What Is Bartonellosis?

Bartonellosis is a term used to describe a disease state caused by one of several species of Bartonella bacteria. These bacterial species can cause disease in mammalian hosts including humans, cats, dogs, or rabbits. Most common of these diseases are cat-scratch disease, Carrion's disease, and trench fever. Transmission of the Bartonella bacteria to the host occurs through insect vectors, usually fleas, ticks, or lice. Antibiotics and insect control are important methods of treatment for bartonellosis.

There are more than a dozen species of Bartonella bacteria that can cause disease in humans. These gram-negative bacteria are transmitted by insects and can infect a variety of mammalian hosts. The most common of these bacteria is Bartonella henselae, which causes cat-scratch disease.

B. henselae is transmitted to the domestic cat by the cat flea. These bacteria reproduce in the digestive tract of the flea and can survive in the flea feces. Once the cat becomes infected with B. henselae, it may be a carrier and have no obvious symptoms. The bacteria can then be passed to humans through a cat scratch, however.

The primary symptom for a human infected with B. henselae is typically a localized red blister at the site of the scratch. There may be swelling of the lymph nodes, a fever, or an achy feeling. Otherwise healthy patients with this form of bartonellosis may need treatment with a two-week course of antibiotics. Patients with immune disorders may not be able to fight off the bacteria as easily and a longer course of antibiotics may be necessary.

A second Bartonella species, Bartonella bacilliformis, causes another form of bartonellosis in humans known as Carrion's disease. The female sandfly, found in river valleys of South America, transmits these bacteria directly to the human host. Acute symptoms of Carrion's disease are fever, headache, and anemia. A two-week course of antibiotics is usually successful at treating the acute phase of this disease. If left untreated, a chronic phase that leads to the presence of blood-filled lesions on the skin can develop.

Trench fever is another form of bartonellosis that is caused by Bartonella quintana. These bacteria are spread to humans by the human body louse. Cases of trench fever appear in populations living in close quarters with poor sanitation. Primary symptoms include fever, chills, headache, or pain in the bones. This disease may resolve by itself, or the patient may need antibiotic treatment.

Bartonellosis is usually diagnosed by culturing blood or tissues from the patient on agar plates containing nutrients. White colonies will appear in the agar. Alternatively, the bacteria can be stained and examined under a microscope. These bacteria usually respond to antibiotic therapy; however, control of the insect vectors can lead to prevention of these diseases.