
• When outdoors, in tick-infested areas, check every 2 to 3 hours for ticks attached to clothing or skin.

Last Updated June 2007