FAQ's - Vaccines and Vaccinations

Does vaccinating cows have any effect on virus test results?

Can calves become infected from vaccinated animals in the herd?

Where a herd is currently vaccinated for BVD, should I vaccinate purchased animals, if not already vaccinated?

When is the most effective time to vaccinate for BVD?

If a farmer purchases all his/her animals through the marts, what is the best way to avoid buying PI animals?

What is the role of vaccination in the BVD eradication programme?

Ref: BVDFAQCOMv10.0 Date: 09.09.2013
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  1. Does vaccinating cows have any effect on virus test results?
    No. Licenced vaccines contain killed virus which will not cause false positive result.
     
  2. Can calves become infected from vaccinated animals within the herd?
    No. Licenced vaccines contain killed virus which cannot spread from vaccinated to unvaccinated cattle. 
     
  3. Where a herd is currently vaccinated for BVD, should I vaccinate purchased animals, if not already vaccinated?
    It is more important to ensure that purchased cattle are not PI. It is best to discuss individual herd health programmes with the herd’s own veterinary practitioner.
     
  4. When is the most effective time to vaccinate for BVD?
    When using a vaccination programme, the primary goal is to protect early pregnancies from becoming PI animals. When done correctly, the vaccination programme should provide maximal protection during early pregnancy. The BVD vaccination course should therefore be completed in the weeks before the animal is bred. This will be easiest to achieve in a seasonal calving herd where most of the herd will be bred at the same time. Choosing a vaccine and vaccination strategy for your herd is best done in consultation with your own veterinary practitioner.
     
  5. If a farmer purchases all his/her animals through the marts, what is the best way to avoid buying PI animals?
    If buying calves/weanlings during 2013 a farmer should seek to buy only those that are shown on the display board as having had a virus negative test result. Even where purchased animals have already tested negative, it is advisable to isolate them for 3-4 weeks (particularly from pregnant stock) if it is possible that they might have been exposed to virus around the time of sale (and therefore be transiently infected). Note that pregnant animals even when test-negative, may be carrying a PI calf. They should therefore be isolated until they have calved and the calf has been tested negative. Over time, an increasing percentage of animals traded will have been born during the lifetime of the programme and will have a negative test result prior to purchase. In the meantime, it will be necessary to test purchased stock to be certain of their status.
     
  6. The goal of the current programme is the eradication of BVD virus. The core element of the programme is testing to identify animals persistently infected (PI) with BVD virus and remove these from the cattle population. Associated with this, adequate biosecurity measures to prevent the accidental introduction (bio-exclusion) and spread (bio-containment) of infection in herds is critical.
    Maintaining the current momentum and compliance levels of the programme will hasten successful eradication of BVD, and equally shorten the period when provision for vaccination is required. It is estimated that approximately 40% of dairy herds and 10% of beef herds currently vaccinate against BVD virus using one of the two vaccines (Bovidec and Bovilis BVD) currently licensed for use in Ireland. Once the national programme has been successfully completed and BVD eradicated there will no longer be a routine need for vaccination.
    In the meantime though, the main purpose of BVD vaccination is to induce a protective immunity in breeding animals to avoid a range of negative outcomes of infection on reproduction, including failure to conceive, abortion, birth defects and most importantly the creation of calves that are persistently infected with BVD virus.
    As the programme progresses, the prevalence of PI animals will decrease, followed by a decrease in the prevalence of animals with natural immunity following exposure. On the one hand this means that the likelihood of pregnant cattle being exposed to virus will decrease but on the other hand the potential negative impact of such exposure would increase. In the absence of natural immunity arising from infection, vaccination may be used as an alternative means of inducing immunity during this period. Vaccination acts as a protective measure should a breakdown in biosecurity occur.
    However, it should be noted that the available BVD vaccines will not provide 100% protection in all circumstances, even when stored and used correctly, particularly where pregnant cattle are exposed to high levels of BVD virus.
    Decisions on the use of BVD vaccine, including when to stop a vaccination programme, are herd-specific and should be taken by each farmer in discussion with their own veterinary practitioner. Key factors for consideration include the likelihood of introduction of infection. Introduced animals are the single biggest risk, particularly in the first year of the programme when the majority of older animals traded will not have been tested within the programme. The risks from other means of spread including direct contact (e.g. at boundaries, shows and sales) and indirect contact (e.g. contaminated environments, equipment, clothing or hands) should also be considered.
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