There are several types of intestinal worms that can cause problems for backyard poultry flocks. The most common intestinal worms seen in Pennsylvania flocks are roundworms (Ascaridia spp.), cecal worms (Heterakis spp.), threadworms (Capillaria spp.), and tapeworms (Raillietina and Choanotaenia spp.). The presence of a small number of worms does not typically cause clinical problems for poultry. Clinical signs associated with high worm burdens can include diarrhea, depression, reduced weight gain, weight loss, anemia, worms in eggs, and decreased egg production. However, many of these signs are not specific for worms so a definitive diagnosis should be made by microscopic examination of the feces for worm eggs and/or larvae. Cecal worms rarely cause clinical issues for chickens but are especially problematic for turkeys as they can carry Histomonas meleagridis, the protozoal parasite that causes Blackhead. There is currently no treatment for Blackhead, so successful control of cecal worms is an important step for the control of Blackhead.
Birds become infected by ingesting worm eggs from feed, water, litter, or grass contaminated by feces or through ingestion of an intermediate host like earthworms, grasshoppers, snails, slugs, flies and beetles containing worm eggs. Worm eggs can survive in the environment for long periods of time and are resistant to killing by common disinfectants.
There are two approaches to deworming backyard poultry flocks: 1) deworm birds on a routine schedule, or 2) only deworm birds when there is a high worm burden. Many veterinary clinics or diagnostic labs can evaluate the worm burden in a bird or flock through examination of feces. The best approach for deworming your flock will depend on many factors including: the size of your flock, if your birds are housed in a coop or if your birds have access to grass pasture, and the history of intestinal worms in your flock.
Fenbendazole is the only product that is currently approved for treatment and control of roundworms (Ascaridia spp.) and cecal worms (Heterakis spp.) in chickens and turkeys in the United States. Fenbendazole is available as a medicated feed labelled for use in turkeys (Safe-Guard) or in a water-soluble formulation to be added to drinking water (Safe-Guard AquaSol) labelled for use in chickens. No withdrawal time is required for consumption of eggs or meat from treated birds when administered according to label directions. Although Safe-Guard is available over-the-counter, a prescription from a licensed veterinarian is required if the drug is used in a manner that differs from the label directions (e.g. used in a different species, at a different dose, for a different duration, etc.). Piperazine (Wazine) was available as a feed/water additive for deworming poultry; however, this product is no longer available for use in the United States. There are currently no effective dewormers approved for control of tapeworms in the U.S.
You should always consult your veterinarian for assistance in the diagnosis, treatment, and control of intestinal worms in your flock.