Seroepizootiological survey of Japanese encephalitis virus and Getah virus in regional horse race tracks from 1991 to 1997 in Japan.

A sero-epizootiological survey was conducted for Japanese encephalitis virus (JEV) and Getah virus (GeV) at 10 to 20 regional horse race tracks from 1991 to 1997 in Japan. It was observed that geometrical mean (GM) antibody titer to JEV and GeV was 10 to 50 times higher than others at several race courses (RCs) almost every year. Of them, several race horses showing high antibody titer, which were suggested to be infected with the virus, were also observed in this survey. These data suggested that the viruses have spread among race horses almost every year in Japan, although, fortunately, no horse showing clinical illness due to these viruses was observed. The calendar years and the names of the race courses in which the spread of JEV was suggested were Sonoda and Nakatsu RCs in 1991, Nakatsu RC in 1992, Arao RC in 1993, Nagoya RC in 1994, Kaminoyama, Urawa, Saga and Arao RCs in 1995 and Ooi and Saga RCs in 1997. Spread of JEV was not observed in 1996. The calendar year and name of the race courses at which the spread of GeV was suggested were at Ooi, Sonoda and Nakatsu RCs in 1991, Arao RC in 1992, Nakatsu RC in 1994 and 1995, Funabashi RC in 1996, Saga RC in 1997. It was suggested that surveillance of JEV and GeV should be continued in the future in at least the southern to middle parts of Japan. It has also been suggested that it is necessary to promote the wider use of vaccines to persons related to horse racing.