Babesiosis: The Other Tick Disease You Should Know

Lyme disease isn’t the only tick-borne disease those of us in the Northeast and Midwest should worry about this summer. A recent report from the CDC found a significant increase in the Northeast of cases of babesiosis (ba-BEE-see-OH-sis), a disease caused by parasites transmitted by the blacklegged tick. The report also found evidence that the disease is becoming more entrenched, marching further north into areas not previously considered babesiosis territory.  

Santiago Sanchez-Vicente, PhD, an associate research scientist in the Center for Infection and Immunity at Columbia’s Mailman School of Public Health who studies tick-borne diseases such as babesiosis, says the report is not surprising since other tick-borne diseases are also on the rise. We spoke with Sanchez-Vicente to learn more about this emerging threat, including how it’s transmitted, how it’s diagnosed and treated, and what makes it different from other tick-borne diseases. 

Why are we hearing about babesiosis now? 

It's been endemic in parts of the Northeast and Midwest for almost 50 years, but it hasn’t been very common. The new report shows that babesiosis cases significantly increased in Northeastern states where the disease has been endemic. And case rates in three other states where the disease was not considered endemic (Maine, Vermont, and New Hampshire) are now similar to, or higher than, rates in the endemic states. 

Climate change is one of the main factors that has led to the geographic expansion of every tick species further north. The higher temperatures and milder winters prolong the life cycle of the tick, so they remain active year-round. The tick population is higher now than ever before. 

How do people get babesiosis? 

Babesiosis is transmitted by the blacklegged tick, the same tick that transmits Lyme disease. If you are bitten by a tick and develop symptoms of Lyme disease, you will also probably get tested for babesiosis. Any primary care doctor can order tests for this disease. 

Ten years ago, doctors probably were not aware of the high incidence of babesiosis or tick-borne diseases other than Lyme disease. 

Is babesiosis similar to Lyme disease? 

Babesiosis can resemble other tick-borne diseases in the early stages of infection though babesiosis doesn’t cause a rash. Some patients are asymptomatic; others have non-specific, flu-like symptoms such as fever and chills and muscle aches. In most healthy people, babesiosis symptoms resolve on their own.  

But the disease can be very severe in the elderly and people who are immunosuppressed, including those who have received an organ transplant, have had their spleen removed, or are HIV-positive.  

Babesiosis is caused by a parasite that infects red blood cells (Lyme disease is caused by a bacterial infection). When red blood cells carrying the parasite travel through the spleen, the organ detects the abnormal red blood cells and produces macrophages that attack them. But in people who do not have a spleen or who are immunocompromised, the body can’t muster the appropriate immune response. In these cases, the disease can be very severe, even fatal. In fact, babesiosis is fatal in between 2% and 9% of those who require hospitalization, whereas Lyme disease is not fatal. 

Is babesiosis diagnosed and treated the same way as Lyme disease? 

The bacteria that causes Lyme disease get cleared from the blood very quickly. It can take up to a month to develop antibodies that can be detected with blood tests, so doctors often make a diagnosis based on clinical symptoms such as the characteristic circular rash (erythema migrans) and by asking if the patient lives in an area where blacklegged ticks are endemic.  

Lyme disease is treated with the antibiotic doxycycline. Most people recover after treatment, but for unknown reasons, 10% to 20% of patients continue to experience fatigue, joint pain, and cognitive difficulties, a condition known as post-treatment Lyme disease syndrome.  

Babesiosis is also diagnosed with a blood test, though instead of antibodies the test looks for the parasite that causes babesiosis. The incubation period after being bitten by a tick is from one to six weeks. As with Lyme disease, a diagnosis of babesiosis should be considered based on clinical symptoms and asking if the patient comes from an area where the parasite is endemic. Asking whether a patient has been bitten by a tick is often not helpful because many people do not notice the tick bite. But a blood test isn’t always able to identify babesiosis in the early or chronic stages of infection, when blood levels of the parasite are low. If the blood test is negative, the doctor can perform a PCR test, which is more sensitive in patients with low levels of the parasite, or repeat the blood test a few weeks later if symptoms persist. 

Babesiosis is treated with a combination of the anti-parasitic drug atovaquone plus the antibiotic azithromycin. If the parasite load is very high, or if the infection doesn’t clear after initial treatment, doctors may treat the infection with clindamycin, another antibiotic, plus quinine, an antimalarial drug that has more severe side effects than the standard therapy. Most babesiosis patients recover completely after initial treatment without long-term complications. In severe cases, a red blood cell exchange transfusion may be needed to decrease the number of parasites in the blood. 

Is there a growing threat from other tick-borne diseases? 

Anaplasmosis, caused by bacteria also transmitted by the blacklegged tick, is increasing. As with babesiosis, the symptoms of anaplasmosis are very nonspecific and can be more severe in people who are immunocompromised, though the disease is not fatal. And the good thing is that if you get treated for Lyme disease, the same antibiotic will also treat anaplasmosis if you are co-infected.  

Another tick-borne disease that is on the rise is called ehrlichiosis. It’s similar to anaplasmosis but the bacteria responsible are transmitted by a different tick species known as the lone star tick. Forty years ago, there were no lone star ticks in the Northeast. Now it’s everywhere. It’s found as far north as Maine and Canada and is now the most abundant tick in Long Island. The blacklegged tick stays in the vegetation and will only attach itself to you if you pass through the bushes. But the lone star tick is very aggressive and will crawl onto you if you are nearby but not touching the vegetation.  

How can you protect yourself from tick-borne diseases? 

You can’t get scared. When you go outside in wooded areas or in your backyard if it is near a forested area with deer, remember to wear protective clothing, including long sleeves and pants, and use tick repellent, which is how I dress when going to an area that might contain ticks. If you are walking in the woods, you should be safe as long as you stay on the trails. Check yourself for ticks frequently and ask other people to check areas of the body you can’t see yourself. You have to have joy, right?