2007 Outbreak of Human Pruritic Dermatitis in Chicago, Illinois Caused by an Itch Mite, Pyemotes herfsi (Oudemans, 1936) (Acarina Heterostigmata Pyemotidae)

To conduct field sampling of mites (Acarina) that cause multiple cases of dermatistis in matitis in humans. In August of 2007, a request was received from the Illinois Department of Public Health for assistance in identifying the causative agent of an unusually large outbreak of unexplained “insect bites” from neighborhoods in Cook and Du Page Counties. The causative agent was suspected to be an itch mite, Pyemotes herfsi (Oudemans, 1936), that had been implicated in outbreaks during 2004 and 2005 in parts of Kansas, Nebraska, Missouri and Texas; however, leaf and sticky card samples sent to entomologists in Nebraska did not yield an identification of the causative agent. The specific objectives of the work reported herein were: 1) to conduct field sampling of oak leaf galls and other suspected habitats to isolate the causative agent of the outbreak, 2) to identify the amplifying insect host of Pyemotes mites, if these prove to be the causative agent, and 3) to obtain independent confirmation of identification of the causative agent from a second entomologist who specializes in the appropriate group of mites or other arthropods.