As temperatures begin to rise, the active vector season for midges that can transmit bluetongue (BTV) is right around the corner, according to Animal Health and Welfare Northern Ireland (AHWNI).
With many cattle still housed and sheep only starting to be turned out now, it “may be the ideal time for many farmers to consider whether they need to vaccinate or not”.
AHWNI warned that it is “highly likely” that bluetongue will spread further this year based on the amount of cases seen across the island of Ireland last year.
Turnout
The animal welfare organisation noted that vaccinating cattle before turnout should make handling bluetongue-infected herds easier in the event that they contract the disease.
While infection is still possible in housed cattle, the risk is reportedly “slightly reduced, especially if there is good ventilation, as midges cannot fly very well in wind”.
AHWNI outlined that herds who have received their dose a few weeks prior to turnout “will be well protected” at this stage.
For sheep farmers, the recommendation from AHWNI is to consider vaccination when a management procedure is being carried out.
Timing
AHWNI stated that midge activity often arrives on farms once temperatures are consecutively over 12°C, while bluetongue tends to replicate within midges when average daily temperatures are above 15°C.
For this reason, it advised farmers to fully vaccinate their livestock by early May when the weather is usually cooler.
If spring calving, vaccination prior to breeding “can give ultimate protection”, according to AHWNI, who outlined that the next coming weeks may be the best time to vaccinate.
For autumn calvers, vaccinating in mid-pregnancy should
“still be effective” as it is considered unlikely for cattle to contract the virus during winter.
However, AHWNI highlighted that vaccinating at very early-stage pregnancy should be avoided due to the negative effect that stress can have on foetus implantation.
Vaccines
Farmers who are vaccinating their cattle for the first time will have to administer two doses to their herd, while sheep may require one or two doses depending on the vaccine used.
As BTV-3 is the only strain of bluetongue detected on the island so far, the only vaccines available in Northern Ireland and the Republic of Ireland are Bultavo 3, Bluevac 3, and Syvazul BTV-3.
Farmers can purchase these vaccines from their local vet practice.
AHWNI said that the same vaccine can be used for sheep and cattle, alongside any other animal over a month old.
The animal welfare organisation recommended vaccinating every animal on farm if possible, including young stock and breeding males, as it will reduce any possibility of unvaccinated animals acting as a reservoir on farm.
It also important for farmers to read the data sheet for the vaccine that they are using, to ensuring that doses are given at the correct time.
Herd risk
AHWNI listed the following questions for farmers to see if their herd may be at higher risk of bluetongue:
- Is your farm close to any other farms where outbreaks have occurred?
- Is there a high density of ruminants in your location?
- Has there been a low vaccination uptake locally?
- Do you plan to move animals from other parts of the country into your flock/herd?
- Do you have a lack of areas on the farm where there could be lower midge activity (e.g. windy, exposed areas may have reduced numbers of midges)?
- Do you have breeding stock?
If a farmer answers yes to several of these questions, AHWNI warned that their herd or flock could be at risk of infection.
Concerns
It has been reported that there are some concerns amongst farmers regarding bluetongue vaccines and their effect on fertility.
According to AHWNI, these claims have “not been substantiated.”
Furthermore, the animal welfare organisation argued that fertility will be certainly be impacted if an animal is infected, potentially causing abortions, stillbirths, foetal abnormalities, and impaired semen quality.
Impacts
One of the most noticeable impacts that has been identified amongst bluetongue-infected herds is calves being born with brain deformations.
A number of these ‘dummy’ calves have been identified in the UK with neurological issues such as blindness and no suckling instinct.
AHWNI stated that this trend emphasises the need for farmers to consider the risk of bluetongue could have on their herd.
“Vaccination is a small price to pay compared with the potentially severe effects of bluetongue.
“Now is the time to consider the damage it could do to the
health of your flock or herd, and the costs of having unviable calves needing euthanised, or having a high infertility rate at scanning,” it said.
AHWNI advised farmers to always consult their vet when considering vaccination in order to get advice that is tailored to their farm circumstances.