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 Bacterial Diseases - BORRELIOSIS

(Relapsing fever, tick-borne relapsing fever, spirochetal fever, vagabond fever, famine fever)

A widely distributed bacterial infection spread from wild rodents by ticks or lice, with high fatality.  Tick-borne relapsing fever occurs in Africa, the Americas, Asia and possibly parts of Europe. The causative agents are Borrelia recurrentis and several other borrelia strains (bacterium). There is no vaccine.

RESERVOIR AND MODE OF TRANSMISSION:

Epidemic louse-borne infection is not considered zoonotic. Endemic tick-borne relapsing fever is transmitted from the natural wild rodent reservoir by tick bites to humans and dogs. Transovarial transmission in ticks occurs. Blood-borne person-to-person and intrauterine transmission have been reported.

INCUBATION PERIOD:

Humans: 1-15 days. Animals. Unknown.

CLINICAL FEATURES:

Humans. Sudden onset of fever lasting for 3-5 days ends with a crisis. Then a febrile period of 2-4 days is followed by one to ten or more recurrences of fever accompanied by severe headaches, nausea, vomiting, diarrhea, jaundice and sometimes a macular rash with bleeding due to thrombocytopenia. Meningitis and cranial nerve involvement are possible.
Animals. Arthritis and fever predominate in infected dogs. The arthritis recurs and may progress to chronic deformity.

PATHOLOGY:

Humans. Many lesions occur, including enlarged, soft, infarcted spleen, hepatomegaly, hemorrhages in bone marrow and skin, myocarditis, bronchopneumonia, and meningitis.
Animals. Arthritis, especially of the phalangeal joints, occurs with the possibility of progression to fibrosis of the joint capsule and ankylosis.

DIAGNOSIS:

Humans. Identify borrelia in thick blood smears. Otherwise isolate the pathogen by inoculation of blood into susceptible animals if possible.
Animals. Inoculate blood or tissues into rats or mice.

PROGNOSIS:

Humans. The fatality rate is up to 40%.
Animals. Although fatality is uncommon, the lesions tend to be progressive.

PREVENTION:

Humans and animals. Control tick vectors and prevent tick bites.

TREATMENT:

Humans. A single dose of tetracycline or erythromycin, 0.5 g orally, or a single dose of procaine penicillin G, 600,000 units intramuscularly, probably constitutes adequate treatment for louse-borne relapsing fevers. Because of higher relapse rates, tick-borne disease is treated with 0.5 g of tetracycline or erythromycin given 4 times daily for 5-10 days. Jarisch-Herxheimer reactions may occur and respond to aspirin given every 4 hours. Pretreatment with steroids is not effective in preventing this reaction. Animals. Tetracycline, penicillin, erythromycin, and ceftriaxone at standard dosages for 21-28 days.

LEGISLATION:

Humans. Louse-borne relapsing fever is notifiable to the World Health Organization. Tick-borne infection may be notifiable in some countries (e.g. the UK).
Animals. None.