In the United States, some effective anthelmintics -- or dewormers -- used for tapeworms aren't approved by the Food and Drug Administration for use in chickens. That means that eradicating tapeworms in chickens relies more on prevention than treatment. While the FDA has strict rules on dewormers used on birds raised commercially for meat and egg production, you can use these dewormers to kill tapeworms in your backyard flock if you aren't selling the eggs and meat.
Tapeworms in Chickens
Various species of tapeworms affect chickens. These intestinal parasites also vary in size and length. Younger birds tend to suffer from tapeworm infestation more often than older flock members. Such infestations mean that young birds grow more slowly than normal, producing fewer eggs than unaffected birds. Adult tapeworms usually lodge in the bird's scolex, or small intestine.
Tapeworms need an intermediate host for a developmental stage before going on to the primary host and completing the life cycle. Chickens consume these intermediate hosts, which harbor tapeworm larvae, and become infected. For poultry, those intermediate hosts are generally insects. For chickens kept in cages, flies often serve this purpose. If free-ranging, intermediate hosts include various insects along with worms, snails and slugs. While fly control in the coop can cut down on this species as an intermediate host, it's much more difficult to eradicate the intermediate hosts of free-range birds safely. One way to keep earthworm consumption down is by removing chicken access to any newly plowed areas.
Snails and Slug Management
Safe, environmentally responsible ways of getting rid of snails and slugs include trapping the creatures beneath boards or upside-down plant pots in your yard. If you're truly motivated, you can handpick snails and slugs by watering areas in which they congregate in the late afternoon. The moisture draws them out. After dark, use a flashlight, pick them off and throw them out in a plastic bag. Although unpleasant and time-consuming, doing this on a daily basis in the beginning can vastly reduce the number of snails and slugs in areas available to your flock; eventually a weekly picking should suffice.
Chicken Parasite Management
Careful management can keep your flock relatively free from tapeworms. This includes regularly cleaning litter from the coop floor and disposing of it in an area inaccessible to chickens. Use appropriate insecticides in coops or free-range areas when birds aren't present. As the Merck Veterinary Manual points out, doing so can destroy intermediate hosts, thus interrupting the tapeworm's life cycle.
Regularly treating your backyard flock with dewormers that are effective against other types of intestinal parasites can keep tapeworms to a minimum. These include fenbendazole, sold under the brand name Panacur. Each treatment requires two doses, given seven to 10 days apart. After dosing your chickens, throw out any eggs laid during the treatment period and for the next seven days. Don't slaughter a bird for meat until at least seven days after the last treatment.