QF vet solves case of a mystery flu in Arabian horses

Horses have a natural cooling system that is located in their head called the “guttural pouch”. It is an air-filled sack with a lot of blood vessels around it, and as the blood goes from the body towards the brain, it passes through this pouch which acts like an air conditioner and cools the blood shortly before it enters the brain. Because brain tissue is considered more sensitive to high temperature compared to other tissues, this mechanism is very useful particularly at times when the horse is undergoing vigorous or prolonged physical activity.

“The guttural pouch is a unique structure found in horses and only a few other species. It is well known that this useful feature can sometimes be a source of illness, particularly in Arabian foals – baby horses,” said Dr. Camilla Jamieson, Senior Clinical Veterinarian at Qatar Foundation’s (QF’s) Equine Veterinary Medical Center (EVMC).

When Dr. Jamieson joined EVMC back in 2018, she noticed a few foals had runny noses that weren’t getting better with the usual treatments. “At first, I thought it’s just a cold, it will run its course and they'll get better. But they didn’t, so we gave them some antibiotics. Two months passed and they still hadn’t gotten better. By this time, it was obvious it wasn’t just one of the usual respiratory infections of foals, and that there was something else going on,” said Dr. Jamieson.

Upon speaking to the vets, Dr. Jamieson learned that this mystery cold, that even antibiotics couldn’t fix, was not unusual among Arabian foals, and for a number of years had been blamed on antibiotic resistance.

Convinced that this was more than just a cold, Dr. Jamieson started investigating by performing endoscopic exams and ultrasound scans. The endoscopic exam is where a small camera was used to visually investigate the airway and the guttural pouch of unwell foals. The guttural pouch is where they found the source of the mystery cold.

“We found that the pouches were full of pus – a condition referred to as guttural pouch empyema. When we flushed the pouches clean – the babies would get better almost overnight. What seemed like a runny nose and cough coming from the lungs, was actually a bacterial infection in the guttural pouch. The pus from the guttural pouch was draining into the back of the nose and throat, and from there to the nasal passages and out of the nostril and giving the foals a runny nose.”

Dr. Jamieson explained that guttural pouch empyema is commonly observed in adult horses from all breeds but is not common amongst foals. “The reason we see it in adult horses is that the pouch cavity in an adult horse is much bigger – think as big as a coffee mug – so it’s more prone to harboring bacteria or even fungus and resulting in an infection.”

Having located the cause of the mystery cold, the next question was why are Arabian foals suffering from a problem normally seen in adult horses.

“Preliminary investigations show Arabians have a unique anatomy of the back of the throat, which means they might be unable to swallow completely normally. The milk that should just be going down into their stomach is actually traveling the wrong way and ending up in the guttural pouch. When the milk starts to sit there, it inevitably brings in bacteria, thereby resulting in an infection.”

The take-home message from this work for vets is that if you have an Arabian foal with a runny nose, the first thing they should do is check to see if they need to flush their guttural pouches.

“This is not something we commonly do in standard global veterinary practice in young horses. It’s usually done in older horses because their pouches are bigger. But what we've seen is in Arabian foals you really should include that in your work-up otherwise you'll be unnecessarily giving them a lot of antibiotics that aren't going to work because the antibiotics don't get into those pouches. By including this first step in your diagnostic strategy you might be able to improve your foals’ recovery times, and also practice better antibiotic stewardship.”