CATTLE DISEASE ADVISORY -BVD UPDATE
Outbreaks of a severe form of bovine viral diarrhea (BVD)
were described in recent releases from the USDA and from
the Indiana State Veterinarian. Case reports cited in these
reports have clinical manifestations of morbidity up to
100% across all age groups on an affected farm; mortality
up to 90% with major signs of high fever (107 degrees or
higher), anorexia, occasional diarrhea, respiratory difficulty
and often death within 48 hours of onset. Owing to the
acute to peracute duration of the disease, gross lesions
of BVD are often not present in dead or dying cattle.
Commonly, herd illnesses began shortly after addition of
new animals to the herd. Herds with up to date and thorough
BVD vaccination practices appeared to have been protected.
Reports of this manifestation of BVD have come from Pennsylvania,
New York, West
Virginia and Canada.
To this date there have been no reports of this severe manifestation
of BVD in herds other than veal calves in Indiana.
Recent information has shown that there are antigenic,
genomic and structural differences between BVD viruses to
separate various isolates into Type 1 (traditional, previously
identified type) and Type 2 (the more virulent, recently
identified type). The Type 2 virus is not new to the U.S.,
it was found to be the etiology of the severe hemor-rhagic
disease seen in veal calves since 1990.
Scientists at the National Veterinary Services Laboratory
in Ames, Iowa
are now using a polymerase chain reaction test
to differentiate the two virus types. In recent conversation
with one of the scientists at NVSL, they are now finding
that 90% of the isolates they receive from veterinarians
or diagnostic labs for identification are of Type 2. Some
dairy practitioners have adopted the practice of vaccinating
herds 4 times a year with killed vaccine to control BVD
infection. It was also learned that even with killed vaccine,
occasional abortions will result in some herds.
Producers may have little control over characteristics
of the virus but they can effectively manipulate the resistance
and exposure of their herd to BVD. The following list of
recommendations was taken from a news release from veterinary
scientists at Pennsylvania
State University.
1. Prevent the introduction of infected animals by improving
biosecurity:
- bring in only animals from uninfected herds.
- bring in only animals from herds with a known effective
vaccination program.
- avoid the purchase of animals from sale barns.
- test new animals for persistent infection in advance
of introduction.
- isolate new animals for 30 days before allowing contact
with other cattle on the farm.
2. Increase the resistance of the herd to BVD by:
- vaccinating strategically as per the product label.
- maximizing colostrumconsumption by newborn calves.
- reducing stress on cattle caused by other diseases,
poor nutrition, uncomfortable housing or poor air
quality.
3. Decrease exposure to BVD by:
- preventing manure contamination of hair, feed and
water.
- housing young calves in individual calf hutches.
- isolating sick animals
. H.L.Thacker,DVM,PhD Director of the Animal Disease Diagnostic
Lab.
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