Relapsing fever
Relapsing fever: Excerpt from Professional Guide to Diseases (Eighth Edition)
An acute infectious disease caused by spirochetes of the genus Borrelia, relapsing fever (also called tick, fowl-nest, cabin, or vagabond fever or bilious typhoid) is transmitted to humans by lice or ticks and is characterized by relapses and remissions. Rodents and other wild animals serve as the primary reservoirs for the Borrelia spirochetes. Humans can become secondary reservoirs but cannot transmit this infection by ordinary contagion; however, congenital infection and transmission by contaminated blood are possible.
Untreated louse-borne relapsing fever normally carries a mortality of more than 10%, but during an epidemic, the mortality rate may rise to 50%. With treatment, however, the prognosis for both louse- and tick-borne relapsing fevers is excellent.
Causes and incidence
The body louse (Pediculus humanus corporis) carries louse-borne relapsing fever (B. recurrentis), which typically occurs in epidemics during wars, famines, and mass migrations. Cold weather and crowded living conditions also favor the spread of body lice.
Inoculation takes place when the victim crushes the louse, causing its infected blood or body fluid to soak into the victim's bitten or abraded skin or mucous membranes.
Louse-borne relapsing fever is most common in North and Central Africa, Europe, Asia, and South America. No cases of louse-borne relapsing fever have been reported in the United States since 1900.
Tick-borne relapsing fever, however, is found in the United States and is caused by at least 15 Borrelia species; the three species most commonly identified with tick carriers are B. hermsii (associated with Ornithodoros hermsi), B. turicatae (associated with O. turicata), and B. parkeri (associated with O. parkeri). This form of the disease is most prevalent in Texas and other western states, usually during the summer when ticks and their hosts (chipmunks, goats, squirrels, rabbits, mice, rats, owls, lizards, and prairie dogs) are most active. In the colder weather, outbreaks sometimes afflict people such as campers who sleep in tick-infested cabins.
Because tick bites are virtually painless and most Ornithodoros ticks feed at night but don’t imbed themselves in the victim’s skin, many people are bitten unknowingly.
Signs and symptoms
The incubation period for relapsing fever is 5 to 15 days (the average is 7 days). Clinically, tick- and louse-borne diseases are similar. Both begin suddenly, with a temperature approaching 105° F (40.6° C), prostration, headache, severe myalgia, arthralgia, diarrhea, vomiting, coughing, and eye or chest pains. Splenomegaly is common; hepatomegaly and lymphade-nopathy may occur. During febrile periods, the victim's pulse and respiratory rates rise, and a transient macular rash may develop over his torso.
The first attack usually lasts from 3 to 6 days; then the patient's temperature drops quickly and is accompanied by profuse sweating. A skin rash on the trunk lasting 1 to 2 days is common after the primary febrile episode. The rash may be petechiae, macular, or papular. About 5 to 10 days later, a second febrile, symptomatic period begins. In louse-borne infection, additional relapses are unusual; but, in tick-borne cases, a second or third relapse is common. As the afebrile intervals become longer, relapses become shorter and milder because of antibody accumulation. Relapses are possibly due to antigenic changes in the Borrelia organism.
Complications from relapsing fever include nephritis, bronchitis, pneumonia, endocarditis, seizures, cranial nerve lesions, paralysis, and coma. Death may occur from hyperpyrexia, massive bleeding, circulatory failure, splenic rupture, or a secondary infection.
Diagnosis
CONFIRMING DIAGNOSIS Diagnosis requires demonstration of the spirochetes in peripheral blood smears during febrile periods, using Wright's or Giemsa stain.
Borrelia spirochetes may be more difficult to detect in later relapses because their number declines in the blood. In such cases, injecting the patient's blood or tissue into a young rat and incubating the organism in the rat’s blood for 1 to 10 days commonly allows spirochete identification.
In severe infection, spirochetes are found in the urine and cerebrospinal fluid. Other abnormal laboratory results usually include a white blood cell (WBC) count as high as 25,000/µl, with increases in lymphocytes and erythrocyte sedimentation rate; however, the WBC count may be normal. Because the Borrelia organism is a spirochete, relapsing fever may cause a false-positive test for syphilis in 5% to 10% of cases.
Treatment
Doxycycline or erythromycin is the treatment of choice and should continue for 4 to 5 days. In cases of drug allergy or resistance, penicillin G may be administered as an alternative. However, neither drug should be given at the height of a severe febrile attack because it may cause Jarisch-Herxheimer reaction, resulting in malaise, rigors, leukopenia, flushing, fever, tachycardia, rising respiration rate, and hypotension. This reaction, which is caused by toxic by-products from massive spirochete destruction, can mimic septic shock and may prove fatal. Antimicrobial therapy should be postponed until the fever subsides. Until then, supportive therapy (consisting of parenteral fluids and electrolytes) should be given.
Special considerations
❑During the initial evaluation period, obtain a complete history of the patient's travels and activities.
❑Throughout febrile periods, monitor vital signs, level of consciousness (LOC), and temperature every 4 hours. Watch for and immediately report any signs of neurologic complications, such as decreasing LOC or seizures. To reduce fever, give tepid sponge baths and antipyretics, as ordered.
❑Maintain adequate fluid intake to prevent dehydration. Provide I.V. fluids as ordered. Measure intake and output accurately, especially if the patient is vomiting or has diarrhea.
❑Administer antibiotics carefully. Document and report any hypersensitive reactions (rash, fever, anaphylaxis), especially a Jarisch-Herxheimer reaction.
❑Treat flushing, hypotension, or tachycardia with vasopressors or fluids, as ordered.
❑Look for symptoms of relapsing fever in family members and in others who may have been exposed to ticks or lice along with the victim.
❑Use proper hand-hygiene technique, and teach it to the patient. Isolation is unnecessary because the disease isn’t transmitted from person to person.
❑Report all cases of louse- or tick-borne relapsing fever to the local public health department, as required by law.
❑To prevent relapsing fever, advise anyone traveling to tick-infested areas (Asia, North and Central Africa, and South America) to wear clothing that covers as much skin as possible and to tuck pant legs into boots or socks. Advise the use of insect repellant to reduce risk.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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