MEDICAL GEOGRAPHICAL STUDY ON SCHISTOSOMIASIS JAPONICA:ON THE TOPOGRAPHY AND SOLL AS CONTROLLING FACTORS OF THE DISTRIBUTION OF ONCOMELANIA HUPENSIS NOSOPHORA (I)

概要

論文の詳細を見る
Schistosomiasis japonica is one of the famous endemic disease found in east and southeast Asia. It has been a preventing factor against the social and economical development in the endemic areas. From the above reason this disease can be taken up as a subject of regional study from the view point of medical geography. In this paper the writers pointed out, as the first step of their study, a remarkable ubiquity of this disease, and examined some factors controlling its distribution. This disease is caused by a pathological complex of three factors-human being, intermediate host (a species of snail named Oncornclania hupcnsis nosophora) and Schistosorna japonicum. It is empirically well known that the most important factor among them is the snail. Taking into account the relation between ecological characters of the snail revealed by papers hitherto reported, and environmental conditions in each endemic area, the writers investigated the topography and soil as controlling factors delimiting the distribution of the disease. The results are as follows: I. The distribution of the disease is limited only to four or five localities in Japan. II. Landf orms of the habitats are classified into following three types, with reference to the landform classification of flood areas. They are: (1) Lower deltaic plain; lowlands formed by fine materials such as silt and clay, on which flood water stands deeply for a long period. To this type belong the main endemic areas, i.e. a greater part of the middle basin of the River Chikugo, the Kannabe basin, and basins of the River Tone and the River Arakawa. (2) Lower alluvial fan ; lands which may be flooded by heavy rain, but the water drains soon after the rain. A part of the basin of the River Chikugo and a greater part of the Kôfu basin are classified as this type. (3) Upper alluvial fan; the surface slope is relatively steep and is well drained, having never experienced recent flood. This type is thought to be of an unusual case. A part of the fan formed by the River Midai in the Kôfu basin is the only example. Thus, in brief, many of the land surfaces of the endemic areas are of the first type, with only a few exceptions. Or, in other word, the distribution pattern of the endemic areas of this disease can be well explained through landform division map by flood-type. However, the largest and the most marked endemic area of Japan, the Kôfu basin, is classified as the second or the third type, suggesting that the flood topography alone may not explain the dis tribution of the disease. III. By observing in detail each topographic unit of the endemic areas where the snail inhabits are maldistributed, it was found that an important factor affecting such micro land conditions might be the soil. However no precise data concerning the soil of the endemic areas has been shown by the previous reports on this disease. The writers tried to breed snails in the laboratory for the purpose of clarifying soil characters which have influence upon the inhabitation of the snail. Soil samples used for the investigation were collected in many localities ; not only in the Kôfu basin but in other plains and basins of Kantô and Chûbu districts. In them were included artificially mixed soil materials with special texture. Experimental items were: separation of particle-size (by ASK method), measurement of soil texture, determination of humus contents (by Tiurin method) and investigation of differences caused by soil parent materials. The results obtained are as follows: (1) Remarkable differences in the numbers of newly hatched snails and in speed of growth and survival rates of youngs were found among samples from, each locality. Especially a sample collected in KOf u habitats showed to be the most suitable for the snail life.
The Association of Japanese Geographersの論文

MEDICAL GEOGRAPHICAL STUDY ON SCHISTOSOMIASIS JAPONICA:ON THE TOPOGRAPHY AND SOLL AS CONTROLLING FACTORS OF THE DISTRIBUTION OF ONCOMELANIA HUPENSIS NOSOPHORA (I)

スポンサーリンク

概要

The Association of Japanese Geographers | 論文

スポンサーリンク