A Handbook on Geographical Distribution, Epidemiology, Prevention and Control of Scrub Typhus (Including Surveillance and Control of Rodents and Mites)

Scrub typhus, one of the most widespread zoonotic diseases, is an acute febrile, infectious illness of variable severity caused by Orientia (Rickettsia) tsutsugamushi, which is an obligatory intra-cellular bacterium and is transmitted to humans by the bite of infected chiggers (larvae) of trombiculid mites (Leptotrombidium sp.). Scrub typhus is a significant health issue amongst military personnel, farmers, park rangers, geologists, miners, as well as oil palm workers. Scrub typhus is distributed in the Tsutsugamushi triangle, which is over 13 million square kilometres bounded by Japan in the east; China, Philippines, and tropical Australia in the south; India, Pakistan, Tibet, and Afghanistan in the west; and the southern parts of the Russian far east in the north. The WHO stated that ‘’scrub typhus’’ is probably one of the most underdiagnosed and underreported febrile illnesses due to a lack of awareness and diagnostic facilities in many countries. Every year, one million cases of scrub typhus are reported, with a 10% fatality rate. The distribution of scrub typhus is closely associated with that of Rattus rattus or Bandicoot sp.. In vertebrates, including humans, they infect the vascular endothelium and reticuloendothelial cells. The clinical manifestations of this disease range from sub-clinical disease to organ failure. One of the typical features of scrub typhus is the presence of a punched-out ulcer covered with a blackened eschar, which indicates the location of the mite bite. Complications manifest as interstitial pneumonia, ARDS, renal failure, meningoencephalitis, myocarditis, gastrointestinal bleeds, jaundice, septic shock, and multiorgan dysfunction syndrome.