Equine Rhinitis A and B

Other Names

Equine Rhinitis Virus A (ERAV); Equine Rhinitis Virus B (ERBV); equine picornavirus infection; equine aphthovirus infection; equine rhinovirus.

What is Equine Rhinitis A and B?

Equine Rhinitis A and B are upper respiratory tract infections of horses caused by two distinct but related picornaviruses: Equine Rhinitis Virus A (ERAV) and Equine Rhinitis Virus B (ERBV). These viruses are widespread in horse populations internationally and are recognised as common, if often underdiagnosed, causes of respiratory disease in horses of all ages and disciplines.

ERAV (formerly classified as Equine Rhinovirus 1) is a member of the Aphthovirus genus — the same genus as Foot-and-Mouth Disease virus — though importantly, ERAV does not cause foot-and-mouth disease in horses and presents no risk to other livestock species in that regard. ERBV (formerly Equine Rhinovirus 2) belongs to a different picornavirus genus and has a somewhat distinct clinical presentation.

Both viruses are transmitted primarily through direct nose-to-nose contact and respiratory droplets, meaning horses in competition yards, at shows, and in shared training facilities are at greatest risk of exposure. The clinical picture ranges from mild, self-limiting respiratory illness to more significant disease, particularly in young, immunologically naive horses or animals that are compromised by other factors.

Causes

ERAV and ERBV are shed from the upper respiratory tract of infected horses in nasal secretions. Transmission occurs through:

Direct nose-to-nose contact between horses
Inhalation of respiratory droplets in shared stabling or transport
Indirect contact via contaminated hands, equipment, water troughs, or feed sources
Carrier horses that shed virus without showing overt illness

ERAV can also be shed in urine for extended periods — sometimes for weeks after the acute infection resolves — which is a notable feature that aids transmission and complicates biosecurity. Horses can develop protective immunity following natural infection, but the duration and completeness of immunity is not fully defined, and reinfection can occur.

Symptoms and Signs

The clinical presentation of ERAV and ERBV infections is broadly similar and often indistinguishable from other equine upper respiratory pathogens without laboratory testing. Signs include:

Serous to mucopurulent nasal discharge — typically bilateral
Mild to moderate pyrexia (elevated temperature), usually between 38.5°C and 40°C
Submandibular or retropharyngeal lymphadenopathy (swollen lymph nodes under the jaw and throat)
Mild pharyngitis — the horse may show discomfort when swallowing or be reluctant to eat hard feed
Coughing — typically mild and dry rather than the severe cough associated with equine influenza
Lethargy and reduced appetite
Exercise intolerance during the acute illness phase

ERAV infections are generally considered more clinically significant than ERBV, with higher rates of pyrexia and more pronounced systemic signs. ERBV tends to produce milder, more localised upper respiratory signs.

Secondary bacterial respiratory infections can develop following viral rhinitis, leading to a more severe and prolonged illness. Bacterial pneumonia as a complication, while less common than following influenza, has been reported.

Diagnosis

Definitive diagnosis requires virological testing — virus isolation or PCR detection of viral RNA from nasal swabs, nasopharyngeal washes, or urine samples. PCR is the preferred method given its sensitivity and speed. Serological testing (measuring antibody titres) can confirm recent infection when paired acute and convalescent samples show a significant rise in titre, though this provides retrospective rather than acute diagnosis.

Because equine rhinitis viruses share clinical signs with equine influenza, equine herpesvirus types 1 and 4, equine viral arteritis, and bacterial upper respiratory infections, laboratory investigation is essential to confirm the specific pathogen involved. Respiratory panels testing for multiple pathogens simultaneously are increasingly available through commercial veterinary laboratories.

Treatment

There is no specific antiviral treatment for equine rhinitis virus infections. Treatment is supportive and aimed at managing clinical signs and preventing secondary complications:

Rest — ideally complete work rest for the duration of clinical illness plus several days following resolution
NSAIDs (phenylbutazone or flunixin meglumine) for fever management and discomfort
Ensuring adequate water intake and palatability of feed — soft hay or soaked hay cubes if the horse is reluctant to eat due to pharyngitis
Antimicrobial therapy only if secondary bacterial infection is confirmed or strongly suspected — not routinely indicated for uncomplicated viral rhinitis
Monitoring for complications including worsening lower respiratory signs or significantly elevated white cell count

Prevention

There is currently no licensed vaccine against ERAV or ERBV in the United Kingdom. Prevention relies on biosecurity management:

Isolating new arrivals or horses returning from competition for at least two weeks
Monitoring returning competition horses for fever or respiratory signs for five to seven days post-event
Avoiding nose-to-nose contact between horses from different yards at competition and training venues where possible
Disinfecting water troughs and shared equipment regularly
Maintaining robust ventilation in stabling to reduce viral load in shared airspace

Prognosis

The prognosis for uncomplicated equine rhinitis virus infection is good. Most horses recover fully within one to two weeks with appropriate rest and supportive care. The principal risk is secondary bacterial infection, which can extend the recovery period considerably. Horses returned to full work too quickly during or immediately following viral respiratory illness risk a more prolonged recovery and possible development of persistent respiratory issues.

When to Call the Vet

Call your vet if your horse develops a temperature above 38.5°C, persistent or worsening nasal discharge, a significant cough, reduced appetite, or swollen lymph nodes under the jaw. Isolate suspected cases promptly to prevent spread to other horses. If multiple horses in a yard are affected simultaneously, veterinary investigation is essential to identify the causative pathogen and implement appropriate yard-wide biosecurity.

Frequently Asked Questions

Is equine rhinitis the same as equine influenza?

No. Equine rhinitis is caused by picornaviruses (ERAV and ERBV), while equine influenza is caused by influenza A viruses. The two conditions share similar clinical signs and cannot be reliably distinguished without laboratory testing. Equine influenza typically causes more severe pyrexia and a pronounced harsh cough, but this distinction is not reliable in individual horses. Vaccination against equine influenza does not protect against equine rhinitis.

How long should a horse with equine rhinitis be rested?

A general guideline is one week of rest for every day of fever, with a minimum of two weeks off work following the resolution of clinical signs. Return to full work should be gradual. Individual recovery varies — your vet can advise on when it is appropriate to resume exercise based on clinical assessment.

Can horses with rhinitis spread the virus through urine?

Yes, particularly for ERAV. The virus can be shed in urine for an extended period after the respiratory signs have resolved. This prolongs the potential for environmental contamination and urinary-route transmission, and is one reason why a full quarantine and hygiene protocol is important even after clinical recovery.

Does vaccination prevent equine rhinitis?

There is currently no licensed vaccine against ERAV or ERBV in the UK. Vaccines against equine influenza and equine herpesvirus are available and should be kept up to date, but these do not protect against rhinitis viruses. Biosecurity remains the primary preventive tool.

For further guidance on equine respiratory disease management, consult the British Equine Veterinary Association (BEVA).