Sero-Epizootiological Study of Racehorses with Pyrexia in the Training Centers of the Japan Racing Association

Abstract

A sero-epizootiological study was conducted on horses which showed clinical pyrexia at two training centers, each of which maintained 1, 200 to 2, 100 racehorses for training, of the Japan Racing Association. It continued from 1980 to 1985 to clarify the cause of pyrexia, so that measures might be considered for the prevention of infectious disease. A total of 3, 849 horses were found to be affected with pyrexia for the 6 years. Of them, 2, 852 horses were tested to equine herpesvirus type 1 (EHV-1), equine rhinovirus type 1 (ERhV-1), rotavirus and equine adenovirus (EAdV) by collecting paired serum samples. As a result, 669 (23.5%) horses showed seroconversion to these viruses; that is, 491 horses (73.4%) to EHV-1, 91 (13.6%) to ERhV-1, 64 (9.6%) to rotavirus and 23 (3.4%) to EAdV. EHV-1, ERhV-1 and rotavirus exhibited a seasonal characteristic in spread. EHV-1 and rotavirus spread in winter and early spring. ERhV-1 spread not only in the cold season, but in changing times of season, such as early spring and early autumn. The percentage of 3 years old in the horses showing seroconversion to EHV-1 was two times higher than those in the horses showing seroconversion to other viruses. All of the horses showing seroconversion to ERhV-1 and EAdV were under 4 or 3 years old, respectively. The mean age of the horses showing seroconversion to EHV-1, rotavirus, ERhV-1 and EAdV were 2.96, 2.73, 2.44 and 2.25, respectively.