Submitted to: American Association of Bovine Practitioners Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/21/2006
Publication Date: 9/21/2006
Citation: Ridpath, J.F., Hessman, B.E., Neill, J.D., Fulton, R.W., Step, D.L. 2006. Parameters of Ear Notch Samples for BVDV Testing; Stability, Size Requirements and Viral Load. In: Proceedings of the American Association of Bovine Practitioners 39th Annual Convention, September 21-23, 2006, Saint Paul, Minnesota. Available: http://www.aabp.org/meeting/program2006.pdf.
Technical Abstract: Infections with bovine viral diarrhea viruses (BVDV) are a major source of economic loss for the U.S. cattle industry. It is estimated that losses in areas where BVD is endemic range between 10 to 40 million dollars per million calvings. Results of serology surveys in the United States suggest that our losses are in the upper end of this range. In 2004, 37.6 million calves were born in the United States; thus U.S. losses by this estimate would be between 376 million to 1.5 billion dollars for 2004. The 2005 calf crop was approximately 37.8 million, making the 2005 estimate very similar to that of 2004. While BVDV infections are well recognized as reproductive pathogens among dairy producers, producers are less aware that BVDV infections are also associated with increased respiratory disease increased severity of secondary infections and decreased milk production. Persistently infected (PI) animals are the major vectors for spreading BVDV within and among herds. Based on studies of dairies of 100 cows or more, it is estimated that the presence of one PI animal in a herd resulted in a loss of $1.93/cwt of milk sold. Studies estimate that 10-15% of U.S. herds have at least one PI animal ranges. In 2004, U.S. dairies produced 170,805 million lbs of milk. If 10% to 15% of dairy herds have at least one PI then the cost to milk production is between 330 to 494 million dollars per year. Control efforts in the United States are geared towards identifying and eliminating PI’s. Several tests based on detection of either antigen or viral RNA in blood, serum, bulk milk or skin biopsies are currently in use. Ear notch samples have become the tissue of choice for screening for PI animals because they are: 1. Easy to collect; 2. Equipment requirements are minimal; 3. Not affected by presence of passive antibodies; and 4. Can be used as sample for a wide variety of tests including immunohistochemistry, real time polymerase chain reaction and antigen capture ELISA. While ear notches have become one of the samples of choice, there is little information available regarding sample size requirements and stability. Further, while pooling of ear notch samples has been proposed for reducing the cost of surveillance programs, the viral load available for detection from ear notch samples is largely undetermined. The purpose of this study was to establish working parameters for sample size, viral detection limit and sample storage conditions for real time PCR and antigen capture ELISA.