[Epidemiological study of tsutsugamushi disease in Gunma prefecture. A special field study and serotype].

An epidemiologically investigated of invasion of Rickettsia tsutsugamushi, inhabitant of mites and serum sample from patients with Tsutsugamushi disease in Gunma prefecture from 1984 to 1994 was made. Our data clearly indicated that Rickettsia tsutsugamushi was not located but widely spreaded throughout the Prefecture. Mites on rodents, were classified into 4 genus and 12 species and about 15% of them were Leptotrombidium pallidum and Leptotrombidium scuttellare, well known virulent vectors. The highest incidence rate of this disease was observed in the northwest area of the Prefecture from October to December, while a smaller number of patients occurred in other areas and in other months. About fifty percent of the serum samples from the patients were positive to the Karp strain. These results suggest that the major cause of this disease is the Karp strain and the disease could occur potentially in various areas of the Prefecture.