Assessment of current Rabies Prevention Act in Japan using infectious disease modelling

Purpose:In Japan, rabies has been eradicated in 1957 after introducing current Rabies Prevention Act, and has not occurred ever since. However, vaccination coverage and dog registration stipulated in the act fell dramatically due to the weakened public interest in rabies caused by the long lasted free status from rabies, and it is worth reviewing the risk of rabies transmission under such circumstance. The objective of this study is to predict rabies transmission dynamics in present situation using mathematical modelling. Methods:An individual-based and spatial mathematical model was developed, expressing onset of rabies, movement of infected dog and generation of secondary cases by rabid dog, taking account vaccination coverage and population density. Hokkaido and Ibaraki Prefectures were selected as study sites for simulation because they had different background related with rabies transmission. For the estimation of parameters: reproduction number, population density-dependency and adjustment of previously reported dispersal kernel in Tanzania, were estimated using the data of past rabies epidemic in Osaka Prefecture between 1919 and 1933, using maximum likelihood estimation. The simulations were repeated 500 times in R. To reveal efficacy of vaccination, simulations were performed with reduced vaccination coverage. Results:Estimated reproduction number was 2.8. The parameters for population density-dependency and adjusting the kernel were 2.28 and 2.24, respectively. In Hokkaido Prefecture, when vaccination coverages were 55%, 45% and 35%, median of final sizes were 2, 4 and 354, respectively. Durations until outbreak dies out were 53.5days, 92.5days and 339.5days, respectively. When vaccination coverages were 55.6%, 45.6% and 35.6% in Ibaraki Prefecture, median of final sizes were 2, 3 and 389, respectively. Durations until outbreak dies out were 35days, 89.5days and 397.5days, respectively. Conclusions:These results showed risk of transmission reflecting current situation. The model will be updated further to reflect changed rearing style and to show efficacy of several intervention options. Relevance:This is informative for risk communication

H. Kadowaki, K. Makita, Karen J. Hampson, A. Yamada, 'Assessment of current Rabies Prevention Act in Japan using infectious disease modelling', Rakuno Gakuen University, 2016