Communicable Diseases

Epidemic Louse-Borne Typhus Fever

Identification

A rickettsial disease with variable onset; often sudden and marked by headache, chills, prostration, fever and general pains. A macular eruption appears on the fifth to sixth day, initially on the upper trunk, followed by spread to the entire body, but usually not to the face, palms or soles. The eruption is often difficult to observe on black skin. Toxemia is usually pronounced, and the disease terminates by rapid defervescence after about 2 weeks of fever. The case-fatality rate increases with age and varies from 10% to 40% in the absence of specific treatment. Mild infections may occur without eruption, especially in children and people partially protected by prior immunization. The disease may recrudesce years after the primary attack (Brill-Zinsser disease, ICD-9 081.1; ICD-10 A75.1); this form of disease is milder, has fewer complications, and has a lower case-fatality rate.

The IF test is most commonly used for laboratory confirmation, but it does not discriminate between louse-borne and murine typhus (ICD-9 081.0; ICD-10 A75.2) unless the sera are differentially absorbed with the respective rickettsial antigen prior to testing. Blood can be collected on filter paper that are forwarded to a reference laboratory. Other diagnostic methods are EIA, PCR, immunohistochemical staining of tissues, CF with group specific or washed type-specific rickettsial antigens, and the toxin neutralization test. Sending lice to a reference laboratory for PCR testing may help detect an outbreak. Antibody tests usually become positive in the second week.

Infectious agent

Rickettsia prowazekii.

Occurrence

In colder areas where people may live under unhygienic conditions and are infested with lice. Explosive epidemics may occur during war and famine. Endemic foci exist in the mountainous regions of Mexico, in Central and South America, in central and eastern Africa and numerous countries in Asia. Recent outbreaks have been observed in Burundi and Rwanda. This rickettsia exists as a zoonosis of flying squirrels (Glaucomys volans) in the USA, and there is serological evidence that humans have been infected from this source, possibly via the squirrel flea.

Reservoir

Humans are the reservoir and are responsible for maintaining the infection during inter-epidemic periods. Although not a major source of human disease, sporadic cases may be associated with flying squirrels.

Mode of transmission

The body louse, Pediculus humanus corporis, is infected by feeding on the blood of a patient with acute typhus fever. Patients with Brill-Zinsser disease (see Identification, above) can infect lice, and may serve as foci for new outbreaks in louse-infested communities. Infected lice excrete rickettsiae in their feces, and usually defecate at the time of feeding. People are infected by rubbing feces or crushed lice into the bite or into superficial abrasions. Inhalation of infective louse feces in dust may account for some infections. Transmission from the flying squirrel is presumed to be through the bite of the squirrel flea, but this has not been documented.

Incubation period

From 1 to 2 weeks, commonly 12 days.

Period of communicability

The disease is not directly transmitted from person to person. Patients are infective for lice during the febrile illness, and possibly for 2–3 days after the temperature returns to normal. Infected lice pass rickettsiae in their feces within 2–6 days after the blood-meal; they are infective earlier if crushed. The louse invariably dies within 2 weeks after infection; rickettsiae may remain viable in the dead louse for weeks.

Susceptibility

Susceptibility is general. One attack usually confers long-lasting immunity.

Methods of control

  1. Preventive measures:
    1. Apply an effective residual insecticide powder at appropriate intervals by hand or power blower to clothes and persons of populations living under conditions favoring louse infestation. The insecticide used should be effective on local lice.

    2. Improve living conditions with provisions for bathing and washing clothes.

    3. Treat prophylactically those who are subject to risk, by application of residual insecticide to clothing (dusting or impregnation).


  2. Control of patient, contacts and the immediate environment:
    1. Report to local health authority: Report of louse-borne typhus fever required as a Disease under Surveillance by WHO, Class 1 (see Reporting).

    2. Isolation: Not required after proper delousing of patient, clothing, living quarters and household contacts.

    3. Concurrent disinfection: Appropriate insecticide powder applied to clothing and bedding of patient and contacts; launder clothing and bedclothes. Lice tend to leave abnormally hot or cold bodies in search of a normothermic clothed body. If death from louse-borne typhus occurs before delousing, delouse the body and clothing by thorough application of an insecticide.

    4. Quarantine: Susceptible persons infested with lice and exposed to typhus fever should ordinarily be quarantined for 15 days, if possible, after application of an insecticide with residual effect.

    5. Management of contacts: All immediate contacts should be kept under surveillance for 2 weeks.

    6. Investigation of contacts and source of infection: Every effort should be made to trace the infection to the immediate source.

    7. Specific treatment: A single dose of doxycycline 200 mg will normally cure patients (though doxycyline cannot be used in children less than eight years of age). When faced with a seriously ill patient with possible typhus, suitable treatment should be started without waiting for laboratory confirmation.


  3. Epidemic measures: The best measure for rapid control of typhus is application of an insecticide with residual effect to all contacts. Where louse infestation is known to be widespread, systematic application of residual insecticide to all people in the community is indicated. Treatment of cases in an epidemic may also decrease the spread of disease. In epidemics, individuals may protect themselves by wearing silk or plastic clothing tightly fastened around wrists, ankles and neck, and impregnating clothes with repellents or permethrin.

  4. Disaster implications: Typhus can be expected to be a significant problem in louse-infested populations in endemic areas if social upheavals and crowding occur.

  5. International measures:
    1. Notification by governments to WHO and to adjacent countries of the occurrence of a case or an outbreak of louseborne typhus fever in an area previously free of the disease.

    2. International travelers: No country currently requires immunization against typhus for entry.

    3. Louse-borne typhus is a Disease under Surveillance by WHO. WHO Collaborating Centres provide support as required. More information can be found at:

  6. Measures in case of deliberate use: R. prowazekii has been produced as a possible bioweapon and was used before World War II. It is infectious by aerosol, with a high case-fatality rate. The initial reference treatment of any suspected case is a single dose of 200 mg of doxycycline.

    For more information on the deliberate use of infectious agents to cause harm, see the section on Deliberate use.

ICD-9

080

ICD-10

A75

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