Controlling the transmission of BoHV-1 via semen

BoHV-1 can be transmitted via the semen of acutely infected or latently infected bulls. The virus is not inactivated by storage in liquid nitrogen and can thus be transferred to insemminated cows or heifers.

Shedding of BoHV-1 in semen

The pattern of viral excretion varies considerably between individual animals, some bulls shed the virus for several days or weeks after acute BoHV-1 infection while in others virus shedding is hardly or not detected at all. A protracted course of intermittent virus excretion may also follow. Additionally, latently infected bulls can be triggered to re-excrete BoHV-1 by corticosteroid treatment or stress. Periods of spontaneous or artificially induced intermittent virus shedding are often unnoticed and can occur for prolonged periods after primary infection.

It should be born in mind that not each extended straw contains the BoHV-1 when the virus titre in the ejaculate is low. The infectivity of BoHV-1 persists during storage in liquid nitrogen and contamination of the pellets with the virus during storage has been reported.

BoHV-1 safe semen

Commercial semen producing companies are obliged to make all necessary efforts that ensure semen safety.

BoHV-1 -safe semen can be defined as the semen collected from a bull, that for 7 days or longer after the semen collection is negative to known infectious agents (seroconversion after infection occurs some 7 days after infection). Semen safety is not defined as such in the Directive 88/407/EEG or in the OIE Code, both of which allow for the semen release during one year after a single determination of negativity for infectious diseases of all bulls in the herd.