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What is babesiosis?

Babesiosis is a rare, sometimes severe, disease caused by a parasite that infects red blood cells. 

How does babesiosis spread?

Babesiosis is usually passed to humans through the bite of a tiny infected tick (in Massachusetts, by deer ticks). The highest risk of disease occurs between late May and September, when ticks are most active. The tick must be attached and feeding for about 36-48 hours before it can pass the germ to a person.

Who gets babesiosis?

Although anyone can get babesiosis, people who spend time outdoors are at an increased risk of exposure.  Ticks infected with babesiosis can be found more often in coastal areas, such as Nantucket, Martha's Vineyard and Cape Cod.  The illness can also be passed through a transfusion of contaminated blood or from a pregnant woman to her child, but these are very rare.    

What are the symptoms of babesiosis?

Most people who are infected by the parasite will show very mild signs of illness or no signs at all. In people who do become ill, the symptoms of babesiosis can range from mild to severe and can last for several days or weeks.  Signs and symptoms include fever, chills, headache, nausea, vomiting, abdominal pain, tiredness, muscle and joint aches, dark urine, and anemia (a low red blood cell count).  The disease can be especially serious in persons who are elderly, who do not have a healthy spleen, who have a weakened immune system, or who have other health problems. It is possible to get babesiosis and other diseases spread by ticks (like Lyme disease) at the same time from a single tick bite.

How soon do symptoms appear?

Symptoms usually start within 1 to 6 weeks after the tick bite.

Can a person get babesiosis more than once?

It is not known if a person who has had past infection with babesiosis can get it again.

What is the treatment for babesiosis?

While many people do not become sick enough with babesiosis to require treatment, there are medications that are effective in treating the illness.  

What can be done to prevent babesiosis?

To prevent babesiosis and other infections spread by ticks, the best protection is to avoid contact with ticks.  When working or playing outside in areas where ticks can be found (especially tall grass, weeds, woods and leaves) you should:

  • Wear light colored clothing (to spot the ticks easily), long sleeved shirts and long pants.
  • Create a "tick barrier" by tucking pants into socks and shirt into pants.
  • Consider using insect repellents, such as 20 to 30% concentrations of DEET or 0.5% permethrin when planning to be outdoors.  If such products are used, follow the manufacturer's directions on the label. After returning indoors wash treated skin with soap and warm water.
  • There are other insect repellents approved by the EPA for ticks. For more information, visit:
  • Check clothing and skin very carefully (especially thighs, groin, arms, underarms, legs and scalp) after being outdoors in tick infected areas.  If ticks are found, remove them promptly using a fine point tweezers.  To remove the tick, grasp the tick as close to the skin as possible and pull the tick straight out with steady pressure.  Once removed, disinfect the area with rubbing alcohol.  
  • Talk with your veterinarian about the best way to protect your pet against ticks. 

Click here to learn more about tick borne diseases.

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