The bot flies are here…again. I ran into my first bot fly eggs this spring in Texas, which I found unusual because I am accustom to seeing them in late summer in Ohio and Maine. In some warmer states, such as Florida, it is possible for bot flies to live year round…I will chalk that up to one down side to a lack of winter.

Bot flies are amazingly good at laying their eggs, each female will lay 150-500 eggs. While riding the other day I noticed my friends horse was covered with bot eggs. She allowed me to video the eggs before she removed them. In the video you will notice that the bot fly lays the eggs in all the places where a horse will frequently scratch, rub, or swat flies away from.  The eggs hatch when heat, moisture and carbon dioxide are present. I found this gross fact (below) and can’t decide if I should try it or not…

Researchers have witnessed this phenomenon using a microscope. “If you breathe on them, they immediately hatch,” says Jack Campbell, PhD, veterinary entomologist at University of Nebraska’s West Central Research and Extension Center. “I’ve had them in a petri dish, getting ready to photograph them, and if you happen to breathe on them, you can see the egg opening up as they come out the end of it.” click here for full article

The unfortunate horse will ingest the eggs, which will hatch in the mouth. The larva spend the winter months in the stomach and then pass through the manure. The adults emerge, lay more eggs and the cycle repeats.

It is important to remove the eggs as soon as possible to reduce the chance of the horse ingesting them but do keep a few things in mind.

  • First, as another friend pointed out “It makes no sense to scrap the eggs off in an area where your horse eats like the stall or as you are hand grazing them…”
  • This same friend also pointed out the fact that there have been cases of humans becoming infected…YUCK! I didn’t want to believe her but a quick google search showed me this article complete with a photo of a horse bot fly larva in a human eye. So remember…wash your hands and don’t rub your eyes!

There are many tools available for removing the bot eggs. I don’t suggest your finger nail after reading the above mentioned fact… My favorite tool, so far it the bot fly knife. My second favorite is the grooming block. What is your favorite tool?

Deworming is also important, ivermectin and moxidectin are both effective although ivermectin is more effective.

This link will take you to the most complete article I found on bots.