strategy to eradicate and prevent strangles (steps)€¦ · strategy to eradicate and prevent...

Strategy to eradicate and prevent Strangles (STEPS)

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Strangles is one of the most commonly diagnosed contagious equine diseases world-wide. Some horses can outwardly show nosigns yet still carry the infection and spread it toother horses. Currently these carrier horses canbe very difficult to identify.

Unfortunately amongst some horse ownersthere is still a stigma about admitting their horsehas strangles, which frequently hinders bothquick diagnosis and effective control of thespread of the disease.

Research is currently underway with the aim offurther improving the diagnosis of and vaccina-tion against strangles. However, maintaininggood biosecurity using isolation and strict hy-giene procedures to prevent the introduction andspread of the disease and early diagnosis will

always remain essential to preventing strangles.Although these measures can be time consum-ing and inconvenient; especially in the middle ofthe competition season, they are essential if weare to reduce the incidence of strangles.

The aims of this Code are to:

• promote an increased awareness of stran-gles and to emphasise the importance ofearly diagnosis and control;

• promote increased openness and communi-cation within the equine community aboutstrangles and any suspected outbreaks;

• provide a simple set of steps to be takenwhere strangles is suspected or confirmed.

Strangles is caused by infection with the bac-terium Streptococcus equi.

Signs include:• fever• loss of appetite• depression• marked ‘snotty’ nasal discharge (this is the

most common sign)• lymph node swelling and abscesses pre-

dominantly of the head and neck• Remember that not all horses will show all (or

any) of these signs

S. equi infection can be transmitted both directlyvia close contact with an infected horse or indi-rectly through shared housing, water and feedbuckets, shared tack and equipment; and con-tact with shared personnel such as groom, in-structor, farrier, veterinary surgeon or moreunexpected sources such as a pet dog.

Voluntary code in the event ofa strangles outbreak

Mucopurulent nasal discharge typical of strangles

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There are some simple steps that we can takeat all times to help reduce the risk:1. When you are away from home, take your

own buckets, water and feed and do notallow other horses to share the buckets.Keep your horses away from nose to nosecontact with other horses. If you handle an-other horse then wash your hands beforehandling your horse again. Disinfect yourboots and outer clothing after each show.

2. At home get into the good practice of havingseparate grooming kits, numnahs, rugs, tackand buckets for each horse.

3. Anyone who moves between yards shouldimplement simple hygiene measures such aswashing their hands, disinfecting their bootsand, if possible, changing outer clothing be-tween yards.

4. All new horses should undergo a three weekperiod of isolation after entry into the prem-ises. This should provide sufficient time forclinical signs to develop and be recognisedbefore mixing with resident horses. Use ofthe strangles blood test during isolation canidentify previously infected and potentially in-fectious horses in a quick and non-invasivemanner. Ideally samples should be taken onarrival and at the end of the three week isola-tion period to check for seroconversion (for in-stance. rising antibody levels indicating animmune response after exposure to S. equi).

5. Keep written records of all the horses thatenter and leave your premises.

Even if you take all the necessary precautions,there is still a chance a horse may become in-fected with S. equi, especially as some horses

can be outwardly healthy carriers of the infectionand go on to infect other horses without showingobvious clinical signs themselves.

Knowing what to do if you suspect strangles isessential so that appropriate action can be takenwithout delay.

.

Abscessed lymph nodes at the base of the head

This code encourages all yards to thinkabout what they would do if they suspect a horse has strangles and to havean agreed procedure ready to be implemented. This Code can form the basisof that procedure


1. Isolate the horse and any other horses thathave had direct, particularly nose-to-nose contact with it. Also isolate those whichhave/may have had indirect contact with the suspect case (such as through sharing ofwater and/or feed buckets, tack, handlers,and so on). Isolation should be away fromother horses in the yard with which they havenot had such contact. Do not allow other an-imals to enter the stable where the infectedhorse was kept or have access to its feed orwater container.

2. Call your veterinary surgeon and discuss withthe appropriate management, sampling andlaboratory strategies to investigate whetherinfection with S. equi is the likely cause of theclinical signs. It may be beneficial to takemore than one sample from more than one

horse or on more than one occasion from thesame horse to confirm or exclude the suspi-cion of strangles. Depending on the type andtiming of sampling of cases, S. equi cansometimes be difficult to confirm and your vetwill be able to advise you further.

3. If the diagnosis is confirmed you should thenagree detailed isolation and handling proce-dures with your veterinary surgeon and im-plement these measures as speedily andeffectively as possible.

