Theoretical Considerations on the Effects of Pig Immunization as Preventive Measures for Japanese Encephalitis

The effects of pig immunization as preventive measures for Japanese encephalitis were theoretically considered, with the aid of the model (slightly modified from Wada, 1972) for Japanese encephalitis epizootic in pigs. From the results obtained, the following points were implied: By the artificial immunization of pigs, the time of epizootic in pigs, and therefore epidemic in man, is delayed, the number of infected pigs decreases, and the rate of pigs having antibody becomes high. The degree of such changes is generally higher, when the density of vector mosquitoes is lower or the number of immunized pigs is larger. The number of transmissible mosquitoes, which is considered roughly proportional to the number of human cases if other conditions are the same, can be reduced greatly by the pig immunization, however the reduced number is still fairly large when the density of mosquitoes is very high.日本脳炎流行の理論モデルを用いて,日本脳炎の予防対策としての豚人工免疫の効果についての理論的考察を加えた結果,次の諸点が推論された:豚人工免疫によって,日本脳炎の流行時期はおそくなり,感染を起す豚数は減少し,抗体保有豚の率は高くなる.これらの変化の程度は,一般には伝搬蚊の密度が低く人工免疫する豚数が多いほど大きい.豚人工免疫は,人が日本脳炎に感染する危険性を大きく減らすことができるが,日本脳炎の予防対策としては,特に伝搬蚊の数が多い場合には,それだけでは不充分である