Moving from horse to horse and barn to barn, farriers are in a key position to recognize equine respiratory diseases, notify horse owners and take steps to help prevent the spread of such illnesses.

The threat is real. For example, although the often-fatal equine herpesvirus myeloencephalopathy (EHM) is considered rare, as of this writing there were confirmed, active cases in Texas, South Dakota, North Dakota, Michigan and California, along with a suspected case in Wyoming. Some of the afflicted animals had traveled to horse events far from home before their diagnosis, potentially carrying the danger across state lines.

This list is not comprehensive. It’s a sampling compiled from the Equine Disease Communication Center at Equine DiseaseCC.org, a voluntary reporting site affiliated with the American Association of Equine Practitioners (AAEP). There is no national database for these equine diseases, so the exact number of cases cannot be known.

More worrisome, EHM, a neurological disease, is thought to develop from a common respiratory illness, equine herpesvirus (EHV). That means controlling the various strains of EHV is critical to preventing cases of EHM.

Farriers should take notice because, aside from preventing the suffering of the horses, the sick animals and often their stablemates are quarantined and usually not available for farrier services. That could disrupt a farrier’s work schedule and wallet for weeks at a time.

Add two other common respiratory diseases, equine influenza and strangles, and farriers have good reason to remain vigilant.

A simple nasal swab is one method veterinarians use to pinpoint the virus or bacteria causing equine illness. Photo: D. Craig Barnett, DVM, Merck Animal Health

Be Alert And Ready

Reports of equine respiratory diseases have increased in recent years, but the diseases themselves might or might not be more prevalent.

“I can’t say for a fact they are on the rise, or if we are just hearing about more of them because of the increased use of social media and the availability of more media outlets,” says Roberta Dwyer, DVM, a professor of Animal Sciences at the University of Kentucky.

Dwyer says farriers should recognize the signs of illness, but she cautions against making a diagnosis without a veterinarian.

“Keep it simple,” Dwyer says. “If the horse has a snotty nose or a cough, maybe there’s a problem. You don’t need to know if it’s EHV-1 or EHV-4, if it’s strangles or influenza. Farriers don’t need to diagnose it, they just need to be aware that the horse is coughing and has a runny nose.”

If a horse shows signs of illness, Dwyer says, a farrier should alert the owner, suggest contacting a veterinarian and reschedule the hoof care for after a vet’s examination. The owner also could be asked about other potential signs of illness, such as the horse having a fever or being off its feed.

“The farrier might be the voice of reason for novice horse owners,” she adds. “Often, it’s the farrier with the more extensive horse experience.”

If the owner says a veterinarian already has diagnosed the horse with a non-contagious illness, such as heaves, Dwyer notes, the farrier can continue working without concern for spreading the illness.

But if a potentially sick horse has not been examined by a vet and truly requires hoof care — a case of lameness, for example — the horse should be treated only after the farrier completes his or her work with other horses at the barn, Dwyer says, or at the end of the work day if possible.

Don’t Be A Carrier

People cannot be infected or sickened by most of the respiratory diseases covered in this article. The rare exception is strangles, Dwyer says. She warns that anyone handling a horse with a thick, pus-like nasal discharge or abscesses should wear protective gloves and clothing.

Farriers can become carriers who transmit illnesses between horses, Dwyer says. If an undiagnosed or sick horse requires care, she suggests taking steps to minimize the chance of spreading an illness.

Don’t let the horse nuzzle your back, where it could leave a virus or bacteria on clothing, she says, and carry several changes of shirts to be used during a day.

“And before you leave the farm, wash your hands with soap and water,” Dwyer advises. “Even if every animal there looks perfectly healthy, wash your hands before you move on to the next barn. Ideally, you would scrub down your shoes to get rid of any fecal matter.”

Wipe off your work apron, if one is used, she says. If a tool might have been contaminated, perhaps when being sneezed on or falling to the ground near a sick horse, you should wash it with detergent, rinse and then dry it to avoid rust, she adds.

Monitoring the horse for nasal discharge can aid with early detection of various respiratory illnesses. Photo: Courtney Wheeler, DVM, Minnesota Board of Animal Health

Recommended Care

Vaccines are available for EHV-1, EHV-4, equine influenza and strangles. Although a vaccination program under a veterinarian’s care is advised, Dwyer cautions, “No vaccine is 100% effective at preventing illness. You can reduce the risk of these diseases, but they are tricky little viruses.”

After a sick horse is diagnosed, supportive care is an important part of treatment. Supportive care includes proper hydration and nutrition, rest and proper shelter with appropriate temperature and without drafts. Active monitoring for secondary infections during treatment and recovery is also recommended.

Here is an overview of respiratory-related diseases farriers might encounter. The information comes from the AAEP.

Equine Herpesviruses

EHV-1 and EHV-4 are common as a mild respiratory disease. Almost all horses have been infected and have no serious side effects. However, the severity of EHV-1 and EHV-4 can include mild illness, abortion and severe neurological disease.

The signs include fever, nasal discharge, lethargy/depression, neonatal death, late-term abortion and neurological disease. Equine herpesvirus myeloencephalitis (EHM), the neurological form of either EHV-1 or EHV-4, is considered rare.

EHV is spread from horse to horse through contact with nasal discharge or through the air via coughing and snorting. Horses also can contract the virus from contaminated surfaces such as stalls, water, feed, tack, tools and transport vehicles. Humans can spread the virus through contaminated hands and clothing.

The incubation period ranges from 2 to 10 days. Horses can spread the virus during the incubation period. Infected horses can spread the virus even when showing no clinical signs. Horses are considered a source of infection until they test negative for the virus. The virus can remain dormant for the lifespan of the horse. Activation is possible from stress, such as being transported or being placed into a new activity.

