BVD IN NEW ZEALAND John Pickering

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BVD IN NEW ZEALANDJohn Pickering
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Plan of attack

• The disease
• Case studies
• Control options

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What is BVD?

• BVD is a viral disease
• It is caused by a pesti virus. Primarily
  affecting cattle.
• BVD can infect other species e.g. sheep, deer,
  alpacas (dead end hosts!!)
• Hairy shaker disease in sheep caused by a related
  pesti virus but does not affect cattle.

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What is BVD?

• NZs most important and most complicated viral
  disease in beef and dairy cattle
• 60 of cattle been exposed to BVD
• 80 of herds been exposed to BVD
• 15 of dairy herds have active infection at any
  one time.
• Beef herds may be a lot higher

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Countries eradicating BVD

• Scandanavia Sweden, Finland, Norway, Denmark
• Shetland Islands (eradicated it)
• Austria
• Parts of Germany, Holland, France, Italy, Greece
• Switzerland. 3 year goal.
• Some states of USA e.g Alabama, Montana,
  Colorado, Wyoming, Michigan, New York (Voluntary
  control)
• BVD notifiable disease in 8 European countries.
• OIE has made BVD a priority disease

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What does it do?

• A, Effects on young stock
• (3-12 mths of age)
• coughing
• Ill thrift
• Rough coats
• Coughing
• Ulcers in mouth (sometimes!!)
• Lameness
• Immunosuppression, like AIDS (other ill health)
• Often confused with parasitism
• High morbidity
• Low mortality

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What does it do?

• B, Effects on fertility

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Infection early in pregnancy failure to conceive
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Early embryonic loss

• Above - normal embryo
• Below - a degenerate embryo from a cow infected
  with BVD in early pregnancy.
• Long returns

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Abortion

• Up to 180 days

Immunosuppressive may also be trigger to
Neospora / fungal abortions
About 15 of diagnosed abortions
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Mummified Foetus
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Developmental defects - hydrocephalus, cleft
palate, cerebellar hypoplasia (120- 150days).
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Developmental defects
90 to 150 days Cataracts
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Stillborn
Live bornDummy calves
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180 days on

• Normal calf

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Persistent InfectionPI Carriers

• Only Occur if foetus is infected with BVD virus
  between 1 4 months of pregnancy in the uterus
• Foetus will become a PI and if it survives
• - will continuously shed millions of virus all
  its life from all its secretions
• - faeces
• - urine
• - saliva
• - nasal
• - milk
• - semen
• - uterine secretions
• - aborted membranes, fluids, foetus
• Across fences. Up to 10metres
• Virus survives in environment no greater
  than 7 days
• - if its a female and later gets pregnant then
  its offspring will be a PI and its offspring
  and so on and so on

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Persistent InfectionPI Carriers

• PIs (BVD carriers!) are the reason this disease
  continues
• No PIs no BVD
• Bought in PI bulls are the no 1 cause of
  introduction of BVD in to a herd
• PIs
• - Most are lost during pregnancy
• - Half are dead by 12 months of age
• - Some are stunted and grow poorly
• - Some normal and survive and make up about 1
  of the adult cattle population.
• - Can be a lot higher in individual herds

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The classic BVD quizz

• Spot the PI amongst this group of heifers
• Should instead be Spot both BVD PI carriers.
• 2nd and 5th from left hand side

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PIs
30 120 days
PI COW
Naive Cow
BVD Virus
Cannot be controlled by vaccination
Can be controlled by vaccination
PI Calf
PI Calf
More than 90 of PIs are born this way, so
vaccination can reduce the PIs
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Mucosal Disease

• PI cattle only
• Occurs when a PI animal is super infected with a
  different strain of BVD virus
• Sudden onset of severe scouring, ulcers in mouth
  and nose, weight loss,
• Always fatal

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Summary
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How poorly do PIs do?

• LIC trial involving 904 FxJ heifers sourced from
  323 herds over two years and reared together.
• Blood tested for BVD
• PI prevalence 1.33

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Milk Production

• PI Non PI
• Days in milk 197 234 84
• Milkfat kg 79 164 48
• Milk protein kg 57 116 49
• Volume (l) 1375 2878 48

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Live weight

• PI Non PI
• Week 3 (kg) 30.2 33.7 90
• Week 91 (kg) 335 403 83
• Growth/wk (kg) 3.4 4.2 81
• Deaths by wk 91 25 7

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THE EFFECT OF BVD VIRUS ON BULLS
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The PI Bull

• Has an impact on reproductive performance by 3
  ways
• Non venereal horizontal spread of virus
• Venereal spread of virus in the semen
• Poor semen quality

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The PI Bull

• PI bulls will constantly shed virus in all their
  secretions including semen.
• Introduction of a PI bull at mating can cause a
  devastating effect on herd fertility
• Can result in a large number of PI calves
  especially in a naïve herd often with a high
  number of calf losses

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The TI Bull

• Bulls that are transiently infected will shed
  virus in their semen for up to 2 weeks
• BVD virus can affect semen quality (motility,
  density, structure and live/dead ratio) hence
  fertility for several weeks. Can be at least 8
  weeks

