Comments
INITIAL SYMPTOMS:
Relapsing fever (fever for 2-7 days alternating with no fever for 4-14 days); Also, patients have flu-like symptoms (headache, myalgia, arthralgia and abdominal pain). [CCDM, p. 510]
FINDINGS:
In the typical case, several days of fever are followed by a fever-free period and then one or more episodes of relapsing fever. GI symptoms are common. Patients with B vitamin deficiencies are at greater risk for neurological involvement. [CCDM, p. 510] Both the tick-borne and louse-borne forms have intervals between fevers of 4-14 days. Other symptoms accompanying the fever are headache, neck stiffness, cough, arthralgia, myalgia, delirium, dizziness, and coma. Splenomegaly is common, and hepatomegaly and hepatitis occurs in about 50% of louse-borne cases and 10% of tick-borne cases. Patients with louse-borne disease may have petechiae, epistaxis, and thrombocytopenia. A small papule with a central eschar may develop at the site of the tick bite. [Guerrant, p. 295-8] In louse-borne disease, platelet counts are <50,000/mm3 in up to 90% of cases. Spirochetes are visible on blood smears during febrile episodes in about 70% of patients. [Cecil, p. 1936] Relapsing fever is relapsing because of variations in borrelial surface antigens. Each relapse occurs when the organism changes its surface antigens and evades the immune system. Other infections that have biphasic or relapsing fever are Colorado tick fever, yellow fever, dengue fever, lymphocytic choriomeningitis, brucellosis, malaria, leptospirosis, chronic meningococcemia, rat-bite fever, echovirus 9, and Bartonella species. [Harrison ID, p. 716-20]
COMPLICATIONS:
Patients with tick-borne disease are more likely to have neurological complications including meningoencephalitis, cranial neuritis, radiculitis, myelitis, and iridocyclitis. Myocarditis and pulmonary edema may be the cause of death in both forms. [Guerrant, p. 297-8] Hemorrhage, including hemoptysis and hematemesis, is common but rarely severe. Up to 30% of patients have neurological findings. After the initial high fever, patients may develop headache, lethargy, meningitis, seizures, and coma. Patients may die from shock or pulmonary edema secondary to myocarditis or a Jarisch-Herxheimer reaction. [Cohen, p. 171]
EPIDEMIOLOGY:
For untreated cases, fatality rates are 2-10%.This infection is caused by spirochetes transmitted by lice or ticks. Wild rodents are reservoirs for the tickborne disease. [CCDM, p. 510-13] In typical tick-borne cases in the US, patients have visited western national parks and slept in cabins infected with rodents. The tick feeds at night and is attached for only 15 minutes. Most patients do not recall a tick bite. Animal reservoirs are wild rodents (tick-borne) and none (louse-borne). [Cecil, p. 1936]
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