Field Survey on the Occurrence of Reproductive Disorders in Boars

Abstract

A survey on reproductive disorders of 40 boars fed on pig farms in Saitama, Kanagawa, Chiba, Nagano, Gifu, Miyazaki and Kagoshima prefectures was carried out between 1975-1980. On pig farms in all of these prefectures except Kagoshima, clinical signs such as fever, anorexia, hyperemia and swelling of the scrotum, swelling or atrophy of the testes, palpable enlargement and increased firmness in the head of the epididymis were frequently observed. Semen from these boars exhibited azoospermia (42. 5%), necrozoospermia (25%), asthenozoospermia (20%) and other abnormal properties (12. 5%). The period of onset of the reproductive disorders in the boars coincided with that of the prevalence of Japanese encephalitis virus (JEV) as reported in the information published by the Ministry of Health and Welfare in Japan each year. In addition, the present seroepidemiologic observations strongly suggested that the reproductive disorders of boars on pig farms in Saitama, Nagano and Gifu prefectures were caused by JEV.