Equine Respiratory Disease

Immunomodulators and biosecurity can help minimize the risk factors for equine respiratory disease.

From Pfizer Animal Health

Travel stress and unfamiliar environments are concerns for horse owners, especially when it comes to equine respiratory disease. In many cases, a stressed horse becomes a sick horse.

Equine rhinopneumonitis caused by equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4) is a common cause of upper respiratory disease in horses. Respiratory diseases typically occur in foals in the first weeks or months after birth, but recurrent infections often are seen during times of stress in weanlings, yearlings and young horses entering training.1 Also, horses that attend events where other horses are congregated or horses that live in large boarding barns are particularly at risk.2

Like other herpesviruses, one of the biggest issues associated with EHV-1 and EHV-4 is that once horses have been infected, they can become lifetime, dormant carriers of the virus. Those horses that are latently infected do not show any external signs of disease, but they carry the virus and can spontaneously begin shedding it during periods of stress, such as during strenuous exercise, long-distance transport, weaning or competitive events.1 The presence of infected animals makes eliminating the viruses nearly impossible; however, a good strategy to help reduce the incidence of EHV-1 and EHV-4 is the combination of a good vaccination program in conjunction with an effective, preventive biosecurity program.

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By implementing a good biosecurity program, you can help reduce the potential for EHV-1 and EHV-4 to make its way to your barn. The most common way for EHV-1 and EHV-4 to spread is directly through coughing horses, but they also can spread indirectly via contact with nasal secretions. Handlers can easily transfer and spread the virus from horse to horse via their hands or clothing and tack, so it’s crucial to practice good barn hygiene and always wash your hands between the handling of each horse to help prevent the spread of disease. Also, if working with a sick horse, remember to handle these horses last and to change clothes and footwear to help avoid infecting healthy horses. Take proper prevention on the road, as well. Always disinfect stalls before moving your horses in, and do not use common water buckets or common feed areas at event grounds.

A proper biosecurity program, a preventive vaccine program and the use of an immunomodulator can help reduce the incidence of EHV-1 and EHV-4. An immunomodulator, such as ZYLEXIS®, can help a horse’s immune system function more efficiently. ZYLEXIS is an inactivated (killed) Parapox ovis virus immunomodulator that stimulates the horse’s immune response to aid in the reduction of equine upper respiratory disease associated with EHV-1 and/or EHV-4 infections. Most important, ZYLEXIS may be administered to horses in anticipation of possible stress or during subsequent disease episodes.

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While respiratory infection cannot always be prevented, the risk of exposure is reduced when a vaccine is used or biosecurity program is in place. Your American Quarter Horses face many stresses when competing or traveling, so take precautions to help them be at their best.

1 American Association of Equine Practitioners. Equine Herpesvirus (Rhinopneumonitis). 2012. Available at: Accessed July 25, 2012.
2 American Association of Equine Practitioners. Respiratory Problems. 2003. Available at: Accessed July 26, 2012.

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