I thought I would add a couple of things to this thread. I have found an enormous amount of awesome information here, although I will admit that I did not read all 16 pages. I called my vet friend because I'm afraid we are starting on this journey with one of our turkeys. Besides what she was able to tell me below , she said animals fed high protein, high carbohydrate diets showed no ill effects of cayenne or capsicum toxicity, and it actually influenced gut retention times. She went on to say that earthworms also carry histomonosis.
I did find a good article on the net about this disease, but it is lengthy.
http://ps.oxfordjournals.org/content/85/6/1008.full.pdf
This next article talks about Tiamulin as an alternative medication that has been found to decrease mortality of turkeys. It says that high levels of the medication were found concentrated in the liver where it was primarily metabolized.
http://www.octagon-services.co.uk/articles/poultry/histomonosis.pdf
This website states that these drugs are FDA approved for blackhead: Carosep, Acidified Copper Sulfate, and Histostat-50.
http://www.poultrysupplies.com/index_files/Page1190.htm
So first off Metronidazole or Fish Zole that everyone has been talking about is also known as Flagyl in human pharmacological terms. It is the antibiotic doctors prescribe first for Colostridium Difficile due to the increase of VRE (Vancomycin Resistant E
nterococci). Metronidazole is only effective against anaerobic (non-oxygen) bacterial infections in humans because the presence of oxygen will inhibit the nitrogen-reduction process that is crucial to the drug's mechanism of action. In animals after the drug enters the body and finds a susceptible organism, it enters the pathogens cell. The cell is first reduced and then the Metronidazole binds to the pathogens DNA, causing loss of the helical structure (replication), strand breakage (transcription), and impairment of DNA function (repair process). Only susceptible organisms (bacteria and protozoa) appear to be capable of metabolizing the drug.
Birds do not detect capsaicin the constituent in peppers and in this case cayenne pepper. Although birds possess the TRVP1 receptor in their nerve cells, it is not activated by capsaicin as it is in mammals (this is what we humans recognize as "this pepper is STINKING HOT"). Liver activity has been shown to be responsible for conversion of capsaicin to the reactive phenoxy radical, which in turn can bind thereby inactivating certain enzymes in the Histomonas meleagridis DNA structure . This mechanism may be responsible for the inhibition of further activation, and the reported protective activity of capsaicin against some chemical, biological carcinogens and mutagens are currently being looked at.
Hope this helps someone. Have a great day everyone!