Roundworms in Chickens
Roundworms are one of the most common internal parasites that you may encounter when raising your backyard poultry. Roundworms can be transmitted in many ways, but luckily they can be diagnosed and treated pretty easily. Chickens can get roundworms from a variety of sources, including wild birds or earthworms, but they are most commonly spread amongst a flock by fecal contamination of food or water supplies.
More obvious signs of roundworms include thin birds with poor feather quality, pale mouths on your birds, and/or diarrhea or droppings pasted to the feathers near their vent. If one or two birds are showing clinical signs, you should probably go ahead and treat the whole flock, since the ones displaying the signs are just the worst ones. If you want to be absolutely certain that you're dealing with a roundworm problem, you can take a fecal sample to your local veterinarian for testing. To collect a sample, isolate any suspect birds in a small cage or container and gather approximately a tablespoon of moist feces in a zip-top bag. Make sure you gather the darker droppings and not the white urates that most people associate with bird droppings. Once you have a diagnosis, you can begin treating your birds using one of the available drugs.
There are multi-worm treatments as well as roundworm-specific treatments such as Wazine. Just be careful with these treatments as most have a withdrawal period - meaning that you cannot eat or sell the meat from the birds that have been treated for a specified amount of time. Most of these treatments can be administered directly to the bird or added to water if you are treating your whole flock. Just be sure to follow the manufacturer's instructions or get advice from your veterinarian. Be aware, Wazine is not approved by the FDA for egg poultry, only for meat poultry, so if you use it you must throw away the eggs during the withdrawal period (do not incubate the eggs, either!).