Strangles continues to be a disease which presents unique and often frustrating challenges for horse owners, yard managers and vets. Thankfully, ongoing research has provided new knowledge and technologies that have driven forward our ability to both prevent and manage the infection in the past decade. As exciting developments emerge, a secondary challenge is to encourage wider use of the latest practices, opportunities and products that enable us to make progress against a particularly intransigent disease that remains far more common than it needs to be.
Strangles Awareness Week was developed specifically to address this challenge in positive and engaging ways. The campaign has grown rapidly since its inception in 2020, and in 2023 it reached more than eight million people through digital and print media in a collaborative and multi-national effort.
Strangles Awareness Week promotes openness and understanding around the disease, and encourages the use of practical, proven steps to help stem the relentless circulation of a potentially life-threatening illness around the UK and beyond. This year, Strangles Awareness Week is focussing on the BEST way to protect horses from the risk of strangles through four actions:
- Boosting immunity through strangles vaccination
- Educating ourselves and others
- Separating unfamiliar horses
- Temperature checking routinely.
These four actions are key steps to helping reduce the hundreds of cases that are still recorded across the UK every year, and with the knowledge that many more outbreaks likely go unrecorded. A straw poll of vets at the British Equine Veterinary Association Congress 2023 showed that these are the steps veterinary professionals also feel would have the most impact to prevent the spread of infection.
Routinely using all four actions offers the greatest protection for horses, but even achieving one or two BEST goals can really make a difference to the health of a horse or equestrian business. The actions also support better outbreak management if needed through increased awareness of the disease and familiarity with vital measures such as using quarantine procedures and taking rectal temperatures. Initial field data suggest that vaccination is also proving to be very effective.
Strangles vaccination – breaking new ground
Since its launch in the UK in 2022, evidence is showing that the most recently developed strangles vaccine is as safe and effective as early trials indicated (Robinson et al, 2020). The vaccine offers multiple benefits that are already enabling it to offer widespread protection to equines (Box 1) and reassurance to owners across both the UK and Europe:
- Administered through straightforward intramuscular injection
- The primary course consists of two vaccine doses, 4 weeks apart, with protection then maintained by a routine booster. Data on adopted protocols in the field are still being gathered, but there is potential for 6-monthly or annual boosters to provide an effective level of immunity
- Contains no live Streptococcus equi or DNA
- Contains no M-protein
- Targets all known global strains of S. equi bacteria
- Minimal reactions to vaccination: 5.6% prevalence of transient temperature rise and/or localised reaction
- Capability to differentiate infected and vaccinated animals, enabling vets to reliably use a full range of serology, PCR and culture testing in vaccinated equines as part of preventative screening or outbreak management situations
- Provides a broad immune response, preventing or reducing clinical signs of disease and reducing lymph node abscessation in horses exposed to disease.
Box 1.Vaccine dataClinical trials that used a high dose of S. equi, which was sprayed directly into the nasopharynx of young ponies, found that vaccination already provided a degree of protection within 2 weeks of the primary course (two vaccinations given 28 days apart), as although all control ponies developed strangles, 31% of vaccinated ponies did not develop signs of infection. Protection increased to 58% in another group of ponies when they were exposed to the bacteria 3 months after the second vaccine dose, and reached 94% in ponies that received a booster vaccination 3 months after their primary course. There was also evidence that a booster given between 3 and 12 months of the primary course restored immune responses, giving optimism that an annual booster may provide a practical level of immunity to horses.
Staying up-to-date
Active, ongoing research into strangles is regularly making new information, advice and products available to both the equestrian sector and veterinary professionals. It is an exciting time, as our understanding of how strangles operates is evolving continuously – remaining abreast of the latest developments is important to allow for using and promoting best practice around disease prevention and management. In addition to availability of an updated strangles vaccine, there are several other areas of recent research and development yielding valuable information and insight.
Insight into outbreaks
Work undertaken as part of a PhD project at the Royal Veterinary College, kindly funded by The Horse Trust, examined S. equi strains from horses in the UK between 2016 and 2022. Results suggested a much quicker change in the predominant group of S. equi strains circulating among horses in the UK than previously expected. The observed speed of changes in circulating strains suggests that acute infection, or recently convalesced (but still subclinical) horses returning to normal activity on the assumption that they are clear of infection may be larger drivers of strangles transmission and endemicity in the UK than previously thought.
Vaccination offers additional protection against recently infected but unscreened horses who may have re-entered the mobile horse population, alongside use of good basic hygiene measures where horses mix (such as at equestrian events). Such measures include keeping a degree of separation from unknown equines, not sharing transport, avoiding direct contact between unfamiliar horses or indirect contact through shared grazing and water sources.
Testing, testing
The development of more testing options also needs to be embraced and encouraged, but in the context of also understanding their limitations. Practice-based tests can offer rapid results, allowing speedier confirmation of the need to maintain the precautionary quarantine an owner would hopefully have set up on the first suspicion of an infectious disease. Practice-based tests may not be suited to running larger batches of samples. Furthermore, the current sensitivity and specificity of these technologies for strangles can leave gaps that are only reliably filled by the more complex sample preparation processes available at dedicated laboratories. False negative results can have a devastating impact on halting a potential out-break, while false positives can cause unnecessary stress, expense and lockdown restrictions. On the other hand, early indications of the spread of strangles in a suspected outbreak allows vets to ensure yards swing into action as soon as possible, with the next-day answers from the main laboratories allowing follow-up management to be carried out with confidence.
