Forestry/ Agricultural Worker Health Risks for Chigger Mite: Exposure to Rickettsioses

PI: Loganathan Ponnusamy, NCSU

Abstract: Farm and forestry workers and their families that frequent and/or live in rural areas are at high risk of acquiring tickborne rickettsioses (bacteria) disease like Rocky Mountain Spotted Fever. The role of ticks as a vector of these bacteria has been extensively studied in the US, but the impact of chiggers (Trombiculid mites) has never been investigated. We have preliminary data in this proposal suggesting this was a mistake. Trombiculid mites in the genus Leptotrombidium are the exclusive biological vector of scrub typhus, caused by Orientia tsutsugamushi, an obligate intracellular Gram-negative bacterium closely related to the genus Rickettsia (Rickettsiales: Rickettsiaceae). One million cases of scrub typhus are reported each year in Korea, Japan, southern Asia, the Asian-Pacific region, and Australia. More recently scrub typhus was reported in the Middle East, Chile, and Africa, changing our thinking about the potential importance of chiggers in human disease in the US. The potential role of chiggers in Spotted Fever Group (SFG) rickettsiosis, a human disease attributed to ticks in the US, has never been studied even though chiggers share the same hosts as ticks, they live in the same geographical areas as ticks, and their human bites are mostly indistinguishable from ticks. Preliminary data are presented in this proposal for the first time showing that chiggers in North Carolina carry Rickettesia and pose a potential health risk. In this pilot proposal, we will investigate for the first time the bacterial microbiome of chiggers in the US. The data generated in this proposal will be used to asses the potential health risk chiggers pose to farm and forestry workers and used to develop proposals to NIOSH, NIH, NIEHS, USDA, EPA, DOE, and/or DOD to further understand the role of chiggers in human health.