Chapter 7 - Rickettsial and Chlamydial Diseases

Abstract

This chapter provides an overview of rickettsial and chlamydial agents that cause natural infection in mice. A general review of taxonomic position, morphology, and other general characteristics of these agents and the diseases they produce in mice is presented in the chapter. Rickettsial diseases are caused by microorganisms of the order Rickettsiales. Three families are accepted in this order: Rickettsiaceae, Bartonellaceae, and Anaplasmataceae. This group of fastidious microorganisms is intermediate between the bacteria and the viruses in the classification scheme. In general, and certainly most notably, the rickettsial diseases occurring in man and some animals belong to the Rickettsiaceae family. Chlamydia is an intracellular parasite that causes disease in a wide variety of animals and man. These intracellular organisms multiply in the cytoplasm of host cells and form membrane-bound cytoplasmic inclusions. The developmental cycle is unique and complicated, consisting of an elementary body that is specialized for extracellular survival and the reticulate body that multiplies within the host-cell cytoplasm. Man is the primary host of C. trachomatis strains that cause trachoma, inclusion conjunctivitis, lymphogranuloma venereum, and other urogenital tract infections. The only strain of C. trachomatis that causes disease other than in man is an agent responsible for causing pneumonitis in mice.