While Lyme is the most prevalent tick-borne disease, ticks can also transmit “co-infections.” A single tick bite can transmit a variety of other harmful illnesses because ticks can carry a variety of bacteria, parasites, and viruses. This resource is designed to educate patients and caretakers about co-infections and typical treatments, utilizing treatment guidelines, published research, and expert opinions. This resource should not be misconstrued as medical advice.
Babesia/Babesiosis
Babesiosis is caused by Babesia, a malaria-like parasite that infects red blood cells, often transmitted by blacklegged tick bites, congenitally, or via blood transfusion. Approximately 40% of people infected with Lyme disease may also be infected with Babesia. Symptoms resemble Lyme disease but frequently include fevers, chills, drenching sweats especially at night, fatigue, anemia, headache, muscle aches, depression, and "air hunger" (shortness of breath). It can be severe or persistent in immunocompromised individuals, the elderly, or those without a spleen, sometimes leading to relapses. But actual incidents of the infection are likely underreported. The severity of Babesia symptoms varies from person to person.
Several species of Babesia affect human health, but the most prevalent in the United States are Babesia microti, Babesia duncani (WA-1), and Babesia divergens. To test for Babesia, we recommend using the CLIA-certified laboratory IGeneX. Additionally, we advise patients to work with a Lyme disease specialist who has advanced training and expertise in diagnosing and treating Lyme and coinfections.
Antibiotic regimens for Lyme disease will not also cover a Babesia infection. Babesiosis is commonly treated using a combination of antiparasitic/antimalarial medications such as Mepron (atovaquone) or Malarone (atovaquone/proguanil) plus antibiotics. Relapses can happen following the completion of treatment, and patients will need to receive additional treatment for the infection. Herbal remedies such as Japanese knotweed, Artemisinin, Cryptolepis, and Chinese skullcap, can also be useful tools in supporting your recovery efforts. Patients are also finding success with another antimalarial drug Tafenoquine (Arakoda) and Methylene blue has seen success in treating Babesia and other co-infections but require G6PD testing because both can cause severe hemolytic anemia in G6PD-deficient individuals.
Bartonella/Bartonellosis
Bartonella bacteria live primarily inside blood vessel linings and red blood cells, multiplying and evading immune detection. Currently, there are 15 known species of Bartonella that cause infections in humans, but that number might be much higher. Cat scratch fever (Bartonella henselae), often transmitted from the lick, scratch, or bite of an infected cat, is the most well-known Bartonella infection. Because most laboratories only test for two species (Bartonella henselae and Bartonella quintana), many Bartonella cases will go undetected. Bartonella species have been detected in numerous types of ticks, but transmission has yet to be definitively proven.
Symptoms vary widely but often include fever, migrating joint/muscle pain, severe headaches, neurological issues such as seizures or neuropathy, streaked stretch mark-like rashes, swollen lymph nodes, and psychiatric symptoms. It can become life-threatening in immunocompromised people, with relapses possible as bacteria cycle in and out of cells.
To test for Bartonella, we recommend using the CLIA-certified laboratories Galaxy Diagnostics, IGeneX, or T-Labs. We also advise patients to work with a Lyme disease specialist who has advanced training and expertise in diagnosing and treating Lyme and coinfections.
Bartonella infection is commonly treated using a regimen of antibiotics such as doxycycline, azithromycin, Bactrim/Septra, or rifampin. However, it can remain a chronic, low-grade infection in the body. Herbal remedies such as Japanese knotweed, Black Walnut, and Cryptolepis, can also be useful tools in supporting your recovery efforts. Even after a person has received a course of treatment, relapses can happen, and re-treatment may be necessary.
Ehrlichia/Ehrlichiosis
Ehrlichiosis is caused by Ehrlichia bacteria (primarily Ehrlichia chaffeensis) that infect white blood cells, transmitted mainly by Lone Star ticks, with rare cases via transfusion or congenitally. Symptoms onset 1-2 weeks post-bite include fever, headache, fatigue, muscle aches, and sometimes rash; it progresses rapidly and can be life-threatening if untreated. It overlaps with anaplasmosis and RMSF as rickettsial infections, often requiring prompt antibiotic treatment like doxycycline. According to canine surveillance data, Florida is considered a high risk state for Ehrlichia. The testing and diagnosis of tick-borne diseases such as Ehrlichia can pose a challenge because the available testing is limited to two species of bacteria, but several other species can infect humans. The presence of morulae, mulberry-shaped masses, can be seen on the blood smears of some patients.
