Bartonellosis: The Uncommon Bug-Bite and Cat-Scratch Bacteria Infection That's Almost Always Treatable — and When It Turns Serious
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 13, 2026. This content is for educational purposes and is not medical advice.
Quick Answer
Bartonellosis is a group of illnesses caused by Bartonella bacteria, including cat scratch disease, Carrión's disease and trench fever. People catch it from cat scratches or bites, sand fly bites or body lice [1]. Symptoms include fever, painful lymph nodes and fatigue [1]. Most types are treated with antibiotics [1]. Go to the ER for chest pain, neck stiffness or confusion [1].
What the research says
Cat scratch disease is most common in young children and in the southern United States. An analysis of national insurance claims from 2005 to 2013 found the highest incidence in children aged 5 to 9 years (9.4 cases per 100,000 population) and in people living in the southern US (6.4 cases per 100,000). The authors estimated that about 12,000 outpatients are diagnosed and 500 inpatients are hospitalized for cat scratch disease each year, and noted that flea control for cats is a helpful prevention measure (Nelson et al., Emerg Infect Dis, 2016) [6].
Unusual, more serious forms are uncommon but carry a much higher hospitalization risk. Atypical manifestations develop in 5% to 20% of patients with cat scratch disease. In a claims analysis from 2005 to 2014, atypical cases made up 1.5% of all cat scratch disease cases and were linked to a higher risk of hospitalization (risk ratio 8.77, 95% CI 6.56 to 11.72), with eye (48.7%), liver and spleen (24.6%), and nervous system (13.8%) involvement the most common (Nawrocki et al., Emerg Infect Dis, 2020) [7].
Most cases clear up without antibiotics. A clinical review reports that most cases of cat scratch disease are self-limited and do not require antibiotic treatment, and that if an antibiotic is chosen, azithromycin was shown in one small study to speed recovery (Klotz et al., Am Fam Physician, 2011) [8].
What Is Bartonellosis?
Bartonellosis is a group of illnesses caused by types of Bartonella bacteria. The most common types include cat scratch disease (CSD), Carrión's disease, and trench fever [1].
Cat scratch disease (CSD) is a Bartonella henselae infection. It most commonly causes large, swollen lymph nodes and bumps or a rash. Carrión's disease is a Bartonella bacilliformis infection. The early stages (Oroya fever) can destroy your blood cells and lead to severe anemia. The later stage (verruga peruana) causes long-lasting bumps on your skin [1]. Trench fever is a Bartonella quintana infection. It causes flu-like symptoms [1]. Some complications can be serious.
Depending on the type, bartonellosis can cause mild symptoms or severe illness. You get infections from bug bites or cat scratches.
How do the three common types spread?
Each type of Bartonella bacteria spreads in different ways. B. bacilliformis spreads through sand fly bites and is only found in the Andes mountains, mostly in Peru [1]. You can get B. henselae from cat scratches or bites, especially from kittens — and cats get it from flea bites [1]. It's found worldwide. B. quintana spreads through body lice and most commonly spreads in crowded living conditions without access to proper hygiene. Trench fever is more common in warm climates, but there have been outbreaks in the U.S., too [1].
Type | Bacteria | How it spreads | Where it's found |
Cat scratch disease (CSD) | B. henselae | Cat scratches or bites, especially from kittens (cats get it from flea bites) | Worldwide |
Carrión's disease | B. bacilliformis | Sand fly bites | Only in the Andes mountains, mostly in Peru |
Trench fever | B. quintana | Body lice, mostly in crowded living conditions without proper hygiene | More common in warm climates; outbreaks have occurred in the U.S. |
Who's at higher risk?
B. henselae infections are most common in kids younger than 15 [1]. People experiencing homelessness or living in crowded conditions are at higher risk for B. quintana infections [1]. You're at higher risk for severe Bartonella infections if you have a compromised immune system (a body defense system that isn't working at full strength).
What Does Bartonellosis Feel Like?
