Are you worming whether or not your chickens actually have worms......or only worming when a fecal float shows it's needed?Need to correct my previous posts re Ivermectin paste wormer. It does not kill Tapeworm. However on a positive note from the research I managed to find Tapeworm is not a common occurrence with chickens.
I love Ivermectin for worming but also have read that wormers need to be rotated to stay effective. So after almost 3 years of using it on my hens I will consult with my vet for a rotation product. Then I can't wait to get back on rotation to use Ivermectin again as it is the easiest exact dosage wormer I have found. One reason I like it is because with other wormers that have to go in feeders/waterers some of my hens eat/drink a lot and others not so much so never know how much each hen has ingested for effective worming. But that's the breaks for chicken health maintenance.
As for "natural" or "organic" worming methods they are not as effective as commercial wormers to cover all parasites. Nothing is ever cut-and-dried easy with chickens - the more I learn the less I know LOL!
What kind of egg withdrawal is there on the Ivermectin you use?