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Title: 日本脳炎流行の理論的考察
Other Titles: Theoretical Considerations on the Epidemic of Japanese Encephalitis
Authors: 和田, 義人
Authors (alternative): Wada, Yoshito
Issue Date: 20-Mar-1975
Publisher: 長崎大学熱帯医学研究所 / Institute of Tropical Medicine, Nagasaki University
Citation: 熱帯医学 Tropical medicine 16(4). p171-199, 1975
Abstract: 日本脳炎は本質的には豚の病気であるとの考えから,豚における流行の数学的モデルを作って,これを人における流行と関連づけた.このモデルを用いてのシムレーションから,以下に述べるような諸点が明らかとなったが,その多くは他の方法では理解が容易でないものである.伝搬蚊の密度と人が感染を受ける危険性とは正の相関があるが,逆に豚の感染状況から人感染の危険性を論ずるのは,多くの場合無理である.蚊の消長のどの時期から豚の感染が始まるかによって,その後の豚及び人での流行様相は大きく変る.豚での流行がそれ以上拡大しないための,蚊及び感受性豚の限界密度が存在する.蚊の日生存率が大きくなると,蚊の密度が高くなった場合と同じように,豚及び人での流行は大きく影響を受ける.豚の人工免疫によって,感染を起す豚数は減少し,抗体保有豚の率は高くなる.また,人工免疫によって,人が感染を受ける危険性を大きく減少させることができるが,日本脳炎の予防対策としては,特に伝搬蚊の密度が高い場合には,それだけでは不充分である. / Based on the view that Japanese encephalitis is essentially a disease of pigs in Japan, a mathematical model for the epizootic in pigs was developed under some assumptions and conditions, and the relation to the epidemic in man was considered. As given in the below, simulation studies with the model revealed several features in pig epizootic and human epidemic, many of which are otherwise not easy to understand. It can be said that the density of vector mosquitoes and the scale of human epidemic are positively related each other, but the increased number of mosquitoes much less sensitively influences the scale of pig epizootic. The time, in relation to mosquito prevalence, of the initiation of pig infection is important to affect the number of infected pigs, and also the number of transmissible mosquitoes which is positively related to the number of human cases. The existence of threshold densities of mosquitoes and susceptible pigs below which the pig epizootic tends to extinguish is clearly indicated. The increase of the daily survival rate of mosquitoes greatly influences the pig epizootic and the human epidemic, as in the increase of the mosquito density. By the artificial immunization of pigs, the number of infected pigs decreases and the rate of pigs having antibody becomes high. Also the number of transmissible mosquitoes, and therefore the number of human cases can be greatly reduced by the pig immunization, but the reduced number is still fairly large when the mosquito density is very high.
URI: http://hdl.handle.net/10069/4172
ISSN: 03855643
Type: Departmental Bulletin Paper
Appears in Collections:Volume 16, No. 4

Citable URI : http://hdl.handle.net/10069/4172

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