Marin/Sonoma Mosquito & Vector Control District
800-231-3236 (toll free)
707-285-2200 (office)
595 Helman Lane, Cotati, CA 94931-9736

PHONE
800-231-3236 (toll free)
707-285-2200 (office)
707-285-2210 (fax)

ADDRESS
595 Helman Lane
Cotati, California
94931-9736

HOURS
Monday through Friday
7:00AM to 3:30PM

5. BABESIOSIS (PIROPLASMOSIS)

Babesias are malaria-like protozoans that live and reproduce inside red blood cells and organs of the circulatory system. Most occur in wild and domestic mammals like opossums, deer, rodents, bats, cattle, sheep, or dogs. Intermediate hosts are ticks, often belonging to the genus Ixodes. Except for the Babesias of veterinary importance, vectors in California are largely unknown, although Ixodes pacificus is a frequent suspect.

Humans become infected with Babesia when they accidently intrude into a natural disease cycle. In the eastern and midwestern U.S., these cases often turn out to be caused by Babesia microti of rodents. A recent case from California's Monterey county was thought to be caused by B. gibsoni, a parasite normally seen in coyotes and dogs.

Human infections in the United States tend to be mild and self limiting, and most probably are never diagnosed. Flu-like symptoms start two to four weeks after a tick bite, and can include sweating, fever and chills, headache, fatigue, muscle pains and weight loss. They usually only become severe in persons with a weakened immune system, or whose spleen has been damaged or removed. The spleen is responsible for clearing out damaged blood cells, so when it is missing these infections can progress out of control.

A Babesia temporarily called WA1 (for Washington case 1; see photo above) has recently been found in half a dozen people in northern California and Washington. In 1993, a 36 year old Sonoma County man died of flulike symptoms associated with babesiosis a month after being bitten by a tick in the Alexander Valley area. His spleen had been removed following an accident some time before.

In 1994, laboratory tests were done on 219 residents in a rural area of Sonoma County where large numbers of ticks had been collected. Nineteen (9%) carried antibodies against Babesia WA1, showing that they had a current or past infection. Marin/Sonoma district personnel are helping in a follow-up study on the WA1 parasite, currently underway at the University of California at Davis.

Helpful references:

Babesiosis in California. by A. F. Jerant and A. D. Arline. Western Journal of Medicine. Volume 158(6):622-25 (1993);   Bug Vectors: Ticks and Human Babesiosis. by J. Goddard. Infections in Medicine. Volume 16(5):319-320, 326 (1999)