Bartonella quintana was formally classified in the Rickettsiaceae family, and is transmitted by the human body louse.
B. quintana is identified as a bacterial agent of trench fever that infected more than one million troops and prisoners living in crowded, unhygienic conditions in the First World War.
Clinical manifestations of trench fever range from asymptomatic infection to severe, life-threatening illness. Few of the common symptoms include headache, pain in the legs and loins, constipation, insomnia, dyspnea, and abdominal pain. Trench fever often results in prolonged disability but no fatalities have been recorded. Patients are profoundly ill in the early state of the disease and continue for 4 to 6 weeks. A minor illness could become chronic – Byman defined chronic trench fever as “a state of marked debility, with or without attacks of slight fever and aching, and characterized by a hyperexcitability of the nervous system in general”. After the primary infection of trench fever resolves, chronic bacteremia develops.
Bartonella are unique among bacterial pathogens in their ability to cause angioproliferative lesions, involving proliferation of endothelial cells. Immunocompromised patients are highly susceptible to bacillary angiomatosis, predominately patients with AIDS.