Animal Health and Welfare NI (AHWNI) is reminding farmers in Northern Ireland to take action to prevent bovine viral diarrhoea (BVD) becoming an issue in their herds.
The advice comes as legislation for BVD herd restrictions has been approved in principle by the Committee for Agriculture, Environment and Rural Affairs (AERA).
BVD is a highly contagious viral disease of cattle that can be transmitted as easily as the common cold. It can be spread directly by infected animals, or indirectly, e.g., by contaminated visitors or equipment.
Transient infections may occur without obvious clinical signs but depending on age, sex and immunity they can lead to a range of reproductive problems, including abortion and poor calf health with scours and pneumonias that respond poorly to treatment.
BVD
AHWNI said that the BVD Programme has already reduced the overall incidence of the virus in Northern Ireland has reduced by more than 70% through early disclosure of persistently infected (PI) calves.
The group noted that maximising herd immunity to the virus through vaccination and reducing the number of opportunities for the virus to enter and spread are key strategies for many farmers.
AHWNI said there is a need for BVD vaccination on certain farms, to produce a protective immunity in breeding cattle.
“The immunity gained means that the negative effects of the BVD virus on fertility and the birth of persistently infected calves can be avoided,” it said.
Although the incidence rate for BVD is decreasing in Northern Ireland, AHWNI said it is important to be aware of an accompanying decrease in natural immunity to the virus, due to reduced exposure.
This reduction in immunity may leave herds more exposed to large outbreaks should an infected animal be introduced or in a high risk situation, such as an outbreak in a neighbouring or associated herd or herds with a greater than normal throughput of people, such as demonstration farms.
Vaccine
AHWNI pointed to recent examples of BVD positive results where the vaccine manufacturers’ recommendations have not been followed.
“If you are vaccinating your herd for BVD, ensure that all breeding stock including breeding heifers have been vaccinated, and that the vaccine and boosters are being given at the right time and in accordance with the manufacturer’s instructions.
“Discuss with your vet how to optimise vaccine use. Remember that stopping a BVD vaccination programme prematurely, where biosecurity risks still exist, could be a very expensive exercise,” it said.
AHWNI outlined that the following key risk factors have been identified at herd level which increase the probability of BVD entering a herd:
- Large herd size;
- A history of BVD in the herd;
- Purchase of cattle;
- Purchase of ‘Trojan’ cattle (in-calf animals carrying a PI calf);
- An increased concentration of BVD positive animals in the vicinity of the herd.
AHWNI said that any herd which has been or is exposed to some or all of these risks in the absence of appropriate control measures has an increased probability of experiencing the spread of BVD into their herd.
In order to reduce the risk of a breakdown, AHWNI issued this advice to farmers:
- Buy low risk animals from low risk BVD herds;
- Quarantine animals on arrival;
- Minimise contact of bought-in cattle with other animals, particularly animals in the first four months of pregnancy;
- Isolate purchased pregnant animals until calved and the calves tested with negative results;
- Step up biosecurity during the breeding season – this is a key period where infections can lead to the birth of PIs;
- Keep boundaries in good condition to prevent contact with neighbouring animals;
- Supply cleaning and disinfection for farm personnel and visitors;
- Clean and disinfect shared equipment.
