Scrub typhus in Sri Lanka – beyond the stethoscope

Scrub typhus, or tsutsugamushi disease, is an acute febrile illness in humans caused by infection with Orientia tsutsugamushi (OT) following a bite of an infected mite vector of the genus Leptotrombidium1. Scrub typhus is endemic in the Asia-Pacific region, extending from Afghanistan to China, Korea, the islands of the western Pacific and Indian Oceans, and northern Australia2,3. This endemic region is often referred to as the tsutsugamushi triangle, and hosts approximately 1 billion people4. The vectors can be found in a variety of ecological conditions, from the mountainous regions of northern India to the tropical climates of the Malay Peninsula and Indonesia2. Trans-ovarial transmission of OT within vectors appears to be essential to maintenance of the agent in nature; thus, the mite serves as both the vector and the reservoir2. Transmission of the etiologic agent to vertebrate hosts occurs during feeding of the larval or “chigger” stage of mites2. While Orientia is vertically maintained in Leptotrombidium mite populations, it may be transmitted horizontally from mites to vertebrate hosts2. The transmission to humans is incidental. Currently, there is no vaccine against scrub typhus5.