I have to know.... did you eat the eggs while you were seeing the worms?I've been meaning to do this for awhile, and the pumpkin seed thread reminded me.
Let me first say, after spending many hours trying to research the impact of tapeworms on poultry, I found more questions then answers. There are precious few studies that deal with worm management in free-range chickens. My sense is when researchers discovered they could eliminate tapeworms in commercial poultry by putting chickens indoors, on concrete, and away from dirt and insects, they saw no need for further research. I hope the situation changes as free-range eggs and chicken become more commercially popular. Finally, I realize I'm sharing but one anecdotal account. This is not intended to be an anti-worming screed or lofty pronouncement that nature knows best. I'm firmly in the camp that believes there is a time and place for using the wonders of technology.
So, about my experience. About 6 or 7 months ago, I found tapeworm segments in my chickens droppings. The chickens were all very healthy, laying like gangbusters, and based on the number of segments per dropping, I believe it was a light infestation. Still, I wanted to treat them, and I learned from the knowledgable people here that Equimax horse dewormer was an effective treatment. However, when I mentioned it to my husband, he was opposed to giving horse de-wormer to hens who's eggs we ate. He wanted studies that showed it was safe, as well as more information on what would happen if we did nothing.
That led me down a rabbit hole of reading everything I could find about tapeworms. I learned there is no approved treatment for tapeworms in chickens in the U.S., and no approved "safe egg withdrawal" period. I learned that chickens acquire tapeworms from eating insects and earthworms, and unless you can control the insect population, any treatment plan will fail, as the tapeworms will just keep coming back. I can't tell you how many "Help, the tapeworms are back!" threads I read on this forum and on others while I was researching this. I also found there were mixed views on how harmful tapeworms are to chickens, and that there were different kinds of tapeworms, with some types being more harmful than others. I saw repeated in many places that light infections were "relatively harmless," but that "heavy" infestations could weaken or even kill chickens. It was almost impossible to find information on what was considered a "light" infestation, or how common "heavy" infestations are. I could find no scientific studies on the long-term effects of dosing chickens with tapeworm de-wormers.
It was all rather depressing. Not only could I not answer my husband's basic questions, but the more I learned, the more doubtful I became that there was a way to eliminate the tapeworms in my chickens, short of permanently confining them indoors. Still I wanted to do something, so I formed a plan.
1) Try natural remedies first.
2) Pick up and dispose of any poop with segments in it
3) Monitor the chickens health, poop, and number of segments in poop do see if the situation was worsening
4) If it got to a point where I believed that the horse de-wormer was necessary, I would time the dosing for late fall, as insect activity would be at a minimum for the next few months, and egg-laying wold have largely stopped for a few months as well.
For my natural remedy, I used cucumbers, which were growing in my garden and contain Cucurbitacin, a substance that one study found had potential as a dewormer. For 3 days in a row, several sliced cucumbers were offered first thing in the morning; repeated 10 days later. I saw some evidence of improvement. In particular, I had one hen who I knew had the most number of segments in her poop out of all the chickens. That hen ate those cucumbers like it was her job. After the "dosing", I never saw any more segments in that hen's droppings. I also saw one dropping with something that looked like exploded tapeworms in it. But, I was still seeing segments in other chicken's droppings. Whether they didn't get enough cucumber, whether it really didn't work, I have no idea.
I implemented my scoop/inspect/remove poop routine. I learned that poops with segments never show up on the overnight poop board, but are almost always dropped between Noon and 4 p.m. each day. Droppings must be inspected while fresh, as the segments crawl off them as fast as they can. Yeah, gross. I felt like I spent my summer trekking though the chicken yard multiple times a day, following chickens, with my poop shovel and stick. The most segments I ever found in any one poop was 18. Several poops had zero. My two broody hens had zero. Most commonly, poops with segments had between 2 and 12. All hens continued to be in great health. Egg laying continued to be excellent.
As the summer wore on, something wonderful and unexpected happened. I noticed that I was seeing fewer and fewer segments with each passing week. At first I was doubting myself, but as Fall began, it became clear that the tapeworms were disappearing. I went through a period of redoubling my search efforts, to make sure that I was not imagining this. I was not. About three weeks ago we butchered cockerel. I saved and snipped open all the intestines and found no worms, and very healthy intestines. I'm obviously thrilled that the tapeworms are gone, but still very curious as to why this happened or whether others here have had similar experiences.
There is some research that suggests chickens -- as well as other animals -- can naturally acquire immunity to tapeworms, or at least to harmful numbers of tapeworms. It might explain the number of "miracle cures" people cite to. The chickens may have been handling the worms themselves, but people credit the garlic drench they just gave their birds.
Here are two studies, one quite old and the other newer, that discuss the idea of tapeworm immunity. I saw reference to other interesting sounding articles, but they were behind paywalls.
The old study is https://core.ac.uk/download/pdf/16477615.pdf. The authors were studying the effect of tapeworms on chickens. When their first experiments showed that the chickens did not appear to be negatively impacted by the tapeworms, they tried to increase the worm load by feeding the chickens more and more tapeworm larvae (actually called "cysticercoids"). However, they were unable to increase the tape worm loads in the chickens and concluded that the chickens had developed immunity.
The newer study is https://www.ecronicon.com/ecmi/pdf/ECMI-14-00511.pdf. This study is looking at developing a tapeworm vaccine, based on the finding that tapeworms can trigger an immunity response in chickens. The passage I found interesting was:
The mechanism of acquired immunity in infections with parasitic worms has been reviewed by Taliaferro  and Taylor . One ofthe first indications is the failure of the number of adult worms to increase as the result of continued reinfection, followed by a reduction in the number of established adult worms. Other manifestations of immunity are also apparent, namely (i) inhibition of reproduction as shown by a decrease in egg output; (ii) a tendency toward growth retardation, indicated by an increase in time required to reach maturity and the smaller size of worms at maturity; (iii) a tendency toward complete inhibition of development beyond the fourth larval stage; (iv) the self-cure phenomenon; and (v) a spring-rise in faecal egg counts associated with a loss of immunity.
I would have loved a cite for the "self-cure phenomenon" but the study didn't give one.