Epidemic typhus

EPIDEMIC TYPHUS

Synonyms

  • Brill-Zinsser disease ( first described by Nathan Brill in 1913 in New York), Camp fever, Jail fever or Gaol fever (often occurs when prisoners are frequently huddled together in dark rooms), Hospital fever, Ship fever, Famine fever, Putrid fever, Petechial fever, Epidemic louse-borne typhus or Louse-borne typhus

Type of zoonosis

  • Anthropo-metazoonosis

Definition

  • It is caused by Rickettsia prowazekii as epidemics following wars and natural disasters. It is transmitted by human body louse, Pediculus humanus corporis, clinically characterized by sudden onset, fever (40ºC), headache, skin rashes, vascular and neurological disturbances.

Etiology

  • It is caused by Rickettsia prowazekii.
  • Rickettsia s are Gram negative, but commonly used stains are Giemsa, Macchiavello and Gimenez. They stain red against green background with Gimenez stain.
  • Rickettsia s are intracellular pathogens and multiply by binary fission in either cytoplasm or nucleus of host cells.

Brief history

  • In 1916, Henrique da Rocha Lima proved the causative agent for typhus and he named it Rickettsia prowazekii after H.T.Ricketts and Stanislaus von Prowazek, two zoologists who died investigating a typhus epidemic in a prison camp in 1915.
  • In 1930, Rudolf Weigl developed an effective vaccine for typhus.

Reservoir and incidence

  • Outbreaks of epidemic typhus were often reported in camps during the time of World War II and killed thousands of people, and also after natural disasters.
  • In India, it is prevalent in Jammu and Kashmir, Kulu valley, Jabalpur, Sagar (Madhya Pradesh), Kota and Bundi in Rajasthan.
  • Epidemic typhus is a major public health problem, and has caused greatest harm in people during the Second World War.
  • Overcrowding in army camps and refugee camps associated with poor hygiene predispose to epidemic outbreaks.
  • Flying squirrel (Glaucomys volans) and human body louse (Pediculus humanis corporis) involved in the natural infection cycle of epidemic typhus.
  • Natural infection follows three years cyclic pattern, includes entry and gradual spread of infection in the first year, epidemic outbreaks in the second year and development of immunity in the third year. However, it develops latent infection, which results in recrudescence even after 10 to 20 years.
  • In the environment, Rickettsia in the dried faeces of louse survives for long period.
  • According to the International sanitary regulations, the affected person should be quarantined.

Transmission

  • Rickettsia prowazekii is transmitted from infected man to another man through human body louse, Pediculus humanis corporis.
  • Louse feeds blood on infected man during rickettsaemia phase, and gets infected. In gut, Rickettsia multiplies and infectious one week after infection, and remain infectious for life of the louse. Infected louse excretes Rickettsia in faeces, or may die within 14 to 15 days.
  • When man scratches at the site of louse bite, Rickettsia present in the faeces of the louse, enter through abraded skin.
  • Aerosol transmission of Rickettsia, from dust in the environment contaminated with dried faeces of the louse.

Disease in animals

  • No evidence of infection has been confirmed in domestic animals (cattle, sheep, goat and camel), but there is a suggestive evidences.

Disease in humans

  • Incubation period ranges from 1 to 2 weeks.
  • Clinical signs start suddenly with high continuous fever (40ºC), headache and skin rashes at the end of first week of illness.
  • Skin lesions are macular and localized initially, followed by dark, purpuric and confluent changes.
  • Gangrene of the toes, finger tips, ear lobes, nose, penis and scrotum may occur due to cutaneous thrombosis.
  • Neurological involvement may lead to coma and vascular disturbances may lead to tachycardia, hypotension and cyanosis during second or third week of infection.
  • Prognosis is grave if untreated at the correct time of infection.
  • The mortality rate may be 10% to 60% if untreated with antibiotics.

Diagnosis

  • Serological diagnosis: Weil Felix agglutination test using OX 19 antigen (OX 19, OX 2 and OX K antigens are “O” antigens of Proteus, to which antigenic components of Rickettsia cross react) to detect rise in antibody titre in paired sera is useful in diagnosis of epidemic typhus. Compliment fixation test, haemagglutination test and FAT can also be used.
  • Animal inoculation test: Guinea pigs are inoculated intraperitoneally with blood from suspected patient, results in development of febrile reactions in about 1 to two weeks. Paired sera should be collected from guinea pigs and tested to detect four-fold rise in antibody titre.
  • PCR technique.

Treatment

  • Chloramphenicol and tetracycline can be given to clinically affected patients. They will become afebrile in two days of time after antibiotic treatment.
  • Intravenous fluid and oxygen therapy should be given.

Prevention and control

  • Control of louse menace using malathion, DDT, lindane and carbaryl.
  • In certain circumstances like army camps and refugee camps, over-crowding should be avoided.
  • Formalin treated killed vaccine can be used as good immunizing agent, but not commercially available in India.
Last modified: Wednesday, 16 May 2012, 5:38 AM