25 - Rickettsiae and Chlamydiae

Abstract

Publisher Summary Rickettsiae and chlamydiae are host-cell-dependent, obligate intracellular, and prokaryotic organisms pathogenic for humans and animals. These infectious agents are currently classified in the orders Rickettsiales and Chlamydiales. This chapter presents laboratory diagnostic methods for detecting these infections in animals as well as approaches to cultivate and identify these agents. The order Rickettsiales contains the Rickettsiaceae, Hemobartonellaceae, and Anaplasmataceae families. The majority of the members of the Rickettsiaceae family are rod-shaped, coccoid, or pleomorphic. They are gram-negative, possess typical bacterial cell walls containing muramic acid, and multiply by binary fission only inside eukaryotic cells. They parasitize the gut cells of arthropods, which transmit the infection to animals. Hemobartonella felis, which is included in the Hemobartonellaceae family, causes an acute or chronic disease in cats. The causative organisms are found in various numbers on the surface of erythrocytes of peripheral blood or bone marrow. The Anaplasmataceae family includes Anaplasma marginale, which parasitizes erythrocytes of cattle or related ruminants and induces anemia. The host range of this organism is limited to ruminants and does not include laboratory animals. The chapter further discusses chlamydiae and their characteristics and pathogenicityand the isolation and identification of chlamydiae from clinical specimens.