What symptoms you have depend on the type of Bartonella you're infected with. Some symptoms could include fever (which might come and go in some infections); large, painful lymph nodes; fatigue; headache; muscle aches; abdominal pain; bone or joint pain; excessive sweating; an enlarged liver or spleen; and bumps, cysts or growths on or under your skin [1]. Skin growths may be red, purple or slightly darker than the skin around it.
Symptom | What it looks like |
Fever | Might come and go in some infections |
Large, painful lymph nodes | Swollen lumps, most typical of cat scratch disease |
Fatigue | Ongoing tiredness |
Headache | Pain in the head |
Muscle aches | Sore, achy muscles |
Abdominal pain | Pain in the belly |
Bone or joint pain | Aching in bones or joints |
Excessive sweating | Sweating more than usual |
Enlarged liver or spleen | Organ swelling a provider can detect |
Bumps, cysts or growths | On or under the skin — red, purple or slightly darker than surrounding skin |
What Causes Bartonellosis?
Bartonella bacteria cause bartonellosis. The most common types that infect humans include B. bacilliformis, B. henselae and B. quintana — and as described above, each spreads in its own way, from cat scratches and flea-carrying kittens to sand flies in the Andes to body lice in crowded settings.
Is Bartonella the same as Lyme disease?
No, Bartonella infections aren't the same as Lyme disease. Borrelia bacteria, spread through a specific type of tick, cause Lyme disease [1].
What Are the Complications of Bartonellosis?
Bartonella can spread to different organs in your body, like your heart, eyes, liver, spleen, brain and bones. Heart inflammation (endocarditis) is the most common complication of bartonellosis [1]. Others include anemia; brain function issues (encephalopathy); excess fluid around your heart (pericardial effusion) or in your lungs (pulmonary edema); heart failure; liver and spleen swelling (hepatosplenomegaly); and inflammation of parts of your eye, including Parinaud oculoglandular syndrome [1].
If you have a compromised immune system, you might develop bacillary angiomatosis or bacillary peliosis [1]. Bacillary angiomatosis causes excess blood vessels to form, creating masses or cysts on your organs and bones. You might get large, raised bumps on your skin. Depending on your skin tone, they might be darker than the surrounding skin or bright red. Bacillary peliosis causes blood-filled cysts on your liver [1].
Complication | What it is |
Endocarditis (most common) | Heart inflammation |
Anemia | A drop in healthy blood cells |
Encephalopathy | Brain function issues |
Pericardial effusion / pulmonary edema | Excess fluid around your heart or in your lungs |
Heart failure | The heart can't pump as it should |
Hepatosplenomegaly | Liver and spleen swelling |
Parinaud oculoglandular syndrome | Inflammation of parts of your eye |
Bacillary angiomatosis | Excess blood vessels forming masses or cysts on organs and bones; large raised skin bumps |
Bacillary peliosis | Blood-filled cysts on your liver |
How Is Bartonellosis Diagnosed?
Healthcare providers diagnose bartonellosis by testing your blood for signs of a Bartonella infection [1]. Your provider may also take a biopsy of cysts or masses on your skin [1].
When you visit a provider, be sure to tell them if you have cats, have been around cats recently, or have traveled recently.
Diagnostic step | What happens |
Blood testing | Your blood is tested for signs of a Bartonella infection |
Skin biopsy | A provider may take a sample of cysts or masses on your skin |
Your history | Tell them if you have cats, have been around cats recently, or have traveled recently |
How Is a Bartonella Infection Treated?
Providers treat most types of bartonellosis with one or more antibiotics [1]. For some types of bartonellosis, like CSD, you might not need treatment. Your provider may drain large nodules [1].
For B. bacilliformis infections, you'll need antibiotic treatment to prevent life-threatening complications [1]. In some cases, you might need a blood transfusion.
Treatment | Used for |
One or more antibiotics | Most types of bartonellosis |
No treatment needed | Some types, like CSD, may clear without treatment |
Draining large nodules | Provider care for large swollen nodes |
Antibiotics (required) | B. bacilliformis infections — needed to prevent life-threatening complications |
Blood transfusion | Some B. bacilliformis cases |
What can I expect if I have a Bartonella infection?
