What is RAO
RAO stands for Recurrent Airway Obstruction, a common respiratory condition in horses. It is important to recognize the symptoms early and begin treatment to prevent permanent damage. A horse’s condition can deteriorate rapidly if left untreated. However, if addressed in time, there will be little to no lasting damage, and the horse will be able to perform at the same level as before the illness.

Symptoms
Paarden beginnen met een lichte hoest die vooral te horen is bij inspanning. Hoesten kan ook gebeuren tijdens of na het eten van kracht- of ruwvoer. Wanneer het hoesten tijdens of na het eten ontstaat kan het paard een klein deel van zijn voer ‘ophoesten’. In een verder gevorderd stadium zal het paard meer moeite krijgen met ademhalen doordat de elasticiteit van het longweefsel verminderd is. Hierdoor kun je bij de flanken het zogenaamde ‘knijpen’ waarnemen. Een paard zal tijdens het uitademen de spieren in de flanken overdreven aanknijpen, dit om de laatste lucht uit de longen te persen. Er zal ook sprake zijn van neusuitvloeiing dit kan variëren tussen helderwit bij de lichtere gevallen en gele pus bij de zware gevallen.

Cause
RAO is caused by mold spores found in hay, haylage, and/or the straw used in the horse’s stall. While eating, the horse inhales these spores, which then settle deep in the respiratory tract. This causes irritation, prompting the body to send white blood cells to the alveoli (air sacs) in the lungs. Antibodies are also produced to eliminate the mold spores, which leads to the formation of mucus in the lungs. The presence of mucus causes the horse to cough. Even if the horse stops inhaling new spores, the antibodies remain active, continuing to trigger mucus production. Without treatment, the lungs remain irritated by fine dust particles in the environment, which perpetuates the problem.

Treatment
In addition to all possible adjustments to the horse’s living environment, veterinary treatment is necessary to prevent the condition from worsening. Respiratory conditions can also resemble one another, so a veterinarian must first perform a physical examination to determine the exact problem. Further diagnostics may be required, such as an endoscopy, where a camera-equipped tube is inserted through the nose to assess the condition of the lungs. A lung wash (bronchoalveolar lavage) may also be performed—by flushing the lungs with fluid, a sample can be collected for culture. This helps identify the specific mold responsible, allowing for targeted treatment. However, a standard treatment protocol is usually started first, as it addresses a wide range of respiratory issues. Only if there’s no improvement will further diagnostics, like those mentioned above, be considered. Initially, the horse may be given oral medication in the form of tablets or syrup, mixed with feed. If your veterinarian prescribes a course of treatment, always complete it, even if the horse appears symptom-free halfway through. The lungs may not yet be fully recovered, and stopping early may cause a relapse. In such cases, repeating the same treatment often proves ineffective, and alternative measures will be required.

Prevention
Prevention is not always possible, but there are several measures you can take. Horses should spend as much time outdoors as possible so they can breathe plenty of fresh air. If horses must also be kept indoors, it’s essential to pay close attention to stable air quality. Remove cobwebs frequently, use dust-free bedding, and never sweep the stable aisle while horses are inside. Where possible, stable the horse away from the manure pile and hay storage, and never muck out while the horse is still in the stall. A horse’s breathing zone is approximately 65 cm (25 inches) around its nose, and this zone must be carefully monitored for dust and mold. Horses with sensitive airways are best kept in a stall with a half-open door. If there’s a window with a flap, keep the flap open. Even in cold weather, it’s better to leave both the top half of the door and the window flap open—just provide the horse with an extra blanket for warmth. Never feed moldy hay or silage, and avoid dusty hay by soaking it with water before feeding. By following these steps, you not only help prevent RAO (Recurrent Airway Obstruction) but also reduce the risk of other respiratory conditions, ensuring your horse stays healthy.