It is that time of year again and as many of us prepare to make the trek to Denver for the National Miniature Hereford Show, some may wonder about the importance of BVD-PI testing for all show and sale animals. The following information is intended to provide a simplified overview of the disease, transmission and herd eradication. For specific information related to your animals’ exposure contact your ranch veterinarian.
What is BVDV?
Bovine Viral Diarrhea Virus (BVDV) is a virus known to infect domestic livestock and some wild animals. For cattle producers the virus causes economic losses through decreased weight gains, decreased milk production, reproductive losses (abortions), and animal death. There are two categories of BVD infections.
1- Transient (acute) infection (“TI”)
• Short term (weeks)
• Acquired after birth
• TI cattle become immune and clear virus
• Greater than 95% of BVD infections are TI
• TI cattle are a minor source of virus spread in herd
2- Persistent (chronic) infection (“PI”)
• Life long persistent infection acquired while in the uterus therefore only fetal infections results in BVD-PI
• PI cattle can never become immune
•Less than 5% of BVD infection are PI
• PI cattle in herds are the major source of virus spread
Over 90% of BVD-PI calves are born from normal dams (no prior BVDV exposure)

Development of BVD PI

Persistently infected (PI) BVD cattle are created when the dam and her fetus become infected with BVD virus between 45 to 125 days after conception. During this period of development, the immune system of the fetus has not yet developed and the BVD infection is not recognized. The fetus is not capable of recognizing the virus and does not develop antibodies against the BVD. Fetuses infected during this period survive and are permanently infected with the BVD virus, shedding the virus throughout their lifetime.

Signs and symptoms of BVD-PI

Most BVDV infection problems in cattle herds go unnoticed since 70-90% of BVD infections do not result in observable signs of disease. When present, the most common disease caused by BVD virus infection in cattle herds is poor reproductive performance including, abortions, poor conception rates, stillbirths, and weak calves. The BVD virus infection can causes suppression of the bovine immune system resulting in increased susceptibility to other infectious diseases such as scours, pneumonia and poor weaning weights.

How is BVDV transmitted?

The main source of BVDV in cattle herds is BVDPI animals. Virus in BVD-PI animals is shed in all body secretions including nasal discharge, saliva, tears, milk, feces, urine and semen. Transmission occurs via ingestion, inhalation, and even such things as boots and vehicles. The most common ways that BVDV can enter a herd are as follows:
• By purchasing replacement cattle at auctions
• By purchasing a pregnant animal with PI calf
• Introducing replacements or show stock without quarantine
• Failure to maintain a BVD vaccination program
• Failure to test replacements for BVD PI
• Contaminated semen or embryos
• Borrowed or unknown bulls

Why test and remove BVD-PI animals from a cattle herd?

Persistently infected (PI) cattle are the major source of BVD infection and disease in cattle because they shed huge amount of BVD virus throughout their lives. The major economic loss associated with BVD in cattle operations is loss of income due to loss of calves either before birth (abortion), at birth (weak calves) or between birth and weaning, or from diseases associated with immunosuppression such as scours and pneumonia.

Can BVDV infection be eradicated from a herd with vaccination?

No, BVD vaccination alone (with either modified-live or killed vaccines) cannot keep a cattle herd free of BVD-PI cattle nor completely control BVD infection according to the Academy of Veterinary Consultants and American Association of Bovine Practitioners. Both groups promote a threepronged approach to BVD control, a combination
of BVD-PI testing and removal, vaccination and biosecurity, (good herdsmanship, sanitation, record keeping, and an active MLV vaccination program).

Ethics-Do the right thing!

Do not knowingly share your BVDV problem with unsuspecting buyers. BVD-PI is a serious problem that if kept unchecked could create devastating losses for a breeder. It is unethical to pass animals with known or suspected BVDV infections on to another breeder.

Lincoln, D. S. (n.d.). Beef Cattle Handbook-Cattle Vaccines and their uses.
Retrieved from Iowa Beef Center.
Washington State University College of Veterinary Medicine. (2007,
October). Washington Animal Disease Diagnostic Lab. Retrieved
November 15, 2009, from Bovine Viral Diarrhea Persistenly Infected
(BVD-PI) Ear Notch Testing Program for Catle Herds.
Peggy and her husband, Bob Potter, own and operate PJ Ranch LLC in
Winton, California where she serves as the Vice President of Animal
Health. They have been Miniature Hereford owners and active
participants in the MHBA since 2002. She is also employed as a critical
care nurse at a local medical center.

Information contained in this article is for general
informative purposes only. Please contact your local
vet for specific recommendations.

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