How to Manage Roundworms in Chickens

How to tell if chickens have worms

How to Manage Roundworms in Chickens

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Roundworms in chickens are an inevitable pestilence with free-range poultry, but we can manage their effect on our flocks. There are about 100 different parasitic worms your birds could contract, but the Merck Veterinary Manual calls the common roundworm, known as Ascaridia galli (A. galli), the most common offender. The Merck Manual estimates infection rate within free-range birds is over 80% on average.

Roundworms in Chickens

Roundworms look much like they sound; they’re round, look something akin to a thin, pale earthworm, and are a semi-transparent shade of white. Adult roundworms can measure between 50 to 112mm long, be thick as a #2 pencil’s graphite core, and are easy to see with the naked eye. A. galli are sexually dimorphic, which means that males and females look different. Males sport a pointed and curved tail where females characteristically have a blunt, straight tail.

How Infection Occurs


Ascaridia galli gains entrance to its avian host by ingestion. Chickens either pick up roundworm eggs from the coop environment that another chicken excreted in its feces or eat an earthworm that’s carrying A. galli eggs. The earthworm serves as an intermediate host, picking up roundworm eggs in its travels.

From Egg to Worm

Once an A. galli egg is ingested, it hatches in the small intestine. The resulting larva burrows into the lining of the gut, mature, then re-enter the small intestine. Roundworms then latch onto the lining of the gut.

Confined flocks can spread and intensify a roundworm infection quickly.

Roundworm Damage

While roundworms in chickens infest the gut, they do damage in several ways. Burrowing larva does the most damage because they destroy tissues that the bird needs for the absorption of nutrients. This damage from burrowing can also cause hemorrhaging (bleeding), causing anemia, much like coccidiosis does. 

An adult A. galli absorbs nutrients directly from the gut, effectively stealing food from the bird and causing nutritional deficiencies. Severe infestation of adult worms can block the intestinal tract altogether, causing intestinal impaction.

Roundworm Cycle

Adult roundworms in the digestive tract will continue their cycle of life by producing eggs that find their way back to the outside environment along with the feces of the bird. These excreted eggs will either infect a new host or reinfect the same host, worsening the parasite load. This feedback loop is exaggerated in confinement, for instance, when birds stay cooped up in the winter and can result in heavy parasite loads quickly.

Signs of Roundworm

Some clinical signs of heavy roundworm infestations are vague, such as pale facial features, reduced manure output, lack of appetite, diarrhea, and general lack of thrift. Meat birds will show stunted growth or weight loss, and layer birds will see a reduction in egg output. The more unique signs of a heavy parasite load are the presence of undigested feed in feces and the telltale presence of adult roundworms in droppings. If you see worms, you’re looking at a significant parasite load.

If you have turkeys and chickens in the same flock, you’ll have to split them up since Aquasol is not labeled for use in turkeys.


Unlike your options for chicken mite treatment, there are only two FDA approved products available for deworming chickens. Fenbendazole, marketed as Safe-Guard® Aquasol, is the only product approved for deworming chickens that I’ve been able to find on the market as of this article’s writing. Be sure to follow the manufacturer’s directions on the label. If you’re raising turkeys with chickens, it’s worth noting that Aquasol is not labeled for use in turkeys, so you’ll need to separate your birds by species. Aquasol is similar to the product Wazine® that many flock owners are familiar with in that it’s fed via water dosage.

Hygromycin B, marketed under the name Hygromix™ is a product fed in a feed ration, however, it’s largely unavailable in the market and you’d need to feed it under the supervision of a veterinarian. Unlike Aquasol which is classified by the FDA as an OTC (Over The Counter, AKA; available to your average farmer), Hygromix™ is classified as a VFD (Veterinary Feed Directive), and the product label states that is must be fed under the direction of a veterinarian

Piperazine, marketed as Wazine®, was the go-to dewormer for roundworms in chickens for years, but according to the FDA, Fleming Laboratories voluntarily withdrew their Wazine® product from the market recently. Unless you manage to locate some old backstock, it appears the product is no longer available on the market and is no longer being produced, or at least it’s not available in America.


Treatment is not a one-and-done solution for an A. galli infection. Once chickens are dosed, the adult worms will exit the bird along with the feces. Just because they’re out, doesn’t mean they’re gone, so it’s good practice to clean out your coop after a dosage or move pastured poultry to fresh ground. Additionally, piperazine only affects the adult worms, not the eggs of roundworms in chickens, so you need to re-dose the flock seven to 10 days after the initial dose. Again, be sure to follow the directions on the label.


When to Deworm

There are differing opinions strewn across the internet, and even between experts. Some learned poultry professionals support routine deworming up to four times a year. Others like veterinarian Maurice Pitesky from the University of California Cooperative Extension system, advocate for restrained use of dewormers. Dr. Pitesky advises treating flocks when parasitic worms are observed in manure, which is a positive identifier of an unhealthy parasite load. Dr. Pitesky argues that the abuse of dewormers can lead to a resistant population of parasites.

Off-Label Use

Other products are effective against roundworms, but you’ll need to use them under the direction of a veterinarian. Products such as Ivermectin, despite its effectiveness, is considered off-label use in poultry. Consult your vet before using any product that isn’t labeled for poultry, and be sure to seek direction on withholding times, which may be different for meat and eggs. These alternatives should be reserved for dealing with resistant worm populations and other special situations.

Originally published in the Backyard Poultry Special Subscriber 2020 issue  Comb to Tail Health  and regularly vetted for accuracy.

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