Bovine Viral Diarrhea Virus

Michelle Arnold, DVM, DABVP

Courtesy of Dr. John Pickering

Transiently Infected(TI)

Naïve

Antigen –

Antibody -

Transient infection

(2weeks)

Antigen +

Immune

Antibody +

Antigen –

4-6 years

BVDV Seroconversion

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

• 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

Ref: Baker, Vet Cl. N. Am. 11:3, 1995

Courtesy of Dr. John Pickering

PI developmentPersistently Infected Carriers (PI’s)

Infection

BVD Virus

1 – 4 months gestation

93% of all PI’s produced this

way

PI’s produce PI’s 100% of

the time

Calf

Persistent InfectionPI 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 (non-PI) 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 quizSpot 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.