Relapsing Fever - Causes, Symptoms and treatments

Defintion:

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 transmited 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 rate of more than 10%, but during an epidemic, the mortality rate may rise to as high as 50%. The victims are usually indigent people who are already suffering from other infections and malnutrition. With treatment, however, the prognosis for both louse-and tick-borne relapsing fevers is excellent.

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. This form of the discase is most prevalent in Texas and other western states, usually during the summer, when ticks and their hosts (chipmunks, goats, prairie dogs) are most active; however, cold-weather outbreaks sometimes afflict people, such as campers, who sleep in tick-infested cabins.

Causes of Relapsing Fever:

The body louse (Pediculus human us var. corporis) carries louse-borne relapsing fever, 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.

Tick-borne relapsing fever is caused by three species of Borrelia most closely identified with tick carriers: B. hermsii (associated with Ornithodoros hermsii), B. turicatae (associated with Ornithodoros turicata), and B. parkeri (associated with Ornithodoros parkeri). Because tick bites are virtually painless, and most Ornithodoros ticks feed at night but do not imbed themselves in the victim's skin, many people are bitten unknowingly.

Signs and symptoms of Relapsing Fever:

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 (40.5° C), prostration, headache, severe myalgia, arthralgia, diarrhea, vomiting, coughing, and eye or chest pains. Splenomegaly is common; hepatomegaly and lymphadenopathy 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. 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 of Relapsing Fever:

Diagnosis requires demonstration of the spirochetes in blood smears during febrile periods, using Wright's or Giemsa stain.

Borrelia spirochetes may be harder to detect in later relapses because their number in the blood declines. In such cases, injecting the patient's blood or tissue into a young rat and incubating the microbe 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/ul, with increases in lymphocytes and erythrocyte sedimentation rate; however, the WBC count may be normal. Because Borrelia is a spirochete, relapsing fever may cause a false-positive test for syphilis.

Differential diagnoses include malaria, Lyme arthritis, dengue, influenza, typhus, yellow fever, leptospirosis, and the enteric fevers.

Treatment of Relapsing Fever:

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 lluids and electrolytes) should be given instead.

Special considerations and Orevention tips:

1. During the initial evaluation period, obtain a complete history of the patient's travels.

2. 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.

3. Maintain adequate fluid intake to prevent dehydration. Provide I.V. fluids as ordered. Measure intake and output accurately, especially if the patient is vomiting and has diarrhea.

4. Administer antibiotics carefully. Document and report any hypersensitive reactions (rash, fever, anaphylaxis), especially a Jarisch-Herxheimer reaction.

5. Treat flushing, hypotension, or tachycardia with vasopressors or fluids, as ordered.

6. 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.

7. Use proper hand-washing technique, and teach it to the patient. Isolation is unnecessary because the disease isn't transmitted from person to person.

8. Report all cases of louse-or tickborne 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, South America) to wear clothing that covers as much skin as possible and to tuck pant legs into boots or socks.