We purchased a high magnification (400x) microscope with the goal of performing our own microscopic fecal exams. We selected two horses that are not easy keepers for us. We performed visual and microscopic fecal exams before during and after worming. We could not be sure that we ever saw or did not see parasites or their eggs. But, we could have also missed their presence entirely given our lack of diagnostic experience. Furthermore, the worming effort did not subsequently affect the "keep 'ability" of these two horses. Just what I don't like: inconclusive results.
Then, our young colt arrived on the ranch. Within 24 hrs we wormed him. Almost immediately thereafter hundreds of dead and dying (hopefully) parasites started showing up in his bowel movements. This positive gave us a chance to baseline our ability to recognize the worms when they are in the fecal matter. The particular parasites we saw were visible to the naked eye.
This is not to say that when an animal has parasites we will always see them in its bowel movements. But, if we are looking, I believe we will see them when they are expressed after worming. The parasite shown on this page was expressed within the first 48 hours of worming. After that, this particular parasite species was mostly gone from the colt's stool. A subsequent worming produced no parasites of this type in the stool.
