I would feel better about using it (ivermectin) if I could be 100% sure that it treated capillary worms and cecal worms. As for the health of my current flock with regards to fenbendazole, I haven't seen any adverse effects when using it, and I'm on my 4th liter of it, but seeing the studies...
More on the five storks:
http://avmajournals.avma.org/doi/abs/10.2460/javma.2002.221.417?journalCode=javma
And this:
http://www.chelonia.org/articles/medical_misinformation.htm
-Kathy
Here's another interesting abstract:
1.Weber MA, Terrell SP, Neiffer DL, Miller MA, Mangold BJ Bone marrow hypoplasia and intestinal crypt cell necrosis associated with fenbendazole administration in five painted storks. J Am Vet Med Assoc 2002 Aug 1;221(3):417-9, 369
Abstract:
Five painted...
I think that all wormers in the same class as fenbendazole *can* cause feather abnormalities when used during molt. One reference I found says they can cause "fret marks"
This Dr. says feather damage can happen with wormers in the same *family* as fenbendazole (Safeguard)...