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Scrub Typhus

scrub typhus

An infection caused by a small bacterium related to the family of Rickettsiaceae. The name scrub typhus was applied after discovery of increased frequency of the disease in scrub or wasteland areas.

Transmission of the disease:

It is transmitted by the ovaries of the mites. The baby mites are then infected and these are known as "chiggers". These mites then pass the infection to humans by biting on exposed human skin.

The baby mites are found in profusion in areas that are close to water bodies and lots of wild vegetation. Hence infections are greatest in the rainy season.
Scrub typhus is rife in Eastern and Southern Asia, Northern Australia but is also found in other regions eg. India, Thailand, Tibet, Japan, Russia and mountainous regions of Nepal.
Scrub typhus can cause outbreaks of high fever of unknown origin. Once infected humans acquire immunity that may last 1 - 3 years. However, people visiting endemic areas may also be infected. Hence this is a real threat in view of the unnaturally high rainfall this year in parts of North India and Himachal and Punjab are Typhus endemic states which have shown a sudden spurt in cases of Scrub Typhus.

Clinical Presentation

Infection with scrub typhus is most often mild and self contained but can occasionally be severe and even fatal. The incubation period is up to ten days and the commonest features are:

  • An area of bite with a thick BLACK SCAB (found in only in 50%)
  • Mite Bite
  • Fever
  • Headache
  • Body Pain
  • Cough
  • Abdominal pain, nausea and vomiting
  • Enlarged Glands
  • A Rash
  • Severe cases can develop encephalitis(Brain Infection) and interstitial pneumonia(Lung Infection) and this may be fatal.

Investigations

1. Indirect Immunofluorescence

2. PCR(Polymerase Chain Reaction) for O. tsutsugamushi from blood of feverish patients.

{Some studies have used PCR (polymerase chain reaction) on specimens obtained from eschars.[4][5] This involves obtaining a small piece of the BLACK SCAB(Eschar) and then amplifying the DNA to look for the genetic sequence of scrub typhus.}

3. Chest X Ray may show pneumonia

Complications

1. Pneumonia(Lung Involvement)
2. Hepatitis(Liver Involvement)
3. Myocarditis(Heart Involvement)
4. Meningoencephalitis(Brain Involvement)
5. Disseminated intravascular coagulation(Bleeding Problems)
6. Multi-organ failure

Management

Antibiotics: Doxycycline orally or Chloramphenicol in more severe cases. There may be antibiotic resistance in some areas. Azithromycin has been used in resistant cases and may be better than Doxycycline - especially in children and pregnant women.

Outlook

Death rates of untreated cases is between 5-10 % and is even higher in adults.

Prevention

Avoiding mite bites by wearing shoes and thick clothes like DENIMS while trekking or working in areas with high prevalence of Scrub Typhus. Mite control and systemic drugs have been used. No vaccine is available.


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