BVD control starts and ends with the cow herd
Dan Thomson, ISU animal science professor

Bovine Viral Diarrhea Virus (BVD) is a pestivirus that causes abortion in cows, birth defects in calves and immune suppression in all types of cattle. This virus is closely related to viruses that cause Hog Cholera in swine and Border disease in sheep. BVD is a reproductive disease that is passed numerous ways (mainly nose to nose contact) in beef herds. There are two genotypes of BVD virus: BVD I and BVD II. Within each genotype, there are two biotypes: cytopathic and noncytopathic. “Cyto” means cell and “pathic” means death. Therefore, cytopathic BVD kills the cells that it infects and noncytopathic is not lethal to the animal’s cells. Regardless of the genotype or biotype, BVD virus causes some major issues in the health and well-being of our cow herd.

There are two types of infections in which cattle can succumb to with BVD virus. Transient infections (TI) are infections that a calf or cow gets which they fight off, recover and rid the virus from their body. Persistent infections (PI) are infections in which the animal never rids the body of the virus and constantly sheds the organism in the environment. The TI cattle shed BVD virus in the environment but only for about 14 to 21 days until they clear the viral infection. How do cattle become TI or PI animals? Cattle that are transiently infected do so through nose to nose contact or contact with body secretions from a BVD infected animal. A PI calf however, must be infected as a fetus (in utero) prior to the fetal immune system being activated which occurs around 120 days gestation. The fetal immune system takes an inventory of cells and proteins when it is activated for the first time. If a fetal calf has BVD virus in its body at this time when the immune system takes inventory, the immune system thinks that BVD virus is actually a part of the calf’s body similar to heart cells, hair follicles, etc. Therefore, the calf never forms an immune reaction against BVD. A persistently infected calf will have BVD virus in every cell in its body for the entirety of its life.

How common is BVD virus in the United States? It is estimated that 1% of the calves born in the United States are persistently infected with BVD. On the ranch, research has shown that about half of the BVD PI calves die prior to weaning. Therefore, based on published literature, the prevalence of BVD PI calves at arrival to the feedyard ranges from 0.3 to 0.5%. Once the calves are in the feedlot, 50% of them will die or be railed during the finishing phase. So, roughly only 25% of BVD PI calves survive to reach the packing plant. Along the way, these PI calves cause many herd health problems in all segments of the beef industry. Control of BVD virus in our beef production system is dependent on the cow-calf segment of the industry through the prevention of PI BVD calves being born.

It is important to work with a veterinarian in designing a BVD prevention program for your cow herd. The Academy of Veterinary Consultants has developed technical briefs to guide practitioners and beef producers in how to control and eradicate BVD from the cow-calf herd. The only way to know the BVD PI status of your herd is through diagnostic testing. There are many BVD diagnostic procedures but understanding which animals to test is key. The AVC BVD bulletin recommends a baseline or initial diagnostic surveillance prior to the breeding season during which a producer should test all calves, non-pregnant females without calves, replacement females and bulls for herds testing for BVD for the first time. See all the AVC BVD resources.

Once they have confirmed there are no BVD PI cattle in the herd, beef producers should work with their veterinarian to design vaccine protocols and biosecurity plans to prevent BVD infections from entering their cow herds. Vaccines for BVD can help control BVD infections in the heifers, cows and bulls, but also there are vaccines that are labeled to protect fetal infections from this virus. A veterinarian is a great resource to help beef producers know how many vaccine doses are required, which cattle need vaccinated and what type of BVD vaccine to use on their cattle. Biosecurity of BVD focuses on new cattle introductions and control of contact with the neighbor's herd. The easiest control point is to allow only BVD PI negative animals on your premise. However, if you don’t know the BVD PI status of the cattle, quarantine and testing the cattle prior to commingling with your herd is recommended. Also, beef producers need to work with their neighbors to understand that introduction of the virus can occur over the fence or when cattle get mixed due to poor fence maintenance.

Bovine viral diarrhea virus is a complex problem that can have crippling economical and biological effects on our beef herds in the United States. Many countries have developed eradication programs for this virus. Working with your veterinarian to develop a herd control program through baseline diagnostics, proper vaccine program design and biosecurity steps is key to controlling this disease in your herd.

Source: Iowa Beef Center, Iowa State University