BVD IN NEW ZEALAND John Pickering Plan of

BVD IN NEW ZEALAND John Pickering

Plan of attack • The disease • Case studies • Control options

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.

What is BVD? • NZ’s 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

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

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

What does it do? • B, Effects on fertility

Infection early in pregnancy = failure to conceive

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

Abortion • Up to 180 days Immunosuppressive –may also be trigger to Neospora / fungal abortions About 15% of diagnosed abortions

Mummified Foetus

Developmental defects - hydrocephalus, cleft palate, cerebellar hypoplasia (120 - 150 days).

Developmental defects 90 to 150 days Cataracts

Stillborn Live born Dummy calves

180 days on • Normal calf

Persistent Infection PI 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 10 metres Virus survives in environment no greater than 7 days - if it’s a female and later gets pregnant then its offspring will be a PI and its offspring and so on

Persistent Infection PI 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

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

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

Mucosal Disease u u 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

Summary

How poorly do PI’s do? • LIC trial involving 904 Fx. J heifers sourced from 323 herds over two years and reared together. • Blood tested for BVD • PI prevalence =1. 33%

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

Live weight PI • • Week 3 (kg) Week 91 (kg) Growth/wk (kg) Deaths by wk 91 30. 2 335 3. 4 25% Non PI % 33. 7 403 4. 2 7% 90 83 81

THE EFFECT OF BVD VIRUS ON BULLS

The PI Bull • Has an impact on reproductive performance by 3 ways 1. Non venereal horizontal spread of virus 2. Venereal spread of virus in the semen 3. Poor semen quality

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

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

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 don’t become TI bulls

PROCEDURE FOR BLOOD TESTING BULLS • Blood test(Elisa) for BVD antigen (not antibody) (>3 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)

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.

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

CASE STUDIES

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

Case Study – Continued Bull examined – Scrotal diameter down to 36 cm _ 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 30 cm, semen still dead permanently infertile – insurance claim

Mucosal disease outbreaks The results of using PI bulls Massey Uni – 38 / 102 AI bred calves died MD @ 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

Effect of PI bull on empty rate heifers (Vetcare Grazing) 1995 1996 1997 1998 Farmer 1 5/68 =7% 15/82 =18% 6/114 =5% 4/126 =3% Farmer 2 3/37 =8% 10/65 =15% 3/94 =3% Total 25/147 =17% 9/208 =4% 8/105 =8% 4/126 =3%

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 2 Yr heifers produce 35 good calves – no panic. • Mating 2005 – 44 2 Yr heifers mated (7 more added) 44 yearling heifers mated.

Heifer Problem – Cont. • Summer 2006 – 2 Yr heifers with calves at foot and yearling heifers run as one mob of 88. • Autumn 2006 – 39/44 2 Yr 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 – 2 Yr 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

Heifer Problem – Conclusion • Early Summer 2006 – only 19 calves survive from 38 yearling heifers - …………………. . 50% lost only 27 calves survive from 39 2 nd calving heifers…………… 30% 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.

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 R 2 surplus sold for breeding • Bull calves kept entire grown to two year old as bull beef

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

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.

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.

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

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 didn’t, then compared their fertility. Active BVD infection No active BVD infection Grotleuschen et al 1996 p< 0. 05 Empty rate cows 11% 6%

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.

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. 074 kg/day) - Increased interval from calving to conception (2. 35 d) - 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

CONTROL OPTIONS

Herd Control Policies 1. Do Nothing 2. Use PI animal(s) as a vaccinator!!!! 3. Eradication and biosecurity 4. Vaccination 5. Eradication and Vaccination (rolls royce option)

PI as a Vaccinator!! • • Need to identify PI’s Spread live virus (live vaccine!!!) PI’s often die so no more vaccine!! PI’s can easily develop Mucosal Disease. Welfare issue!! • Immunisation is not 100%

R 2 jersey heifers immune status (Vetcare Grazing) Ag-ve Ab +ve (Immune) 69% Ag +ve Ab -ve (PI’s) 12% Ag –ve Ab –ve (Non Immune) 19%

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.

Investigating the BVD status of a Lactating Dairy Herd Using milk PCR Unknown BVD status Negative Bulk Tank Milk PCR result once all cows are milking (max n=400) Positive PI or PI’s present in 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 Test each individual cow by blood test. Start with lowest producing 10% of the herd Remove any PI’s found No PI’s present Recheck bulk milk with PCR. Once negative no PI’s remain

Finding BVD in a beef herd

Finding a PI with PCR Dairy or Beef herds

Finding a PI with Elisa

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. Don’t miss any • Destroy all PI’s • Maintain biosecurity (border control) and +/- vaccinate • Test all incoming stock for Antigen • Including offspring of pregnant “trojan” cows • Annual Surveillance

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

Vaccination Bovilis 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

Bovilis BVD • Vaccine developed for foetal protection • Gives 100% foetal protection within 6 months of vaccination • 12 months protection against clinical disease • C 86 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

Efficacy of Vaccination when (PI) heifer introduced to milking herd Number services/ pregnancy Pregnancy rate to first service Calving to service interval Overall pregnancy rate Control 2. 5 24% 65 days 90% Vaccinated 2. 0 49% 75 days 97%

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 >95% if vaccination carried out as per label.

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

BVD website www. Control. BVD. org. nz

Questions?