The organism downregulates the host defense mechanism by downregulating the GP-96 on the macrophages and the endothelial cells, which plays a prime role in antigen presentation, functioning of the dendritic cells, antibody production, and cross-priming of the immune system. The cytotoxic T-lymphocytes and the NK T-cells play an important role in destroying the infected host cells. It induces the formation of several cytokines such as granulocyte-colony-stimulating factor (CSF), macrophage-CSF, interferon γ, and tumor necrosis factor-α.
tsutsugamushi invades endothelial cells to produce disseminated vasculitic and perivascular inflammatory lesions, which results in significant vascular leakage and ensuing end-organ injury of various organs such as lungs, heart, and kidney.
The severity of the disease depends on the strain of organism involved and also on the host. Scrub typhus is endemic and re-emerging in eastern and southern parts of Asia. Gradually, the disease became prevalent in many parts of India. In India, scrub typhus broke out in an epidemic form in Assam and West Bengal during the Second World War. tsutsugamushi encountered.ĭuring the Second World War, scrub typhus emerged out to be the most dreaded disease among the soldiers of the Far East. Mortality rates for scrub typhus range from < 1% to 50% depending on proper antibiotic treatment, status of the individual infected, and the strain of O. While scrub typhus is confined geographically to the Asia Pacific region, a billion people are at risk and nearly a million cases are reported every year. Humans are accidental hosts in this zoonotic disease. It affects people of all ages including children. Scrub typhus, first described in Japan in 1899, caused by Orientia tsutsugamushi (formerly Rickettsia), is an acute infectious disease of variable severity that is transmitted to humans by an arthropod vector of the Trombiculidae family. Tetracycline or chloramphenicol remains the main stay of therapy. Serious complication in the form of myocarditis, pneumonia, meningoencephalitis, acute renal failure, gastrointestinal bleeding, and even acute respiratory distress syndrome may develop. It may affect the central nervous system, cardiovascular system, renal, respiratory, and gastrointestinal systems. Other features are fever, maculopapular rash starting from the trunk, and spreading to the limbs. Later, an ulcer forms with black necrotic center and an erythematous border along with regional lymphadenopathy. Eschar is the characteristic lesion that starts as a vesicular lesion at the site of mite feeding.
Scrub typhus appears particularly to be distributed in the tsutsugamushi triangle which is distributed over a very wide area of 13 million km 2 bound by Japan in the east, through China, the Philippines, tropical Australia in the south, and west through India, Pakistan, possibly to Tibet to Afghanistan, and southern parts of the USSR in the north. In fact, scrub typhus is confined geographically to the Asia Pacific region, a billion people are at risk and nearly a million cases are reported every year. It is the most common re-emerging Rickettsial infection in India and many other South East Asian countries. Scrub typhus is caused by Orientia tsutsugamushi (formerly Rickettsia) and is transmitted to humans by an arthropod vector of the Trombiculidae family ( Leptotrombidium deliense and L.
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