[Tentative study of geographical epidemiology of schistosomiasis japonica in Yunnan province].
Schistosomiasis prevails in 17 counties and cities in Yunnan Province. Approximately, a population of 301,511 were affected and the snail-ridden area amounted to 219,000,000m2 in the past years. These endemic areas were not evenly distributed, but rather scattered. The endemic foci were vertically distributed at an altitude of 1,350-2,450 metres above sea level. Human cases were found mostly in areas with an elevation of greater than or equal to 1,800 metres, and became progressively fewer with the ascent. However, in areas with an-elevation of less than or equal to 1800 metres, the infection rate in the inhabitants decreased with the descent. In areas with an average temperature of 11.8-19.5 degrees C and the annual rainfall up to 574-970mm, transmission of the schistosomiasis was always present, suggesting an annual mean temperature around 15.7 degrees C and rainfall 800-900mm were favourable factors for schistosomiasis transmission. The cultivated areas with paddy soils were most suitable for the breeding of Oncomelania snails, where schistosmiasis was severely prevalent. Only a few Oncomelania snails and patients were observed in areas covered with red loam. No patient or snail was found in areas with brown loam or mountain meadow soil.
Tan
H Q
HQ
Institute of Parasitic Diseases, Chinese Academy of Preventive Medicine.
Luo
Y J
YJ
Zhang
R
R
Zhang
X Q
XQ
Yuan
B C
BC
Wang
Y A
YA
Xie
F X
FX
D000818:Animals; D002681:China / Q000453:epidemiology; D004463:Ecology; D006801:Humans; D015995:Prevalence; D012554:Schistosomiasis japonica / Q000453:epidemiology*; D012908:Snails / Q000469:parasitology; D012987:Soil
D012987:Soil