Problems on the land leech-induced biohazard spreading in various districts of Japan--Especially the environmental-medical pursuance in southern area of Boso Peninsula--

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1) Fixed point ivestigation on the explosive propagation of the land leech that occured in 1985 in Amatsu-Kominato-machi. Chiba Prefecture was continued since 1987. As As the sesults, the propagation and the leech population reached at peak in 1992, but after then these showed finally a downward tendency in 1993. It is highly provable that the mitigation of the propagation might be caused by the both of so-called cold summer as well as decrease of stroll of the deers in the street.2) The state of land leech in other ditant habitates in Tanzawa mountainious area (Kanagawa Pref.), Southern part of Akita Prof., Kinkazan is. (Miyagi Prof.) and Kasugayama primeval forest (Nara Pref.) were explored in comparing with that of Boso Peninsula In original habitates, where the land leechs coexist with the deers, such as Kinkazan and Kasuga-yama, the leech-induced biohazard scarcely occured in the inhabitants except for such persons as several biologists who enter the bushed in order to pursue deer … More s orto seek peculiar organisms.3) It was found in the deers of Boso distrct in 1991 that the deers acted as if the proper host of the land leechs which lived upon the extremities of deers and that there was a kind of hollowed tumor, within the hollow of which existed a entering leech, between the 3-4th toes of deers. However, the curious relationship of this kind between land leechs and deers could not be seen in other habitates than Boso district.4) The rumored falling attack from overhead tree could be never proven by indoor experiment using 10 indivisuals of the leech on a tree-branch that was put 20 cm over the head of the researcher who blowed his expiration against them.5) A stray dog showed a powerful mediating ability against he leech and possesed by seven individuals within 10 minutes strolling through the habitate with high population of the leech. The 5 individuals, which blood-sucked the dog already excepting hungry 2 individuals, among the avobe-mentioned 7 individuals of the leech died within 2 days. Accordingly it was considered that the anti-land leech antibody was produced in the dog through repeated blood-sucking by land leeches. Less