Rocky Mountain spotted fever (RMSF) was first made reportable to New Jersey public health officials in 1961. RMSF is caused by the bacterium Rickettsia rickettsii and is transmitted primarily by the American dog tick, Dermacentor variabilis. The percentage of infected ticks in New Jersey is unknown. The brown dog tick, Rhipicephalus sanguineus, has recently been implicated as a secondary vector. Transmission occurs through the bite of an infected tick, or by contact through breaks in the skin or mucous membranes with crushed tissue or feces of the tick. The principal source of the pathogen in nature (reservoir host) is the meadow vole, Microtus pennsylvanicus, although the infection is also maintained between tick life stages (transstadial transmission) and from females to eggs (transovarial transmission).
Following an incubation period of 3 to 14 days, the disease is marked by sudden onset of fever, which may persist for several weeks in untreated cases, malaise, muscle pain, severe headache, chills, and conjunctivitis. A spotted rash appears on the palms and soles in about 50% of cases, and may spread rapidly to other parts of the body. The fatality rate may reach 15% to 20% in untreated cases. An average of 10 confirmed cases of RMSF are reported annually in New Jersey.