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Clinical manifestation of BVDV infection in cattle can vary from subclinical to fatal [16]. BVDV is transmitted primarily by direct contact with bodily fluids of infected cattle. Venereal transmission via semen from acutely and persistently infected bulls is also well documented [17, 18]. Cattle that are born persistently infected with BVDV shed large amounts of the virus and are considered the major reservoir. Control of BVDV centers around elimination of these persistently infected individuals combined with vaccination and biosecurity measures to prevent exposure to BVDV [16].

The bull is also capable of maintaining a prolonged testicular infection that persists beyond the initial viremia [19, 20]. These localized prolonged testicular infections can persist for at least 2.75 years and have been induced by vaccination of seronegative peripubertal bulls with a modified live vaccine containing non‐cytopathic BVDV [20, 21]. Semen from one bull with prolonged testicular BVDV infection was capable of infecting heifers through artificial insemination (AI); however, others studies evaluating transmission from bulls with prolonged testicular infection have not resulted in transmission [20, 22]. While the exact risk of transmission from these bulls appears to be low, further studies are needed before the use of vaccines containing non‐cytopathic BVDV can be recommended in breeding bulls [14, 20]. Current recommendation are to vaccinate all bulls with a vaccine containing cytopathic modified live BVDV at least 28 days prior to breeding and booster according to the product label recommendations [14].