Todayโs path rounds are on ๐๐๐ฌ๐ญ๐๐ซ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ! Otherwise known as bot flies.
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ฌ๐ญ๐๐ซ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ larvae are the most common parasites of the equine stomach. There are six different species that can affect horses, but the most common ones are ๐๐๐ฌ๐ญ๐๐ซ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ ๐ข๐ง๐ญ๐๐ฌ๐ญ๐ข๐ง๐๐ฅ๐ข๐ฌ and ๐๐๐ฌ๐ญ๐๐ซ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ ๐ง๐๐ฌ๐๐ฅ๐ข๐ฌ. In their adult form, these flies are frequently seen buzzing around livestock.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Any horse can get this! It is extremely common for horses to have some amount of bots within their stomach.
๐๐จ๐ฐ ๐๐จ ๐๐ฅ๐ฒ ๐ฅ๐๐ซ๐ฏ๐๐ ๐๐ง๐ ๐ฎ๐ฉ ๐ฅ๐ข๐ฏ๐ข๐ง๐ ๐ข๐ง ๐ญ๐ก๐ ๐ฌ๐ญ๐จ๐ฆ๐๐๐ก ๐จ๐ ๐ก๐จ๐ซ๐ฌ๐๐ฌ?
There are some species differences, but the basic life cycle is that the adults lay their eggs onto the horseโs lower body, legs or around the mouth, and then are licked off by the horse. From there, the eggs hatch in larvae within the mouth, migrate down the esophagus and take up residence in the stomach. Gross.
๐๐ก๐๐ญ ๐๐จ ๐ญ๐ก๐ ๐ฅ๐๐ซ๐ฏ๐๐ ๐๐จ ๐ข๐ง ๐ญ๐ก๐ ๐ฌ๐ญ๐จ๐ฆ๐๐๐ก?
Once in the stomach, the larvae fasten themselves to the stomach wall via mouth hooks, where they bore into the mucosa and feed on blood and feed material. They will live their quite happily until they are ready to become adult flies, at which point they will let go of the stomach wall and pass into the outside world along with the horseโs feces. Extra gross.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Gasterophilus larvae generally donโt cause issues for horses. Most horses will live quite happily with their little larval friends in their stomach. That said, the larvae do cause small areas of damage to the stomach wall that may be problematic in severe infestations. These small areas of damage are usually ulcerations, which can be uncomfortable for horses (see our post on gastric ulcers!). Because the larvae migrate through the mouth, they can also cause small lesions that can lead to oral pain. Usually these horses will have chewing problems, irritation of the lips and gums, and may salivate excessively.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
It is pretty much assumed that all horses have some degree of bot larvae infestation. If there is a suspicion of severe infestation, then ๐ ๐๐ฌ๐ญ๐ซ๐จ๐ฌ๐๐จ๐ฉ๐ฒ (a long camera passed into the stomach) can be used to visualize the larvae directly.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Thankfully, Gasterophilus are very responsive to our typical deworming protocols! So one treatment is generally sufficient to remove these little friends.
๐๐ก๐๐ญ ๐๐๐จ๐ฎ๐ญ ๐ฉ๐ซ๐๐ฏ๐๐ง๐ญ๐ข๐จ๐ง?
As mentioned previously, the flies lay their eggs on the horseโs legs and body. These can be seen as little yellow specks that are quite difficult to remove! Owners that are concerned about bot fly burden can remove the eggs with a bot knife routinely, to prevent the eggs from making it into their equine friend.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-5) Various photos of bot fly larvae in the stomach of horses.
๐๐จ๐ฎ๐ซ๐๐๐ฌMaxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 2. Sixth Edition.
Photos 1-3 courtesy of University of Calgary Diagnostic Services Unit.
Photos 4-5 courtesy of Noahโs Arkive.