What to expect depends on what type you have. For example, CSD usually goes away on its own, without treatment. But left untreated, B. bacilliformis infections can be fatal [1].
Even with treatment, your symptoms might take some time to get better. Swollen lymph nodes from CSD can last two to eight weeks [1]. Verruga peruana growths (late-stage Carrión's disease) can last several months to a year [1].
Can Bartonellosis Be Prevented?
Avoiding cat scratches and bug bites is the best way to prevent bartonellosis [1]. You can also protect your cats from flea bites to reduce their risk of carrying Bartonella.
Specific strategies include keeping your cats indoors and asking your veterinarian for other ways to protect them from flea bites; not petting or picking up stray cats or kittens; adopting a cat over a year old rather than a kitten [1], especially if you have a weakened immune system; and covering any scratches or wounds with a bandage — don't let cats lick scratches or wounds.
Outdoors, cover as much skin as possible: wear long pants, tall socks and a long-sleeved shirt, and use bug spray proven to repel sand flies or any other insects you're trying to avoid. For hygiene-based protection against B. quintana, shower or bathe your whole body with soap and warm water regularly; change and wash your clothing at least once a week; and don't share bedding, clothing, towels or personal items with others. If you have lice on your clothing, wash your clothes with hot water and dry them on high heat — if you can't wash clothing in a machine, you can also kill lice by putting clothing in sealed plastic bags for two weeks [1].
When Should I See a Healthcare Provider?
See a healthcare provider if you have symptoms of a Bartonella infection, especially if you're at higher risk for an infection.
Go to the emergency room if you have symptoms of serious illness, including severe fatigue or weakness; dizziness; shortness of breath; chest pain; severe headache; neck stiffness; or confusion or other mental changes [1].
What's the Bottom Line?
Bartonellosis is uncommon but can cause serious illness — and the good news is that Bartonella infections are almost always treatable with antibiotics. The three main culprits each have their own route: kittens and cat scratches for CSD, sand flies in the Andes for Carrión's disease, and body lice in crowded conditions for trench fever. Avoid cat scratches and bug bites, protect your cats from fleas, and tell your provider about any recent cat exposure or travel if you feel sick. If severe symptoms hit — chest pain, confusion, neck stiffness, or trouble breathing — don't wait: go to the ER.
Conclusion and What to Do Next
Most Bartonella infections respond well to antibiotics, and cat scratch disease usually clears up without treatment at all [1]. If you develop fever, swollen lymph nodes or unusual skin bumps after a cat scratch or bug bite, the safest first step is to see a healthcare provider and share your recent exposures — and to seek emergency care immediately for any severe or worsening symptoms.
Explore Rinnit.com's library of clear, practical health guides — from cat scratch disease and insect-borne infections to antibiotics and immune health.
Frequently Asked Questions
What is bartonellosis?
Bartonellosis is a group of illnesses caused by types of Bartonella bacteria. The most common types include cat scratch disease (CSD), Carrión's disease and trench fever.
How do you get bartonellosis?
From bug bites or cat scratches. B. henselae comes from cat scratches or bites (especially kittens, which get it from flea bites); B. bacilliformis spreads through sand fly bites in the Andes; and B. quintana spreads through body lice in crowded living conditions.
Is cat scratch disease the same as bartonellosis?
Cat scratch disease is one type of bartonellosis — a B. henselae infection that most commonly causes large, swollen lymph nodes and bumps or a rash.
Is bartonellosis the same as Lyme disease?
No. Bartonella infections aren't the same as Lyme disease. Borrelia bacteria, spread through a specific type of tick, cause Lyme disease.
What are the symptoms?
Depending on the type: fever (may come and go), large painful lymph nodes, fatigue, headache, muscle aches, abdominal pain, bone or joint pain, excessive sweating, an enlarged liver or spleen, and bumps, cysts or growths on or under the skin.
Who's at highest risk?
