 Dr. Allie Sowerwine DVM, Miss Rodeo Wyoming 2009 | The sport of rodeo requires animals to cross state lines, which often results in potential exposure to sick horses. Therefore, it is vital to stay updated on recent disease outbreaks. Viral diseases are the LARGEST concern for infectious disease outbreaks. A vaccine can protect a horse from showing clinical signs (being sick) or allow their body to adequately fight the infection before it causes negative health issues, but it should be noted that NO vaccine is 100% effective. Recently, in Wyoming there was an outbreak of the neurological form of "Rhino" virus. This caused numerous barrel races, rodeo practices, public, and private arenas to shut down for 3-6 weeks. |
Below is a little back ground information on "Rhino" to help you better understand this specific virus.
EQUINE “RHINO” | EQUINE HERPES VIRUS
| Equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) infect the respiratory tract. Clinical infection is characterized by fever, lethargy, anorexia (not eating), nasal discharge, cough, and mandibular lymphadenopathy (swollen lymph nodes under the jaw). Some horses will show no clinical signs and be silent carries of the virus. Infection of the respiratory tract with EHV-1 and EHV-4 typically first occurs in foals in the first weeks or months of life, but recurrent infections are seen in young horses entering training, especially when horses from different sources are commingled. |  |
EHV-1 can cause outbreaks of abortion in non-exposed mares, the birth of weak nonviable foals, or a sporadic neurologic disease (equine herpesvirus myeloencephalopathy-EHM). EHM may cause thombi (blood clots) in the small blood vessels supplying the spinal cord and brain affecting the horses capability to walk. Most common clinical signs; weakness in the hind end, ataxia, incoordination. These signs are similar to West Nile Virus.
 | TRANSMISSION Both EHV-1/4 are transmitted primarily by the respiratory route, indirect/direct contact with nasal secretions, and by contact with aborted fetuses and placenta. Like herpesviruses of other species, these viruses establish latent (no clinical signs) infection in the majority of horses. These horses become asymptomatic carriers of one or both viruses. Such horses may shed the virus at a later time when stressed. Pregnant mares, if infected, may abort if stressed. Existence of a carrier state seriously compromises efforts to control these diseases and explains why outbreaks of EHV-1 or EHV-4 can occur in closed populations of horses. |
| PREVENTION In case of a current outbreak:
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None of the available vaccines can directly prevent the neurologic form of EHV-1 infection. The vaccine may assist in limiting the spread of outbreaks of EHM by limiting nasal shedding of EHV-1. We recommend vaccinating in the face of an outbreak. Only afebrile, healthy horses should be vaccinated and protection against clinical EHM should not be an expectation.
VACCINATION IN FACE OF OUTBREAK
- The simplest approach is to vaccinate all horses in the exposure area—independent of their vaccination history. If horses are known to be un-vaccinated, the single dose may still produce some protection.
- If previously un-vaccinated or unknown, it's recommended to vaccinate a series of 3 vaccines of the inactivated EHV-1/EHF-4 or modified-life EHV-1 vaccine, at 4-6 weeks apart.
- It is essential to understand that strict quarantine, isolation, and monitoring protocols are more effective at controlling outbreaks than any vaccination protocol.
Dr. Allie Sowerwine is originally from Sheridan and has spent most of her life residing in Wyoming. While growing up she was very active in 4-H and FFA, showing and judging numerous species of animals and livestock; including, horses, dogs, poultry, pigs, and lambs. She continued her education earning an A.D. in Engineering/Mathematics at Casper College, before attaining her Bachelor’s degree in Animal Science at the University of Wyoming. She represented rodeo in Wyoming and served as the State Ambassador as Miss Rodeo Wyoming 2009, where she brought home a National Horsemanship Title. She attended Colorado State University College of Veterinary Medicine, in Fort Collins, CO and achieved her DVM in May, 2016. Dr. Sowerwine currently works for Red Hills Veterinary Hospital in Gillette, Wyoming. She sees a large diversity of animals including: horses, cattle, dogs, cats, goats, sheep, ferrets, hamsters/rats, and the occasional rabbit. She proudly calls Gillette her home, where she resides with her husband and their numerous animals. Her passion in life continues to be horses where you will find her riding at every opportunity.
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