富士山東山麓におけるタテツツガムシ, フトゲツツガムシの分布様式と恙虫相

Abstract

The distribution patterns of Leptotrombidium scutellare and L. pallidum, the vector species of tsutsugamushi disease, were surveyed with Tullgren's funnel method on the eastern slope of Mt. Fuji, Gotenba-Oyama District, Shizuoka Prefecture, in the autumn of 1988 and 1989 and in february, 1990. L. scutellare was shown to be distributed at well-drained sites at the foot of the mountain, and the specific habitat for this species was the sparse Miscanthus grassland developed on the sunny granular soilbed, which was sporadically seen in this district. But no evidence of recent spreads of such specific habitat was found coincidentally with the recurrent outbreaks of tsutsugamushi disease. L. pallidum was distributed in various types of habitats as previously observed in Nagano Prefecture, but the most common habitat for this chigger was the larger paddy banks that have recently been made during the paddy zone reconstruction program. Environmental changes brought about by the construction of many larger banks are thought to have contributed to an increase in vector population density and are probably responsible for the recurrent outbreaks of tsutsugamushi disease transmitted by L. pallidum. The larva of L. scutellare was observed not to overwinter, while the larva of L. pallidum was densely populated in both autumn and early spring of the next year. The chigger fauna of this district consisted of 16 species, inclusive of the 3 species that usually infest birds.