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.