|Budget Amount *help
¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 2001 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 2000 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
The land leech, Haemadipsa zeylanica japonica, is a common blood-sucking leech in Japan, but its distribution area and its density are usually localized and low. However the range and density of the land leech have increased suddenly since 1985 in the southern Boso Peninsula, Chiba Prefecture. To develop control measures against the land leech, study on its population fluctuation and taking measures of its biohazard have been made.
The main reasons why expansion of distribution and population increase of the land leech, occurred are that the population of the Sika deer is increasing. The Sika deer seems to be one of the most suitable host and transporter for the land leech. Seasonal occurrence of the land leech closely related with temperature, precitation and humidity, however annual fluctuation had no clear relationship to meteorological conditions. Some periodical annual fluctuation was recognized independent on Sika deer population dynamics and weather conditions.
Based on laboratory observations, the average life span is about 2 years, the longest being about 5 years. After hatching it sucked blood 4 or 5 times, then it become mature enough to deposit cocoon in which average number of eggs was 5, maximum being 13. Once it sucked animal blood adequately, it survived for about 2 years without additional sucking. Deposition of and hatching from cocoon occurred at the temperature above 15℃. Sucking and mating behavior were observed above 10℃.
At present the most convenient way to avoid being attacked by the land leech is the use of effective repellents such as DEET that is available commercially. The other effective method rolls wet clothes dipped in salt water at your feet.