Kids younger than 15 are most commonly infected with B. henselae. People experiencing homelessness or living in crowded conditions are at higher risk for B. quintana. Anyone with a compromised immune system is at higher risk for severe infections.
Is it serious?
Depending on the type, bartonellosis can cause mild symptoms or severe illness. Left untreated, B. bacilliformis infections can be fatal. Heart inflammation (endocarditis) is the most common complication.
What complications can it cause?
Bartonella can spread to the heart, eyes, liver, spleen, brain and bones — causing endocarditis, anemia, encephalopathy, fluid around the heart or in the lungs, heart failure, liver and spleen swelling, and eye inflammation. People with weakened immune systems can develop bacillary angiomatosis or bacillary peliosis.
How is it diagnosed?
Providers test your blood for signs of a Bartonella infection and may biopsy cysts or masses on your skin. Tell your provider if you have cats, have been around cats recently, or have traveled recently.
How is it treated?
Most types with one or more antibiotics. CSD might not need treatment at all, and a provider may drain large nodules. B. bacilliformis always requires antibiotics to prevent life-threatening complications, and some cases need a blood transfusion.
How long does cat scratch disease last?
Swollen lymph nodes from CSD can last two to eight weeks, even with treatment. CSD usually goes away on its own without treatment.
Can it be prevented?
Yes — mainly by avoiding cat scratches and bug bites and protecting your cats from flea bites. Key steps include keeping cats indoors, avoiding stray kittens, bandaging scratches, covering skin outdoors with bug spray, and maintaining regular hygiene.
Can I still adopt a cat?
You can reduce risk by adopting a cat over a year old rather than a kitten, especially if you have a weakened immune system, and by having your veterinarian protect your cat from fleas.
When should I go to the ER?
Go to the emergency room for symptoms of serious illness: severe fatigue or weakness, dizziness, shortness of breath, chest pain, severe headache, neck stiffness, or confusion or other mental changes.
Is it contagious from person to person?
The infections come from cat scratches or bug bites (sand flies, body lice), not from direct person-to-person contact. Protecting cats from fleas reduces their risk of carrying Bartonella.
Related Reading
Endocarditis: Symptoms, Causes, Types, Diagnosis, Treatment and When to Seek Emergency Care — What You Need to Know: the most common complication of bartonellosis.
References
Cleveland Clinic. Bartonellosis. Cleveland Clinic. Updated August 11, 2025. https://my.clevelandclinic.org/health/diseases/bartonellosis
Centers for Disease Control and Prevention. About Bartonella. CDC. Updated March 23, 2026. https://www.cdc.gov/bartonella/about/index.html
Lins KA, et al. Cutaneous manifestations of bartonellosis. An Bras Dermatol. 2019;94(5):594-602. PMID 31780437. https://doi.org/10.1016/j.abd.2019.09.024
Cheslock MA, et al. Human Bartonellosis: An Underappreciated Public Health Problem? Trop Med Infect Dis. 2019;4(2):69. PMID 31010191. https://doi.org/10.3390/tropicalmed4020069
Bush LM, et al. Bacillary Angiomatosis. Merck Manual Professional Version. Updated June 2024. https://www.merckmanuals.com/professional/infectious-diseases/gram-negative-bacilli/bacillary-angiomatosis
Nelson CA, et al. Cat-Scratch Disease in the United States, 2005-2013. Emerg Infect Dis. 2016;22(10):1741-6. PMID 27648778. https://doi.org/10.3201/eid2210.160115
Nawrocki CC, et al. Atypical Manifestations of Cat-Scratch Disease, United States, 2005-2014. Emerg Infect Dis. 2020;26(7):1438-1446. PMID 32568056. https://doi.org/10.3201/eid2607.200034
Klotz SA, et al. Cat-scratch Disease. Am Fam Physician. 2011;83(2):152-5. PMID 21243990. https://pubmed.ncbi.nlm.nih.gov/21243990/
Medical disclaimer
The information in this article is for general informational purposes only and is not intended as professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.
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