Anaplasma/Anaplasmosis
Anaplasmosis (human granulocytic anaplasmosis) is caused by Anaplasma phagocytophilum infecting white blood cells, primarily transmitted by blacklegged ticks. Symptoms appear 1-2 weeks after bite with fever, headache, muscle aches, chills, and fatigue, similar to ehrlichiosis but generally milder rash. It can be severe in elderly or immunocompromised patients and is treated with doxycycline, with underreporting common due to overlapping Lyme symptoms. According to canine surveillance data, Florida is considered a high risk state for Anaplasma.
Rocky Mountain spotted fever (RMSF)
Rocky Mountain spotted fever (RMSF) is a serious and potentially deadly bacterial disease caused by Rickettsia rickettsii and spread through the bite of infected ticks. In the United States, the primary tick vectors are the American dog tick (Dermacentor variabilis) in the eastern and central regions, the Rocky Mountain wood tick (Dermacentor andersoni) in the western states, and the brown dog tick (Rhipicephalus sanguineus) in certain southwestern areas and along the United States-Mexico border. The lone star tick (Amblyomma americanum) is now also recognized as a competent vector of RMSF primarily in the south and east coast of the United States.
Symptoms typically begin 3–12 days after an infected tick bite with sudden onset of fever, severe headache, muscle pain, and sometimes nausea or abdominal pain. A characteristic rash usually appears 2–4 days after fever starts, often beginning as small, flat red spots that may develop into pinpoint petechiae, commonly involving the wrists, ankles, palms, and soles. Other common symptoms include fatigue, chills, and body aches, though not all patients develop a rash.
RMSF is the most severe tickborne rickettsial illness in the U.S. and progresses rapidly, potentially causing life-threatening complications like vascular damage, organ failure, amputation, or death if not treated promptly. The recommended treatment is doxycycline, which is the antibiotic of choice for patients of all ages, including children, and should be started immediately upon suspicion without waiting for confirmatory tests. Early treatment with doxycycline within the first 5 days of illness can prevent severe outcomes and death, while use of other antibiotics increases the risk of fatal complications.
Borrelia Miyamotoi
B. miyamotoi is an emerging tickborne illness transmitted to humans through the bites of infected blacklegged ticks (Ixodes scapularis in the eastern and midwestern United States) and western blacklegged ticks (Ixodes pacificus on the Pacific Coast). Researchers first discovered B. miyamotoi in Japan in 1995, but it wasn’t found in the United States until 2013. Many of its symptoms overlap with Lyme, but a key differentiator is that it’s rarely associated with a rash. Ticks may pass B. miyamotoi to their offspring, so the infection can be found in tick larva, the early stage of a tick’s life cycle after it hatches from an egg.
Symptoms typically appear around 2 weeks after a tick bite, though the incubation period can range from 3 days to 6 weeks; common symptoms include high fever (often the primary sign), chills or shakes, severe headache, fatigue, muscle and joint aches, arthralgia, and sometimes nausea or vomiting. Relapsing fever episodes have been documented in approximately 10–28% of cases, with recurring fevers possible if untreated. Antibiotic treatment, most commonly doxycycline, often leads to symptom improvement.
Borrelia Mayonii
B. mayonii is a recently discovered Borrelia species (2013, Mayo Clinic) causing Lyme-like disease, transmitted by blacklegged ticks in the Upper Midwest. It presents with fever, headache, muscle/joint pain, diffuse rashes (often larger than Lyme rash), nausea/vomiting, and higher spirochetal bacterial blood concentrations than B. burgdorferi. Symptoms may include more gastrointestinal involvement and widespread rashes, treatable with similar Lyme antibiotics.
Colorado Tick Fever
Colorado tick fever (CTF) is a viral infection transmitted by Rocky Mountain wood ticks, primarily in western U.S. high-elevation areas. Several hundred cases of the disease are reported annually throughout the United States and Canada, but actual cases may be misdiagnosed or undiagnosed, according to the National Organization of Rare Diseases. Some people will experience a “biphasic” fever, where it lasts for several days, abates for several days, and returns a second time for a shorter duration. Symptoms include sudden fever, chills, severe headache, muscle/joint pain, fatigue, nausea/vomiting, and sometimes rash or enlarged spleen. It often has a biphasic pattern with relapsing fever and resolves on its own but can cause complications like meningitis.
