Dermatosis caused by the bite of trombiculid mite larvae, Leptotrombidium intermedium (Nagayo, Mitamura et Tamiya, 1920) (Prostigmata : Trombiculidae)

Human dermatosis caused by the bite of trombiculid mite larvae, Leptotrombidium intermedium, was observed by exposing the larvae to the skin of two volunteers (A and B). A total of forty unfed larvae were exposed to the forearm of A. Six larvae bit, but five out of the six detached within 45min. postinfestation. Only one larva enlarged, fully engorged, and detached itself by 66hrs. postinfestation. On the site of the infestation, a vesicle with pain and itchiness appeared. A total of ninety unfed larvae were exposed to B. Only one out of ninety unfed larvae engorged and dropped off by 72hrs. postinfestation. Instead of a vesicle, a small erythematous macule with slight pruritus was noticed at the bitten site. Moreover, the feeding period of infesting mites on human skin was almost the same as that on mice, but the infesting ratio to human skin was much lower than that of mice.