About Bartonella Infection
Bartonella are gram-negative bacteria that live inside cells, especially the cells lining blood vessels. More than 20 species are known, and 3 are established causes of human disease. Bartonella henselae causes cat scratch disease and spreads when a cat infected by fleas scratches or bites a person. Bartonella quintana causes trench fever and spreads through the feces of human body lice. Bartonella bacilliformis causes Carrion's disease, spread by sand flies in parts of Peru, Ecuador and Colombia, where it can cause a life-threatening fever and anemia followed by wart-like skin growths. Rarely, Bartonella has spread through organ transplants.
Whether ticks spread Bartonella is a real scientific disagreement, and it helps to know who says what. On one side, the CDC's position, updated in March 2026, is that there is no evidence Bartonella spreads to people through tick bites, and a 2010 review by Telford and Wormser, along with a 2014 review by Lantos and Wormser, concluded the case for tick transmission is unproven. On the other side, a growing body of peer-reviewed work points the other way: Bartonella henselae DNA has been found in blacklegged ticks across the eastern United States and in Ixodes ticks in Europe, a 2008 study by Cotté and colleagues showed Ixodes ricinus ticks passing live Bartonella henselae to blood meals in the laboratory, and a 2011 study by Reis and colleagues showed ticks transmitting Bartonella birtlesii to mice. Angelakis and Breitschwerdt, writing in the CDC's own journal Emerging Infectious Diseases in 2010, argued that transmission to people by ticks is plausible. Columbia University's Lyme and Tick-Borne Diseases Research Center describes the evidence for tick transmission as circumstantial but fairly strong, and the Johns Hopkins Lyme Disease Research Center lists Bartonella among the coinfections it considers in patients with Lyme disease. Physicians who follow ILADS guidelines generally treat tick transmission as likely. A fair summary is that ticks can carry Bartonella and can pass it to animals in the lab, that transmission to a person through a tick bite has not been directly documented, and that absence of proof is not proof of absence. In LymeDisease.org's 2014 survey of 3,090 people with chronic Lyme symptoms, 28% reported a Bartonella coinfection; those figures were self-reported and the sample was self-selected, so they describe the patient experience rather than measured rates.
Most cat scratch disease clears on its own within a few weeks to months. The serious forms are different: Bartonella can infect heart valves (endocarditis), which is one of the leading causes of endocarditis with negative blood cultures and needs prolonged antibiotics and sometimes valve surgery. It can also cause bacillary angiomatosis and peliosis hepatis in people with weakened immunity, and neuroretinitis (swelling of the optic nerve and retina) or encephalopathy in a small share of cat scratch cases.
Diagnosis usually combines the history (cat or kitten contact, lice, travel to the Andes) with antibody tests and, for severe or unusual cases, PCR on blood or tissue. Antibody tests can be negative early in infection and cannot always tell species apart. Specialized enrichment cultures sold by a few commercial labs can increase detection, but their results have not been validated in large independent studies. Treatment depends on the form: azithromycin for typical cat scratch disease when treatment is used at all, doxycycline plus gentamicin or rifampin for trench fever and endocarditis, and chloramphenicol or ciprofloxacin regimens for Carrion's disease. Reports of prolonged antibiotic combinations for suspected chronic Bartonella rest on case series rather than randomized trials, and claims that gene variants such as MTHFR affect treatment reactions have no supporting clinical evidence.
Common Symptoms of Bartonella Infection
Recognizing the signs of Bartonella Infection early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.
- Prolonged low-grade fever and fatigue
- Swollen, tender lymph nodes, usually near a cat scratch or bite
- Bone pain and joint inflammation
- Skin lesions including bacillary angiomatosis in immunocompromised patients
- Neurological symptoms including headaches, cognitive difficulty, and encephalopathy
- Heart valve inflammation (endocarditis) in severe cases
Who Bartonella Infection Affects
Can affect people of any age. Cat scratch disease is most common in children and in people who handle kittens or cats with fleas. People with weakened immune systems, including organ transplant recipients and people with HIV, are at highest risk for severe forms such as bacillary angiomatosis (blood vessel growths in the skin and organs) and peliosis hepatis (blood-filled spaces in the liver). Bartonella quintana mainly affects people with body lice, including people experiencing homelessness. Bartonella bacilliformis affects people living in or visiting the Andes mountains of South America.
Some patient surveys of people treated for chronic Lyme disease report Bartonella as a coinfection, but these are self-reported and often rest on tests that are not standardized, so the true rate is unknown.
Find Your Next Step
FDA-Approved Treatments for Bartonella Infection
There are currently 4 FDA-approved medications for Bartonella Infection. These therapies represent the current standard of care and may be used alongside or compared against investigational treatments in active clinical trials.
Source: openFDA drug labeling data. This list may not include all treatments. Always consult your doctor.
Help Paying for Bartonella Infection Treatment
Charity funds and drugmaker programs for Bartonella Infection, checked at the source.
- Zithromax (Azithromycin) · Generic from many makers
- Rifadin (Rifampin) · Generic from many makers
- Vibramycin (Doxycycline) · Generic from many makers
Side Effect Explorer
Real-world side effect reports from the FDA Adverse Event Reporting System (FAERS). Includes both FDA-approved drugs and investigational therapies from active clinical trials. Click any drug to see what patients reported.
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Diagnosis and Testing
Bacterial infection (Bartonella henselae, B. quintana or B. bacilliformis); diagnosed by antibody tests or PCR, not genetics.
Trusted Bartonella Infection Resources
Reputable organizations and medical references for learning more about Bartonella Infection, including disease registries, foundation resources, and clinical guidelines.
- CDC - About Bartonella (reviewed March 23, 2026)
- CDC - Clinical Overview of Bartonellosis
- CDC Emerging Infectious Diseases - Cat-Scratch Disease in the United States, 2005-2013 (Nelson et al., 2016)
- CDC Emerging Infectious Diseases - Bartonella spp. transmission by ticks not established (2010)
- Lantos PM, Wormser GP (2014) - Chronic coinfections in patients diagnosed with chronic Lyme disease: a systematic review - American Journal of Medicine
- Cotté V et al. (2008) - Transmission of Bartonella henselae by Ixodes ricinus - Emerging Infectious Diseases
- Reis C et al. (2011) - Vector competence of the tick Ixodes ricinus for transmission of Bartonella birtlesii - PLoS Neglected Tropical Diseases
- Angelakis E, Breitschwerdt EB et al. (2010) - Potential for tick-borne bartonelloses - Emerging Infectious Diseases
- Columbia University Lyme and Tick-Borne Diseases Research Center - Bartonellosis
- Johns Hopkins Lyme Disease Research Center - Frequently asked questions (coinfections)
- Johnson L et al. (2014) - Severity of chronic Lyme disease compared to other chronic conditions: a quality of life survey - PeerJ
- ILADS - Evidence-based guidelines for the management of Lyme disease (2014)
- NORD - Bartonellosis
- Orphanet - Bartonella bacilliformis Infection
- NC State - $4.8 Million Awarded to Develop Treatment for Bartonella-Related Disease