Definition Zoonoses, derived from the Greek words zōio (animal) and nósos (disease), are infectious diseases transmitted from animals, both wild and domestic, to humans or from humans to animals. Among emerging or reemerging infectious diseases, 60 to 75% are zoonoses.…
Q fever (for query fever, the name given following an outbreak of febrile illness in an abattoir in Queensland, Australia) is rarely reported in children but is probably underdiagnosed. Symptomatic patients can have acute or chronic disease. Etiology Although previously…
Etiology Ehrlichiosis in humans was 1st described in 1987, when clusters of bacteria confined within cytoplasmic vacuoles of circulating leukocytes (morulae), particularly mononuclear leukocytes, were detected in the peripheral blood of a patient with suspected Rocky Mountain spotted fever (RMSF).…
Members of the typhus group of rickettsiae (see Table 255.1 in Chapter 255 ) include Rickettsia typhi, the cause of murine typhus, and Rickettsia prowazekii, the cause of louse-borne or epidemic typhus. R. typhi is transmitted to humans by fleas,…
Scrub typhus is an important cause of acute febrile illness in South and East Asia and the Pacific and could be emerging in the Middle East and South America. The causative agent is distinct from, but related to, Rickettsia species.…
Rickettsia species were classically divided into spotted fever and typhus groups based on serologic reactions and the presence or absence of the outer membrane protein A (ompA) gene. Sequencing of at least 45 complete genomes has refined distinctions. However, there…
Until 1987, infections by members of the family Anaplasmataceae, including the genera Ehrlichia, Anaplasma, and Neorickettsia, were known mainly as veterinary diseases ( Table 192.1 ). Canine ehrlichiosis was first described in 1935 by Donatien and Lestoquard in Algeria. This…
In 1922, Hone first described human infections “closely resembling typhus fever.” Since 1926, when Maxcy successfully identified murine typhus as a distinct clinical and epidemiologic entity, and 1931, when Dyer isolated a new typhus group named Rickettsia from rats and…
Introduction Rickettsial infections are caused by related obligate intracellular bacteria in the families Rickettsiaceae (vasculotropic rickettsioses) and Anaplasmataceae (ehrlichiosis and anaplasmosis). Clinical similarities among these infections result from alterations or injury to vascular endothelial cells, either by direct infection and…