Orientia tsutsugamushi: Diversity and Distribution in India: A Review

Scrub typhus is a disease caused by Orientia tsutsugamushi which is an obligate, intracellular gram-negative bacterium. It is endemic to a part of the world known as “tsutsugamushi triangle.” This extends from Japan, China, Taiwan, South Koria, Nepal, Pakistan, Papua New Guinea, Australian states of Queensland and Northern New South Wales. In India, it has been recognized for several years and the disease widely spread all over the country. The severity of scrub typhus disease has been reported to be strain dependent in humans. Orientia tsutsugamushi strains have been examined by various research tools. PCR amplification and sequencing of 56-kDa antigen gene is one of the most advanced tool in identifying O. tsutsugamushi strains and genotypes. In the present review, English-language literature for reports of Orientia tsutsugamushi genotype diversity and distribution in India was searched using PubMed and Google Scholar databases. The search terms scrub typhus or mite typhus or tropical typhus or tsutsugamushi disease or Orientia tsutsugamushi or Rickettsia tsutsugamushiwere used in combination with the term genotypes or strains or serotypes. The result of present review revealed limited Information related to genotype diversity and distribution in the country. Understanding a more detailed regional genetic diversity is required in region-specific vaccine development strategies andsero-diagnostics tools.