Worms are frequently shed in manure after de-worming, and the number of worms seen roughly parallels the worm load that the horse was carrying prior to de-worming. If a horse had not been recently de-wormed, the presence of adult worms in the manure may (but not necessarily) mean that a horse has a severe worm infestation.

The most common parasite seen in manure are bot larvae (large, orange grub-like larvae). Large pale worms that looks like bean sprouts are usually Ascarid roundworms. Tiny, thread-like worms may be small Strongyles. Many species are tiny and only seen with careful examination of the manure. Worms eggs are microscopic and can only be seen in laboratory examination.