Drugs and Antibiotics Used for Babesiosis

Facts About Babesiosis

Babesiosis is a disease caused by a parasite, Babesia spp., that is spread via the bite of infected ticks. Similar to Plasmodium, which causes malaria, the Babesia parasite invades red blood cells and causes hemolytic anemia and high fevers. Ticks carrying the Babesia parasite are endemic to southern New England, and most cases in North America originate in this region. The disease affects other animals, including livestock, as well as humans.

Symptoms of babesiosis are sometimes negligible to mild and require no treatment, but some patients experience severe or even life-threatening symptoms. Those at highest risk for the more severe course of the disease are people whose spleens have been surgically removed, people with suppressed immune systems, and the extremely young or extremely old. For these patients, treatment for babesiosis may be a matter of life and death.

Drugs and Antibiotics Used for Babesiosis

The standard treatment for babesiosis in humans has long been a combination of quinine and the antibiotic clindamycin. The drugs are given orally three times a day at dosages of 650 mg and 600 mg, respectively, for a period of 7-10 days. This treatment is not well-tolerated by many patients, as the bitter quinine often causes vomiting. Quinine is also associated with side effects involving the sense of hearing, including tinnitus (ringing in the ears) and temporary hearing loss.

Clindamycin is a lincosamide antibiotic used for treating anaerobic bacteria and single-celled parasites, including Babesia. Although it is effective by itself against these parasites, it acts slowly; for this reason, it is paired with the alkaloid quinine.

Advances in the treatment of malaria revealed a different combination of drugs that have been shown to be effective for babesiosis as well: atovaquone and azithromycin. Atovaquone is an antifungal and antiparasitic drug, and azithromycin is a common macrolide antibiotic.

Which is Better?

A small, multicenter study compared these two combinations of drugs and antibiotics used for babesiosis. After three months, slightly more patients receiving quinine and clindamycin had symptoms disappear than patients receiving atovaquone and azithromycin, but the difference was within the margin of error. The side effect profiles of the two regimens were strikingly different. Under atovaquone and azithromycin treatment, the most common side effects were diarrhea and a mild skin rash, each in 8% of patients. Under quinine and clindamycin treatment, side effects were much more alarming, as well as more common: tinnitus or ringing in the ears (39%), diarrhea (33%), and reduced hearing (28%).

The Centers for Disease Control and Prevention considers either of these courses of treatment to be appropriate for most cases, but considers quinine and clindamycin to be the standard of care for patients with life-threatening cases of babesiosis.

References

• CDC website (cdc.gov).

• Krause, P.J., et al. “Atovaquone and azithromycin for the treatment of babesiosis.” New Engl J Med 2000 Nov 16;343(20):1454-8.

• <em>Babesia</em> life cycle image: PNG version of public-domain SVG image by “LadyofHats,” Wikimedia Commons.