Canker in Chickens: Causes, Signs & Prevention

Health note: This guide is general information, not veterinary advice, and our writers are not veterinarians. If a bird is sick, injured or not improving, contact a poultry vet, and always follow product labels and your vet's instructions for any medication. How we write health content.

Canker in chickens is an infection of the mouth, throat and crop caused by the single-celled parasite Trichomonas gallinae, and chickens usually pick it up from water contaminated by pigeons or doves. It is far more common in pigeons and doves than in chickens, but outbreaks do happen in chickens and turkeys. There is no vaccine, the drugs often mentioned online are prohibited in laying hens, and diagnosis needs a veterinarian. This guide covers what canker looks like, how it spreads, and how to keep it out of your flock.

Key Takeaways

Canker (trichomonosis) is caused by the protozoan Trichomonas gallinae, not by a worm or bacteria.
Contaminated drinking water is probably the most important source of infection for chickens.
Early lesions are small yellowish spots in the mouth that can grow into cheesy masses in the throat and crop.
There is no vaccine, and metronidazole and dimetridazole are prohibited in food-producing birds in the US.
Birds that recover can carry the parasite without showing signs.

Correction: an earlier version of this article wrongly named the worm Tetrameres as the cause of canker, described a canker vaccine that does not exist, recommended antibiotics, natural remedies and metronidazole, and listed rodents as a source; these errors have been removed.

What causes canker in chickens?

Canker, also called trichomonosis or avian trichomoniasis, is caused by Trichomonas gallinae, a microscopic protozoan parasite with whip-like flagella. It lives on the lining of the mouth, throat and crop.

The parasite is most common in pigeons and doves, which pass it to their young through crop milk. Chickens and turkeys are less often affected, but severe outbreaks have been recorded in both.

Canker is sometimes confused with Tetrameres, a red roundworm that lives in the chicken’s proventriculus (glandular stomach) and is spread by grasshoppers and cockroaches. That worm has nothing to do with canker. For worm problems, see our guide to worms in chickens.

How chickens catch canker

For chickens, contaminated water is probably the most important source of infection. Pigeons, doves and other wild birds that drink from or bathe in your flock’s waterer can leave the parasite behind. It can survive roughly 2 to 24 hours in water, which is long enough to pass between birds sharing an open waterer.

Contaminated feed can also carry the parasite. Birds that have recovered can keep carrying it in the throat without looking sick, so a flock can be reinfected from its own members.

Signs of canker to watch for

The first lesions are small, yellowish areas on the lining of the mouth. As the infection progresses, they can become raised, cheesy (caseous) masses in the mouth, esophagus and crop. Other signs include:

Yellow or cream-colored plaques or ‘buttons’ in the mouth or throat
Rapid weight loss
Weakness and listlessness
Death, sometimes within 8 to 10 days in severe cases

Several other conditions can look similar, including fowl pox, candidiasis (thrush), aspergillosis, salmonellosis and vitamin A deficiency. You cannot tell them apart reliably by eye, which is why a diagnosis matters. Our overview of chicken diseases and symptoms describes several of these.

How canker is diagnosed

A veterinarian confirms canker by taking a swab or scraping of mucus or fluid from the throat and looking for the moving parasites under a microscope (a wet mount), or by growing them in culture.

If a bird dies, your veterinarian or state diagnostic laboratory can examine it to confirm the cause and protect the rest of the flock.

Treatment: why you need a veterinarian

Canker is caused by a protozoan, not bacteria, so ordinary antibiotics do not treat it. There is no evidence that natural or home remedies cure it.

Many online guides suggest metronidazole or dimetridazole. In the US, extra-label use of these nitroimidazole drugs is prohibited in food-producing birds, and backyard laying hens whose eggs are eaten count as food-producing animals. Do not give them to your flock.

Any drug that is not labeled for chickens can only be used under a veterinarian’s direction, with an egg withdrawal time. Since June 2023, medically important antibiotics for animals also require a veterinarian’s prescription. Ask a veterinarian which options, if any, are legal and appropriate for your birds.

How to prevent canker in your flock

There is no vaccine for canker, so prevention depends on hygiene and keeping wild birds away from your flock’s feed and water.

Keep pigeons, doves and other wild birds out of the run and away from feeders and waterers.
Use covered feeders and waterers that wild birds cannot easily reach.
Clean waterers often and replace water daily. See how to clean a chicken waterer.
During an outbreak, Merck describes removing feeders and waterers for about 2 weeks and cleaning them with a 10% bleach solution.
Keep new birds separate for 30 days before adding them to the flock, and follow good biosecurity, since recovered birds can carry the parasite without signs.

FAQs

Is canker in chickens contagious?

Yes. The parasite spreads mainly through contaminated water and feed, and birds that recover can carry it without signs. Pigeons and doves are the usual source.

Is there a vaccine for canker?

No. No vaccine for avian trichomoniasis is available. Prevention relies on clean feeders and waterers and on keeping wild birds away from your flock.

Can I treat canker with metronidazole?

Not in laying hens or other food-producing birds in the US. Extra-label use of metronidazole and dimetridazole is prohibited in these birds. A veterinarian should confirm the diagnosis and advise on legal options.

Do antibiotics cure canker?

No. Canker is caused by a protozoan, not bacteria, so ordinary antibiotics do not treat it.

Conclusion

Canker is a parasitic infection that chickens usually catch from water shared with pigeons and doves. Keep wild birds away from feed and water, clean waterers often, and have a veterinarian confirm any mouth lesions before treatment, because the commonly suggested drugs are prohibited in laying hens.

Sources

Checked September 2026. Labels change, so always read the label on the product you buy. See our editorial policy for how we research health articles.