STUDY POINTS TO BREED- SPECIFIC INFECTION RISK

In addition to large eyes and a concave profile, some Arabians have an unusual throat structure that can affect the ability to swallow—and increase the risk of a rare infection.

The Arabian Horse is known for the beauty of its concave profile, large eyes and broad forehead. But a less obvious characteristic is also common to the breed—an unusual throat structure that may affect the ability to swallow.

Indeed, centuries of breeding to accentuate the beauty and refinement of the Arabian head may have led to increased risk for a rare infection.

When a Middle Eastern Arabian breeding farm reported that 20 to 30 percent of each year’s foal crop was developing respiratory infections that did not respond as expected to antibiotic therapy, researchers and veterinarians at the Equine Veterinary Medical Center (EVMC), a branch of the Qatar Foundation, investigated.

The 14 affected foals were paired with 10 healthy youngsters on the property for comparison. All foals were given complete physical workups and underwent endoscopic and ultrasound examinations.

The researchers also flushed each youngster’s trachea (main airway) and guttural pouches, and collected the fluids for cytological analysis and culture to determine which bacteria were involved.

In the foals showing signs of respiratory infection, the researchers found evidence that milk had aspirated into the guttural pouches, two air-filled sacs that connect a horse’s pharynx to the middle ear.

Analysis of the youngsters’ guttural pouch fluids revealed high levels of Streptococcus equi ssp. zooepidemicus and other pathogens.

This mixture of bacteria supports the theory that the origin of the infection was the aspirated milk, which passed through the mouth to the back of the pharynx and entered the guttural pouches instead of ending up in the stomach, as in normal swallowing.

Milk and bacteria that enter the gutteral pouches become trapped there— spontaneous drainage is impossible. Infection develops as the bacteria feed on the sugars and protein in the milk.

All the affected foals made a full recovery after their guttural pouches were flushed with a saline and povidoneiodine solution.

The researchers conclude that “show-type Arabian foals presenting with upper respiratory disease with nasal discharge may be aspirating milk into the GPs [guttural pouches].” They call for “familial analysis of affected foals, evaluation of dynamic swallowing function, and trace vitamin and mineral status to determine potential inciting causes for pharyngeal dysfunction and dysphagia (inability to swallow normally) in these foals.”

Ultimately, these findings may help establish a new strategy for diagnosing and treating respiratory conditions in Arabian foals, say the researchers. “When faced with juvenile Arabian horses, clinical signs of respiratory pathology that present as unilateral or bilateral nasal discharge should be investigated endoscopically prior to initiation of antibiotic therapy.”

Reference: “A case-control study of atypical guttural pouch empyema in Arabian foals,” Veterinary Medicine and Science, July 2023