Dr. Julia Ridpath – Managing BVDV Risk Factors For Optimum Dairy Herd Health
Posted on November 9, 2012 in
Bovine viral diarrhea viruses, also known as BVDV, affect all kinds of animals, including cattle, swine, llamas and more, according to Dr. Julia Ridpath with the USDA-Agricultural Research Service’s National Animal Disease Center.
Even though the word “diarrhea” is included in the name, the primary target of the virus is the immune system rather than the digestive tract. One of the results of infection is a weakened immune system, which leaves the animal with an increased vulnerability to subsequent infections with other viruses and bacteria.
How can BVDV spread and infect other animals? The main sources of infection are animals persistently infected with BVDV. Persistently infected animals are created when a fetus is infected during the first trimester of pregnancy. When a fetus is infected at this point in gestation, their immature immune systems are not able to eliminate the virus. The end result is an animal with an immune system that can’t tell the difference between itself and the virus, and so virus is present in all its organs and tissues for the remainder of its life.
BVDV can spread from these animals to other animals through direct and indirect contact with bodily fluids such as mucus. These fluids can originate from the eye, mouth, nose, mammary gland, and urinary or reproductive tracts. Products that may be contaminated with BVDV include milk, colostrum, fetal bovine serum and semen.
Symptoms following BVDV infection range from mild to severe, depending on the virulence of the infecting strain and the presence of other pathogens. These infections may present as respiratory, enteric and/or reproductive disease. Thus, BVDV infections cannot be diagnosed based on observation of clinical signs. Diagnosis of BVDV infections is based on detection using laboratory tests such antigen capture ELISA (or ACE), which detects the presence of viral proteins, or polymerase chain reaction, which detects the presence of the viral genetic material.
Ridpath recommended these three steps to control BVDV within your herd:
- Develop a surveillance program to detect and remove persistently infected animals.
- Develop biosecurity strategies aimed at preventing the introduction of infected animals.
- Develop a vaccination program to increase herd resistance to BVDV infection.
Producers can choose from multiple ways to conduct BVDV surveillance within a herd. These range from the low cost-high risk approaches, such as use of sentinel animals, to the high cost-low risk, such as testing of every animal in the herd. It is up to every operation to work with their management team and veterinarian to determine the best cost/risk approach for that operation.
Ridpath recommended close monitoring and good records for improved biosecurity. If BVDV is to be controlled in operations such as heifer raisers, cooperation among the source herds is very important. The biosecurity of the heifer raising operation is only as strong as the weakest biosecurity program of the source herds.
Similar to surveillance programs, a range of vaccination options is available, from low cost-high risk to high cost-low risk. Resources for management teams that are trying to develop BVDV vaccination programs for their operations have been generated by the Academy of Veterinary Consultants and can be found at http://www.avc-beef.org/links/BVDLinks.asp. In addition, a BVDV risk assessment tool that includes vaccination reliability guide can be found at http://www.mtbqa.org/news/09BVDPI/BVD%20risk%20assessment.pdf
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