Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock.
QUESTION: What can I do to prevent respiratory infections in young sales horses?
DR. LILLY HAYWOOD: Breeding stock sales serve as the “perfect storm” for the development of respiratory disease in weanlings and short yearlings. Horses arrive from multiple farms and states, are housed together and are stressed.
Fortunately, most young horses arrive to the sale healthy – but the stress of shipping, new cohorts and new activities can take their toll. Two of the most common pathogens that affect these horses can lie latent in healthy horses (equine herpes virus 1 and 4 [EHV-1 and EHV-4]) and can recrudesce (recur) in stressful situations. Both EHV-1 and EHV-4 typically manifest with fevers and nasal and ocular discharge.
Equine influenza is another common respiratory virus in young horses, and also presents with fevers, nasal discharge and coughing. All three of these diseases are capable of spreading rapidly through nose-to-nose contact, aerosolization of viral particles via coughing and fomite transmission (such as human hands and water buckets). The herpes viruses, EHV-1 and EHV-4, are especially concerning at breeding stock sales, as EHV-1 may cause abortion in mares and neurologic disease in horses of all ages. In addition, both viruses can set young horses up for more serious secondary bacterial infections.
So, what can be done to help prevent these viruses from spreading?
First, ensure that your horses are adequately vaccinated for both herpes and influenza prior to arriving at the sale. Follow the manufacturer's and your veterinarian's guidelines regarding type of vaccination, age at primary vaccination and booster vaccinations. Both Keeneland and Fasig-Tipton require proof of vaccination against EHV-1 to be noted on the health certificate. Thorough vaccination is not a guaranteed prevention of infection, but it does significantly decrease the risk.
Most importantly, implement good biosecurity practices while at the sale. Limit nose-to-nose contact between horses as this is the most effective way for the virus to spread. Encourage frequent hand-washing, use of alcohol-based hand sanitizer and even disposable exam gloves among staff, especially around any horses displaying clinical signs of infection.
It is also important to thoroughly clean and disinfect equipment such as water and feed buckets and chifney bits between horses. Monitoring temperatures twice daily on all young sales horses can help catch disease in the early stages so that more stringent biosecurity measures can be taken to prevent spread. Finally, limit staff overlap and contact between pregnant mares, racehorses and young horses as much as possible.
Good biosecurity does not end at the sales grounds. It is common for a healthy-appearing sales weanling or yearling to arrive back on a farm, and spread a respiratory virus throughout a barn of non-sales horses. New arrivals should be isolated for two weeks and be monitored closely for clinical signs of disease. Ideally, farms should house new arrivals in a separate barn from native horses; in situations where this is not possible, farms should strive to turn out new arrivals separately, minimize shared equipment and encourage hand-washing among staff. Any young horses that exhibit signs of disease should be evaluated by a veterinarian.
One last disease of concern among sales horses of all ages is Streptococcus equi equi, commonly known as strangles. Strangles is a bacterial disease that causes fevers, severely swollen lymph nodes on the head and nasal discharge. It can spread rapidly throughout a population of horses and can be very difficult to eradicate once established on a farm. Good biosecurity is a key element in preventing its spread, but testing can also be useful. One easy screening test for all new arrivals is a nasopharyngeal wash; the collected sample can be submitted to look for bacterial DNA.
Respiratory disease can represent a significant cost to farms and clients. In cases where viral disease progresses to secondary bacterial infection, treatment with antibiotics can be lengthy and expensive. In rare instances, horses may even end up hospitalized. Additionally, horses with upper respiratory tract infections may have temporary changes on their upper airway endoscopy exams, which can impact their value. Finally, several of these respiratory viruses can have effects beyond just the respiratory tract – such as abortion. Vaccination and good biosecurity practices are relatively inexpensive and can be key in preventing these impacts.
Dr. Lilly Haywood grew up riding and showing hunters in Raleigh, N.C. Haywood attended the University of Pennsylvania for veterinary school, graduating in 2013 with an equine focus. She joined Rood and Riddle in June of 2013. Her areas of interest include emergency medicine, primary and preventative care, and neonatal medicine.
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