Industry research in Northern Ireland has suggested the continued emergence of Bovine Viral Diarrhoea (BVD) in 2021 is evidence of the carryover of infection in herds from 2020.
In some cases, the carryover can be attributed to the retention of BVD Positive (BVDP) cattle and the probable infection of susceptible females during the first to fourth months of pregnancy.
During January 2021, there were 96 individual cases of BVD disclosed in 70 herds. Of these herds, over three quarters (54 of the 70 herds) had the virus present during 2020.
A spokesman for Animal Health and Welfare NI explained that while it is possible that there may have been other sources of infection affecting these premises, the picture presented suggests that there are a significant number of cases where the BVD virus continues to circulate on farms.
'Every day a PI is alive is a risk to other animals'
While BVDP ‘retention’ refers to those BVD Positive cattle that are still alive 35 days after notification of their first positive result, any persistently infected animal constitutes a risk to other cattle every day that it is alive.
Delays in isolating, retesting or culling BVDP animals increase the risk of spread of the virus to other cattle on the holding and to neighbouring herds.
The number of BVDP cattle being retained on NI farms has approximately halved since the start of July last year, according to AHWNI's latest analysis.
In the past seven months, the total number of retained living BVDPs has dropped from 192 to 97 and the number of herds with retained BVDPs in this period fell from 127 to 66.
In addition, the rolling annual prevalence of BVD, which is a measure of the number of BVD positive animals disclosed over a 12 month period, has fallen to 0.29% from a level of 0.66% at the end of the first year of the compulsory programme.
A spokesman for AHWNI explained the presence of BVD in herds affects the health and welfare of stock and causes significant economic losses for farm businesses.
"These figures reflect the fact that more farmers are now making the prudent decision to destroy BVDPs, but it is going to take concerted action by all affected farmers and all stakeholders in the programme to see the level of BVD infection driven down to allow progress to eradication," he said.
Given that BVD positive animals are restricted to their herds and that abattoirs are refusing to accept them for slaughter, the best option in these circumstances, in line with veterinary advice, is to minimise losses by culling the positive animals at the earliest opportunity.
"In cases where farms have a history of BVD and where calves are tagged promptly after birth, many herd owners decide to put the positive calves down straight away, as there is a very high likelihood that the virus is persistently infecting their calves."