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Two to fourteen days after a bite by an infected tick, mild chilliness, loss of
appetite, and malaise appear. Chills, fever, bone and muscle pain, severe
headache, and confusion follow these mild symptoms. Abdominal pain, joint pain,
and diarrhea may be present. The triad of fever, severe headache, and rash
occurring in the spring, summer, or fall, should suggest rickettsial infection.
Diagnosis is aided by a history of a tick bite in an endemic area.
Younger patients usually develop the rash earlier. Most often small, flat, pink,
nonpruritic macules, which blanche when pressure is applied, first appear on the
wrists, forearms, and ankles. Eventually the lesions become raised and spread over
the entire body, frequently including the palms and soles. However, the
characteristic petechial rash is usually not seen until the sixth day or later after the
onset of symptoms, and this rash occurs in only 35 to 60 percent of infected
individuals. This rash is caused by hemorrhages into the skin from infected,
inflamed blood vessels. In severe cases, blotchy red areas appear all over the body
and the individuals appear seriously ill.
RMSF can be a very severe illness and patients often require hospitalization. The
organisms infect endothelial cells throughout the body, and may involve the
respiratory system, central nervous system, gastrointestinal system, or renal
system. Untreated infections last about two weeks and have a mortality of 20 to 30
percent; treatment reduces mortality to 3 to 10 percent. Severe or fatal infections are
associated with advanced age, male sex, African-American race, chronic alcohol
abuse, and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency.
Initiate appropriate antibiotic treatment immediately on the basis of clinical and
epidemiologic findings whenever Rocky Mountain spotted fever is suspected.
Treatment must not be delayed until laboratory confirmation is obtained. If the
patient is treated within the first four of five days, fever generally subsides within
twenty-four to seventy-two hours. Failure to respond to a tetracycline antibiotic
argues against a diagnosis of RMSF.
Preventive therapy in individuals who have had recent tick bites is not
recommended and may, in fact, only delay the onset of disease.
D. Ehrlichiosis: The ehrlichia are obligate intracellular bacteria that infect a variety
of animals and are usually vectored by ticks. Infection in humans, which were
first recognized in the United States in 1986, take two forms: human monocytic
ehrlichiosis (HME) in which morules are formed in peripheral blood monocytes,
and human granulocytic ehrlichiosis (HGE) in which morules are formed in
peripheral blood granulocytes.
Most HGE infections have occurred in the north central United States (Minnesota
and Wisconsin,) and in New England (Connecticut and New York). The same
Ixodes ticks that vector Lyme disease and babesiosis, I. scapularis in the
northeastern United States and I. Pacificus in the western coastal United States,
transmit the agent.
