Canker in Chickens: Everything You Need to Know

Discovering yellow plaques or sores inside your chicken’s mouth can be alarming. One of the most common causes is canker, also known as avian trichomoniasis. This disease can spread quickly under the right conditions and may become life-threatening if left untreated.

The good news is that with early detection and proper treatment, many chickens recover fully. Understanding how canker spreads, recognizing the symptoms, and knowing what to do if your flock has been exposed are essential for protecting your birds.

In this guide, we’ll cover everything you need to know about canker in chickens—from causes and symptoms to treatment and prevention.

What Is Canker in Chickens?

Canker is an infectious disease caused by the microscopic protozoan parasite Trichomonas gallinae.

Unlike bacterial or viral diseases, canker is caused by a single-celled parasite (protozoa) that infects the mouth, throat, crop, and sometimes the upper digestive tract.

The parasite forms yellow or cheese-like plaques inside the mouth and throat that can make eating and breathing difficult.

Download our free infographic here:

https://shegrows.koasinag.com/wp-content/uploads/2026/07/Shegrows-Canker-in-Chickens-infographic.pdf

What Type of Disease Is Canker?

Canker is classified as a:

• Protozoal disease
• Parasitic infection
• Infectious disease

It is not caused by bacteria, fungi, or viruses.

Because it is a protozoan infection, antibiotics alone will not cure it. Specific antiprotozoal medications are needed.

What Causes Canker?

The parasite survives in the saliva and crop contents of infected birds.

Chickens become infected through:

• Drinking contaminated water
• Eating contaminated feed
• Sharing feeders and drinkers
• Direct beak-to-beak contact
• Parents feeding chicks
• Contact with infected wild birds

The parasite doesn’t survive for long outside a bird, but it spreads efficiently when birds share water or feed.

Can Wild Birds Spread Canker?

Yes.

Wild birds are one of the biggest sources of infection.

Species commonly carrying Trichomonas gallinae include:

• Pigeons
• Doves
• Raptors (after eating infected prey)
• Some songbirds

If wild birds drink from your chickens’ waterers or eat from their feeders, they may introduce the parasite into your flock.

Is Canker Contagious?

Yes.

Canker is highly contagious, especially in crowded flocks.

Birds may spread the parasite before obvious symptoms appear.

Risk increases when chickens:

• Share water bowls
• Eat from the same feeders
• Live in overcrowded housing
• Experience stress
• Have weakened immune systems

Symptoms of Canker in Chickens

Early symptoms may be subtle.

Watch for:

• Difficulty swallowing
• Drooling
• Wet feathers around the beak
• Reduced appetite
• Weight loss
• Bad breath
• Depression
• Puffy face
• Head shaking
• Gaping

As the disease progresses, you may notice:

• Yellow or white cheese-like plaques inside the mouth
• Thick material in the throat
• Difficulty breathing
• Crop problems
• Inability to eat
• Severe weight loss

Never pull off the yellow plaques. They often bleed heavily and can make the infection worse.

How Is Canker Diagnosed?

A veterinarian may diagnose canker by:

• Examining the lesions
• Taking a swab from the mouth
• Looking at the sample under a microscope to identify the parasite

Although experienced poultry keepers may recognize the disease, laboratory confirmation is recommended because other illnesses can cause similar lesions.

Diseases That Can Look Like Canker

Several diseases can resemble canker, including:

• Fowl pox (wet form)
• Vitamin A deficiency
• Oral injuries
• Fungal infections
• Bacterial abscesses

A correct diagnosis is important because treatment differs for each condition.

How to Treat Canker

Early treatment offers the best chance of recovery.

Treatment usually includes antiprotozoal medications prescribed or recommended by a veterinarian. Commonly used medications include:

• Ronidazole (where legally available)
• Metronidazole (availability varies by country and food-animal regulations)
• Dimetridazole (restricted or banned in many countries)

Always follow your local veterinary regulations, as some medications are not approved for use in food-producing poultry in certain countries and may require egg or meat withdrawal periods.

Supportive care is also important:

• Isolate sick birds immediately.
• Provide clean, fresh water at all times.
• Offer soft, easy-to-swallow feed if eating is difficult.
• Keep birds warm and reduce stress.
• Clean and disinfect feeders and drinkers daily.

If a bird cannot eat or breathe because lesions are blocking the throat, seek veterinary care immediately.

Should You Remove the Yellow Plaques?

No.

The yellow plaques are attached to delicate tissue.

Removing them can cause:

• Severe bleeding
• Pain
• Secondary bacterial infections
• More tissue damage

The plaques usually shrink and detach on their own once treatment begins.

What If Healthy Chickens Have Been Exposed?

This is one of the most common questions poultry keepers ask.

If healthy birds have shared housing, feeders, or water with an infected chicken:

1. Separate the Sick Bird

Immediately move sick birds into quarantine.

2. Watch the Rest of the Flock Closely

Monitor all exposed birds for at least 2–3 weeks, checking daily for:

• Reduced appetite
• Drooling
• Mouth lesions
• Weight loss
• Difficulty swallowing
• Lethargy

Early detection makes treatment much more successful.

3. Clean and Disinfect Equipment

Wash and disinfect:

• Drinkers
• Feeders
• Water containers
• Housing surfaces
• Perches

Replace water daily and prevent contamination from wild birds.

4. Consult Your Veterinarian

In some outbreaks, a veterinarian may recommend treating exposed birds, particularly if multiple birds are showing early signs or if the flock is valuable. Routine flock-wide treatment is not appropriate in every situation, so veterinary guidance is important.

Can Chickens Recover?

Yes.

If diagnosed early and treated promptly, many chickens recover completely.

Advanced cases are more difficult to treat because:

• Birds stop eating
• Severe weight loss occurs
• Breathing may become obstructed
• Secondary infections may develop

Early intervention greatly improves the prognosis.

How to Prevent Canker

Good management is the best defense.

Keep Feeders and Drinkers Clean

Scrub water containers regularly to reduce contamination.

Prevent Wild Bird Access

• Cover feeders.
• