What is Babesia? A Closer Look at This Lyme Coinfection
By Kaleigh Schmidt
Did you know that ticks carry other illnesses in addition to Lyme disease? Ticks are capable of transmitting more than one infection, called coinfections, to their host. One example of a coinfection is a malaria-like parasite that may lead to a disease called Babesiosis.
What is Babesia?
Babesia is a microscopic parasite that infects red blood cells. It is primarily transmitted through the bite of an infected Ixodes scapularis tick, also known as the blacklegged tick or deer tick. In Illinois, at least three counties have blacklegged ticks that carry this malaria-like disease, according to the Illinois Department of Public Health (IDPH), but many counties have yet to be sampled. Although babesia isn’t as common throughout the United States as other tick-borne diseases, cases of Babesiosis throughout Illinois are on the rise.
There are more than 100 species of babesia, however, and humans can become a popular host for about five species of this pathogen. Babesia microti is the most common species to infect people. Currently, the counties where Babeisa microti has been found include Peoria, Carroll, Ogle and Lake. Peoria county poses the highest threat of black-legged ticks carrying babesia.
While Lyme disease is the most recognized tick-borne disease in Illinois, babesia can cause mild to life-threatening symptoms and should be taken seriously.
How is Babesia Transmitted?
It is important to recognize the many ways someone can contract babesia. The main way babesia is transmitted to humans is through the bite of an infected blacklegged tick. Ticks can be small and difficult to see (about the size of a poppy seed). Due to their minute size, some people who contract babesia may not recall seeing the tick or tick bite.
But tick bites are not the only form of transmission. IDPH states that babesia can also be spread by contaminated blood transfusions. Less commonly, it can be spread via maternal-fetal transmission during pregnancy or delivery.
Symptoms of Babesia
Unlike other tick-borne diseases, including Lyme disease, babesia can be more challenging to diagnose because it may not have a distinct set of characteristics. In fact, many people who become infected with babesia do not present with symptoms at all. However, when a person does develop symptoms, typically they will appear within a few weeks after initial infection. In certain people, babesia can lead to life-threatening risks and serious health complications.
If babesia is undiagnosed or left untreated, it can lead to ongoing symptoms, and in some cases, fatality. Babesia symptoms to look for are as follows:
Acute Symptoms
If symptoms appear, they typically begin within one to six weeks of becoming infected. Acute symptoms may include:
fever
chills
sweats
headache
body aches
loss of appetite
nausea
fatigue
Progressive Symptoms
The following symptoms may develop as babesia progresses:
drenching night sweats
muscle aches
chest pain
hip pain
shortness of breath (“air hunger”)
hemolytic anemia (red blood cells break down faster than your body can make them)
Babesia Prevention
Besides Lyme disease, it’s also important to be mindful of Babesiosis whenever you spend time outdoors. About one-fifth of patients with babesia may be coinfected with Lyme disease.
To reduce your risk of babesia, pay close attention to your surroundings. Wooded or brush areas are known to thrive with ticks.
Be sure to apply tick repellents such as:
DEET
picaridin
IR3535
oil of lemon eucalyptus (OLE)
para-menthane-diol (PMD)
2-undecanone
Additionally, perform tick checks, checking for ticks behind your knees, groin, underarms, and scalp, after being outside. After all, you can never be too careful!
To learn more about babesia, tick-borne disease, and tick bite prevention, red our tick prevention article.
Sources:
About Babesiosis. Centers for Disease Control and Prevention website.
https://www.cdc.gov/babesiosis/about/index.html
Babesiosis. Columbia University Irving Medical Center website.
https://www.columbia-lyme.org/babesiosis
Babesiosis. Illinois Department of Public Health website.
https://dph.illinois.gov/topics-services/diseases-and-conditions/tickborne-illnesses/babesiosis.html
Lyme Disease Co-Infection. National Institute of Allergy and Infectious Diseases website.
https://www.niaid.nih.gov/diseases-conditions/lyme-disease-co-infection
Preventing Babesiosis. Centers for Disease Control and Prevention website.
https://www.cdc.gov/babesiosis/prevention/index.html
Zimmer AJ, Simonsen KA. Babesiosis. Stats Pearl. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430715/
