Texas Equine Veterinary Association

www.texasequineva.com | 22 e attenuated live vaccine is given intranasally with the head up to allow the vaccine to reach the pharynx. It should be administered to only healthy horses. e initial doses are scheduled in a 2-dose series, 2-3 weeks apart and a booster annually to follow. When giving this vaccine, it is best to give it last to all horses on the farm or on a separate day from any procedures. It is live bacteria that can cause abscessation aer performing injections, castrations, etc. It is oen recommended to give this vaccination 2 weeks before traveling into a high-risk area or event. Maternal antibodies aer typical pre-foaling vaccination are significantly increase in the colostrum. e foal's passive immunity appears to be mediated by IgGb in the serum and mucosal secretions, not the typical mucosal immunoglobulin, IgA. Biosecurity Vigilant farm owners do what they can to limit exposure. Ideally, horses with unknown history or exposure would be quarantined for 3 weeks. is is especially important in horses that have been or potentially been exposed. It can be hard to do on some farms with limited space, frequent movement of horses, and busy schedules. Disinfecting and cleaning potentially contagious equipment is important in biosecurity measures. Educating all caretakers on how to use proper hygiene and monitor for signs of disease is valuable. Serology screening can be used to protect a herd. Paired serum samples taken 10-14 days apart will show evidence of recent infection if the titer has a 4-fold or greater increase. If the horse has no signs of disease and titer hasn't changed then the horse is allowed into the general population. Horses testing positive on the initial test and those that seroconvert should be scoped for chondroids. If no evidence of disease is seen on endoscopy, then a guttural pouch flush is recommended to send off for PCR testing. If negative, the horse may enter the herd. Horses with guttural pouch infection are tested via PCR again 3 weeks aer the last clinical case is cleared of infection. Outbreak management A good history from all people involved about horse movement, cleaning and feeding management, and vaccination history is a good place to start in an outbreak. Aer a thorough farm evaluation, it's important to collaborate with the owner or herd manager to come up with a logical and practical plan. A good plan always starts with identifying all horses with clinical signs and removing them from the healthy-looking population. It's also best to keep the horses with known exposure away from others with little risk of exposure. Stop all movement of horses on and off the premises until quarantine is lied. Rectal temperatures should be taken twice a day. When fever starts then the horse should be moved to the disease group. Dedicated equipment and, ideally, personnel will be assigned to each group. When it's a one-man-show, then always use good hygiene and start working with the low-risk group and move to the high-risk group. Never go back until clothes, shoes, and equipment have been disinfected appropriately. Ideally, quarantine will last at least 3 weeks past the last clinical sign. Once horses appear clinically recovered, then testing to identify carriers can commence 3 weeks following. One guttural pouch wash PCR is more efficient and sensitive than performing 3 nasopharyngeal washes, but not always easy to do in every scenario. Washing equipment in between each horse is important. Animals are considered safe to go back into general population when there is no pathology visually observed in the guttural pouch and PCR negative on a guttural pouch wash. Treatment Most horses require little to no treatment. ey only require monitoring while the disease runs its course. Monitoring should include rectal temperature, appetite, and breathing effort. Flunixin meglumine (1.1 mg/ kg IV or PO) is given for fevers over 103.5˚F or if lethargic and inappetent. Horses with trouble breathing need to be monitoring closely. Sometimes the abscess compressing the airway can be opened and drained to all allow better airflow. When this can't be accomplished the patient may need a temporary tracheostomy placed. Antibiotic use for S. equi infection beckons different opinions. Antibiotic use is necessary in horses with respiratory distress, bastard strangles, purpura hemorrhagica, and myositis. Antibiotics are also administered in guttural pouches aer lavaging clean to help clear or prevent the carrier state. Conclusive data regarding the role of antibiotics on increasing risk of occurrence of bastard strangles is lacking. Concerns when using antibiotics are delaying the maturation of abscesses, allowing the recurrence of abscesses when the antibiotics are discontinued, and diminishing the development of protective immunity. It's also possible to lead to antibiotic resistant S. equi if antibiotics are stopped too early. Antibiotics have and can be used in horses during an outbreak that begin to have a fever. Starting early treatment prevents abscessation. Treatment can be stopped when fevers subside and bloodwork normalizes. e antibiotic of choice is Penicillin (22,000 – 44,000 IU/kg IM q12h or IV q6h). For horses requiring long term treatment cephalosporins, macrolides (when age appropriate) and tetracyclines have been used. Trimethoprim-sulfadiazine does not work well in vivo. Cephalosporins should be reserved for those difficult to treat to honor antibiotic use stewardship. Good nursing care of abscesses can shorten the duration of disease. Mature abscesses can be opened easily with a surgical blade. Deeper retropharyngeal abscesses can be opened with good ultrasound skills and knowledge of anatomy. Open abscesses can be flushed 1-2 times a day with 3-5% povidone iodine solution. Once the retropharyngeal lymph nodes have opened into the guttural pouches, most horses drain appropriately, fevers cease, and endoscopy with guttural pouch lavage isn't warranted until the nasal drainage has slowed or stopped. Some horses don't drain well and require guttural pouch lavage to help their fevers cease and mentation return to normal. With this knowledge, we can help our clients come through these frustrating times. It can be financially and mentally draining for them. References AG Boyle, JF timoney, JR Newton, MT Hines, AS Waller, BR Buchanan; Streptococcus equi Infections in Horses: Guidelines for Treatment and Prevention of Strangles – Revised Consensus Statement, JVIM, 2018, 32, p633-647 AS Waller. New perspectives for the diagnosis, control, treatment, and prevention of strangles in horses. Vet Clin North Am Equine Practice 2014; 30: 591-607 K Verheyen, JR Newton, NC Talbot, et al. Elimination of guttural pouch infection and inflammation in asymptomatic carriers of Streptococcus equi. Equine Vet J 2000; 32: 527-532 JS Weese, C Jarlot, PS Morley. Survival of Streptococcus equi on surfaces in an outdoor environment. Can Vet J 2009; 50: 968-970. RE Holland, DG Harris, A Monge. How to control strangles infections on the endemic farm. Proc Am Assoc Equine Pract 2006; 52: 78-80. V Baverud, SK Johansson, A Aspan. Real-time PCR for detection and differentiation of Streptococcus equi subsp. equi and Streptococcus equi subsp. zooepidemicus. Vet Microbiol 2007; 124: 219-229. U Christmann, C Pink. Lessons learned from a strangles outbreak on a large Standardbred farm. Eq Vet Educ 2017; 29: 138-143.

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