Diagnosis is made through nasal swabs or blood tests. Supportive care and rest are the chief treatments. Medications are used to control fever, pain and inflammation. In most cases, horses recover in a few weeks, and when fully rested, can gradually return to work.

Vaccinations are available for prevention of the respiratory and abortive form, but there is no vaccine for the prevention of EHM. The best prevention is to maintain current EHV vaccinations of all horses on the property and to follow biosecurity measures when traveling or introducing new horses to the premises.

Equine Herpesviruses Myeloencephalopathy (EHM)

EHM is a neurological disease associated with EHV infections. It is not known why some EHV-infected horses develop the potentially fatal neurological form. The common EHV-1 virus most often causes EHM. In extremely rare cases, EHV-4 also can develop into EHM.

Because EHM develops from EHV, it shares the same methods of transmission. Likewise, the incubation period ranges from 2 to 10 days, and horses can spread the virus during the incubation period and even when not showing any signs of the disease.

EHM typically causes a two-phase fever. The horse will have fever on day 1 or 2 and again on day 6 or 7. Neuro­logical signs might not be present until the second fever, and some horses might not develop a fever at all.

Other signs include nasal discharge, depression, lack of coordination, hind limb weakness, loss of tail tone, loss of bladder control with urine dribbling or an inability to urinate along with a “dog sitting” position, leaning against a fence or wall to maintain balance, lying down, and an inability to rise.

A veterinarian diagnoses EHM through nasal swabs or blood tests. Horses with neurological signs who test positive for EHV-1 are considered positive for EHM. The prognosis in EHM cases is often poor, with fatality rates as high as 30%.

Although there is no cure for EHM, supportive care should be provided and medication can be used to reduce fever, inflammation and pain. In rare cases, horses can recover from the infection but retain neurological impairments.

Watching for swollen lymph nodes in the horse’s neck and jaw area can help owners monitor their animal’s health. Photo: Courtney Wheeler, DVM, Minnesota Board of Animal Health

Equine Influenza (Flu)

Influenza is a viral illness most commonly transmitted by coughing or snorting particles through the air, where the virus can travel as much as 150 feet. Exposure is also possible through contact with contaminated surfaces. Humans can spread the virus via contaminated hands and clothing.

The illness is highly contagious. A horse showing signs of respiratory disease should be isolated immediately until a veterinarian can determine the cause.

The incubation period ranges from 24 hours to 3 days. Contagiousness typically lasts for 7 to 10 days post-infection in horses that were infected for the first time or were unvaccinated. The period is shorter in partially immune horses that were previously infected or vaccinated.

Flu symptoms usually are moderate and fatalities are rare. However, horses can be out of performance for 3 weeks and as long as 6 months.

Signs and symptoms include nasal discharge, a fever as much as 106 degrees Fahrenheit, lethargy, anorexia (off feed), muscle pain/weakness (stiff gait), slightly enlarged and mildly painful lymph nodes around the head and neck, which can be more severe in donkeys and mules. Rarely, clinical signs can include swelling of the lower legs and decreased heart function.

A dry, harsh to hacking cough usually precedes fever. The cough can last as long as 6 weeks after all other signs have abated. Influenza should be suspected when multiple horses in a group develop a sudden onset of hacking cough with at least some of the horses having a fever.

Nasal discharge is initially clear or watery but can become yellow or white because of secondary bacterial infections, which are common in horses with influenza. The illness is diagnosed through nasal swabs.

Supportive care and rest are the chief treatments. Medications are used to control fever, pain and inflammation and to improve feed consumption. Antibiotics are used when a fever lasts for more than 3 or 4 days, or when complications such as bacterial pneumonia develop.

Horses recovering from influenza should be restricted from strenuous exercise and kept in well-ventilated stalls to reduce inhalation of dust. Wetting of the hay can also reduce dust.

Recovery time for mildly affected horses is usually 2 to 3 weeks but can take as much as 6 months for severe cases. Horses should be restricted from all strenuous activity for at least 3 weeks. During that time, horses are extremely susceptible to secondary bacterial complications such as pneumonia.

Vaccination is the primary mode of prevention. Biosecurity measures are recommended for areas where horses live or interact, and handler hygiene procedures should be performed between each horse or group of horses.

Streptococcus Equi (Strangles)

Strangles is an extremely common and highly infectious bacterial infection. It spreads from horse to horse through direct contact, or through contact with contaminated surfaces. Most horses are exposed and/or infected at a young age.

The incubation period is 3 to 14 days. Infected horses that appear healthy can continue to incubate and spread the disease. A recovered horse might be a source of infection for at least 6 weeks after symptoms have resolved. Some horses that have recovered from the disease can become long-term, periodic shedders and can cause outbreaks when introduced to new herds.

The severity of strangles is considered low. Symptoms include a fever that usually precedes other signs by 24 to 48 hours, abscesses in lymph nodes in the throatlatch and below the jaw, nasal discharge of often thick white and yellow mucus, inflammation of the throat, difficulty swallowing, wheezing, coughing and bleeding from capillaries that can cause red spots on the mucous membranes.

In rare cases with complications, symptoms might include swelling of the muscles, limbs and head.

Diagnosis is made through a nasal swab or via pus from abscesses. Supportive care is the primary treatment. Medications are limited to cases with severe clinical signs such as respiratory difficulty. Horses treated with antibiotics early in the infection can avoid lymph node abscesses but might not develop immunity to the disease.

Strangles is rarely fatal and horses usually fully recover in 3 to 4 weeks. Horses that have been infected can maintain long-term immunity to that strain.

July/August 2018 Issue Contents