Heartland Virus
Heartland virus disease is a potentially serious emerging illness caused by a phlebovirus (Heartland bandavirus) transmitted primarily by the bite of an infected lone star tick (Amblyomma americanum). First identified in Missouri in 2009, cases have now been reported across the central, eastern, and southern United States, with over 70 confirmed or probable cases documented by CDC as of 2025. Symptoms usually begin 1–2 weeks after a tick bite and include fever, fatigue, headache, muscle or joint pain, loss of appetite, nausea, diarrhea, and low white blood cell and platelet counts; many patients require hospitalization. No specific antiviral treatment exists, and care is supportive; while most people recover, severe cases and fatalities (about 5–10%) have occurred, especially in older adults or those with weakened immune systems. Prevention relies entirely on avoiding lone star tick bites through the use of repellents, permethrin-treated clothing, tick checks, and showering after being outdoors.
Powassan Virus
Powassan virus is a rare but serious tickborne flavivirus that can cause severe neurologic disease, including encephalitis and meningitis. It is transmitted to humans primarily by the blacklegged tick (Ixodes scapularis) in the Northeast and Great Lakes regions and by the groundhog tick (Ixodes cookei) in some areas; unlike most other tickborne pathogens, Powassan virus can be transmitted in as little as 15 minutes of tick attachment. Symptoms include fever, headache, vomiting, weakness, confusion, seizures, and memory loss; approximately 10–15% of symptomatic cases are fatal, and about half of survivors have permanent neurological damage such as paralysis, headaches, or memory problems.
Q Fever
Q fever is caused by Coxiella burnetii, a bacterium that can be transmitted to humans through the bite of infected ticks, including the lone star tick (Amblyomma americanum), American dog tick (Dermacentor variabilis), and Rocky Mountain wood tick (Dermacentor andersoni). Acute symptoms can be mild or severe; symptoms typically appear 2–3 weeks after exposure and include high fever, severe headache, profound fatigue, muscle aches, chills, sweats, nausea, vomiting, and sometimes non-productive cough, chest pain, or pneumonia. Chronic Q fever, though rare, can develop months to years later, most commonly as endocarditis. The CDC recommends doxycycline as the treatment of choice for acute Q fever in adults and children of all ages; treatment should be started early and continued for at least 14–21 days, with longer courses or combination therapy (doxycycline plus hydroxychloroquine) required for chronic cases.
Southern Tick-Associated Rash Illness
Southern Tick-Associated Rash Illness (STARI) is a Lyme-like condition transmitted by lone star ticks, possibly involving Borrelia lonestari. It features a bull's-eye rash similar to Lyme, with early symptoms similar to Lyme disease such as fatigue, fever, headache, and muscle pain. The exact cause is unknown, there are no reliable lab tests, and no recommended treatments. STARI is generally presumed to be milder than Lyme but there is no credible research to support this presumption.
Tularemia
Tularemia (also known as rabbit fever or deer fly fever) is a potentially serious bacterial disease caused by Francisella tularensis that can be transmitted to humans through the bite of infected ticks—primarily the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni), and the lone star tick (Amblyomma americanum), as well as through handling infected animals, inhaling contaminated dust, or drinking contaminated water. Symptoms usually appear 3–5 days after exposure (range 1–14 days) and vary by form of the disease. The most common presentation is ulceroglandular tularemia, which presents with a skin ulcer at the bite site, swollen and painful lymph nodes, fever, chills, headache, and exhaustion; other forms include glandular, oculoglandular, oropharyngeal, typhoidal, and pneumonic. According to the CDC, early treatment with antibiotics such as streptomycin (preferred) or gentamicin (alternative) is highly effective, and doxycycline or ciprofloxacin may be used for milder cases or post-exposure prophylaxis; treatment should be started as soon as tularemia is suspected because delays can lead to severe illness or death.
Brucella/Brucellosis
Brucellosis is a zoonotic bacterial infection caused by Brucella species (most commonly B. melitensis, B. abortus, B. suis, and B. canis in the United States), primarily transmitted to humans through consumption of unpasteurized dairy products, undercooked meat, or direct contact with infected animals (such as cattle, goats, pigs, feral swine, or dogs) or their tissues/fluids. According to prominent Lyme specialist Stephen E. Phillips, MD, Brucella has been isolated in ticks and is an underdiagnosed close bacterial cousin to Bartonella that can produce highly overlapping chronic symptoms and therefore it should be considered as part of the differential diagnosis for complex tick-borne illness cases. Symptoms are often nonspecific and include acute or chronic undulating fever, severe headache, profound fatigue, night sweats, muscle/joint pain, weight loss, and potential complications like arthritis, endocarditis, hepatosplenomegaly, or ocular, or neurologic issues. Treatment per CDC guidelines involves prolonged combination antibiotics—typically doxycycline plus rifampin (or streptomycin/gentamicin for severe cases) for at least 6 weeks—with early initiation critical to prevent chronic sequelae.
