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…
Rickettsia prowazekii is the only rickettsial species that can cause devastating, naturally occurring epidemics capable of killing a substantial proportion of human populations infested with body lice. Epidemics are associated with conditions that prevent bathing and washing of clothes in…
The spotted fevers comprise a large group of tick-, mite-, and flea-borne zoonotic infections that are caused by closely related rickettsiae. These include Rocky Mountain spotted fever (RMSF), boutonneuse fever, African tick bite fever, North Asian tick typhus, lymphangitis-associated rickettsiosis,…
Introduction The unusual bacterial pneumonias described in this chapter are caused by agents that are phylogenetically diverse and reside in a wide variety of locations, ranging from extracellular Mycoplasma attached to respiratory epithelium to obligately intracellular organisms. The obligately intracellular…
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…
Key Points Treatable rickettsial infections, including life-threatening Rocky Mountain spotted fever, boutonneuse fever, epidemic typhus, murine typhus, scrub typhus, human monocytotropic ehrlichiosis, and human granulocytotropic anaplasmosis, are seldom diagnosed serologically during the acute stage of illness owing to absence of…
Introduction During the last two decades, the approach to histopathologic diagnosis has been dramatically transformed by immunohistochemistry, specifically in the diagnosis and classification of tumors and, more recently, in the diagnosis of infectious diseases in tissue samples. Pathologists play an…
Key features ▪ Rickettsiae are small, obligately intracellular, Gram-negative bacteria that reside within an arthropod host (tick, flea, louse, or mite) during part of their life cycle ▪ The arthropod vector transmits the rickettsiae in its saliva or feces during…