Bit & Bridle

Equine Pharyngitis

Other Names

  • Throat Infection in Horses
  • Equine Throat Inflammation
  • Nasopharyngitis (when nasal passages are also involved)
  • Upper Respiratory Pharyngitis

What is Equine Pharyngitis?

Equine Pharyngitis is inflammation of the pharynx — the region at the back of the throat that connects the nasal passages and mouth to the oesophagus and trachea. In horses, the pharynx plays a critical role in both respiration and swallowing, and inflammation in this area can cause a range of signs from mild nasal discharge and coughing to significant respiratory compromise and difficulty eating.

Pharyngitis rarely occurs in isolation — it is most commonly associated with broader upper respiratory tract infections involving the nasal passages (rhinitis), guttural pouches, and larynx. It is one of the most common findings in horses with respiratory disease and may be viral, bacterial, or a combination of both. In performance horses, even mild pharyngitis can significantly impact respiratory efficiency and athletic performance.

The condition can be acute — developing rapidly over days — or chronic, persisting for weeks or months. Chronic pharyngitis in sport horses is a particularly important cause of poor performance and requires thorough investigation to identify and address contributing factors.

Causes

Pharyngitis in horses is most commonly caused by infectious agents, either acting alone or in combination:

  • Equine Herpesvirus (EHV-1 and EHV-4): Common viral causes of upper respiratory disease in horses; EHV-4 in particular is a frequent cause of pharyngitis and rhinopharyngitis in young horses
  • Equine Influenza Virus: Highly contagious; causes severe respiratory disease including significant pharyngeal inflammation, particularly in unvaccinated populations
  • Equine Rhinitis Viruses (ERAV and ERBV): Underdiagnosed viral causes of upper respiratory disease and pharyngitis in horses of all ages
  • Streptococcus equi subspecies equi: The cause of strangles — characterised by severe pharyngitis and lymph node abscessation
  • Streptococcus equi subspecies zooepidemicus: A commensal organism that can become a secondary bacterial invader in viral upper respiratory disease
  • Environmental and management factors: Dusty hay or bedding, poor stable ventilation, ammonia from urine, and high levels of airborne particles all irritate the pharyngeal mucosa and predispose to inflammation — even in the absence of infection

Immunological pharyngitis — a lymphoid follicular hyperplasia in the pharynx — is common in young horses in training and may represent an exaggerated immune response to normal viral or bacterial exposure rather than active infection.

Symptoms and Signs

Signs vary with the severity and cause of pharyngitis:

  • Nasal discharge — serous (clear and watery) in early viral infection; mucopurulent (thick, cloudy) in bacterial secondary infection
  • Coughing — often dry and hacking, particularly at the beginning of exercise or when eating
  • Dysphagia — difficulty swallowing; affected horses may drop food (quidding) or show reluctance to eat
  • Enlarged submandibular or retropharyngeal lymph nodes — particularly notable in strangles cases
  • Fever — especially in acute infectious pharyngitis
  • Reduced appetite and lethargy
  • Abnormal respiratory noise (roaring or gurgling sounds) if the larynx is also involved
  • Reduced performance and respiratory compromise in sport horses with even mild disease

Diagnosis

Diagnosis is typically confirmed by endoscopic examination:

  • Endoscopy (nasopharyngoscopy): Visualisation of the pharynx via a flexible endoscope passed through the nostril. Allows direct assessment of pharyngeal redness, swelling, mucus accumulation, lymphoid follicle hypertrophy, and any structural abnormalities such as soft palate displacement or guttural pouch openings.
  • Nasopharyngeal swabs: Collected during endoscopy or by passing a swab blindly into the nasopharynx. Used for bacterial culture and sensitivity, and viral PCR testing.
  • Guttural pouch lavage: To rule out guttural pouch infection as a source of persistent pharyngeal discharge.
  • Blood work: Elevated white cell count and inflammatory markers support an infectious cause; useful to monitor response to treatment.
  • Haematology: Neutrophilia with a left shift suggests active bacterial infection; lymphocytosis may be seen in viral disease.

