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Bot Flies in Horses - Symptoms & Prevention

Bot Flies in Horses - Symptoms & Prevention

Being out in the elements, there are many pests that may affect your horse. One of the pests we commonly see is bot flies. Our Gillette vets share some information about the symptoms of bot flies in horses and what you can do you prevent this parasite from infesting your horse.

What Are Bot Flies?

While bot flies aren't one of the worst parasites to infect horses they can still cause distress internally and externally for them making them very uncomfortable.

The main irritation from a bot fly happens externally. A bot fly is fairly large and will spend its life with the goal of laying eggs in the hairs of a horse's body. While they don't bite the horse they land on, they create irritation by landing and walking around while depositing their eggs.

Types of Bot Flies

Here are the three types of bot flies we see on horses:

Common Bot Flies

The eggs of common bot flies are grayish-yellow to yellow in color and typically attached near the end of the horse hair in a place where the horse can reach the eggs while grooming or itching.

As the eggs hatch, the larvae make their way into the horse's mouth during these times and will eventually travel down into the stomach where they will live until the spring.

These larvae will use their hook life mouth to remain attached to the mucous membrane of the stomach for the length of the winter. At this time they will be expelled with feces.

After a month in the dry soil, adult flies emerge and begin the cycle all over again. Female bot flies are able to lay approximately 500 eggs within a week.

Throat Bot Flies

The eggs of throat bot flies are typically laid near the skin and are whitish-yellow in color.

Female bot flies aim to lay their eggs around the throat of the horse and lays roughly 500 eggs just as the common bot fly does.

In about three to five days the larvae hatch and crawl along the jaw, enter the mouth, and make their home in the gum line of the horse. This infestation of the gums can create distress for the horse as pockets form. At this point the larvae begin to mature and just as with the common bot fly they will make their way into the stomach for the winter and be expelled in the spring to begin their lifecycle all over again.

Nose Bot Flies

When it comes to nose bot flies the color of the egg is brownish-black, and the eggs are typically laid in the ahirs surrounding the nose of the horse. These bot flies can be especially irritating as they will go in to lay eggs on at a time and are capable of laying roughly 160 eggs.

The eggs hatch and burrow into the lip and tongue in only two days. After 5 or 6 weeks they will make their way into the stomach and continue the cycle like the other types of nose bots do.

Symptoms of Bot Flies in Horses

Some of the signs and symptoms of a bot fly infestation that may be noted in horses are:
  • loss of condition
  • impeded digestion
  • increased body temperature
  • restlessness
  • kicking at the belly
  • loss of appetite
  • intermittent diarrhea
  • constipation
It is also possible for bot flies to potentially cause more severe issues such as gastritis, stomach ulcers, and more rarely, peritonitis which is an inflammation of the membrane lining the abdominal cavity and can be fatal.

How to Treat Bot Flies in Horses

When it comes to bot flies, their life cycle lasts approximately a year and breaking this cycle is necessary for treatment to be successful.

The first and main step in the treatment process is to consistently remove all bot fly eggs from the horse. This must be done on a daily basis.

Next, you will need to treat the horse with deworming medication to irradicate the marvae thriving in the stomach.

Your vet will be crucial in this stage of treatment as they can help you manage the timing and dosage in order to provide effective treatment for your horse.

How to Prevent Bot Flies in Horses

One of the easiest ways to prevent bot flies in horses is through effective sanitation of the area your horse spends their time. 

Here are some of the things you can do to help reduce the possibility of bot flies infesting your horses:

  • Manure should be routinely cleaned up and properly composted. The heat generated during the process will kill the larvae of bot flies.
  • Proper pasture management including frequent mowing and chain harrowing.
  • Utilize rotational grazing and if possible allow livestock to graze a pasture between horses.
  • Avoid feeding your horses from the ground.
  • Water Clean water, free of feces contamination, should be provided year-round.
  • Monitor your horse and keep up with egg removal as they are spotted.
  • Ensure that you keep your horse on a regular deworming program to minimize risk.

It is also recommended that you have fecal exams performed on your horse regularly to monitor for signs of any parasitic infections including bot flies.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Have you noticed the signs of bot flies on your horse? Book an appointment with our Gillette vets today to discuss treatment and preventive measures. 

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