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# Bartonella infections (cat-scratch disease, Carrion disease)

Bartonella bacteria, spread by cat scratches, lice or sand flies, cause swollen lymph nodes, fever, anaemia or skin bumps depending on the species.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Neck lymph nodes](https://durgical.com/en/anatomy/lymph-nodes-of-neck/)
- [Cubital nodes](https://durgical.com/en/anatomy/cubital-nodes/)
- [Central axillary nodes](https://durgical.com/en/anatomy/central-axillary-nodes/)
- [Retina](https://durgical.com/en/anatomy/retina/)
- [Liver](https://durgical.com/en/anatomy/liver/)
- [Spleen](https://durgical.com/en/anatomy/spleen/)

## Why it happens

- [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/)
- [The red cell life cycle and the spleen](https://durgical.com/en/physiology/the-red-cell-life-cycle-and-the-spleen/)
- [Lymph node and spleen under the microscope](https://durgical.com/en/histology/lymph-node-and-spleen-under-the-microscope/)

## What it is

Infections by Bartonella species, small gram-negative intracellular bacilli that infect red blood cells and blood-vessel lining. B. henselae causes cat-scratch disease and bacillary angiomatosis, B. quintana trench fever and endocarditis, and B. bacilliformis Carrion disease in the Andes.

## Who gets it

Cat-scratch disease occurs worldwide, mostly in children and young adults with kittens. Trench fever and B. quintana endocarditis affect homeless people with body lice. Carrion disease is endemic in Andean valleys of Peru and also in Ecuador, with historical foci in southern Colombia (Nariño); it is transmitted by Lutzomyia sand flies and causes outbreaks with high mortality when untreated.

## Causes

- B. henselae: scratch or bite of a cat (usually a kitten) carrying infected fleas
- B. quintana: faeces of human body lice rubbed into the skin
- B. bacilliformis: bite of Lutzomyia sand flies in Andean valleys
- Rarely, transfusion or organ transplant

## Risk factors

- Contact with kittens or flea-infested cats
- Homelessness, crowding and body lice
- Living in or travelling to endemic Andean valleys
- Advanced HIV infection or other immunosuppression (bacillary angiomatosis, disseminated disease)
- Pre-existing valve disease (endocarditis)

## Pathophysiology

In cat-scratch disease the bacteria drain to the regional node and cause necrotising granulomas with stellate microabscesses. In immunosuppressed hosts they stimulate endothelial proliferation, producing vascular tumours of skin and organs (bacillary angiomatosis and peliosis). B. bacilliformis invades red blood cells, which are removed by the [spleen](https://durgical.com/en/anatomy/spleen/) and [liver](https://durgical.com/en/anatomy/liver/), causing severe acute haemolysis and transient immunosuppression (Oroya fever); weeks later angiogenic skin nodules appear (verruga peruana).

## Classification

- Cat-scratch disease (B. henselae): typical lymphadenitis and atypical forms (Parinaud oculoglandular syndrome, neuroretinitis, hepatosplenic, encephalopathy)
- Bacillary angiomatosis and peliosis hepatis (B. henselae or B. quintana) in immunosuppression
- Trench fever and culture-negative endocarditis (B. quintana, also B. henselae)
- Carrion disease (B. bacilliformis): acute haematic phase (Oroya fever) and eruptive phase (verruga peruana)

## Symptoms and signs

- Papule or pustule at the scratch site, followed 1–3 weeks later by tender regional lymphadenopathy (axillary, epitrochlear, cervical)
- Low-grade fever, fatigue and headache
- Red eye with pre-auricular node (Parinaud syndrome) or sudden visual loss (neuroretinitis)
- Relapsing fever with shin pain in trench fever
- High fever, pallor, jaundice and enlarged liver and spleen in Oroya fever
- Red-purple vascular skin nodules in verruga peruana and bacillary angiomatosis

## Red flags

- Severe anaemia, jaundice or altered consciousness in a person from an Andean valley (Oroya fever)
- Prolonged fever with a new murmur and negative blood cultures (Bartonella endocarditis)
- Vascular skin lesions or fever in a person with advanced HIV
- Visual loss, seizures or encephalopathy

## Diagnosis

**Clinical**
Cat-scratch disease is often diagnosed clinically: regional lymphadenitis after a cat scratch, with a papule at the inoculation site. Travel to endemic valleys and anaemia point to Carrion disease.

**Tests**
Bartonella serology (indirect immunofluorescence) and PCR of node, blood or valve tissue; cultures grow very slowly. In Oroya fever, a peripheral blood smear shows bacilli inside red blood cells, with haemolytic anaemia. Node or [skin](https://durgical.com/en/anatomy/skin/) biopsy shows granulomas or vascular proliferation with silver-stained bacilli.