4. All horses should remain on the premises toprotect neighbouring yards and other equinecommunities.

5. If possible, create three colour-coded groups: RED - presumed infected horses that haveshown clinical signs consistent with strangles(note - that not all strangles cases show allclinical signs and some may have less severesigns than others); AMBER - horses that have had direct or indi-rect contact with the infected horses in theRED group and as such are believed to havebeen at risk of exposure to S. equi but havenot themselves shown clinical signs; GREEN - horses that remained detached fromthose in RED and AMBER groups withoutknown direct or indirect contact and which didnot demonstrate clinical signs.

6. Colour code buckets and other equipment toensure that mixing between groups does notoccur and wherever possible use dedicatedstaff for each colour-coded group. If separatestaff are not an option staff should alwaysmove from the lowest risk to highest riskgroups such as GREEN to AMBER to REDgroups in that order and not back again.

7. No horses should be allowed in, or out, of theyard at this time. All horses in the yard shouldremain under the care of the attending veteri-nary surgeon(s), and the highest possible

If you suspect strangles, take the following stepsimmediately:

Muco-purulent nasal discharge typical of strangles


standards of hygiene should be implementedand maintained.

8. Contact owners of the affected horse andowners of all other horses in the yard and ex-plain the position to them. They will muchrather hear it from you now than learn laterwhen their animal may have also contractedthe disease.

9. Keep a very close eye on all other horses inthe yard. Young, old and immunocompro-mised horses (for instance those with a his-tory of other disease problems) are mostsusceptible to infection and should be moni-tored closely. The temperature of all horsesshould be taken daily and any horse showingan increase in temperature should be iso-lated (moved to RED group) and seen by yourveterinary surgeon.

10. Where possible, in multi-owner yards, oneveterinary practice or the owner/manager ofthe yard should take the lead and co-ordinateall the veterinary procedures in the yard eventhough they may not be responsible for car-rying them all out.

11. Establish and agree communication proce-dures among all veterinarians, owners andriders of every horse in the yard and keeplines of communication open throughout theoutbreak.

12. Notify any neighbouring premises with horsesthat you have a suspected case of stranglesand suggest they monitor their horses andseek veterinary advice.

13. No presumed clinically affected horse in theRED group in the yard should be releasedfrom isolation or removed from veterinary su-pervision until three consecutive negative na-sopharyngeal swabs or washes have beentaken over a two-week period. Nasal swabscould be used, but may be less effective forthe isolation of S. equi being shed from theguttural pouches. Alternatively endoscopicallyguided guttural pouch lavage may be a pre-ferred method of sampling. Samples shouldbe tested for the bacterium by both cultureand PCR (Polymerase Chain Reaction) to max-imise test sensitivity. The yard should not open

to normal activities until after all horses areconfirmed to be uninfected. Animals still test-ing positive for S. equi will be required to re-main in isolation until they are shown to havegone negative, which may require treatmentappropriate for persistent infection such as ofthe guttural pouches.

14. Screening of horses in the AMBER and GREENgroup using the strangles blood test shouldbe performed to identify other horses thatwere exposed before or during the outbreakthat could be carriers of strangles, which if leftuntreated could trigger subsequent out-breaks. Animals testing positive by the bloodtest should be placed in isolation and investi-gated by nasopharyngeal swabbing and/orguttural pouch endoscopy to establish if theyare positive for S. equi. Any carriers identifiedin this way will be required to remain in iso-lation until they are shown to be negative, thismay require treatment appropriate for per-sistent infection such as of the gutturalpouches.

15. Carriers can usually be successfully treatedby removal of chondroids (dried pus from ab-scesses that have drained into the gutturalpouch) via guttural pouch endoscopy and acourse of antibiotics. A subsequent gutturalpouch wash (tested by culture and PCR) canthen confirm infection-free status.

Chondroid removed from a guttural pouch with transendo-scopic basket forceps


Since strict hygiene procedures are essential tominimise the spread of infection it is good prac-tice to draw up a list of the hygiene rules to beadhered to by everyone connected to the yard.Give a copy of the rules to all owners/riders ofthe horses in the yard and pin up a copy of thelist in the yard where it can be clearly seen.Colour coding (RED, AMBER and GREEN) isola-tion areas, equipment and clothing can greatlyassist biosecurity compliance.

It is a good idea to make rules on correct gen-eral biosecurity available before there are anycases of strangles as good biosecurity can re-duce the likelihood of getting the infection in thefirst place.

These notes provide general guidance on isola-tion procedures. Where any of these steps arenot possible a suitable alternative should beagreed with your veterinary surgeon.

