Equip Artervac (Zoetis) vaccine provides stallions and teasers with some protection against challenge with equine arteritis virus (EAV) and is recommended for use by the HBLB’s International Code of Practice for equine viral arteritis (EVA). Booster doses are required to be administered every six months; usually in January before the breeding season and later in the summer when the six-month booster date comes due. 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. However, the current batch of Equip Artervac is due to expire in late March 2023.
On 21st December 2022 the TBA was made aware by Zoetis (UK) that due to a vaccine constituent supply problem, that they do not expect a new batch of Equip Artervac to be available from their European production plant until September 2023; a precise date for re-supply is not currently available. 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.
Therefore, as things stand there will be no licensed Equip Artervac EVA vaccine available in summer 2023 to booster vaccinate European stallions and teasers in accordance with the manufacturer’s product datasheet requirements, leading to stallions having ‘lapsed’ EVA vaccination records later in 2023. This will present issues for Defra as EVA is a notifiable disease in the UK under the Equine Viral Arteritis Order 1995. Under this legislation seropositive lapsed vaccinated stallions may need semen sampling and testing to prove that they are not shedding EAV in their semen and unfortunately using out of date vaccine supplies does not solve the ‘lapsed’ vaccination issue.
A similar problem with potential interruption of supply of Equip Artervac occurred back in 2018 and we are again recommending a practical means by which stallions/teasers can be monitored by antibody analysis of stored blood samples. Evidence of stable/declining antibody levels during the period when EVA vaccination lapses occur will be consistent with absence of exposure to EAV infection and preclude the need for semen testing. Defra agreed this approach in 2018 and we are hopeful that it will again be acceptable; Defra are also now aware of the potential 2023 Equip Artervac supply issue.
The proposal is that in addition to routine annual Code of Practice blood sampling, a further blood sample is collected from vaccinated stallions around 2-3 weeks after they receive their booster dose of Equip Artervac vaccine in January 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.
Further guidance on stallions ‘shuttling’ to the southern hemisphere seasons in 2023 will be issued in due course.