Analysis on Change in Snail Habitat Areas in Hunan Province from 1990-1999

Objective To analyse the change tendency of snail habitat areas in Hunan Province from 1990 to 1999. Methods Data on snail habitat areas submitted from all endemic areas were collected and analysed. Results New endemic areas were found every year except 1992, 1993 and 1994. For instance, 30 and 52 new endemic villages were found in 1996 and 1998 respectively and 11 new endemic townships were found in 1998 which showed a marked increase over other years. The snail habitat areas decreased from 1990 to 1994 but increased from 1995 to 1999. The snail areas increased 2.54% in 1996 and 1.56% in 1998 as compared with last year 1996 and 1997. The areas carried out snail control measures revealed decreasing tendency except 1992. The snail control area was 17 million m 2 in 1999 which reduced 54.2% as compared to 1990. After snail control measures, the snail free areas inside embankment were larger than that outside embankment every year except 1991. Since 1996, no snail free area has been found in outside embankment. The largest snail free area inside embankment reached 2.462 million m 2 in 1998. Conclusions The snail habitat areas showed not only increasing tendency but pressing on towards the city areas in Hunan Province during the studied period from 1990 to 1999. The main reason might be flood disaster,but changeable water level, large snail habitat areas, expansive snail control measures, unsatisfactory snail control effect were also the objective causes. Activities such as snail surveillance in outside and inside embankment, comprehensive snail control measures in inside embankment, snail control and cercaria killing measures in higher risk areas of outside embankment should be strengthened.