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Blood Test and Vaccinate Bulls

• It should be farm policy for all service bulls
  to be blood tested for BVD virus (once only) and
  vaccinated prior to mating each year.
• So PI bulls are culled
• So Clean bulls dont become TI bulls

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PROCEDURE FORBLOOD TESTING BULLS

• Blood test(Elisa) for BVD antigen (not antibody)
  (gt3 months of age) or blood test (PCR) or skin
  test (Elisa) at any age before mating
• If ve Certify BVD negative (PI-ve)
• Transiently infected (TI)
• If ve
• Persistently infected (PI)
• either cull
• or reblood test 4 weeks later
• If ve Persistently infected (PI). Cull
• If -ve Was transiently infected
• Certify BVD negative (PI-ve)

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Procedure for Vaccinating Bulls

• BVD antigen ve bulls to be vaccinated twice 3-4
  weeks apart to protect them from
• - transient infection
• - temporary infertility
• Annual booster required to maintain immunity.

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ONLY PURCHASE Blood tested and vaccinated bulls

• Most bull breeders are now doing this but still
  check
• It is now compulsory to test and vaccinate all
  bulls before they can attend the beef expo

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CASE STUDIES
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Case Study Stud Beef Bull

• Winter - Stud bull purchased
• - Semen tested
• 
  --Scrotal diameter.40cm
• 
  -- BVD tested antigen -ve
• At mating single sire mated 40 cows
• heat detectors
• daily observation
• each mating recorded
• Red alert 2nd cycle cows returning!
• bull withdrawn replaced
  older sire

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Case Study Continued

• Bull examined Scrotal diameter down to 36cm
• _ semen test all
  dead
• blood test BVD
  antibody positive
• TI Bull.
• Cows examined blood test BVD antibody ve
• sick calf BVD
  antigen ve
• PI animal
• Scanning one cow in calf to new bull
• the rest, in calf late to
  older bull
• Bull retested Scrotal diameter down to 30cm,
  semen still dead
• permanently infertile
  insurance claim

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Mucosal disease outbreaks

• The results of using PI bulls
• Massey Uni
• 38 / 102 AI bred calves died MD _at_ 4-6 months
• Marlborough
• 70 AI heifer calves
• 22 died MD
• 24 culled PI
• 24 normal
• Vetcare Grazing
• 165 heifers
• 9 died MD
• 23 culled PI
• 133 normal

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Effect of PI bull on empty rate heifers (Vetcare
Grazing)
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• Hawkes Bay Beef Breeding Herd
• Horror Story
• Spring 2004 44 yearling heifers mated.
• Summer 2005 38 scanned in calf, 86.
• Early Spring 2005 1 undersized calf dies at 1
  mth.
• post mortem
  BVD virus positive
• blood test 4
  heifers BVD Ab -ve
• 
  interpretation no panic
• Late Spring 2005 37 x 2Yr heifers produce 35
  good
• calves no
  panic.
• Mating 2005 44 2Yr heifers mated (7
  more added)
• 44 yearling
  heifers mated.

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• Heifer Problem Cont.
• Summer 2006 2Yr heifers with calves at foot and
  yearling heifers run as one mob of 88.
• Autumn 2006 39/44 2Yr heifers scanned in calf -
  89.
• 38/44 yearling
  heifers in calf 86
• definitely no panic
• Winter 2006 Both heifer mobs started aborting
• BVD virus found in
  foetal tissues
• PANIC 2005 born
  weaners blood tested
• 1 PI
  calf found 2Yr heifer mob
• Spring 2006 calving becomes a horror story
• still births, small
  retarded calves
• many die before 1 week
  of age
• BVD virus found in post
  mortem samples

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• Heifer Problem Conclusion
• Early Summer 2006 only 19 calves survive from
  38 yearling
• heifers -
  ..50 lost
• only 27
  calves survive from 39 2nd
• calving
  heifers30 lost
• - All 2006
  born calves subjected to
• the new
  PCR virus test
• 8 more PI
  calves detected in the heifer
• mobs
• A True Horror Story 88 heifers mated in the
  spring of 2005
• 39 calves
  lost from production
• all because
  one PI virus carrier was not
• detected and
  removed before the first
• five months
  of pregnancy.

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Infection in a commercial beef herd the herd
history

• A commercial Hereford herd
• Dry hill country and fertile flats
• Purchased Hereford bulls
• 100 to 105 cows to the bull
• Producing 98 to 100 calves annually
• Heifer calves grown out to R2 surplus sold for
  breeding
• Bull calves kept entire grown to two year old as
  bull beef

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What happened

• December 1999 - 100 cows mated
• Autumn 2000 Scanning. 90 in calf 10 dry
• Spring 2000 - 85 cows calved. 5 more empty
• Winter 2001 - One weaner faded and died- No
• Panic

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What happened

• August 2001 Three yearling heifers sick.
• Faded and died.
• Farmer concerned.
• September 2001 Two yearling bulls sick. Lame,
  skin peeling, mouth ulcers, profuse scour.
• - farmer alarmed
• - Vet called, Blood test
• - BVD Ag Positive P.I animals.