• The principal aim of isolation is to preventcontact between the isolated horses - thosesuspected or confirmed of having strangles- and the other horses in the yard. Ideallythe isolation facility should be in a separatebuilding or a separate field at least 10m butpreferably 25m away from any other horses(additional fencing can be used to create a10m/25m sterile zone if necessary). If this isnot possible then even simple steps likeboarding up any grills between stables, fit-ting door grills so that horses cannot touchother horses over the door, and similarmeasures will help to contain infection, al-though this is less than ideal.

• A separate water supply must be availablefor the isolated horses. This should be-

cleaned on a regular basis (ideally daily withthorough rinsing to remove detergent) andany mucopurulent nasal discharge removedto minimise the infectious dose given to incontact horses. This will reduce the severityof clinical signs and increase the speed ofrecovery.

• Separate equipment and utensils used forfeeding, watering, grooming and cleansingmust be used for horses in isolation andshould be colour coded RED (see section oncolour coding). These must not be removedor used on other horses unless they are firstthoroughly cleaned and then decontami-nated with an approved disinfectant.

• As few people as possible should come intocontact with the isolated horses and appro-priate measures. Communication with own-ers and notices at the entrance to thepremises should be used to enforce this.

Guidance on isolationand hygiene

The guttural pouch is a diverticulum in the eustachiantube which runs between the middle ear and the back ofthe throat


This includes pet dogs and cats living at orvisiting the yard.

• Preferably attendants of the isolated horsesshould have no contact with any otherhorses during the isolation period. Whereother contact is unavoidable, it should bekept to a minimum and only after thoroughwashing and disinfection of hands and achange or thorough disinfection of clothingincluding boots and impervious outer cloth-ing. If staff cannot avoid handling both in-fected and uninfected animals then, inaddition to the disinfection and clothingchanges mentioned, they should attend touninfected animals first (GREEN) and onlythen deal with the exposed horses (AMBER)before finally attending to infected animals(RED), ideally as their last task on the yard.

• Used bedding, uneaten food and watermust be disposed of carefully. Bedding anduneaten food should be carefully disposedof (such as on a muck heap >30 metresaway from grazing/exercise areas) and

water should be discharged to the sewer or septic tank to avoid cross contamination.

• Protective clothing (such as disposableboiler suits, separate boots and disposablegloves) must be available at the entrance tothe isolation facility and must be disposed ofproperly by being double-bagged and

taped shut. The outside of the bag shouldbe disinfected before disposal.

• After use, all movable equipment and uten-sils for feeding, grooming and cleansingwithin the isolation facility must be disinfec-ted using a disinfectant approved by Defrafor general purpose under the Diseases ofAnimals (Disinfectants) Order 1978. A list ofthese is provided on the Defra website:(http://disinfectants.defra.gov.uk/Default.aspx?Location=None&module=Approval-sList_SI). After the isolation area is vacated itmust be cleaned and washed down with anapproved disinfectant.

Guidance on vaccination

A live attenuated vaccine is now available inthe UK to aid in the management and preven-tion of strangles. It can be used in horses fromfour months of age and is administered by sub-mucosal injection into the upper lip.

A primary course of two vaccines, four weeksapart, is required with re-vaccination boostersevery three-six months. The duration of immu-nity is three months so the booster intervalshould be determined on a strangles risk as-sessment. Veterinary advice should be soughtto determine if the use of the vaccine is appro-priate and how often booster vaccinations aregiven. If a six month re-vaccination regime isadvised, a prompt booster will be required if anoutbreak occurs more than three months sincethe last vaccination.

In situations where vaccination is deemed to beuseful it is important that all horses on the yardare vaccinated. This will help to develop herdimmunity and lower the infectious challenge.

It is important to note that the vaccine is a tool instrangles management and is not a replace-ment for good stable management andbiosecurity.

Abscessed lymph node discharging infected pus


For more information please contact:1. Your veterinary surgeon 2. www.strangles.org 3. www.strangles.info

4. www.equine-strangles.co.uk 5. www.beva.org.uk 6. www.bhsscotland.org 7. www.worldhorsewelfare.org 8. www.bhs.org.uk

The British Horse Society Scotland, Woodburn Farm, Crieff PH7 3RG©2011 The British Horse Society, Registered Charity Nos. 210504 and SC038516

Cover images, clockwise, from top, left: Administering the vaccine; endoscopically guided guttural pouchlavage; nasal swab showing length of swab required

This leaflet is sponsored by Intervet/Schering-PloughAnimal Health, manufacturers of Equilis StrepE

These revised guidelines benefitted from discussionsthat took place at the ‘Getting to Grips with Strangles’meeting, 27-28 May 2010, Ulfsunda Slott, Stockholm,Sweden, which was sponsored by Intervacc AB, PfizerAnimal Health and Intervet Schering-Plough AnimalHealth.

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