BVDV Prevention

Biosecurity must be a standard management goal.

Effective biosecurity practices are absolutely essential to successful BVDV prevention and control efforts. The introduction or addition of animals, especially pregnant animals, is the most common method by which BVDV is introduced into beef and dairy cow herds. Is essential that standard operating procedures are developed that outline the conditions for the entry of animals.
The purchase of open heifers, open cows and bulls presents the least risk of BVDV introduction when:

1. these animals are tested to ensure that they are not persistently infected
2. they are quarantined for 30 days prior to introduction into the herd.

A 30 day quarantine period must the basis of all biosecurity procedures to prevent the introduction of transient (acute) infections. If bred females are purchased, the unborn calf (fetus) must be treated in the same manner as a new addition. The bred females must be tested to ensure negative persistent infection status and the newborn calf must be tested to ensure it is not persistently infected prior to introduction of the cow-calf pair into the base herd.

Contact of the base herd with any animal of unknown BVDV test status (persistent infection) must be prevented.

Other methods of BVDV transmission, such as fomites, embryo transfer, artificial insemination, and wildlife, must be considered for their potential for the introducing BVDV. It is recommended that semen used for artificial insemination be collected according to certified semen services (CSS) guidelines.

Effective vaccination programs

In addition to the removal of PI reservoirs, BVDV transmission to and within the herd can be reduced with an appropriate vaccination program. From experimental and field studies, it is clear that empirical recommendations regarding effective vaccination program provide value and limit postnatal and gestational BVDV transmission. Although, there are variations in the vaccine-induced virus neutralizing antibody titers induced by various types inactivated and modified-live BVDV vaccines, vaccination reduces viremia and transmission of BVDV and reduced the associated post-infection disease losses. Serum antibody titers are an inadequate measure of vaccine-induced or natural protection. Vaccinated dams exposed to BVDV during early pregnancy have given birth to persistently infected calves.

The benefit of preventing clinical disease in vaccinated cattle exposed to BVDV is negligible when considering the overall prevention and control of the disease. Vaccination programs in breeding herds must be primarily designed to prevent fetal infection which is more difficult that prevention of clinical disease following transient or acute infection. Experimental evidence indicates that vaccination provides some protection of the fetus when the dam is experimentally challenged, but that protection does not extend to 100% of fetuses of exposed dams. The efficacy of maternal vaccination in providing fetal protection when the dams were experimentally challenged has been reported to range from 25% to 100% for inactivated vaccines and from 58% to 88% for modified live vaccines. Although not 100% effective, dams have measurable levels of anti-BVDV antibody following vaccination and fetal protection appears to be improved by vaccination. Therefore, planned vaccination programs are important for BVDV control. However it is very important to remember that, a sufficient amount of virus is able to escape inactivation by circulating antibodies in some dams to cause transplacental infection, abortion, and the development of persistent fetal infection, making vaccination programs inadequate to control BVDV by themselves.