What are you calling Avitrol? Can you please post some photos of the product?
Is her crop emptying overnight?
@dawg53 knows more about worms and de-wormers than I do. I "think" that Levamisole will treat Gapeworm.
https://www.backyardchickens.com/threads/levamisole-wormer-info-needed.1217453/post-22102503
http://www.poultrydvm.com/condition/gapeworms
THANK YOU for getting back to me so quick!
Her crop has been empty for 2 days - she's not eating. Her poop is now only the white stuff.
Note at the top of the directions - "not to be used in food producing species" but this product is the only one that is recommended for gapeworm