**Imaging**
Ultrasound of affected nodes and [abdomen](https://durgical.com/en/anatomy/region/abdomen/) (hepatosplenic microabscesses); echocardiography when endocarditis is suspected; eye examination for neuroretinitis.

## Differential diagnosis

- Other causes of lymphadenopathy: tuberculous lymphadenitis, toxoplasmosis, infectious mononucleosis
- Lymphoma
- Malaria and other haemolytic febrile illnesses (for Oroya fever)
- Kaposi sarcoma and pyogenic granuloma (for vascular skin lesions)
- Infective endocarditis by other organisms

## Goal of treatment

Relieve symptoms of self-limited cat-scratch disease, and eradicate infection quickly in disseminated, cardiac or Andean forms, where untreated disease can be fatal.

## Treatment

**Conservative**
Typical cat-scratch disease usually resolves in weeks to months; reassurance, analgesia and warm compresses.

**Medical**
A macrolide (azithromycin) may shorten node swelling in cat-scratch disease; prolonged courses of a macrolide or doxycycline, sometimes with rifampicin, for bacillary angiomatosis, neuroretinitis and trench fever.

**Medical**
Carrion disease: prompt antibiotics in the Oroya phase (a fluoroquinolone or chloramphenicol, often combined with a beta-lactam to cover secondary infections); a macrolide or rifampicin for verruga peruana.

**Acute**
Blood transfusion and supportive care for severe haemolytic anaemia; antibiotics combined with an aminoglycoside and surgical assessment for endocarditis.

**Procedure**
Needle aspiration of a painful fluctuant node (incision is avoided because it can leave a draining sinus).

## Complications

- Suppurative lymphadenitis
- Neuroretinitis and Parinaud oculoglandular syndrome
- Encephalopathy and seizures
- Hepatosplenic granulomas and peliosis hepatis
- Culture-negative endocarditis with valve destruction
- Oroya fever: severe haemolysis and secondary infections (for example Salmonella, toxoplasmosis)

## Prognosis

Cat-scratch disease is benign and self-limited in most immunocompetent people. Untreated Oroya fever has a very high mortality, which falls markedly with timely antibiotics. Bartonella endocarditis often requires valve surgery.

## Prevention

- Flea control in cats, avoiding rough play with kittens and washing scratches promptly
- Delousing, clothing hygiene and access to showers and laundry
- Insect repellent, bed nets and protective clothing in endemic Andean valleys at dusk and night
- Prophylactic measures and early care for people with advanced HIV

## Test yourself

Think of the answer, then tap the question to see it.

## A child has tender axillary lymphadenopathy two weeks after playing with a new kitten. What is the likely diagnosis?

Cat-scratch disease caused by Bartonella henselae.

## What causes the severe anaemia of Oroya fever (Carrion disease)?

Bartonella bacilliformis invades red blood cells, which are destroyed, causing acute haemolytic anaemia.

## Which insect transmits Carrion disease?

Lutzomyia sand flies, in Andean valleys of Peru, Ecuador and southern Colombia.

## What skin lesion does Bartonella cause in people with advanced HIV?

Bacillary angiomatosis: red-purple vascular papules and nodules that can mimic Kaposi sarcoma.

## Which Bartonella species causes trench fever and endocarditis in homeless people?

Bartonella quintana, transmitted by body lice.

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## Related conditions

- [Cervical lymphadenopathy](https://durgical.com/en/conditions/cervical-lymphadenopathy/)
- [Infectious mononucleosis](https://durgical.com/en/conditions/infectious-mononucleosis/)
- [Toxoplasmosis](https://durgical.com/en/conditions/toxoplasmosis/)
- [Hodgkin lymphoma](https://durgical.com/en/conditions/hodgkin-lymphoma/)
- [Non-Hodgkin lymphoma](https://durgical.com/en/conditions/non-hodgkin-lymphoma/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Infective endocarditis](https://durgical.com/en/conditions/infective-endocarditis/)
- [Kaposi sarcoma](https://durgical.com/en/conditions/kaposi-sarcoma/)
- [Malaria](https://durgical.com/en/conditions/malaria/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Clinical Overview of Bartonellosis | Bartonella Infection | CDC](https://www.cdc.gov/bartonella/hcp/clinical-overview/index.html) (Centers for Disease Control and Prevention, 2024); [About Bartonella | Bartonella Infection | CDC](https://www.cdc.gov/bartonella/about/index.html) (Centers for Disease Control and Prevention, 2024); [Cat-scratch disease: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001614.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/bartonella-infections/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/bartonella-infections/