What Is Equine Rhino?

“Rhino” refers to rhinopneumonitis, which is the near equivalent of a common cold for horses. However, it is likely closer to resembling COVID-19 in that this mostly harmless infection also has a dark and deadly side. Rhino arises after exposure to the equine herpes virus strains EHV-1 and EHV-4, which can go beyond the respiratory system and infect other areas of the body. It can be benign, but many horse vets have seen it become dangerous. Here is an overview of the rhino and how to prevent and treat it.

Transmission and symptoms

Rhino is highly contagious. Horses spread it through touching noses, sharing food or being in turnout together. Like other herpes viruses, the infection never completely goes away, and may go dormant only to re-emerge when a horse is facing stress or another illness.

Generally, symptoms include fever, lethargy, cough and nasal discharge. Mild infections often go away within two weeks of care and rest. However, it can lead to more serious symptoms, especially for pregnant mares. If the virus goes beyond the respiratory system, it will infect the uterine lining and trigger a miscarriage. Fluids from the lost pregnancy contain the virus, which can infect other mares and also cause them to lose their foals. This is referred to as an “abortion storm,” and it can travel swiftly through a herd.

Another serious illness that arises from the virus is equine herpesvirus myeloencephalopathy (EHM). This is an inflammation of the blood vessels that supply the spinal cord and brain. Infected horses show neurological signs like altered gait, urinary leakage, a floppy tail and ataxia.

Treatment and prevention

As indicated, most rhino cases resolve within a few weeks. Horses may receive drugs to lower fever and prevent secondary infection if they have respiratory symptoms. For horses who develop EHM, they recover as long as they can remain on their feet. Otherwise, horse vets may treat the illness with supportive care and support slings to keep your horse upright and able to recover.
If you are going to breed your mare, it’s a good idea to get her vaccinated for rhino first. There are many products available, including some designed to prevent abortion. Once pregnant, mares may be vaccinated during the fifth, seventh and ninth months of pregnancy. That prevents miscarriage and also passes immunity to the foal. Vets will also vaccinate horses who live near the mare to ensure they do not shed the virus and infect her.

Also, since these infections are often caught early in life, you should start vaccinating foals at four to six months of age and give a second booster at 10 to 12 months. If your foal is high-risk, continue vaccinating them at six-month intervals.

Finally, if you suspect a horse is infected with rhino, take measures to prevent contact with other horses and give the infected horse their own water and feed buckets. Since the virus can remain alive on your clothes and hands, wash your hands frequently and change clothes if you are handling horses other than the infected one.

Cannon Veterinary Services Ltd. is a horse vet in Cannon Falls, MN. Call us and schedule an appointment if you suspect your horse caught rhino, or if you would like to establish a vaccination schedule.