At my equine veterinary clinic, poop arrives in various ways. It can be packaged in plastic bags and mailed, wrapped in exam gloves in our doctors’ trucks, or brought in by owners in buckets or scoops. Sometimes, it even shows up on our doorstep with a note identifying the horse it came from. Knowing the horse’s history, deworming schedule, and living conditions is crucial for interpreting fecal testing results accurately.
Understanding how fecal testing works in horses is essential for obtaining reliable results and creating an effective parasite-control plan. If you have adopted a strategic deworming plan that includes fecal egg counts, you are already on the right track. Research has shown that parasite resistance to common dewormers is increasing, making routine rotational deworming less effective.
Veterinarians now recommend evidence-based parasite control using fecal egg count testing to determine which horses need treatment, which horses are high parasite shedders, and whether the deworming program is still effective. Proper timing and collection of fecal samples are vital for meaningful results.
Postpone fecal testing until at least 16 weeks after deworming with moxidectin, 12 weeks after ivermectin, and nine weeks after pyrantel or benzimidazole products. Regular sampling can help monitor the program’s success, with high shedders tested quarterly and low shedders biannually.
Fecal samples should be collected within 12 hours of being passed, stored in airtight containers, and refrigerated. Mail-in testing services are available for areas where fecal testing is scarce, but it’s essential to understand and interpret the results correctly.
Not all fecal tests are the same. Quantitative tests with a sensitive detection level are the most reliable for estimating the number of eggs per gram of feces. Techniques like the modified-Wisconsin method or modified-McMasters test are commonly used for horses.
Fecal egg counts primarily focus on small strongyles, with roundworm and tapeworm eggs rarely counted. Deworming should target high shedders more frequently, while low shedders should be monitored regularly. Treatment for tapeworms, bot flies, and pinworms may require additional testing or specific medications.
Interpreting fecal test results correctly is key to developing an effective deworming program for your horse. High egg counts may indicate the need for immediate deworming and follow-up testing to confirm efficacy. Regular monitoring and proper deworming strategies can help combat parasite resistance and keep your horse healthy.