Last Reviewed: July 2017

What is babesiosis?

Babesiosis is a rare, sometimes severe, disease caused by the bite of a tick infected with Babesia microti, a microscopic (tiny, not seen without a microscope) parasite that infects red blood cells. In New York State, the Babesia species that infects people is Babesia microti, which is spread by the bite of an infected blacklegged (or deer) tick. Babesiosis can affect people of any age.

Who gets babesiosis?

While anyone can get babesiosis, it can be more severe in the elderly, people who have had their spleen removed, and people who have weakened immune systems (for example, those who have cancer, HIV/AIDS, or a transplant). Cases of this disease in the U.S. have been primarily reported during spring, summer and fall, when ticks are active. Most cases occur in coastal areas in the Northeast and upper Midwest, particularly in parts of New England, New York State, New Jersey, Wisconsin, Minnesota and in some European countries. In the Northeast, babesiosis occurs in both inland and coastal areas including offshore islands, such as Nantucket and Martha's Vineyard, which are off Massachusetts, as well as Long Island and the Hudson Valley in New York State.

How is babesiosis spread?

Babesiosis is spread by the bite of an infected blacklegged (or deer) tick, Ixodes scapularis. It can also be spread by transfusion of contaminated blood and possibly from an infected mother to her baby during pregnancy or delivery. Babesiosis is not spread from person to person.

What are the signs and symptoms of babesiosis?

Many people who are infected with Babesia microti feel fine and do not have any symptoms. Some people develop nonspecific flu-like symptoms such as fever, chills, sweats, headache, body aches, loss of appetite, nausea (the feeling of sickness in the stomach), or fatigue. It can also lead to a special type of anemia called hemolytic anemia (a condition where red blood cells are destroyed) lasting from several days to several months. In severe cases, blood clots, organ failure, unstable blood pressure, and rarely death may occur. It may take from one to nine weeks, sometimes longer, after exposure for symptoms to appear. However, many people who are infected do not have any symptoms.

How is babesiosis diagnosed?

Symptoms and possible tick bite exposure may cause a health care provider to suspect babesiosis. It can usually be diagnosed by looking at a blood sample under the microscope to see if the parasites are present in red blood cells. To confirm a diagnosis, a blood test may be done by specialized laboratories.

What is the treatment for babesiosis?

While many people do not become sick enough with babesiosis to require treatment, there are effective drug therapies, usually either a combination of the drugs quinine and clindamycin or a combination of atovaquone and azithromycin. It is possible to become infected with babesiosis and Lyme disease at the same time, so be sure to talk with your health care provider and seek medical attention if you become sick after a tick bite.

What can be done to prevent babesiosis?

Steps can be taken to reduce the risk for babesiosis and other infections caused by tick bites. The best prevention is through awareness. Generally, ticks cannot jump or fly onto a person. They wait in vegetation and cling to animals and humans when they brush by. Domestic animals can carry ticks into areas where you live such as your house or garage, so brush off animals and look for ticks before they enter these areas. The best prevention is through awareness. Check after every two to three hours of outdoor activity for ticks on clothing or skin. A thorough check of body surfaces for attached ticks should be done at the end of the day. If removal of attached ticks occurs within 36 hours, the risk of tick-borne infection is minimal. For proper tick removal, please watch the video at Tick removal.

Insect repellents can be effective at reducing bites from ticks that can transmit disease. If you decide to use a repellent, use only what and how much you need for your situation. More information on repellents can be found at Environmental Protection Agency - insect-repellents.

In addition:

  • Be sure to follow label directions.
  • Try to reduce the use of repellents by dressing in long sleeves and pants tucked into socks or boots.
  • Children should not handle repellents without adult supervision. Adults should apply repellents to their own hands first and then gently spread on the child's exposed skin. Avoid applying directly to children's hands. After returning indoors, wash your child's treated skin and clothing with soap and water or give the child a bath.
  • Do not apply near eyes, nose or mouth and use sparingly around ears.
  • After returning indoors, wash treated skin with soap and water.

How should a tick be removed?

Grasp the mouthparts with tweezers as close as possible to the attachment (skin) site. Be careful not to squeeze, crush or puncture the body of the tick, which may contain infectious fluids. Pull firmly and steadily upward. After removing the tick, thoroughly disinfect the bite site and wash hands. The NYSDOH has created a video on proper tick removal (Proper Tick removal) and a printable card with steps on how to remove ticks (How to Remove a Tick Card). See or call a doctor if there are concerns about incomplete tick removal. Do not attempt to remove ticks by using petroleum jelly, lit cigarettes or other home remedies because these may actually increase the chance of contracting a tick-borne disease.

Actual size of a tick

tick #1 image