Seminal shedding of bluetongue virus in experimentally infected bulls

Twenty bulls were inoculated with bluetongue virus (BTV) to study the frequency, duration and pathogenesis of seminal shedding of the virus. BTV was isolated from 19 of 181 ejaculates collected from these bulls during the period of viremia, but from none of 79 ejaculates collected after the viremia. Three categories of bulls were recognized on the basis of frequency and duration of seminal shedding of BTV. Virus was never isolated from semen in a majority (13 of 20) of bulls. In another group (5 of 20), virus was isolated from semen in low titer and from only 1 to 3 ejaculates. However, 2 bulls did shed relatively large quantities of virus in semen over a period of 2 to 3 weeks. Seminal shedding of BTV in infected bulls closely followed peak virus titers in blood and in no case was virus isolated from semen without its concurrent isolation from blood. Semen was processed and frozen from 1 bull that shed BTV. Six of 9 heifers inseminated at estrus with this semen became pregnant, and 3 of 9 became viremic and seroconverted. An additional heifer developed antibody to the virus, but did not become detectably viremic. No evidence of fetal infection was found in the heifer that became pregnant and infected, or in 5 heifers that became pregnant, but did not became infected.