Rocky Mountain spotted fever is a serious disease, and it is likely that many cases are not reported. Initial symptoms, which can resemble other illnesses, usually appear about 5-10 days after a tick bite and can include fever, nausea, vomiting, severe headache, muscle pain and lack of appetite. Further symptoms include a rash, abdominal pain, joint pain and diarrhea. The rash generally appears 2-5 days after the onset of fever. Children and young people typically develop a rash earlier than older persons, but about 10-15% of patients never develop a rash.
Rocky Mountain spotted fever usually requires hospitalization. Cells lining blood vessels are infected, and the respiratory, gastrointestinal, renal and central nervous systems can be affected. The occurrence of severe or fatal Rocky Mountain spotted fever has been linked to advanced age, male sex, African-American race, chronic alcohol abuse and deficiency of a specific enzyme (G6PD). People who survive acute infection can develop chronic health problems including partial paralysis of the lower extremities, gangrene, hearing loss, loss of bowel or bladder control and language disorders.
There is no vaccine for Rocky Mountain spotted fever, but there are laboratory tests to confirm the disease, and early treatment with antibiotics proves effective. In fact, prompt and appropriate treatment is imperative. According to the Centers for Disease Control and Prevention (CDC), approximately 3-5 % of cases are fatal.
What is Rocky Mountain spotted fever and how is it transmitted?
Rocky Mountain spotted fever is caused by a small bacterium, Rickettsia rickettsii, which is transmitted by members of the hard tick family, Ixodiae. The two major tick vectors in the United States include the dog tick, Dermacentor variabilis, and the Rocky Mountain wood tick, Dermacentor andersoni.
Dermacentor variabilis distribution of dog tick
Dermacentor andersoni distribution of Rocky Mountain wood tick
The dog tick prefers dogs as hosts, but it feeds readily on other large mammals including people. Larvae and nymphs of the Rocky Mountain wood tick feed on rodents and other small animals, and adults feed on large mammals.
Rickettsia is transmitted through the saliva of an infected tick. It usually takes several hours of feeding for transmission to occur, and the proportion of infected ticks is low—approximately 1%-3% of the population in areas where human cases have been reported.
Rocky Mountain spotted fever rash
How many cases of Rocky Mountain spotted fever occur annually in the United States?
Between 250 and 1,200 cases of Rocky Mountain spotted fever occur each year.
How is Rocky Mountain spotted fever treated?
Because it is a bacterial infection, Rocky Mountain spotted fever is treatable with antibiotics, usually doxycycline. Patients generally respond well to treatment if started early, and the fever usually subsides within 72 hours. If Rocky Mountain spotted fever is not treated promptly, possible organ damage and failure means patients will need more intensive care. Infection generally confers lifelong immunity.
How can I protect myself?
You should take measures to prevent tick bites. Insect Shield® Repellent Apparel is proven and registered to repel ticks—as well as mosquitoes, ants, flies and chiggers. The United States Environmental Protection Agency (EPA) requires extensive effectiveness data to prove a product's ability to repel insects. Many species and varieties of these insects have been tested, including those that carry dangerous diseases such as Rocky Mountain spotted fever.