In performance horses with persistent or recurrent pharyngitis, environmental assessment — hay dust levels, stable ventilation, bedding type — is as important as microbiological investigation.

Treatment

Treatment is directed at the underlying cause and supportive management:

  • Rest: All horses with acute pharyngitis should be rested from work. Returning to exercise too early prolongs recovery and risks secondary complications including lower respiratory disease.
  • Antibiotics: Indicated when bacterial infection is confirmed or strongly suspected. Penicillin is first-line for streptococcal infections; treatment course is typically 7–14 days minimum.
  • Anti-inflammatory medication: NSAIDs such as phenylbutazone reduce pain and inflammation, improving comfort and appetite.
  • Environmental management: Improve stable ventilation, use low-dust bedding (rubber matting, paper, or dampened shavings), soak or steam hay to reduce airborne particles, and minimise time in dusty environments.
  • Steam inhalation: Helps loosen mucus secretions and soothe irritated mucosa.
  • Mucolytics: Agents such as dembrexine may help reduce mucus viscosity and aid clearance from the pharynx.
  • Viral disease: No specific antivirals are available for equine viral pharyngitis; management is supportive with rest and anti-inflammatory treatment. Secondary bacterial infections may require antibiotics.

Prevention

Preventive measures focus on vaccination and environmental management:

  • Vaccinate against equine influenza and equine herpesvirus according to current BEVA guidelines
  • Maintain good stable ventilation — this is one of the most impactful changes for horses with recurrent pharyngitis
  • Use dust-extracted or soaked/steamed hay for all horses, particularly those in intensive training
  • Quarantine new horses for a minimum of three weeks before mixing with existing horses
  • Test for and manage strangles status in yards where the disease has been present

Prognosis

Most cases of acute infectious pharyngitis resolve fully with appropriate rest and treatment, typically within 10–21 days. Chronic pharyngitis — particularly environmental in origin — may require ongoing management changes rather than resolution per se. Performance horses with chronic lymphoid hyperplasia often improve with environmental management changes and rest. Horses that return to work too quickly following acute pharyngitis are at risk of developing secondary lower respiratory disease, which significantly worsens prognosis for a rapid return to competition.

When to Call the Vet

Contact your vet if your horse:

  • Develops nasal discharge, particularly if purulent or blood-tinged
  • Has a persistent cough, especially if accompanied by fever
  • Shows difficulty swallowing or is dropping food
  • Has enlarged lymph nodes around the jaw or throat
  • Shows unexplained reduced performance in a sport horse context

Frequently Asked Questions

How long should a horse rest with pharyngitis?

The general guideline is one week of rest for every day of fever, with a minimum of two weeks off work for any horse with confirmed respiratory infection. For viral pharyngitis, a conservative rest period of three to four weeks is recommended before a gradual return to work, as the respiratory epithelium takes time to fully recover even after clinical signs resolve. Returning to full competition too quickly risks both relapse and spread to other horses.

Is pharyngitis contagious between horses?

Infectious pharyngitis caused by equine influenza, EHV, or strangles is highly contagious. Affected horses should be isolated immediately, and strict biosecurity measures — including hand washing, separate equipment, and restricted yard movement — implemented. Environmental pharyngitis (dust-related) is not contagious.

Can pharyngitis permanently affect a horse’s performance?

Most horses recover without permanent deficit. However, horses that develop chronic lymphoid follicular hyperplasia, persistent guttural pouch infection, or lower respiratory disease as a complication of pharyngitis may have lasting performance implications. Horses with persistent respiratory noise or poor performance after apparent recovery should be re-evaluated endoscopically.

Is lymphoid follicular hyperplasia a form of pharyngitis?

Lymphoid follicular hyperplasia (LFH) of the pharynx is a common finding in young horses and represents reactive hypertrophy of lymphoid tissue rather than true infection. It is often classified as a mild form of inflammatory pharyngitis. Most horses with LFH are asymptomatic or show only mild performance limitations. The condition typically improves with age, adequate rest, and optimised stable environment. See also: Equine Rhodococcosis for an important bacterial respiratory condition of foals and guttural pouch anatomy.