Risk factors associated with the within-farm transmission of bovine viral diarrhea virus and the incidence of persistently infected cattle on dairy farms from Ibaraki prefecture of Japan

• Published in: Research in veterinary science 2020-04, Vol.129, p.187-192
• Main Authors: Akagami, Masataka, Seki, Satoko, Kashima, Yuki, Yamashita, Kaoru, Oya, Shoko, Fujii, Yuki, Takayasu, Mariko, Yaguchi, Yuji, Suzuki, Atsushi, Ono, Yoshiko, Ouchi, Yoshinao, Hayama, Yoko
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Antigens; Bovine viral diarrhea virus; Calves; Cattle; Dairy cattle; Dairy farming; Dairy farms; Dairy industry; Diarrhea; Disease control; Epidemiology; Farms; Health risks; Immunization; Infections; Japan; Milk; Pasture; Persistently infected cattle; Risk analysis; Risk factors; Risk factors for within-farm transmission; Serology; Studies; Summer; Veterinary medicine; Viruses
• ISSN: 0034-5288; 1532-2661
• DOI: 10.1016/j.rvsc.2020.02.001

For understanding the factors affecting bovine viral diarrhea virus (BVDV) transmission, this study investigated the distribution of BVDV and the epidemiological features of persistently infected (PI) cattle in Ibaraki Prefecture of Japan, and identified farm-level risk factors associated with BVDV infection, with a focus on within-farm transmission and PI animal detection. Among all 377 dairy farms, forty-four PI cattle were identified on 22 farms. Thirty-eight and six PI cattle were born on their current farms or purchased, respectively. Twenty-six PI cattle were born from pregnancies on their current farms, seven from pregnancies in summer pastures, and eight from pregnancies on other farms. The within-farm seroprevalence on farms with PI animals was significantly higher than that on farms without PI cattle. Of 333 farms holding homebred cattle without movement records, antibody-positivity in homebred cattle was observed on 194 farms; these cattle were likely infected by within-farm transmission. Herd size, summer pasturing, and BVDV infection status of the nearest dairy farm were risk factors associated with within-farm transmission. Likewise, herd size, summer pasturing, and the proportion of purchased cattle were related to PI animal occurrence. This study shows the risk of within-farm transmission and occurrence of PI animals after the introduction of BVDV via purchasing and summer pasturing, and illustrates the significant role of PI cattle in circulating BVDV. More effective measures for screening BVDV infection and PI animals, including intensive tests targeting moved cattle and newborn calves, and bulk milk surveillance, are required to control the spread of BVDV in Japan. •Farm-level bovine viral diarrhea virus (BVDV) seroprevalence was 58.3% on dairy farms in Ibaraki Prefecture, Japan•Persistently infected (PI) cattle were identified on 5.8% of dairy farms•Herd-size, summer pasturing, and BVDV-infection on neighboring farm were risk factors for herds being serologically positive•Herd-size, summer pasturing, and cattle purchases were risk factors for PI animals in a herd