Relapsing fever (also known as tick fever, recurrent fever or famine fever) is an infectious disorder caused by the Borrelia species which are transmitted by ticks (tick-borne relapsing fever) or lice (louse-borne relapsing fever).
Relapsing fever is a disease caused by the spirochetes of the Borrelia genus that are transmitted by the tick of lice bites. Depending on the disease transmitter there are two types of relapsing fever distinguished – tick-borne relapsing fever (TBRF) and louse-borne relapsing fever (LBRF). The symptoms of the disease include episodes fever, muscle aches, vomiting, headache lasting for 3-5 days alternating with asymptomatic periods when a person generally feels well. As the disease is caused by bacterial infection antibiotics are necessary for the treatment of relapsing fever.
The disease is caused by a bacterial infection. Spirochetes are the helical shaped gram-negative microorganisms 8 to 30 µm long and 0.2 to 0.5 µm wide; in case of relapsing fever, the causative organisms are Borrelias which are transmitted by the bite of the human body lice (Pediculus humanus) or the soft ticks which in turn become infected upon feeding on ill animals. Louse-borne relapsing fever is caused by the Borrelia recurrentis while tick-borne relapsing fever may be caused by B. hermsii, B. turicatae or B. duttoni.
Bacteria enter through the skin and mucous membranes into the bloodstream and spread to the internal organs especially the spleen, bone marrow, and central nervous system.
- Louse-borne (epidemic) relapsing fever Borrelia recurrentis is transmitted through the skin with the lice feces. Occasionally a person can be infected by direct contact with contaminated blood. The louse-borne disease is endemic in some regions of Africa such as Ethiopia and Sudan (the Horn of Africa).
- Tick-borne (endemic) relapsing fever Argasidae ticks transmit borrelias while biting humans. More than 8 Borrelia species are known to cause TBRF. Tick-borne relapsing fever is common in Russia, the Mediterranean region, Africa, Mexico, Central, and South America and Canada.
The symptoms of the disease usually develop in-between 2 to 18 days (with a median incubation period of 7 days) after the person was bitten. Typically, the disease manifests with episodes of fever lasting for approximately 3 days followed by 7 afebrile days (this episode may last from 4 to 14 days).
During the fever episodes, a person can also experience muscle aches and joint pain, headache, dizziness, and vomiting. Sometimes lymph nodes may appear enlarged (lymphadenopathy), as well as the liver and the spleen. The rash develops in less than 1/3 of the affected individuals.
The nervous system may also be involved: lymphocytic meningitis, altered mental status, Bell’s palsy (flaccid paralysis of the facial muscles on one side of the face), other cranial nerve palsies, paralysis, and seizures may be seen.
In TBRF there may be up to 30 episodes of fever whether in LBRF usually, relapse occurs only once.
The diagnosis is made when the bacteria are identified in the blood smear, though sometimes the spirochetes cannot be detected (however, relapsing fever shouldn’t be excluded). Serologic testing is used to confirm the diagnosis, mouse inoculation or culture in modified Kelly medium can also confirm the diagnosis.
Relapsing fever requires antibiotics administration. Spirochetes are susceptible to doxycycline, tetracycline, and penicillin.
Sometimes after the initiation of antibiotic treatment Jarish-Herxheimer reactions (fever, rigors, and reduced white blood cell count) may develop.
Tick-borne relapsing fever
- Doxycycline 100 mg twice a day should be given for at least 7-10 days;
- Tetracycline 500 mg four times a day;
Louse-borne relapsing fever
- A single dose of tetracycline (500 mg);
- Doxycycline 200 mg;
- Penicillin G procaine 400000 to 800000 units intramuscularly;
Relapsing fever prevention implies the elimination of the bacteria-carrying ticks and lice as well as pests and avoidance of exposure to rodents. For example, one should avoid staying overnight in the buildings where rodents may reside. Repellents containing at least 20% DEET or 0,5% permethin have to be used to prevent tick bites. Furthermore, long-sleeved shirts and trousers should be worn while spending time outdoors, and later after coming back it is recommended to check carefully if there are no ticks on the closes or skin.
Personal hygiene is a key to LBRF prevention.
If a person was already exposed postexposure prophylaxis is recommended – 200 mg of doxycycline should be taken on the first day with subsequent administration of 100 mg once a day for 4 days.