Focus > Herd Health - March 2021
An enhanced BVD programme and the end in sight
Maria Guelbenzu, programme manager, bovine viral diarrhoea and infectious bovine rhinotracheitis, Animal Health Ireland, outlines next steps to be taken to achieve BVD freedom in 2023
The Irish bovine viral diarrhoea (BVD) programme has been very successful in reducing the number of BVD-positive animals born each year in Ireland. In 2013, the first year of the compulsory programme, 0.66% of calves were BVD virus-positive (Figure 1) while in 2020, only 0.03% were (Figure 2).
On December 30, 2020, there were 13 BVD-positive calves alive, only three of which had been retained on farm for over three weeks. These represent the lowest levels recorded since the start of the programme, with many counties not having any BVDV-positive animals at that time.
Figure 1: Map showing distribution of BVD virus-positive births during 2013. Each hexagon represents an area of approximately 10km2.
The new Animal Health Law (AHL) which comes into force in April 2021, sets out, for the first time, the requirements for recognition of BVD eradication programmes at EU level. As the BVD programme enters its final stages, the BVD Implementation Group (BVDIG) plans to apply for recognition of the Irish programme in 2021 and to meet the conditions for freedom by 2023. This includes having negative herd status (NHS) for 99.8% of all herds (currently over 95% of breeding herds) representing at least 99.9% of cattle. Recognition of freedom would bring to an end compulsory tissue tag testing for the majority of herds after 2022.
To achieve this goal, the BVDIG has developed a series of enhanced measures to maximise the proportion of herds with NHS and to rapidly identify and resolve the small number of herds with positive/inconclusive results in 2021 (projected in the region of 250-270 herds), and in 2022 to minimise the risk of onward transmission of infection.
Figure 2: Map showing distribution of BVD virus-positive births during 2020. Each hexagon represents an area of approximately 10km2.
Steps to BVD freedom
In order to achieve BVD freedom under AHL, tissue tag testing will remain compulsory for all herds in 2021 and 2022 and there will be a focus on ensuring all animals have a BVD status (including those born before January 1, 2013) and for all herds to obtain NHS. Around 3% of herds contain small numbers of animals that either do not have a valid test result or have not yet produced a negative calf. The presence of these animals prevents herds attaining NHS and also accessing lower cost testing. It is now a legal requirement to test animals of unknown status born before 2013, in addition to those born after this date. Each herd’s annual TB test provides an ideal opportunity to sample animals that need a BVD test, and it is possible to use your ‘handhelds’ to identify these (for guidelines on how to do this, see https://animalhealthireland.ie/?page_id=227). Alternatively, these animals can be identified on each herd’s Irish Cattle Breeding Federation (ICBF) BVD dashboard.
Herds qualify for NHS by having a negative BVD status for every animal currently in the herd (on the basis of either ‘direct’ or ‘indirect’ results) and by not having had any virus-positive animal(s) in the 12 months preceding the acquisition of NHS. From 2021, this period will be extended to 18 months.
The option to retest animals with initial inconclusive or virus-positive results will no longer be permitted, and herd owners will be encouraged to isolate and remove these animals as soon as possible. Financial supports from the Department of Agriculture, Food and the Marine (DAFM) and associated timelines for removal are unchanged from 2020, with higher support where these animals are removed within 10 days of the date of the test.
In 2021, herds where a positive/inconclusive result for BVD is disclosed become immediately restricted (as opposed to the situation previously where only retaining herds were restricted) for both moves in and out. While restricted, movements out of the herd to slaughter or to non-breeding herds, may be granted on a case-by-case basis under permit by the regional veterinary officer (RVO), provided that the animals move directly to their destination. Neighbouring herds will receive a biosecurity notification informing them of their increased risk, and on a monthly basis thereafter, in the absence of removal of the suspect animal(s) with positive or inconclusive results.
An initial three-week period of herd restriction, beginning on the date of removal of the suspect animal, will serve as a ‘circuit-breaker’ to allow circulation of any additional transient infections established by the suspect animal(s) to diminish or cease. After this period, the restrictions will be lifted following completion of each of the following three measures by a trained private veterinary practitioner (PVP) nominated by the herd owner:
- Blood sampling and testing of all animals in the herd with negative results or removal of any further virus-positive animals identified;
- Completion of a herd epidemiological investigation conducted under the Targeted Advisory Service on Animal Health (TASAH) within the Rural Development Programme; and
- Vaccination of all female animals aged 12 months old and above by the nominated PVP.
Each of these measures should be completed as soon as practicably possible after the initial three-week period and must be finished in advance of the commencement of the next breeding season, except where this is not biologically feasible. These three measures are fully funded, with necessary payments made directly to PVPs. DAFM staff on the BVD helpdesk will contact the herd owner by telephone to identify their nominated PVP. Following lifting of restrictions, the herd owner is required to:
- Continue to tissue tag test for a minimum of 24 months after the removal of the last suspect animal;
- Continue the vaccination programme in the herd in the following year, with this again delivered by the PVP and funded by the DAFM;
- Not sell any female that was in calf at the time of birth of the (first) suspect animal until its calf has been born and tested for BVD; and
- Clean and disinfect buildings and handling facilities which may have been contaminated by the suspect calf at birth or subsequently, as soon as practicable but in advance of the next breeding season.
A BVD TASAH refresher webinar, explaining in detail the requirements for the new, enhanced programme, is available to AHI BVD-trained vets through AHI’s Service Provider Portal.