Equine McMasters Fecal Egg Count

For many years it has been recommended that horse owners deworm their horses every six to eight weeks, rotating dewormers, or using a feed through dewormer daily and deworming twice a year with an oral paste dewormer. This frequent use of dewormers has caused parasite resistance to some deworming products. In an effort to avoid further resistance a new deworming protocol, McMasters Fecal Egg Count, has been established. This new protocol helps customize your deworming schedule to your horses parasite burden, in turn, this will make your deworming more effective, may reduce how often you deworm, and save you money in the years to come.
What is a McMaster Fecal Egg Count? It is a laboratory test that screens your horse’s feces, identifying and counting the parasite eggs present in that sample. The results are reported in eggs per gram of feces and categorized into three groups to identify the parasite load. The three groups are Low Shedders (feces contained less than 200 parasite eggs per gram), Moderate Shedders (feces contained 200-500 parasite eggs per gram), and High Shedders (feces contained more than 500 parasite eggs per gram). Horses may have High Shedder results due to ineffective deworming, large parasite population in the environment or parasite resistance. Some parasites only shed their eggs intermittently, so a low or negative fecal egg count does not necessarily mean the horse is at no risk for parasites. For this reason, we still recommend deworming with specific dewormers twice a year.
Your horses deworming schedule will be based on McMaster’s Fecal Egg Count results, the age of your horse, and time of year and parasite exposure (i.e. pasture, other horses). The McMasters Fecal Egg Count should be done ten to twelve weeks after the last time you dewormed your horse. Please feel free to drop off a fecal sample from your horse or have it ready for us to pick up the next time we visit your farm. The sample should be a couple manure balls, less than twelve hours old, kept refrigerated and in a sealed plastic bag with you and your horses name on it.