Abstract
Although influenza C virus (ICV) and influenza D virus (IDV) circulate mainly among humans and cattle, respectively, recent studies in the USA have reported both viruses to be significantly related to the symptomatic bovine respiratory disease complex (BRDC), which causes economic losses in cattle farming. In this study, we conducted a serosurvey of ICV and IDV infections using cattle samples collected from five prefectures in Japan during 2020-2023. Hemagglutination inhibition testing indicated that the overall seroprevalence was 27.0 % for ICV and 48.5 % for IDV, the regional seroprevalence varied from 4.0 % to 36.9 % for ICV and from 10.8 % to 57.7 % for IDV, and the annual seroprevalence varied from 3.4 % to 23.2 % for ICV and from 21.8 % to 53.5 % for IDV. These results indicate that ICV and IDV are circulating widely among cattle in Japan, suggesting their possible involvement as the causative agents of BRDC.