Trying to assess the parasite burden of a horse from its external appearance is virtually impossible. Only in the case of extremely heavy, long term parasite infestations might you see signs that range from a dull hair coat and general unthriftiness to colic and death. Internal parasites can cause extensive internal damage without the horse owner even knowing they are heavily infested. Heavy parasite burdens also lower the horse’s resistance to infections, rob the horse of vital nutrients and can cause permanent damage to internal organs.
A valuable and accurate diagnostic test for assessing the burden of strongyles and ascarids parasites in a horse is the Fecal Egg Count (FEC). This test, which you can access through your veterinary clinic, identifies the eggs of these parasites in a fecal sample from a horse. The standard Fecal Floatation will only identify what types of parasite eggs are present whereas a Quantitative Fecal Floatation (McMaster) will assess the actual number of parasite eggs being shed per amount of feces (number of eggs per gram of feces). By assessing the worm burden, you can make a decision as to whether your horse is in a Low, Medium or High Risk category and through consultation with your veterinarian, incorporate the appropriate treatment.