Vaccines represent a significant cost to the farming enterprise and as such their use can often be questioned. This is especially the case where there has not been an outbreak of disease for quite some time and it is not readily apparent that this is due to the vaccine keeping issues at bay.

The disruption to the availability of many popular vaccines in recent years also added to uncertainty for some producers. There are some vaccines that need to be continually used once disease occurs and a good example of this is vaccination for enzootic abortion. Orf is another disease with a high level of repeatability once it enters a flock while some flocks will suffer significant losses due to clostridial diseases when others never experience a problem.

This reinforces the fact that every flock is different and as such the risks should be reviewed and addressed in each farm’s health plan.

This includes reviewing the farm’s biosecurity measures. The other factor that needs to be considered is that to get a return on your investment, vaccines need to be handled in a manner that optimises their efficacy.

Correct handling

All too often a significant investment is outlaid on vaccines only for incorrect handling to render them worthless. This article looks at a number of vaccines, which may be in the spotlight at present and summarises some important handling tips.

Clostridial vaccination

The vaccination of sheep for clostridial diseases is under the spotlight following the inclusion of the clostridial vaccination in the National Sheep Welfare Scheme. Where producers have vaccinated their payable number of ewes then they have already satisfied action requirements, but where ewes have not been vaccinated and the action is selected then the progeny of these ewes must receive a full course of vaccination – ie an initial vaccine followed by a booster shot.

How to maximise efficacy?

  • Only limited protection is expected from the first vaccination. The second vaccination is required to provide optimum protection to clostridial disease strains covered by the vaccine.
  • The storage of the vaccine during transport has a major influence on its efficacy. The vaccine needs to be maintained at the optimum temperature, which is generally between 2o degrees celcius and 8o degrees celcius. The ideal situation is where vaccines are stored in a cooler bag during transit that will help maintain this temperature range.
  • Take great care if using freezer packs to try and regulate temperature, as it can be potentially more damaging for the vaccine temperature to drop below 2 degrees celcius as it can be for the vaccine to exceed 8 degrees celcius. A tip previously given by MSD vet Sarah Campbell where freezer packs are being used is to wrap the vaccine packaging in bubble wrap to avoid close contact and better maintain the temperature. It is also important to recognise any issues with the refrigerator where the vaccine is stored as a common fault is a fridge freezing towards the back. If in doubt it is possible to get a temperature probe that reads the temperature over time and indicates if the fridge goes outside the acceptable range. Another option is to place a max-min thermometer in the fridge and this will at least indicate if the correct temperature range has been breached.
  • Shake the vaccine well before use and intermittently during use.
  • Vaccines will typically maintain their efficacy for up to eight to 10 hours (varies across products) where handled and stored correctly once the seal is broken. No actions such as trying to seal the rubber bung will prolong this period and this is why it is advised to purchase pack sizes that best suit the number of sheep that can be treated in the application window.
  • It is important to handle equipment carefully and to change needles as frequently as possible as dirt can contaminate needles easily as well as the vaccine, adversely affecting its safety and efficacy. This is part of the reason why it is advised to administer vaccines on a dry day. The ideal approach is to change to a new sterile needle for each animal though this increases time and cost of inputs.
  • Orf vaccination

    Zoetis Animal Health launched the Scabigard vaccine earlier this year to combat Orf. Immunity will develop about two weeks after successful administration and according to Zoetis will last for more than 12 months.

  • The vaccine must be applied using the Scabigard or Scabivax Forte applicator. Attempting to administer the vaccine in an incorrect manner such as trying to use a needle to deliver a scratch and solution will be hit and miss and potentially lead to the vaccine becoming contaminated.
  • Refrigerate between 2 degrees celcius and 8 degrees celcius, taking care not to freeze it. It is recommended to use the vaccine on the day of opening and to discard any vaccine not used. This is as “bacteria and/or fungi may contaminate the vaccine during use, multiply during storage, and cause unwanted infections and/or reduce vaccine efficacy”.
  • Orf is a zoonotic disease meaning humans can also contract the virus. As such is advised to wear gloves when administering the vaccine and also to avoid subsequent contact with the application site. Accidental self-injection will typically trigger an inflammatory response and medical advice should be sought quickly in the case of any injection of concern.
  • Footvax footrot vaccine

    The Footvax vaccine is targeted at providing protection against lameness caused by footrot in sheep. It is mainly preventative but the manufacturers of the vaccine also claim some treatment properties. Sheep can be vaccinated from four weeks of age and the onset of immunity is three weeks after the primary vaccination course, providing six months cover.

    Equipment should be kept clean and needles changed regularly to reduce the risk of contaminating the solution.

    The initial dose consists of two doses administered six weeks apart. The manufacturers’ guidelines advise that re- vaccination may be required at six month intervals where sheep are constantly exposed to a disease challenge.

  • Store unopened vaccine in a refrigerator (2°C - 8°C). Protect from light and do not freeze. Use the product immediately once opened.
  • The site of administration is important - on the side of the neck, two to three inches behind the ear and subcutaneous.
  • Sterilise syringes and needles before use and administer through an area of clean, dry skin, taking strict precautions against contamination in order to reduce the possibility of abscess formation.
  • Ewes should not be vaccinated in the window from four weeks pre-lambing to four weeks post-lambing.
  • Not to be used in lactating dairy sheep.
  • Sheep should not be vaccinated within six to eight weeks of shearing.
  • Product guidelines advise that “sheep destined for show or sale should not be vaccinated within the previous six months because of possible severe local reactions. Such reactions may produce local pigment changes in wool”.
  • Great care is needed to avoid self-injection. If this occurs seek prompt medical advice.
  • Maintaining carcase value

    Processors report significant losses each year where sheep have been injected in higher value areas such as the rump and abscesses have subsequently formed. The recommended injection site for administering a vaccine, irrespective of the product used is the animal’s upper neck region to one side.

    This eliminates the risk of damaging higher value areas.

    Young lambs should be restrained well to reduce the risk of injury but also to cut down on the important risk of self-injecting which, as described already, can have grave consequences, especially with oil-based formulations.