Transiently Infected (TI) Seroconversion BVDV Naïve Antigen – Transient infection Antibody - (2weeks) Antigen + Courtesy of Dr. John Pickering Immune Antibody + Antigen – 4-6 years BVDV Disease – Acute (TI) • Incubation 5-7 days • Viremia (virus in blood circulation) 4-5 d after infection (up to 15 d) • Seroconversion 2-4 wk later • Virus shedding For 1-2 weeks. Low concentrations compared to PI Ref: Baker, Vet Cl. N. Am. 11:3, 1995 • Diarrhea,slobbering, fever • Ulcers - lips, gums, esophagus, etc. • Immune suppression • Fetal infections • Most infections are not noticed - estimate 70-90% are subclinical but can be severe (death) if virulent strain PI development Persistently Infected Carriers (PI’s) 1 – 4 months gestation Infection 93% of all PI’s produced this way Calf PI’s produce PI’s 100% of the time BVD Virus Courtesy of Dr. John Pickering Persistent Infection PI Carriers • If fetus becomes a PI and survives - will continuously shed millions of virus all its life from all its secretions - feces - urine - saliva - nasal - milk - semen - uterine secretions - aborted membranes, fluids, fetus - Across fences. Virus survives in environment up to 7 days • If it’s a female and later gets pregnant then its offspring will be a PI and its offspring and so on and so on Viral shedding rate • RED DOT = Normal Calf (nonPI) with a BVDV infection sheds 10,000 viral particles per day and recovers in 10–14 days. • YELLOW DOTS = PI calf sheds 10 million viral particles EVERY DAY (1000 x non-PI). • Now you can understand how one calf that is persistently infected can affect so many other cattle. . What does it do? Effects on young stock (3-12 months of age) • Unthrifty/Rough coats • Diarrhea • Coughing • Ulcers in mouth (sometimes!!) • Lameness • Immunosuppression • Often confused with parasitism • High morbidity • Low mortality The classic BVD quiz Spot the PI among this group of heifers: Should instead be: Spot both BVD PI carriers Diagnosis How do you find out if you have BVD? • By blood or milk testing • By skin testing • Testing tissues of a dead animal. PI Diagnosis • Antigen Capture ELISA of Ear Notch or Serum identifies PI animals TI usually test – Calves must be 3 months old or precolostral to use serum Screening replacement heifers, bulls, stockers, purchased cows and show animals Screening prior to sale by seedstock producers Sick or dead calves-esp. BRD Diagnosis in Live Animals • Any positive test for PI in valuable animals can be confirmed by segregating the animal then retesting with serum ELISA or whole blood VI/PCR at least 3 weeks later to eliminate TIs and false positives. • BVDV Serum Neutralization Test-detects and quantifies antibodies. Differentiation of titers due to vaccination or field virus exposure is difficult. BVD Vaccination - Calves • Vaccinate calves after 4 months of age • Modified Live: 1 dose is protective; 2 doses best • Killed: Two shots, 3 - 4 weeks apart is required • Best if done at least two weeks before stress (weaning/transport/commingling) • 12 months protection against clinical disease From the OSV: • BVD-PI has significant impact on the health of Kentucky cattle herds. • BVD including PI is reportable by labs, vets, owners, and others having knowledge. • Both privately owned and university laboratories are currently reporting positive results From the OSV: • Interpretation of test results is currently being evaluated. It appears that the (AC) ELISA test provides a significant confidence level for identifying PI positive cattle. • [Note from Arnold: The test kit used at the UKVDL requires two positive test results at minimum 3 weeks apart in order to call an animal “BVD-PI”; however, this may not be the case at other laboratories] From the OSV: • Actions by OSV upon receiving positive test results: • Contact the owner/attending veterinarian regarding the current status and location of the animal. • Provide an opportunity for the owner to understand the impact of the disease and the laws governing SV response. Options for the Owner: • Isolate and retest in 2-3 weeks to confirm the diagnosis. • Transport to slaughter with OSV permit. • Isolate either on owner’s farm or at permitted feedlot and feed to slaughter only. • Euthanize and dispose of by an approved method. • Test positive animal is not to be sold, given away, or transported without approval of the SV Other Issues Under Consideration • Official I.D. of tested animals recorded on laboratory accession sheet. • Confirmed positive animal is officially ID’d and branded as positive. • All movements of positive animal shall be documented by USDA 1-27. • Target education at the cow/calf level.