Babesiosis is mostly caused by a microscopic parasite, Babesia microti. The main way people get babesiosis is through the bite of an infected Black-legged (“deer”) tick (Ixodes scapularis). Although very rare, it is possible for the bacteria to be transmitted through a blood transfusion or from an infected mother to her baby during pregnancy or delivery. Many people who are infected experience no symptoms. When people do get sick from the infection treatment is available; however if it is delayed, or there are underlying medical conditions, symptoms can become more severe. The best way to prevent babesiosis is to prevent tick bites.
Information for Clinicians
Clinical Guidance (CDC)
Directory of Clinical Testing Services provided by the State Public Health Laboratory
State Public Health Laboratory Contacts – for additional information
Tick-borne Diseases of the United States – a Reference Manual for Healthcare Providers
Connecticut Babesiosis Surveillance
The Connecticut Department of Public Health (DPH) added babesiosis to the list of state-wide reportable diseases in 1990. The Centers for Disease Control and Prevention established a surveillance case definition in 2011. Since 2011, an average of 216 cases (range 52 to 311) have been reported to the DPH annually. Babesiosis is the second most commonly reported tick-borne disease in Connecticut. Due to the delay in follow-up, current case counts do not represent all cases of babesiosis.
This page last updated 11/2/2022.