9 Most Common Internal Horse Parasites

Although disgusting to think about one of the mainstays of good horse ownership is controlling your horses internal parasite or worm burden. Depending on the type these worms can cause anything from discomfort and tailrubbing poor haircoat weight loss or even lifethreatening gastrointestinal obstruction and colic. Drugs called dewormers also known as anthelmintics were wildly successful at treating the most common and devastating horse worms for decades. However just like bacteria against antibiotics the worms have found a way to fight back and develop resistance1 . It is important for caretakers to know the different types of horse internal parasites and to develop an educated deworming strategy. 

Small Stronglyes
Small strongyles are the most common internal parasite in horses today. They are found worldwide and any grazing horse is infected with some amount of these worms. Horses will only experience disease if the numbers of internal worms are quite high. Small strongyle eggs are passed in horse manure and hatch on pasture. The horse eats the larvae which burrow into the horses intestinal wall emerging seasonally to hatch and produce more eggs. The intestinal wall affected by lots of larval burrowing is less able to digest and absorb nutrients. Therefore a poorquality haircoat potbellied appearance poor muscling diarrhea and other signs of illthrift are signs of high cyathostomin burden.