Quantitative risk assessment of the introduction of rabies into Japan through animals accidentally placed in international freight containers.

Japan has been free from rabies since 1958 and various preventive measures are in place to protect the country from the introduction of the disease. With an increasing number of freight containers arriving in Japan every year, there is a concern that rabies might be reintroduced into Japan through animals arriving in international freight containers. A stochastic simulation model was built assuming the following entry and exposure pathway as being the most likely route of rabies entry: a rabies-infected animal is accidentally placed in a freight container in the country of origin; it survives transportation from the moment the container is sealed in the country of origin until it is opened at the destination in Japan; and it escapes from the container when it is opened at the destination in Japan. Input parameter values were based on surveys of container handling and warehouse agencies and scientific data from the literature. The annual probability of rabies introduction through this pathway worldwide was 5.47 × 10 (90 % PI: 9.72 × 10-1.33 × 10), or rabies would enter Japan every 368,864 (90 %PI: 75,267 - 1,027,568) years. Among sub-regions, the annual probability was highest for South-eastern Asia (4.54 × 10 (90 % PI: 8.04 × 10-1.11 × 10)), followed by Eastern Asia and Southern Asia. The rabies introduction risk from other sub-regions was negligible. The result of scenario analysis indicated that even if any of the main parameters changes, the risk of rabies introduction still remains very low, suggesting that unintentional movement of animals through international freight containers is not a very important pathway of rabies introduction into Japan.