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Pathology of Scrub Typhus (Tsutsugamushi Disease)

Dr Sampurna Roy MD




Scrub typhus (Tsutsugamushi disease) is caused by Rickettsia (Orientia) Tsutsugamushi :

Infected mites pass the infection transovarially to their larvae (chiggers), which crawl to the tips of vegetation, scrub and bush plants. These larvae attach to a passer-by rather than to the usual host, the rat. While feeding, the mite passes the rickettsia into the skin.

A multiloculated vesicle forms at the inoculation site and ulcerates, after which an eschar (a dry scab or slough formed on the skin) forms.

As the eschar heals, there is a sudden onset of headache, malaise, anorexia, weakness, and fever, followed by pneumonia, a macular rash (on the trunk before the limbs), lymphadenopathy, hepato-splenomegaly, and conjunctivitis.

Mild infections may exhibit only fever.

The most common gastrointestinal symptoms of scrub typhus patients included vomiting, nausea, diarrhea and hametamesis or melena.

Gastrointestinal signs included hepatomegaly, jaundice and abdominal pain.

Since multiple serotypes exist and cross-immunity is transient, recurrent infections are common.

Severe infections are complicated by meningoencephalitis involving cranial nerves, focal myocarditis, pneumonia and circulatory collapse.

Mortality rate range up to 30%.

The rickettsiae grow in the endothelial cells and produce vasculitis.

There are "typhus nodules", but these are usually smaller than those of epidemic typhus.

Necrosis of the skin and lymph nodes and a dense mononuclear infiltrate in the heart and lungs are seen in severe cases. 

Visit: Epidemic Typhus

Further reading:

Effects of meteorological factors on scrub typhus in a temperate region of China.

Scrub typhus complicated by acute respiratory distress syndrome and multiorgan failure; an unrecognized alarming entity in central India: a report of two cases.

Human Spotted Fever Group Rickettsioses Are Underappreciated in Southern Taiwan, Particularly for the Species Closely-Related to Rickettsia felis.

Causes of non-malarial fever in Laos: a prospective study.

Acute pancreatitis due to scrub typhus.

Pancreatitis in scrub typhus.

Scrub typhus presenting as an acute abdomen.

A prospective study on distribution of eschar in patients suspected of scrub typhus.

A rare case of Guillain-Barre syndrome following scrub typhus.

Hepatic impairment induced by scrub typhus is associated with new onset of renal dysfunction.

Validation of a clinical risk-scoring algorithm for severe scrub typhus.

Comparison of a conventional and nested PCR for diagnostic confirmation and genotyping of Orientia tsutsugamushi.

Transient adrenal insufficiency and post-treatment bradycardia in scrub typhus - a case report.

Clinical profile and improving mortality trend of scrub typhus in South India.

Etiology and Outcomes of ARDS in a Rural-Urban Fringe Hospital of South India.

Diagnosis of scrub typhus: introduction of the immunochromatographic test in Korea.

A case series of possibly recrudescent Orientia tsutsugamushi infection presenting as pneumonia.



Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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