Chickens can get several different types of worms. Roundworms, which looks like what it is your picture, is one of the only types to be able to be seen without a microscope by a vet. Valbazen (albendazole) is an excellent dewormer that gets most all possible worms in chickens. Dosage is 0.08 ml per pound (or 0.5 ml for a 4-6 pound chicken) given orally once, and then repeated in 10 days to get any newly hatched worms from worm eggs. It is available in some feed stores, but easily found online.
SafeGuard Liquid Goat Wormer or horse paste is fenbendazole. It can treat many worms in chickens. Dosage depends on what worms you are treating. Dosage is 0.25 ml given once and in 10 days for roundworms. Give it orally for 5 days, and it will test hard to treat worms such as gapeworms, capillary (thread) worms. Always shake these wormers well, give orally undiluted, and use a syringe for accurate dosage. Taking some droppings in to a vet for a fecal float can tell you if they have more than just roundworms.
