Bartonellosis

Bartonellosis is a general term used to describe a group of infectious diseases caused by bacteria of the genus Bartonella. These bacteria can cause a variety of clinical manifestations in humans and animals. Bartonella species are zoonotic pathogens transmitted through vectors (flea, ticks, fleas like). Among the best-known Bartonella species are Bartonella henselae (the causative agent of cat scratch disease), Bartonella quintana (the causative agent of trench fever), and Bartonella bacilliformis (the causative agent of Oroya fever and verruga peruana). These diseases differ in their clinical features and geographic distribution.

Etiology and Pathogenesis

Bartonella species are Gram-negative facultative intracellular bacteria. These bacteria are capable of multiplying within endothelial cells and erythrocytes. Infection is typically transmitted via vectors. For example, Bartonella henselae infections are usually transmitted from cats to humans through cat scratches or flea bites. Bartonella quintana is carried by body lice and is particularly prevalent under poor hygiene conditions.

After adhering to mansion cells, the bacteria invade endothelial cells and multiply there. This invasion triggers activation of vascular proliferation and inflammatory responses. Bartonella species have developed various mechanisms to evade the host immune system, which can lead to chronic infections.

Clinical Manifestations and Classification

Bartonellosis causes different clinical presentations depending on the Bartonella species and the host’s immune status. The most common clinical forms are:

1. Cat Scratch Disease

This disease, caused by Bartonella henselae, typically develops after a cat scratch or bite. It is characterized by the formation of a papule or pustule at the infection site, followed by regional lymphadenopathy (swelling of lymph nodes). Fire, fatigue and head pain may also occur as systemic symptoms. In immunocompromised patients, disseminated infection can develop.

2. Trench Fever

This disease, caused by Bartonella quintana, is transmitted by body lice. Historically, it was widespread among soldiers during World War I. The illness is characterized by recurrent fever, headache, bone pain and fatigue.

3. Oroya Fever and Verruga Peruana

Bartonella bacilliformis is a species endemic to the Andes Mountains of South America. Oroya fever presents as an acute hemolytic anemia, while verruga peruana is characterized by angiomatous skin lesions. These two clinical painting represent different stages of the same infection.

4. Bacillary Angiomatosis and Peliosis Hepatis

These conditions are observed particularly in patients with immunodeficiency such as HIV/AIDS. They result from infection with Bartonella henselae or Bartonella quintana. Bacillary angiomatosis causes vascular proliferative lesions in the skin and mucous membranes. Peliosis hepatis is characterized by the formation of cystic spaces in the liver.

Diagnosis

The diagnosis of bartonellosis is based on clinical findings, epidemiological story and laboratory tests. Serological tests (IFA, ELISA) are used to detect Bartonella antibodies. Molecular methods (PCR) provide high sensitivity and specificity for detecting bacterial DNA. Histopathological examination can be helpful in diagnosing bacillary angiomatosis and verruga peruana.

Treatment

Treatment of bartonellosis varies according to the clinical form of the infection and the patient’s immune status. In mild cases such as cat scratch disease, symptomatic treatment may be sufficient. However, systemic or immunocompromised patients require antibiotic therapy. Antibiotics such as azithromycin, doxycycline and erythromycin are commonly used. The duration of treatment depends on the severity of the infection and the clinical presentation.