Comments
INITIAL SYMPTOMS:
Flu-like illness with fever, headache, myalgia, conjunctivitis, transient rash, eschar or eschars, and lymphadenopathy; [CCDM]
FINDINGS:
"Punched out" skin lesions (papules then eschars) appear at the sites of attachment of the infected mites. A rash appears on the trunk one week after onset of the fever in about 1/2 of patients. Pneumonitis is common and may progress to ARDS. Confusion or hearing loss may occur. In untreated cases, fever lasts for 14 days, and the case-fatality rate varies from 1% to 60%. [CCDM, p. 666] The rash starts on the trunk and spreads to the extremities, sparing palms/soles. Hepatosplenomegaly is common. [ID, p. 1488-9] Regional lymphadenopathy is usually present when the eschar appears. In a typical case, there is fever, rash, eschar, lymphadenopathy, and transient hearing loss in a patient 5-20 days after visiting an endemic area. Hematemesis and melena occur frequently. [Guerrant, p. 336] Some patients have elevated liver enzymes. Lymph nodes may be tender. Leukopenia occurs. Some patients have relapses. [Cecil, p. 1960]
EPIDEMIOLOGY:
Workers are infected in scrub-overgrown terrain or other mite-infested areas. In military operations in "typhus islands," a large percentage of troops may become infected. [CCDM, p. 667] Infected mites live in rural areas suitable for rodent populations. The chiggers feed on rodents, but do not infect them with O. tsutsugumushi.. [Guerrant, p. 334] Case-fatality rate is about 7%, but would be lower if all mild cases were diagnosed. [Harrison ID, p. 735]
COMPLICATIONS:
Rare complications are meningoencephalitis, convulsions, and coma. Pericarditis may develop. [Guerrant, p. 336] Findings may include delirium and myocarditis. [Merck Manual, p. 1285] The pale and transient, macular rash is reported in only about 30% of cases. In severe cases, the disease causes hemorrhages and multiple organ failure. Fatal complications include ARDS, shock, renal failure, DIC, and encephalitis. [PPID, p. 2498, 2529-30, 3643]
For updated text and symptoms of infectious diseases, see iddx.com.
Diagnostic
Serology (IFA, indirect immunoperoxidase, and enzyme immunoassays): PCR analysis of eschars and blood; [Harrison, p. 676]