bovine viral diarrhoea
TRANSCRIPT
Bovine Viral Diarrhoea (BVD)
Mount Vets
Prevalence of BVD*
Disease Dairy Beef
BVD 57% 66%
Leptospirosis 68% 51%
IBR 67% 65%
*From DairyCheck and BeefCheck 2009
Herds Testing Positive to Disease Exposure
Exposure to Herds tested on project
What is BVD?
● Stands for Bovine Viral Diarrhoea● Spread mainly in faeces and nasal and ocular secretions● Can cause a transient scour● Has various effects depending on age and situation● Naïve/unvaccinated pregnant animal
Lose the calf – EED, mummified calf or abortionNot lose the calf – mutated, Persistent Infector or vaccinated
● Young naïve/unvaccinated non-pregnant animalWeakens immune system preventing protection and recovery
from scours and pneumonias, etc.
0 1 2 3 4 5 6 7 8 9
Months of gestation
Earlyembryonicdeath
Foetal death andmummification
Foetal death and abortion
Pregnancy – No Live Calf Born
0 1 2 3 4 5 6 7 8 9
Months of gestation
Earlyembryonicdeath
Foetal death andmummification
Foetal death and abortion
Congenital defects
Sero-positive / vaccinated calf
Pregnancy – Calf Born Alive
Congenital Defects
● Classically cerebellar hypoplasiaAtaxia/ Incoordination
● AlsoHydrocephalusOcular lens cataractsMicro-ophthalmia
0 1 2 3 4 5 6 7 8 9
Months of gestation
Earlyembryonicdeath
Foetal death andmummification
Foetal death and abortion
PI (persistently infected)
Congenital defects
Sero-positive calf
Pregnancy – Calf Born Alive
The Persistent Infector animal
● A BVD virus “factory”Sees BVD virus as “self”One tube of PI bood diluted with
7000 litres of water is still infectious1000 times more infective than an
infected adult
● Often poor doersBut may appear normal
● The “Trojan Cow”Often route onto farm
The main source of c
ontinued
BVD infectio
n on the fa
rm
The Life of a PI
● Survival50% die by the age of 180% die by the time they are 2BUT some live to be up to 8 years old showing that it is possible
for them to enter the adult breeding herd
● A PI cow always gives birth to a PI calfMaintains virus in the herd
Number of herds with PI animals found
PI’s by farm type
Mucosal disease
● PI animal becomes ‘super-infected’ with BVD virus
● Virus destroys the whole gut surface● Severe ulceration, dehydration● Death after about 2 weeks● No treatment.● Domino effect on groups of
PI’s
BVD Infection Suppresses the Immune System
● Diseases which increase when BVD on farm:Calf scours - Rotavirus and Coronavirus Pneumonia - RSV, IBR and PastuerellaSalmonellaJohnesFoul in the Foot
● Control and Eradication schemesSignificant improvement in calf disease levels
Typical Picture of BVD in an Infected Herd
● Often not initially noticedEffects build up, like a dripping tap
● Visual effectsSporadic deathAbortions and congenital deformities
● Less obvious signsImmune disruption
Poor calf health – scour, pneumonia
Mastitis etc.
Poor fertility
Control of BVD within a Herd
Control Strategy for BVD
● Assess Herd BVD StatusBulk milk test in dairy herds or blood sampling in beef.
● Remove BVDv from herdIdentify and cull PIs through blood sampling
● Assess herd biosecurity and put in place extra measures if necessary
● Implement vaccination programme
Numbers of Pi’s on each project farm
Scenario No. 1 - Herd 31
● Naïve herd in November 2010 - -ve on Bulk milk sample
● Bought a freshly calved heifer which was a PI in December 2010 and put her straight into the milking herd
● Heifer died in April
● July 2011 persistent pneumonia in youngstock. Bloods taken to find causative agent. Bulk milk also taken.
● All positive for BVD antibodies therefore must have been in contact with a PI. Bulk milk now very high Ab reading.
● Herd BVD vaccination commenced
● 21 PI’s found to date but have stopped finding them as got to the point at which the vaccine started to protect the cows
Keeping Clear – Good Biosecurity
● Assess your riskBuying-in cattleNeighbours stockOn farm visitors
● Ideal situationClosed herdDouble fencingQuarantine and test
● Just how secure can you be?
Did you test the bull before you bought him?
Practical Vaccination Regimes why and when
● To prevent birth of PIsUse in an endemically infected herd while we identify
and cull PI’sNaïve herd to reduce impact if virus enters
● Vaccinate the whole breeding herd● Calves?● Ongoing
Annual boosting injectionsVaccination of heifers a minimum of 2 months prior to
breeding
Bovilis BVD
● DosingPrimary course 2 doses
4 weeks apart 2nd dose at least 4
weeks before 1st service
Annual booster
● It protects the foetusPrevent birth of PI’s
Two Initial Injections are important
4 weeks apart Annual booster
Please Read the Vaccine Instructions
● Keep refrigerated at all timesDo not freeze
● Follow directionsShake bottle well before use
● Good vaccination techniqueSterile injection equipment
● Do not keep open vialsUse within timescale on datasheet
● Use at the right time! For BVD before bull goes in with heifers (or cows)
Scenario No. 2 Incorrect Vaccination protocol - Herd 32
● Endemically infected herd● Full vaccination program in place. Different vaccine to that
we normally use. Choice was due to timing i.e. can serve 3 weeks after second dose.
● Heifers have received 1st service before 3 weeks after the 2 nd injection
● 13 PI’s found. 12 from heifers before vaccination complete● 1 PI from a few days after. Drug company contacted and
investigation started
Scenario 3 – Commencing a vaccination program without blood sampling for PI’s - Herd 13
● Small beef herd● Previous problems with BVD● Vaccinating for 5 years● Blood screen showed 4 PI’s● Has vaccination not worked?● One of PI’s an older suckler cow. Two of the PI’s her
offspring● 4th PI was a poor doing calf that had been given to the
farmer. So vaccination had worked but had been put into place with a PI already breeding in the herd
Thank you for your attention