b'DEWORMING GuideHOW TO DEWORM ADULT HORSES FOR STRONGYLES1 In the spring and fall, collect manure samples from each horse, and have your veterinarian perform fecal egg counts.2 Based on FEC results, determine whether your horse is a low, moderate, or high shedder.Low 0-200 epg no other treatments besides spring and fallModerate 200-500 epg 1 more treatmentmid-summer1 more treatmentHigh 500 epg mid-summer and late fall (if grazing seasons SHELLEY PAULSONlonger than 6 months)3 Give all horses their Horse owners should perform targeted dewormingspring and fall treatments seven days to prevent parasitic disease in their horses, minimizelater (regardless of parasite egg shedding on their properties, and helpshedding status). Macrocyclic prevent anthelmintic resistance.lactones are most effective against strongyles.TERMS TO KNOW 4 Have your vet perform a fecal egg count reduction test in 10-14 Anthelmintic A deworming drug. The main classes of anthelmintics used in horses aredays to determine whether benzimidazoles (e.g., fenbendazole), pyrimidines (e.g., pyrantels), and macrocyclicthe drug used is effective lactones (e.g., ivermectin, moxidectin). against the parasites on Anthelmintic resistance An inherited trait in which parasites survive dewormeryour farm.treatment and pass the drug resistance on to subsequent generations of worms.Fecal egg count (FEC) The number of parasite eggs per gram (epg) in a horses manure5 Test each anthelmintic sample before deworming. class at least once every three Fecal egg count reduction test (FECRT) The percent reduction in parasite eggsyears, and base future based on an FEC performed 10-14 days post-deworming. deworming decisions and Refugia The unreached population of worms during treatment (e.g., those parasite stagestiming on drug efficacy on pasture or in untreated horses). The more parasites in refugia, the less chance ofand horses shedding them developing resistance. Ideally, we want to deworm when refugia levels are at theirstatus.highest, in spring and fall.22April 2020The Horse|TheHorse.com'