Deworming by fecal egg count (FEC) is advocated as a way to avoid overexposure of parasites to deworming drugs. It's important to understand the effect of deworming by FEC is primarily to minimize environmental contamination, not optimally protect the individual. Young horses, PPID horses, and seniors, in general, are at high risk for parasitism. Even some young adult horses have poor parasite resistance. Much damage is done by immature forms that are not even laying eggs yet.
The problem with FEC is their limited capacity to detect parasites.
- They only reflect adults that are actively laying eggs at the time of the test
- Egg-laying activity may vary seasonally
- Tapes are often missed because eggs are laid in packets/segments, not evenly mixed in the manure
- Can't detect tissue forms or immature stages in the lumen but these can be the most harmful for the host
- Bots missed
- Pinworms missed (lay their eggs on the perianal skin)
- Strongyloides in adults not detected
- Roundworms (Ascarids): Ivermectin, moxidectin, pyrantel
- Strongyles: Fenbendazole, pyrantel, albendazole
- Pinworms: https://wp.me/p2WBdh-G5