Louseborne Relapsing Fever

Organism Borrelia recurrentis, a spirochaete indistinguishable from B. duttoni in stained preparations, and with some cross-immunity between the two.

Clinical features Louse-borne relapsing fever is an epidemic disease occurring in the same situations or even at the same time as epidemic typhus. The disease is very similar to tick-borne relapsing fever (see below), with periods of fever lasting for a few days and then recurring after 2-4 days, but the number of relapses is generally less. The onset of fever is sudden with headache, myalgia and vertigo. A transitory petechial rash can occur and other symptoms, such as bronchitis and hepato-splenomegaly, may develop.

Diagnosis is by darkfield illumination of fresh or stained blood taken during a pyr-exial episode.

Transmission Pediculus corporis humanus is infected when it feeds on humans during the pyrexial period, the spirochaete invading the haemocoel of the louse. The spirochaete is not transmitted when the louse feeds, but when it is crushed, the Borrelia entering the bite wound or any abrasion. Crushing lice between the fingernails or teeth are possible ways of acquiring infection. The spirochaete can also enter through mucous membranes and possibly even unbroken skin. The greatest risk then is to the attentive parent or acquaintance delous-ing a member of the family or a friend.

Sub-clinical infection must also occur because the lice are killed even though the person does not show any symptoms. Humans are the only reservoir of the louse-borne infection.

Incubation period 5-15 days, normally 8 days.

Period of communicability Humans are most infectious during periods of pyrexia, but as reservoirs, they can infect lice at any time. The louse becomes infectious 4-5 days after an infected blood meal.

Occurrence and distribution The disease is associated with poor personal hygiene and overcrowding, in which lice flourish. Distribution is similar to epidemic typhus, being found in the highland areas of Africa, India and South America. There is an endemic focus in Ethiopia from which epidemics appear to originate, all the conditions being favourable about once every 20 years.

Control and prevention is the same as for epidemic typhus above, with delousing and improvement of hygiene.

Treatment is with a single dose of procaine penicillin (300,000 units) on the first day, followed by tetracycline 250 mg on the next day. Severe reactions to antibiotic therapy are commoner in louse-borne than tickborne relapsing fever.

Surveillance Cases of louse-borne relapsing fever must be notified to WHO and neighbouring countries. Routine inspections for lice should be carried out where facilities permit, such as in prisons, institutions and to new arrivals coming into refugee camps.

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