Rickettsia rickettsii - Agent of Rocky Mountain spotted fever. Rocky Mountain spotted fever is a tickborne disease with a worldwide occurrence. A variety of hosts, including man, are susceptible to infection. Infection may result in a spectrum of disease ranging from subclinical to severe or fatal multiorgan collapse. The disease is maintained in nature in small mammals and ticks, especially Dermacentor andersoni and D. variabilis .
Ticks can transmit the disease both transstadially and transovarially.
Canines are infected following bites from infected ticks. Dogs do not develop a sufficient enough rickettsemia to act as a reservoir and as such are not involved in the direct transmission of the organism. They do serve as an ideal sentinel indicating infection rates in specific areas. Early clinical signs in the dog are often nonspecific. Laboratory testing generally indicate a thrombocytopenia.