Assessing the Risk of Rickettsial Pathogens in Thailand

Location: Thailand

Alumni: Kaya Garringer

Faculty: John Grieco

Rickettsial diseases are caused by a group of zoonotic pathogens transmitted to humans by a variety of arthropod vectors, including ticks and mites. Certain rickettsial diseases are endemic in Southeast Asia, including scrub typhus disease, a common cause of human febrile illness and one of the most medically relevant rickettsioses. Leptotrombidium spp. mites are the only confirmed vectors of scrub typhus disease. This study was intended to provide additional, relevant insight to the distribution of scrub typhus risk throughout the country of Thailand. Vector collections were performed in Kachanaburi province, Thailand. Collection sites were mapped using hand-held GPS units and displayed using QGIS software. Collection methods employed resulted in no Leptotrombidium spp. being collected during the study period, so an existing dataset from South Korea was instead used to develop an ecological niche model to assess the selected variables associated with a presence of Leptotrombidium spp. A model was successfully developed that showed agreement between mite species presence and positive cases of scrub typhus for South Korea. This model showed that human population density had the greatest contribution to species presence. Additionally, most of the scrub typhus cases in South Korea in 2015 were located in areas with a higher estimated probability of mite presence. Future attempts at translating this model to Thailand could result in improved vector control and prediction of disease risk. Survey results revealed that a basic awareness of scrub typhus disease exists, but that detailed knowledge is lacking and it is generally not perceived as a threat; this may affect the diagnosis and provision of appropriate treatment for scrub typhus and other rickettsial diseases.

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