Scrub Typhus in Mainland China, 2006–2012: The Need for Targeted Public Health Interventions

Scrub typhus is a vector-borne disease carried by the chigger mite. The aetiological agent is the rickettsia Orientia tsutsugamushi, which is endemic to several countries in the Asia-Pacific region, including China [1]. It is also a travelassociated disease [2] and of great importance among military personnel [3,4]. During the Second World War, scrub typhus was associated with a higher case fatality ratio than any other infectious disease in the China-Burma-India theatre of operations [1,3]. Clinical presentation in patients varies from asymptomatic to life-threatening disease [5], including acute hearing loss and multiple organ failure [6,7]. To date, there is still no effective and reliable human vaccine against scrub typhus and no point-of-care diagnostics available [1]. In China, scrub typhus is primarily transmitted by the larvae of the chigger mites Leptotrombidium deliense and L. scutellare, which usually feed on rodents, including Rattus spp. (R. losea, R. flavipectus, R. norvegicus, and R. confucianus), Apodemus agrarius, and Suncus murinus [8,9]. Humans become infected when they are exposed to areas where the chigger-infected rodent cycle occurs: for example, during agricultural and recreational activities. Excessive deforestation, changing patterns of agricultural activities, unplanned exploration of natural resources, and climate change may increase the transmission and expansion of the hosts and vectors of scrub typhus [10,11]. For the purpose of more efficient, targeted surveillance and control for scrub typhus, it is important to investigate the spatiotemporal epidemiological pattern of outbreaks in China. Historically, scrub typhus was first reported in China in Guangzhou (Guangdong Province) in 1948 [9]. In recent years, local outbreaks of scrub typhus have occurred in many areas of China, and recently identified endemic foci of scrub typhus are reported to be expanding [8,9]. However, the nationwide characteristics of scrub typhus epidemics are unclear and their spatiotemporal patterns need to be investigated. Spatial epidemiological tools have been widely used to identify spatiotemporal clustering, determine important environmental drivers and predict the distribution of a range of infectious diseases [12–14]. A detailed understanding of China’s scrub typhus epidemics is needed to develop more effective public health responses to scrub typhus outbreaks.