Keep in mind that tapeworms get into your chickens via an intermediary host -- typically beetles, ants, flies, or earthworms. Basically your chicken poops out the tapeworm segment, the intermediary host eats the segment, and the chicken then eats the intermediary host. Chickens cannot get a tapeworm from directly eating the segments.
This is important because as long as the chickens remain on the same ground, eating the same beetles, ants, etc., they will continue to be re-infected, no matter what drug you use to treat them. Thus, any attempt to get rid of the tapeworms requires a plan for getting rid of the intermediary hosts. Moving your chickens to entirely new ground away from the original ranging area is one way to do this. Enlisting the help of a vet or specialist to identify the type of tapeworm and associated host, and then trying to spray/trap the hosts is another.
Also keep in mind that none of the drugs that treat tapeworms have been approved in the U.S. for use in poultry so there is no "official" egg withdrawal period. Most people who have used these drugs on tapeworms have practiced a 14 egg withdrawal period and feel comfortable with that. But, I think it's the case from a legal standpoint, that you should never sell/give away your eggs again.
If you want to make sure that your chickens actually have tapeworms before embarking on the above, you need to look for fresh poop in the middle of the day. For whatever reason, tapeworms segments aren't shed at night and checking the poop boards won't tell you much.
Finally, although many like take an aggressive approach to treating tapeworms -- and it some cases it is absolutely necessary -- it is not always the case that tapeworms are a death sentence Not all tapeworms are equally harmful and not all chickens are equally susceptible to dangerous levels of worm infestations.
Below, I've linked a study on chickens and tapeworms done in a time way back before there were even drug options available to treat tapeworms. Two conclusions reached were:
"9.Light infestations R.cesticilus have comparatively little effect upon the gain of
weight or upon the amount of food consumed by growing chickens.
10.Increased resistance is developed in chickens, two and half or more months old, to the viability and growth of the tapeworm R.cesticilus. This age resistance limits the sizes of infestations and inhibits the growth of the tapeworms."
From:
https://core.ac.uk/download/pdf/16477615.pdf.
I'm not saying that you should not treat your chickens, but take some time to know what you are dealing with, and how to go about it, if you decide treatment is warranted.
