On the 23rd December Zoetis (UK) announced that the current inventory of Equip Artervac has an expiry date of 29th March 2023 and due to supply issues they are not expecting a new batch to be available until the end of September 2023. The currently available licensed batch of Equip Artervac is still in plentiful supply so there should be no problems with vaccinating stallions ahead of the 2023 breeding season. A precise date for re-supply is not currently available and we therefore have to assume the worst-case scenario that it may not be available until after the 29th September; a gap of over six (6) months. Unfortunately, Zoetis have indicated that it will not be possible to extend the vaccine’s expiry date nor is importation of an alternative product a realistic possibility.
Equip Artervac (Zoetis) is the only licensed vaccine in the UK & European Union against equine arteritis virus (EAV) and is recommended for use by the HBLB’s International Code of Practice for the prevention of equine viral arteritis (EVA). The data sheet states that boosters should be administered at six (6) month intervals. This will present stallion owners with an issue if stallions’ vaccinations lapse as EVA is a notifiable disease in the UK under the Equine Viral Arteritis Order 1995. Under this legislation seropositive stallions with lapsed vaccinations, will need to demonstrate they have not been infected during a period when they were considered susceptible i.e. when they were outside of the data sheet recommendations. Disease freedom needs to be demonstrated, ideally prior to re-vaccination.
The Thoroughbred Breeders Association (TBA) have offered guidance to its members and have presented a strategy to manage Thoroughbred stallions and teasers which may not be vaccinated when their boosters are due. They are again recommending a practical means by which stallions/teasers can be monitored by antibody analysis of stored blood samples; the same approach that was adopted in 2018, when Equip Artervac last had supply issues.
Many Thoroughbred stallions will be vaccinated in January ahead of the breeding season and six months later, however, BEVA and the wider industry appreciates that Sports horse stallions may be routinely vaccinated at different times of year to Thoroughbreds and therefore we recommend veterinary surgeons looking after Equip Artervac vaccinated Sports horse stallions should consider discussion of this with their clients/stallion owners.
As there should be no issues in obtaining vaccine up to the date of expiry of the current batch of Equip Artervac (29th March 2023), it should be possible to bring vaccinations forward up to and before the 29th March 2023, making them next due for booster vaccination by 29th September 2023. Stallions due imminently could be vaccinated and then potentially re-vaccinated early up to and before the 29th March 2023 making them also next due by 29th September 2023.
If the worst-case scenario happens and Equip Artervac is not available by the 29th September then one could plan to collect a semen sample from the stallion and submit for EAV virus isolation and/or PCR to demonstrate the stallion is not a carrier, prior to restarting vaccination. One must also however give consideration to the fact that the stallion will have been outside of data sheet recommendations and may therefore have been susceptible to infection. As such a risk assessment should be performed to determine if additional sampling above and beyond a single semen test is necessary as per the guidance given in Crabtree & Newton 2020. Clients should be reminded of the increased risks of contracting the infection through international travel and breeding activities in circumstances where biosecurity measures are either minimal or inadequate with respect to EVA, for example, where potential in-contacts are not screened for EVA and/or are not of equivalent health status.
Such a retrospective approach, with semen sampling, may be relatively simple for some stallions to achieve, however, it is acknowledged that this may not be straightforward for some stallions that are either not trained for semen collection, or that need to visit a semen collection centre for collection (noting that such a centre may require a stallion to demonstrate freedom fromEAV infection to enter in the first place).
Consequently, one could alternatively follow the prospective approach and monitor antibody levels as per the TBA’s guidance for Thoroughbred stallions and teasers. The strategy is to collect a blood sample around 2-3 weeks after the stallion receives their booster dose of Equip Artervac up to 29th March 2023, by when peak antibody levels from vaccination should be present. This sample should be sent by the vet, accompanied by the special submission form specifically designed for this purpose, for storage and later testing by Rossdales Laboratories, Newmarket. A further blood sample should be taken at the time that the stallion receives their next Equip Artervac booster when the new batch of vaccine is available; with this sample also sent to Rossdales Laboratories for pairing up with the previous sample and testing together as necessary. DEFRA agreed this approach in 2018 and the industry are hopeful that it will again be acceptable. Should there be any issues it may be necessary to revert to semen testing.