Occurrence of a house-infesting Tropical rat mite (Ornithonyssus bacoti) on murides and human beings

In Germany there is little information available about the distribution of the Tropical rat mite (Ornithonyssus bacoti) in rodents. A few case reports show that this haematophagous mite species may also cause dermatitis in man. All developmental stages are exclusively bloodfeeder. Three children (4, 11 and 15 years old) of a family and a 23-year-old medical student were attacked by the Tropical rat mite. Prior to the consultation of our institution, the patients' conditions had been diagnosed as allergic dermatitis of unclear origin and treated by several antiphlogistic agents, however without success. The conclusive diagnosis, Tropical rat mite dermatitis, was based on the identification of the arthropod Ornithonyssus bacoti in the flats of the patients (husbandry of gerbils, etc.). The diagnosis of a Rat mite dermatitis requires the detection of the parasite, which is more likely to be found in the environment of its host than on the hosts' skin itself.