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Louse-Borne Relapsing Fever: Pathology, Clinical Presentations, Diagnosis, Treatment And Prevention
Lice On The Human Body
Pathology And The Clinical Manifestations Of Louse-Bourne Relapsing Fever
Relapsing fevers are caused by organisms of the genus Borrelia which are actively motile spirochetes 10 to 12 in length and showing 6 to 8 irregular spirals. They are stainable by aniline dyes and can be demonstrated in stained blood film. Several species of Borrelia affect man. They are classified broadly into two groups: louse-borne relapsing fever and tick-borne relapsing fever depending on the mode of transmission.
Louse-Borne Relapsing Fever
This disease is caused by Borrelia recurrentis. It affects only man. Epidemics used to follow wars, famines or natural catastrophes such as floods or earthquakes. Overcrowding, malnutrition, and unhygienic surroundings start off epidemics in the tropics and temperate zones. The vector is the body louse (pediculus humanus corporis) which is infected by blood meal containing the organism from infected persons. The louse becomes infective in 5 to 15 days and the organisms are found in its body cavity. It remains infective for its whole life-span (1 month). Lice leave their host when the temperature is high or when the temperature drops after death, to seek new hosts. Pruritus caused by their bites leads to scratching and the lice are crushed. Smearing of their infected body contentes and excreta to the bite wound results in infection of the host.
Pathology: In the early phase of infection bacteremia develops and borreliae can be demonstrated in blood films outside the cells. They invade most of the viscera, especially the spleen, liver, brain, meninges, kidneys and the heart. Skin, mucous membranes and serous surfaces show petechial hemorrhages. Consumption coagulopathy may occur resulting in thrombocytopenia. Renal involvement leads to proteinuria and hematuria. Macrophages in the liver, spleen, lymph nodes and bone marrow may show engulfed borreliae. After an attack of fever, the spirochetes disappear from the blood to reappear again during relapse. Probably immunological factors are important in producing clearance of these organisms.
Clinical features: The incubation period varies between 2 to 12 days but is usually 7 to 10 days. Onset is abrupt with high fever, rapid pulse, headache, body pains, conjunctival congestion, epistaxis and sometimes a petechial rash. Herpes labialis may develop. The liver and spleen enlarge and become palpable. Jaundice, meningism and intestinal hemorrhage may occur. In four to ten days the fever comes down by crisis, but in some cases, it returns after 5 to 7 days. Two or three such relapses may occur in succession. The relapses are generally milder and less prolonged. In epidemics, the mortality used to be as high as 40%, especially in children and the elderly. After recovery from the illness, immunity lasts for 1 to 2 years.
Louse Bourne Relapsing Fever
Diagnosis And Treatment Of Louse Bourne Relapsing Fever
Diagnosis: Examination of blood films stained with Giemsa’s or Leishman’s stain reveal the borreliae. Dark ground or phase contrast microscopy of fresh blood may show the motile organisms.
Treatment: The disease responds well to penicillin and tetracycline in the usual doses, the former is slower in action. Drug therapy may lead to severe Jarisch-Herxcheimer reaction with profound fall in temperature, shock and cardiac failure within a few hours. This potential complication should be expected and supportive measures instituted promptly. Initial administration of procaine penicillin 500,000 units on the first day, followed subsequently by tetracycline 2 to 4g/day has been recommended as a safer course.
Prevention: The disease can be prevented by undertaking delousing measures. Use of 10% DDT powder effectively kills the lice. Boiling the clothes and bed linen for 30 minutes destroys the lice and their eggs.
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