Are bots invading your horses' gums and causing serious disease?

Poor dental health often leads to “premature ageing and ill thrift” in horses. It also can lead to poll and neck problems, weight loss, head carriage problems such as head tossing, head tilting, lugging, rearing, rough transitions etc. Dental care is a very worthwhile investment in your horse's health — both in the short and long term. For the average horse, proper dental care once or twice yearly will cost just $2 to $5 per week. Compare that to other essential husbandry costs such as feet, feed, training, competition fees etc!

The horse is a prey animal and so if they show signs of illness or weakness, they are at risk of being pushed down their pecking order by herd mates, or being singled out by predators in the wild. Thus they are genetically designed to hide their weaknesses and so may not show obvious signs of dental disease until it is too late!

As high quality dental techniques improve, we're becoming increasingly aware of the potential harm the common bot fly can do to our horse's mouths.

We have recently noticed that bot fly larvae (maggots) are damaging the gums of horses in Australia. So next time your equine dental practitioner examines your horse's mouth, be sure to request that they closely look for any pockets in the gums and probe them (see right). If maggots are found they need to be evacuated, the pocket flushed and the horse dewormed with an appropriate product. Early intervention could prevent irreversible gum and dental disease here.

Why has the “quick old style tooth rasping” been missing these problems?

Some problems in the mouth can be seen but not felt e.g. swelling and colour changes with infected gums, and some can be felt better than visualised e.g. sharpness of the enamel. This is why it is important that your dental practitioner thoroughly examines the horse's mouth by looking and by palpation to detect problems early when they are, hopefully, still treatable.

How bot fly larvae invade your horse

Bots are a family of flies which avoid the cold winter months by spending time in the warm internal environment of a horse. The female bot fly glues eggs on the hairs of the horse's legs, mane, neck etc. (pic 2 - right) In the presence of warmth moisture and carbon dioxide, the eggs will hatch. So if a horse licks the hair e.g. nuzzling its knees or grooming another horse, the eggs hatch.

Then small larvae emerge rapidly from the eggs and attach to the lips or tongue of the horse.

The larvae then molt and embed themselves in the gums of the upper cheek teeth. Here they can cause swelling and inflammation to the gums. (pic 3 - below right)

This can lead to permanent gum disease if the mouth is not cared for.

Ultimately, the larvae are swallowed and carried to the stomach and intestine of the horse.

When the weather warms up, the larvae leave the gut wall and pass out of the horse in the faeces. There they develop into adult flies and the cycle continues.

Worming for the stomach stage of bots is best done after the first hard frost hits. That's when the flies have stopped laying eggs, and so most of the bot population is inside of the horse where the wormer can act. At this time it is important that the eggs are destroyed on the hairs of the horse. This can be through physical scraping. Also, warm soapy water will stimulate the eggs to hatch and then the larvae can be washed off. Some owners have reported success through coating the eggs with Vaseline or Kerosene (but beware possible skin contact irritation or eye damage from kero!).

For an extensive list of equine veterinarians throughout Australia who have undertaken post graduate training in equine dentistry, see our vets list here or contact us for further advice.

Training courses are also being run for equine vet students in Australian veterinary schools and are sponsored by EVA (Equine Veterinarians Australia).