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What happened

• October 2001
• Three more yearlings go down with acute illness
  Real Panic.
• Remaining 76 calves blood tested for BVD
• Five more BVD Ag positive or PI animals detected.
• Three survive to be processed as vealers.

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Summary

• 10 Dry cows
• 5 Pregnancies lost
• 12 P.I. animals died
• Cost 30 of production in one year
• Likely source of infection - bulls

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BVD effect on empty rate

• USA, 128 cow calf beef herds
• 19000 calves bled for PI
• Determined which herds had active BVD infection
  and which didnt, then compared their fertility.

Grotleuschen et al 1996
plt 0.05
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Recent NZ beef herd study

• A comparative study on 94 low and high fertility
  herds
• 61/94 (65) herds had active BVD infection.
• Overall 5 lower pregnancy rate in affected
  herds.
• Up to 15 lower pregnancy rate in worst herds.

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Economic Effects of BVD in NZ Dairy
Herds(Heuer,Healey and Zerbini)

• Study in 590 herds. (Northland, Waikato, Bof P)
• In the 15 affected herds
• - Decline in milk production (0.074kg/day)
• - Increased interval from calving to conception
  (2.35d)
• - Increase in abortion rate (2.03)
• - Increase induction rate ( 0.33)
• Figures based on 4.05/kg MS and 876 replacement
  cost.
• Annual avg cost per affected herd 21,921 87
  per cow
• Based on 7.00/kg MS and 1500 replacement cost
• Annual avg cost per affected herd 58,771
  180 per cow

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CONTROL OPTIONS
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Herd Control Policies

• Do Nothing
• Use PI animal(s) as a vaccinator!!!!
• Eradication and biosecurity
• Vaccination
• Eradication and Vaccination (rolls royce option)

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PI as a Vaccinator!!

• Need to identify PIs
• Spread live virus (live vaccine!!!)
• PIs often die so no more vaccine!!
• PIs can easily develop Mucosal Disease. Welfare
  issue!!
• Immunisation is not 100

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R2 jersey heifers immune status(Vetcare Grazing)
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Eradication

• How do you find out if you have BVD?
• By blood or milk testing
• (Elisa or PCR)
• By skin testing
• (Elisa) Ear knotch
• Testing tissues of a suspected dead PI e.g BVD
  antigen test on spleen.

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Investigating the BVD status of a Lactating Dairy
Herd Using milk PCR   Unknown BVD
status    
Bulk Tank Milk PCR result
once all cows are milking (max n400)  
Negative
Positive
 
PI or PIs present in the herd
  No PIs present
Test each individual cow by blood test. Start
with lowest producing 10 of the herd
Milking Herd clear of PI cows. Maintain
biosecurity /- vaccinate. Screen all incoming
stock for BVD (beware pregnant Trojan
cows) Bulk milk PCR each lactation when all cows
are milking until sure no infection has been
introduced    
Remove any PIs found
Recheck bulk milk with PCR. Once negative no PIs
remain
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Finding BVD in a beef herd
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Finding a PI with PCR Dairy or Beef herds
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Finding a PI with Elisa
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Herd Eradication Summary(steps to take)

• Find and eradicate PIs
• Blood or milk test all the herd when not in calf
  (prior to mating)
• Test all the herd. Dont miss any
• Destroy all PIs
• Maintain biosecurity (border control) and /-
  vaccinate
• Test all incoming stock for Antigen
• Including offspring of pregnant trojan cows
• Annual Surveillance

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Biosecurity Risks

• Bought in untested stock
• Trojan cows
• Neighbours stock (over or through the fence)
• Stock trucks
• Stock returned from grazing

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VaccinationBovilis BVD

• Killed vaccine
• 2 doses, 3-4 weeks apart
• Single annual booster
• Young stock from 4 months of age
• Breeding stock 4 weeks before mating (No earlier
  than 12 weeks before mating)
• Require good immunity 2 weeks prior to mating

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Bovilis BVD

• Vaccine developed for foetal protection
• Gives 100 foetal protection within 6months of
  vaccination
• 12 months protection against clinical disease
• C86 strain gives good cross protection
• Prevent
• acute BVD disease
• infection of the foetus
• reproductive losses
• the birth of PI animals
• Breaks the cycle of BVD infection in herds

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Efficacy of Vaccination when (PI) heifer
introduced to milking herd
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Computer Modeling(Reichel, Hill and Voges)

• Showed that
• - Vaccination
• is a cheaper option than living with the
  disease in an infected herd over a 1 to 10 year
  period even with the efficacy of the vaccine
  assumed to be only 60
• Efficacy of Bovilus BVD vaccine is gt95 if
  vaccination carried out as per label.

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Conclusion Act on clinical information in the
herd

• Poor scanning results
• Long returns
• Late calvers
• Weaner ill thrift
• Abortions
• Mummified foetuses
• Deformed calves
• Calf losses
• Yearling deaths
• In an infected herd the HIDDEN cost could be
  substantial

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BVD websitewww.ControlBVD.org.nz
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Questions?