Tracking strains
Redwings would also appeal to colleagues to consider running culture tests alongside at least one of the positive PCR cases in an outbreak to allow the wider industry to continue to monitor how strangles is evolving (McGlennon et al, 2021). Gathering key data from cases that veterinarians are dealing with is crucial to enable further research into the disease. This is crucial if we are to monitor and guide efforts to reduce and even eradicate strangles in the UK.
Thermochip technology
Thermochips are now available for horses which require implantation of an identification microchip. Studies show that temperatures recorded by microchips correlate significantly with rectal temperatures taken concurrently (Auclair-Ronzaud et al, 2020). The chips offer a new way for owners and vets to easily and safely monitor a horse's temperature. Fever is associated with a wide range of clinical issues, including the onset of infectious disease. Routine temperature checking plays a critical role in spotting strangles before an infected horse is likely to have become contagious, providing a unique window of opportunity to contain the disease. New opportunities to facilitate and encourage temperature checking are a welcome addition to the resources that help prevent and manage strangles outbreaks.
Strangles Awareness Week 2024 takes place between 6th and 12th May, and seeks to show horse owners, yard managers and other professionals that by bringing together BEST practice in regard to strangles they can not only avoid the risk of infection but also feel reassured if they find themselves in contact with a case. Making BEST use of advancing knowledge and technologies not only helps protect horses and businesses from strangles, but also offers valuable security in the face of other equine infectious diseases already circulating within the UK or presenting an increasing threat to our equine herd and the equestrian sector as a whole.
Strangles is a highly contagious bacterial infection that can spread rapidly through yards, causing distress to horses and significant disruptions to yard operations. Recognising the critical need to raise awareness and promote proactive measures to combat this disease, The British Horse Society are pleased to collaborate with Redwings to support the Strangles Awareness Week campaign. As part of Strangles Awareness Week this year, we are empowering owners and professionals, including yard managers, to implement the campaign's BEST actions, so everyone can take proactive steps to safeguard all horses and prevent the spread of disease.
Redwings
The charity has screened all new equines for strangles for over 30 years and dealt with hundreds of cases of the disease, including complex presentations. Redwings coordinates Strangles Awareness Week, an annual event developed by a collaboration of researchers, campaigners and equine welfare professionals. The week aims to make practical information and guidance accessible to the equestrian world as part of global efforts to tackle strangles.
Maintaining the health and wellbeing of horses is paramount in any equestrian setting, whether it is a professional training facility or a small-scale yard. With an emphasis on biosecurity, prevention is key to avoiding the spread of infectious and contagious diseases among equine populations. Two crucial aspects of this preventive approach are the implementation of robust protocols for separating horses and conducting routine temperature checks.
The British Horse Society Approved Centre Scheme offers invaluable guidance and support in this regard, emphasising the significance of biosecurity plans tailored to prevent and control the spread of diseases. These plans encompass various elements including quarantine protocols, health monitoring and hygiene measures, which are instrumental in safe-guarding the health of horses within equestrian establishments.
In a study undertaken by the Royal Veterinary College as a part of research for a PhD, 67% of strangles outbreaks had a new arrival or horse return from loan in the two weeks before the outbreak began. Although it could not be confirmed whether these horses were the source of the outbreak, separating and quarantining new horses is an important step to reduce the risk of infectious diseases spreading to other horses on the yard.
Guidelines outlined by the British Horse Society Approved Centre Scheme encourage yard managers to embrace proactive measures and separate every new horse for a minimum of 21 days, and always ensure the quarantine area is sufficient to meet the horse's physical and mental welfare needs.
Another cornerstone practice highlighted in the British Horse Society Approved Centre biosecurity plan is the isolation of horses showing signs of suspected infectious or contagious diseases. By promptly isolating such individuals and implementing a stringent assessment process, centres can mitigate the risk of disease transmission within their facilities. With a sudden rise in temperature being the most common early sign of strangles, routine daily health monitoring of new and isolated horses, including daily temperature checks, is a key preventative measure we recommend.
Through this year's Strangles Awareness Week campaign and its new BEST Actions, we will be shining a light on this inexpensive, easy and vital way of checking a horse's overall health. The educational content will encourage regular temperature checks for all horses and especially those returning from events, to provide a 2–3 day early warning for strangles infection. By knowing their horse's normal resting temperature, yards can take swift action by separating horses with high temperatures from others to prevent the spread of disease.
The importance of separating horses and implementing routine temperature checks cannot be overstated in the context of equine health and biosecurity. By implementing the Strangles Awareness Week BEST Actions, adhering to the guidelines outlined by the British Horse Society Approved Centre Scheme and embracing proactive measures, our equestrian establishments can create safer environments for horses and actively safeguard their welfare. In supporting Strangles Awareness Week, the British Horse Society reaffirms its dedication to protecting the welfare of horses and promoting responsible horse management. By raising awareness, promoting prevention strategies, and fostering collaboration, we can collectively work together and take back control against the disease.
The British Horse Society
Equine charity, The British Horse Society, is dedicated to education, equine welfare, protecting and increasing access to bridleways and places to ride and carriage drive off road and safety for horse and riders. The charity's thriving and active community of staff and volunteers is committed to improving the lives of horses everywhere.