Ever wondered what those tiny yellow dots are at the end of the hairs on your horse’s chest, legs, and undersides? While many people have heard of ‘bots,’ they are often mismanaged and can seem to be a never ending problem, particularly in year-round warm of Florida.

The life-cycle of the bot-fly is centered on the horse – a bot is the larval stage of the adult bot-fly. They can be extremely irritating, and the irritation the horse experiences perpetuates the life-cycle.  The cycle begins when the bot-fly (which resembles a small yellow honeybee) lays the small yellow eggs on your horse’s coat.  When the horse licks, rubs, or bites the area of the coat where eggs are laid.  Irritation by the horse stimulates the larvae in the eggs. The threadlike juveniles move into the horse’s mouth, where they burrow into the gums. Here they remain, nestled between teeth, for about four weeks.  Then they move into the stomach, where they attach to the walls and grow to a fat red bean covered in rows of black spines. They mature and move through the remainder of the digestive tract, emerging with the feces when they are ready, and burrowing into the ground until adulthood is reached. One complete cycle takes approximately a year. Thanks to the Florida weather, what it typically a seasonal nuisance is a year-round infestation.

Bot-fliescan affect humans as well as animals, so diligence is important when caring for a horse with a bot problem.  There are three species:  the common bot (Gastrophilus intestinalis), the throat bot (Gastrophilus nasalis), and the nose bot (Gastrophilus haemorrhoidalis). They each tend to lay eggs in a particular area. The common bot lays eggs over the body, the throat bot’s eggs are generally under the neck and jaw, and the rare nose bot focuses on the lips. Ulcers (or larvae) can sometimes be found in and around the mouth, and teeth may be loose or have nearby pus pockets. Colic and gastric ulcers can be caused or exacerbated by bots, whether from direct damage or blockage from a mass of larvae. Inappetance, diarrhea, choke, weight loss, lethargy, and general unthriftiness can result from infection. Other complications include anemia, stomach rupture, and peritonitis (infection in the abdominal cavity).

Diagnosis is by simple fecal exam – they can collect a sample at your appointment, or you can drop a fresh ‘apple’ by the office for Danielle & Michelle to process. You can collect it with a zip-lock bag within 2-4 hours of passage, and store it in your fridge (up to 24 hours) until you can bring it to us. Sometimes larvae are discovered in the soil, or in your horse’s feces, mouth (eg, during a dental). Worms are easily identified in the stomach on gastroscopy (putting a 3 meter camera into the stomach), or rarely in the gastric reflux when tubing during a colic.

Treatment is simple enough, ivermectin usually does the trick – but wait until the average temperature is above 80 degrees F. Prevention is more difficult – good fly control measures and careful removal of eggs. Again, be aware – bot-fly larvae have been found in the skin, eyes, and stomachs of humans. Eggs should be removed from the skin with a bot knife, which is used to scrape the side of the skin to remove the eggs without injuring the skin. A grooming stone/block, pumice stone, and clippers also work well. As many eggs and hairs should be caught and disposed of as possible – preventing eggs on the ground from being ingested. Keep these simple tricks in mind, and you will find it is a problem worth managing!

As always, may your litter box be clean and your food bowl full!