Relapsing Fever

Key Features

Essentials of Diagnosis

• Episodes of relapses fever, chills, malaise

• Occasional rash, arthritis, cough, hepatosplenomegaly, conjunctivitis

• Diagnosis suggested by direct microscopic identification of spirochetes in smears of peripheral blood

• Diagnosis confirmed with serologic testing

General Considerations

• There are two forms: epidemic relapsing fever is transmitted to humans by body lice (Pediculus humanus) and endemic relapsing fever by soft-bodied ticks (genus Ornithodoros)

• Tick-borne relapsing fever is endemic in the western United States

• Transmission usually takes place during the warm months, when ticks are active and recreation or work brings people into contact with ticks

• Ticks are nocturnal feeders and remain attached for only 5–20 minutes; consequently, the patient seldom remembers a tick bite

• Rarely, neonatal relapsing fever results from transplacental transmission of Borrelia

• Both louse-borne and tick-borne relapsing fever may be acquired during foreign travel

Clinical Findings

Symptoms and Signs

• Incubation period is 2–18 days

• Attack is sudden, with high fever, chills, sweats, tachycardia, nausea and vomiting, headache, myalgia, and arthralgia

• After 3–7 days, the fever falls

• Relapses occur at intervals of several days to weeks and duplicate the initial attack but become progressively less severe

• In louse-borne relapsing fever, there is usually a single relapse

• In tick-borne infection, 2–10 relapses occur

• Hepatomegaly, splenomegaly, pneumonitis, meningitis, and myocarditis may appear later in the course of the disease

• An erythematous rash may be seen over the trunk and extremities, and petechiae may be present

• Jaundice, iritis, conjunctivitis, cranial nerve palsies, and hemorrhage occur more commonly during relapses

Diagnosis

• During febrile episodes, the patient's urine contains protein, casts, and occasionally erythrocytes

• Marked polymorphonuclear leukocytosis is present

• Spirochetes can be found in the peripheral blood by direct microscopy in approximately 70% of cases by darkfield examination or by Wright, Giemsa, or acridine orange staining of thick and thin smears

• Spirochetes are not found during afebrile periods

• Immunofluorescent antibody (or ELISA confirmed by Western blot) can help establish the diagnosis serologically

Differential Diagnosis

• Malaria

• Leptospirosis

• Dengue

• Typhus

• Rat-bite fever

• Colorado tick fever

• Rocky Mountain spotted fever

• Collagen-vascular disease

• Any fever of unknown origin

Treatment

• For children younger than age 8 years penicillin or erythromycin should be given for 10 days

• Older children may be given doxycycline

Outcome

Complications

• Facial paralysis

• Iridocyclitis, optic atrophy

• Hypochromic anemia

• Pneumonia

• Nephritis

• Myocarditis, endocarditis

• Seizures

Prevention

• Measures that decrease exposures to soft ticks and body lice will prevent most cases

• Soft-bodied ticks often are found in rodent burrows or nests, so decreasing rodent access to homes and eliminating rodents in the home is helpful

• Body-louse infestation can ...