Download Bovine Virus Diarrhea and PI`s

Bovine Virus Diarrhea
and PI’s
Brendan Kraus, DVM
Spur Ridge Vet Hospital
Marion, KS
What is BVD?
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Bovine Virus Diarrhea
2 Biotypes & 2 Genotypes
A contagious disease transmitted in bodily
fluids
Causes a wide range of clinical symptoms
Cause marked suppression of immune
system
Biotypes of BVD
(Type does not affect immune response!)
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Cytopathic
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Kills cells in tissue
culture
Arises from a virus
mutation
Most common strain in
vaccines
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Noncytopathic
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Does not change
culture cells
Most common biotype
found in nature
Genotypes of BVD
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Type 1
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Original strains of BVD
that were isolated
Is included in all BVD
vaccines
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Type 2
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*There is some cross
protection with
vaccines between
types 1 & 2
This type was more
recently discovered
Hemorrhagic
syndrome strains
Is included in most
BVD vaccines now
BVD symptoms
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70-90% of infections
are subclinical
Pneumonia
Fever
Rhinitis
Diarrhea
Oral and GI ulcers
Immune suppression
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Abortions
Stillborns
Birth Defects
Mycoplasma Joint
What is Persistent Infection?
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A PI calf is born infected with the virus
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This can happen if the dam is a PI animal
This can happen if the dam is transiently infected
during pregnancy from another animal
*The virus must be non-cytopathic*
The calf must be infected between 40-100 days
approximately
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During this time the calf has no immune system so it
recognizes the virus as “self” and never clears it
After this time, the calf’s immune system is developed
enough to fight the virus
Manifestations of Calves infected in
utero
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PI calf (Body does not recognize
virus)
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Virus is always circulating in
body
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May die soon after birth
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Many are clinically normal
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This is the natural reservoir of
the virus
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Infected in utero but not
PI (infected around or after day 100)
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Congential defects
 Skeletal problems
 Dome shaped head
 Shortened lower jaw
 Eye abnormalities
 Brain defects
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Abortions
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Clinically normal calves
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Calves that are not killed can
clear the virus and go on
PI Calves
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PI calves are more likely to die than nonPI calves in the first year
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Pneumonia
Diarrhea
Poor doer
Many look and perform like a healthy calf
Pasteurella mult. Lungs
Mucosal Disease
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This is Highly fatal syndrome in which the
mucous membranes become ulcerated
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Mouth
Stomach
Intestine
Teats
Coronary bands of hooves
Abomasal Ulcers
Mucosal Dz, cont
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For mucosal disease to occur a PI calf
(noncytopathic) must be superinfected
with a cytopathic strain.
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The more closely related the viruses are
genetically, the worse the disease
When a noncytopathic virus found in nature
mutates to cytopathic & the calf is exposed
When the PI calf’s own noncytopathic strain
mutates
PI Calf Shedding
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PI calves shed the virus their entire life
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Some periods they may shed a lot, and others
not as much
Virus shed in saliva, tears, urine, feces, blood
There is so much virus shed, that most
vaccines cannot protect other cattle against a
PI
Continue to infect cow herds and create more
PI’s
PI Diagnosis
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Ear Notch Elisa
Ear Notch Immunohistochemisty
Polymerase Chain Reaction
Virus Isolation
These tests can be done at anytime in a PI’s life and only need to
be done once. If positive, will always be positive. If negative,
can be infected with BVD but will not be a PI
If transiently infected, some tests may be positive, but the calf may
need to be tested again in a month to confirm PI status
BVD Control
& Prevention
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Vaccination with a vaccine using Type 1
and Type 2 strains
Modified live vaccine creates a stronger,
more natural immunity, is cheaper, and
less doses required
Newer vaccines have label claims that if
given to cow pre-breeding can successfully
prevent PI in fetus
BVD Control & Prevention, cont.
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Test herds for PI calves and remove all
animals to quarantine**
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Test all dams of PI calves to see if they are
also PI
Test all purchased breeding animals before
entry into herd
Questions?