Babesiosis

These parasites infect and destroy red blood cells. In the US, the most common one is Babesia microti. Most people get it from the bite of an infected blacklegged tick (Ixodes scapularis). This is the same tick that spreads Lyme disease and anaplasmosis. Less often, it can spread through a contaminated blood transfusion. It can also pass from a pregnant person to their baby during pregnancy or birth. The Lone Star tick (this site's main species) is not a known carrier.

• Often none (many infected people never get symptoms)
• Fever, chills, and sweats
• Headache, body aches, and tiredness
• Loss of appetite and nausea
• Anemia from the parasite destroying red blood cells (hemolytic anemia). In more serious cases this can cause weakness, dizziness, dark urine, or yellow skin or eyes

When symptoms appear, they usually start within a few weeks to a couple of months of exposure, often about 1 to 4 weeks after a tick bite. They can start around a week after infection. They may first appear or come back months later, most often in people with weakened immune systems (CDC).

A doctor diagnoses babesiosis using your symptoms, exposure history, and lab tests. The main test is a manual (not machine) microscope check of a blood smear. It looks for parasites inside red blood cells. Molecular tests (such as PCR) and antibody tests can add supporting evidence. A doctor decides on testing and reads the results. You cannot diagnose it yourself.

People with no symptoms often need no treatment. When treatment is needed, CDC guidance describes a typical course of atovaquone plus azithromycin. Another option is clindamycin plus quinine. A course is about 7 to 10 days in otherwise healthy people. Severe cases, such as very high parasite levels or severe anemia, may need longer treatment, a hospital stay, or an exchange transfusion. Drug choices and doses are decisions for a licensed doctor. This includes special care during pregnancy and for people with weakened immune systems.

There is no vaccine, so preventing tick bites is the best protection. Use an EPA-registered repellent and permethrin-treated clothing. Stay toward the center of trails, away from leaf litter and brush. Check your whole body for ticks after being outdoors. Remove any attached tick right away with fine-tipped tweezers. CDC notes that blacklegged tick nymphs usually must stay attached more than 36 to 48 hours to pass on the parasite. So removing ticks quickly lowers the risk.

Most US cases occur in the Northeast and upper Midwest, matching the blacklegged tick's range. Cases cluster in the warmer months, when young (nymph) ticks are most active. Because the same tick spreads them, it is often found in the same places as Lyme disease and anaplasmosis.