Jul 09, 2018

Respiratory Disease in Horses: Common Types, Significance, and Prevention

By Bryant Craig DVM - Merck Animal Health

Brought to you by Merck Animal Health, the Official Animal Health Care Provider of the USEA.

Runny nose, fever, cough, fatigue. Infectious upper respiratory disease can have significant consequences for our horses’ health and come in several forms. The most common causes in the horse include equine influenza virus (EIV), equine herpesvirus (EHV) – also known as rhino – and Streptococcus equi subspecies equi (S. equi) – better known as strangles. In a nationwide surveillance study by Merck Animal Health, equine influenza and equine herpesvirus type 4 (EHV-4) are diagnosed more frequently than strangles and equine herpesvirus type 1 (EHV-1).

Some of the biggest risk factors are travel, exposure to new horses and environments, and stress from training or work pressure. Vaccination coupled with good husbandry is the most economical and effective way to protect these individuals.

Equine Influenza Virus

Equine influenza virus is one of the most common infectious upper respiratory diseases of the horse. It is widespread in the equine population of the United States and throughout the world. It spreads quickly because the incubation period is only 24 to 48 hours, and the virus can be transmitted through the air. In fact, coughing can spread nasal droplets more than 200 yards. Horses that are sick for the first time can shed the virus in nasal secretions for as long as seven to 10 days. Indirect transmission of the virus can also occur via hands, clothing, and common use articles such as bits, brushes, and buckets.

Recovering horses require a minimum of three weeks of rest or at least one week of rest for every day of fever. Premature return to exercise may be associated with complications including secondary bacterial infections, reactive airway disease, and exercise intolerance.

Once thought to be a disease primarily of the young, Merck Animal Health has discovered through its ongoing respiratory disease surveillance program (conducted in partnership with University of California, Davis) that EIV is common in broader age groups as well. The equine influenza virus is constantly undergoing change (known as antigenic drift) and the latest changes seem to have made older horses more susceptible to the disease.

A strict vaccination protocol incorporating the modified live EIV vaccine (Flu Avert® I.N.) coupled with good biosecurity measures is the best method of prevention of equine influenza.

Equine Herpesvirus

Equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) can each infect the respiratory tract, causing disease that varies in severity. EHV-4 is typically associated with upper respiratory disease in younger horses; while EHV-1 can cause respiratory disease, late-term abortions, early foal deaths, and neurologic disease. After initial infection, equine herpesvirus remains dormant (latent) in the horse. Stressful events, such as hauling, handling, and training can reactivate the virus and viral shedding can occur “silently” – without symptoms.

A horse affected by the neurologic form of EHV-1 does not typically show outward signs of respiratory disease associated with EHV-1 but does exhibit fever and depression in addition to neurologic deficits. Currently, there is not a vaccine labeled to prevent the neurologic form of EHV-1. Vaccination protocols decrease the severity of respiratory disease and reduce nasal shedding in infected horses, thereby increasing herd immunity.

Both EHV-1 and EHV-4 spread via coughing horses, by direct and indirect contact, nasal secretions, and in the case of EHV-1 abortion, contact with aborted fetuses, fetal/placental fluids, and the placenta.

Strangles (Streptococcus equi)

Strangles is a highly contagious disease caused by the abscess-forming bacteria Streptococcus equi. Also referred to as “distemper,” strangles commonly affects young horses, but horses of any age can be infected. A hallmark of the disease is enlarged, swollen, and tender lymph nodes around the head, under the jaw, and around the throat latch that frequently abscess, rupture, and drain. Abscesses can develop in other places of the body, both externally and internally. The bacteria itself is hardy and survives in a moist environment and organic debris such as manure for up to six to seven weeks. While vaccination is available, a good biosecurity plan is paramount in controlling this disease.

Take Home Message

Equine infectious respiratory diseases can attack suddenly and be devastating to your horse, as well as other horses in the herd, farm, or stable. Preventing disease through proper vaccination is far safer, easier, and more economical than treating the disease after the horse is already sick. Consult with your veterinarian to design the most appropriate vaccination protocol for your horses and remember a critical part of any preventive care plan is proper biosecurity measures. For more information, visit www.Merck-Animal-Health-Equine.com.

Copyright © 2018 Intervet Inc., d/b/a Merck Animal Health, a subsidiary of Merck & Co., Inc.

May 08, 2021 Competitions

Smith Swaps Horses, but Maintains Standings at Jersey Fresh International CCI4*-L

While her two horses swapped places for first and second after cross-country, Tamra Smith maintained both the lead and second place with two clear rounds and minimal time faults at the Jersey Fresh International Three-Day Event Presented by BW Furlong and Associates and Zoetis. The 16-year-old Hanoverian mare En Vogue (Earl x Laurena) is just a little more experienced than her barn mate Danito, also owned by Ruth Bley, so she was also a little quicker around the big, challenging course that twisted and turned through the Horse Park of New Jersey. En Vogue leads on a 27.1 and Danito is second with 31.9, with Boyd Martin maintaining third place with the 10-year-old Holsteiner gelding Luke 140 (Landos x Omega VI), owned by the Luke 140 Syndicate.

May 07, 2021 Competitions

Tamra Smith Tops CCI4*-L Leaderboard After Dressage at Jersey Fresh; Boyd Martin Leads CCI4*-S

California rider Tamra Smith holds the lead and second position in the CCI4*-L at the Jersey Fresh International (JFI) CCI at the Horse Park of New Jersey in Allentown. Smith scored 23.9 today with Danito, Ruth Bley’s 12-year-old Hanoverian gelding (Dancier x Wie Musik), to take the lead from her other mount, the 16-year-old Hanoverian mare (Earl x Laurena) En Vogue, also owned by Bley, who was the overnight leader after scoring 24.3 yesterday. Boyd Martin of Cochranville, Pa. holds third place with Luke 140, a 10-year-old Holsteiner gelding (Landos x Omega VI) owned by the Luke 140 Syndicate, on a score of 25.6.

May 07, 2021 Eventing News

Land Rover Burghley Horse Trials 2021 Cancelled Due To Continued Covid-19 Uncertainty

It is with immense sadness that we announce the cancellation of Land Rover Burghley Horse Trials 2021 which was due to be held later this year from September 2-5, 2021.

Despite the continued easing of lockdown measures, the nationwide vaccination program, and the hope within the Government Roadmap for unlocking the country, there have been and remain too many variables and uncertainties due to the Covid-19 pandemic to deliver this much-loved international event.

May 07, 2021 Young Riders

USEA Young Rider Program: Age Increase to 25

The United States Eventing Association (USEA) is pleased to announce the increase in age for eligibility in the USEA Young Rider program to USEA members aged 25 and under, effective immediately.

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