Miss Juliette Edmonds graduated from the University of Liverpool in 2004 and subsequently completed an equine internship at a busy equine referral hospital in York. Since 2010, Miss Edmonds has been based at an equine clinic in Hertfordshire, focusing primarily on leisure and sport horses. Her main interests lie in lameness and poor performance, but she possesses extensive experience in all aspects of equine practice, including stud work, orthopaedics, dentistry, and emergency medicine.
It is very likely that you will attend equine patients for vaccination on your first day of equine practice, but do you really know:
- What is needed and when?
- How will you advise these clients with regard to competition rules?
- Where will you inject the vaccine?
- And how will you address concerns regarding vaccination reactions?
‘Core’ Equine Vaccines
The ‘core’ equine vaccines given in the ‘annual vaccination’ visit consists of Influenza and Tetanus vaccines. ‘Flu is the main requirement for competition horses as it is compulsory for horses competing under pony club and riding club rules, and under affiliated rules of the major sporting associations: British Eventing, British Showjumping, British Dressage, and the British Horseracing Association. The primary course for these vaccinations required by the sporting bodies is similar, however there is some variation in the requirement for booster vaccination intervals (in recent years this has also been subject to change!)
Current requirements as of October 2024 for Influenza vaccinations in racehorses are as follows:
1st Vaccination
2nd Vaccination 21 – 60 days
3rd Vaccination 120 – 180 days
Booster Not more than 6 months apart
In reality it is the horse owners’ responsibility to ensure that their horse is vaccinated in line with any sporting requirements, however in practice owners’ will often ask for advice and guidance with regards to which vaccine is needed and when, and it is important that you understand the vaccination schedules, and can access current information regarding the relevant associations’ booster requirements. At present (2024), following a primary course of vaccines as above, booster requirements are:
British Dressage – Yearly
British Showjumping – Yearly
British Eventing – Booster must be given within 6 months and 21 days of event.
Pony club and riding club- Yearly
FEI (international competitions) – Boosters within 6 months and 21 days.
Competition Rules
Vaccinations for all disciplines must not be given less than 7 days before competition. It is also important to note that these vaccination schedules do not entirely align with the recommended intervals on the data sheets! The first two vaccinations are required as a minimum before the horse is eligible to compete. ‘Flu vaccinations are usually started in the foal at around 5-6 months of age, prior to this the presence of maternally derived antibodies (MDA) may reduce vaccine efficacy.
Tetanus
Tetanus is usually given as a combined vaccine with Flu, with boosters given on alternate years. It is occasionally used as a solo vaccine, often these patients are older/retired equines and others who are not in travelling or in contact with others who are leaving the premises.
Equine Herpesvirus (EHV)
Equine Herpesvirus (EHV) vaccination is available to give protection against EHV- 1, and EHV- 4. These strains are primarily responsible for causing respiratory disease and abortion. EHV-1 is also indicated in the development of Equine Herpesvirus Myeloencephalopathy (EHM, neurological disease), against which vaccines do not offer any protection. Vaccination protocols vary according to the situation, for protection against respiratory disease it is advised to give two vaccinations 4- 6 weeks apart, followed by booster vaccinations every 6 months. For the prevention of EHV abortion pregnant mares should be vaccinated in months 5, 7 and 9 of pregnancy. Vaccination is not advised for exposed horses in the face of an outbreak. It should also be noted that EHV vaccinations are a compulsory requirement for racehorses intending to race in France.
Equine Rotavirus
Equine Rotavirus vaccinations are available to protect newborn foals against Rotavirus-induced diarrhoea. Pregnant mares are vaccinated in months 8,9 and 10 of pregnancy. Immunity is passed to the newborn foal via the colostrum.
‘Strangles’ (Streptococcus Equi)
More recently there has become available a licensed vaccine for ‘Strangles’ (Streptococcus Equi), Strangvac®. This is an intramuscular vaccination, whereas previous vaccinations for Strangles have used other routes of administration. The primary course requires two vaccine doses given four weeks apart. There appears to be insufficient evidence at present to indicate how long protection can be expected to last following a single re-vaccination dose, however data sheet advice is to administer 6 monthly boosters following the primary course. Interestingly a vaccinated horse will not test positive on serology for S. Equi, which is useful for differentiating vaccinated horses from recently exposed horses when non-symptomatic animals are blood sampled to screen for S.Equi exposure. It is not advised to vaccinate horses directly in contact with known cases as this increased challenge to the immune system may cause the worsening of clinical signs of disease.
Administration Techniques
All the above vaccinations are administered by intra-muscular injection, but which muscle is best to use? Most commonly vaccinations are given in the neck muscle, above the spine and below the nuchal ligament, but there can be problems if an adverse vaccination reaction is encountered. This muscle is essential for the horse to lower the head to eat/drink and to lie down. Pain and swelling at this site can make it difficult for the horse to function normally. Inflammation in the neck can also occasionally induce ataxia. This usually responds well to anti-inflammatory treatments and time; however it can be quite shocking for the owner to experience. It is possible that a reaction at the injection site could be caused by abscess formation, usually characterised by a firm swelling appearing within weeks of a vaccination. Abscesses require drainage and flushing to enable resolution, and adequate drainage can be difficult to achieve in the neck. Often abscesses forming at vaccination sites are sterile, but it is useful to take a swab for culture if an abscess is identified. A septic abscess can spread infection locally, and in the neck a septic osteomyelitis of the vertebrae would be a potential sequela.
Alternative sites for vaccination include the pectoral muscles and gluteals. The pectoral muscles are downward facing and so it is much easier to achieve drainage should an abscess occur. The horse would not be at risk of any consequences of neck pain as described above, although a sore pectoral muscle can give a shortened forelimb gait in the acute phase. As the pectoral muscles are softer and downward facing they are more prone to transient swelling in the days after vaccination, which may be of cosmetic concern.
The gluteal muscles are certainly less prone to swelling, but this would be a very difficult site to achieve drainage should an abscess occur!g, but this would be a very difficult site to achieve drainage should an abscess occur!
References and Resources
- BHA vaccination calculator BHA – Vaccination Calculator (horseracing.software)
- British Eventing Rule changes 2024 FINAL-Rules-Summary-for-2024-v2.pdf (britisheventing.com)
- British Dressage Rulebook 2024 p64 BD Members Handbook (pagesuite-professional.co.uk)
- British Showjumping Rulebook 2024 p43 British Showjumping Rulebook (pagesuite-professional.co.uk)
- British Riding Club Rules Rules – British Riding Clubs (area17-brc.org.uk)
- Pony Club Website Useful Information – Zetland Hunt (pcuk.org)
- www.dechra.co.uk/strangvac