Rocky Mountain Spotted Fever
Zoonosis Update Rocky Mountain spotted fever Ronald D. Warner, DVM, MPVM, PhD, DACVPM, and Wallace W. Marsh, MD, FAAP ocky Mountain spotted fever (RMSF), a classic SFG rickettsiae are transmitted by arthropods and cause Rmetazoonosis that involves both vertebrate and non- various illnesses worldwide, R rickettsii is the only one vertebrate reservoir hosts, is a seasonal disease of dogs known to be pathogenic for both animals and humans and humans in the Americas. The clinical illness was in the Western Hemisphere. first described among Native Americans, soldiers, and settlers in the Bitterroot River and Snake River valleys of Cycle of the Organism in Nature Montana and Idaho during the late 1890s, but remained and the Vectors unrecognized in dogs until the late 1970s. The causative Rickettsia rickettsii are maintained in nature by organism, Rickettsia rickettsii, was first described by transstadial passage within, and transovarial (vertical) Howard T. Ricketts in 1909 and is maintained in nature transmission between, generations of ixodid ticks. These by ixodid (hard-bodied) ticks via transmission to-and- ticks also vector R rickettsii to and from various rodent from various rodent reservoirs. As primary reservoir reservoirs and other small mammals. Naïve larval and hosts, the ticks vector R rickettsii to larger mammals; nymphal ticks become infected while feeding on small however, dogs and humans are the only ones that dis- rodents (eg, mice, voles, squirrels, or chipmunks) with play clinically recognizable illnesses. Rickettsia rickettsii acute rickettsemia.2,5 To enable transovarial transmission, are not naturally transmitted dog-to-dog, dog-to- female ticks need to ingest numerous rickettsiae or be human, or human-to-human.
[Show full text]