Epidemic typhus

Typhus is an acute anthroponotic rickettsiosis with a transmissible mechanism of pathogen transmission, capable of mass spread. This disease is characterized by a severe cyclic course, the development of generalized vasculitis, roseolous-petechial rash and predominant damage to the nervous and cardiovascular systems.

Two forms of typhus are distinguished and registered separately:

• epidemic (louse-borne) typhus;
• relapsing typhus (Brill's disease).

Epidemic typhus has the following synonyms: historical, head, louse typhus, war, hunger typhus, prison fever, camp fever; typhus exanthematicus (lat.); epidemic typhus fever.

ICD-10 code

A75.0. Epidemic typhus.

What causes epidemic typhus?

Epidemic typhus (European, classical, louse-borne typhus; jail fever) is caused by Rickettsia prowazekii. Symptoms of epidemic typhus are prolonged and include high fever, intractable headache, and a maculopapular rash.

Humans are the natural reservoir for R. prowazekii, which has a worldwide distribution and is transmitted by lice when their feces are rubbed into a bite or other skin lesion (sometimes the conjunctiva of the eyes or mouth). In the United States, in rare cases, people can become infected with epidemic typhus after contact with a flying squirrel.

Mortality from the disease is low among children under 10 years of age, but increases with age and can reach 60% among untreated patients over 50 years of age.

What are the symptoms of epidemic typhus?

Epidemic typhus has an incubation period of 7-14 days. It is followed by a sudden onset of fever, headache, and prostration. Within a few days, the temperature reaches 40 C and remains high. Minor morning drops in temperature are noted. The febrile period lasts about 2 weeks. The headache is generalized and intense. On the 4th-6th day of the disease, typical symptoms of epidemic typhus appear: small pink macules that quickly cover the body, usually starting from the upper part of the body and armpits. In most cases, the rash does not appear on the palms, soles, and face. Later, the rash darkens and becomes maculopapular. In acute cases, the rash becomes petechial and hemorrhagic. In some cases, splenomegaly can be detected. Hypotension occurs in the most severe patients. Poor prognostic signs include vascular collapse, renal failure, signs of brain damage, ecchymosis with gangrene, and pneumonia.

How is epidemic typhus diagnosed?

Epidemic typhus must be differentiated from other acute infections, primary meningococcemia, measles and rubella. A history of exposure to lice, tick bites or presence in an endemic region may be helpful in diagnosis, but is often not available. Clinical features may help differentiate the diseases.

In the subacute form of meningococcemia, the rash may be pink, spotted, maculopapular, or petechial. In the fulminant form of meningococcemia, the rash may be petechial-confluent or ecchymotic (hemorrhagic). In the acute form of the disease, the rash appears quickly, and in the case of an ecchymotic rash, the elements are usually sensitive to palpation.

With measles, the rash first appears on the face, spreads to the trunk and arms, and soon becomes confluent. The rash with rubella usually does not merge. Enlargement of the retroauricular lymph nodes and mild intoxication indicate rubella.

Diseases caused by rickettsiae and similar microorganisms also need to be differentiated from each other. Since many rickettsiae are distributed in certain geographic regions, information about the place of residence and recent travels may be useful in terms of diagnosis. However, special tests are usually required. The most significant tests for detecting Rickettsia rickettsii are indirect immunofluorescence (IFA) and PCR testing of biopsy material from the rash. Culture testing is difficult to perform and has no clinical significance. For detecting Ehrlichia, the best test is blood PCR. Serological diagnostics do not allow diagnosing acute disease, since they become positive only by the time of recovery.

How is epidemic typhus treated?

Primary treatment for epidemic typhus includes doxycycline 200 mg orally once, followed by 100 mg 2 times daily until clinical improvement and absence of fever for 24-48 hours. Treatment of epidemic typhus with doxycycline should continue for at least 7 days. Second-line treatment is chloramphenicol 500 mg orally or intravenously 4 times daily for 7 days.

How to prevent epidemic typhus?

The presence of lice is usually obvious and should prompt suspicion of typhus. Epidemic typhus can be prevented by lice control and immunization. These vaccines are not available in the United States. Lice can be eliminated by spraying infected people with malathion or dan.

Prevention of tick infestation includes walking on designated trails in the woods, tucking pant legs into boots or socks, wearing long-sleeved shirts in the woods, and applying insect repellents such as diethyltoluamide topically. These should be used with caution in young children as toxic reactions have been reported. Permethrin applied to clothing is effective in killing ticks. Good personal hygiene is essential for prevention, with frequent tick searches, especially on hairy areas of the body and on children. Engorged ticks should be removed with care. Crushing a tick between the fingers is unacceptable as it can spread infection. The tick's body should not be squeezed. Ticks should be removed by gradual traction on the head using small tweezers. The bite site should be wiped with alcohol. Vaseline oil, alcohol, and any other irritants are ineffective and should not be used.

There is no way to rid an entire region of ticks, but tick populations can be reduced in endemic areas by controlling small animal populations.