Bartonella henselae

Bartonella henselae is a gram-negative bacterium that is primarily known as the causative agent of cat scratch disease (CSD), also known as cat scratch fever. This bacterium can also cause other conditions such as bacillary angiomatosis, peliosis hepatis, and endocarditis in immunocompromised individuals. Bartonella henselae is a zoonotic pathogen, meaning it can be transmitted from animals to humans, with cats being the main reservoir.

Transmission

Transmission of Bartonella henselae to humans typically occurs through a scratch or bite from an infected cat. The bacterium can also be transmitted by the cat flea, Ctenocephalides felis, which acts as a vector. Direct contact with flea feces on cat fur or in the environment can lead to infection if the bacteria enter through broken skin.

Pathogenesis

Once Bartonella henselae enters the human body, it targets the endothelial cells lining the blood vessels and red blood cells. This interaction can lead to the proliferation of endothelial cells, resulting in the formation of vascular lesions characteristic of diseases like bacillary angiomatosis. The bacterium's evasion of the host's immune response is a key factor in its pathogenesis.

Clinical Manifestations

The clinical manifestations of Bartonella henselae infection can vary. In immunocompetent individuals, it most commonly presents as cat scratch disease, characterized by localized lymphadenopathy (swollen lymph nodes) near the site of the scratch or bite, fever, and fatigue. In more severe cases, especially in immunocompromised patients, it can cause bacillary angiomatosis, peliosis hepatis, or endocarditis, which require prompt and aggressive treatment.

Diagnosis

Diagnosis of Bartonella henselae infection is primarily based on the patient's history of cat exposure and clinical presentation. Serological testing can detect antibodies against Bartonella henselae, and PCR (polymerase chain reaction) testing can identify the bacterial DNA in tissue samples. Imaging studies and biopsy of affected tissues may be necessary for diagnosing more severe conditions like bacillary angiomatosis or peliosis hepatis.

Treatment

Treatment of Bartonella henselae infection depends on the severity of the disease. For uncomplicated cases of cat scratch disease, supportive care and monitoring may be sufficient. Antibiotics, such as azithromycin, doxycycline, or erythromycin, are recommended for severe or systemic infections. Patients with bacillary angiomatosis, peliosis hepatis, or endocarditis may require prolonged antibiotic therapy.

Prevention

Preventive measures against Bartonella henselae infection include avoiding rough play with cats to reduce the risk of scratches and bites, controlling flea infestations in pets, and maintaining good hygiene practices to minimize the risk of transmission.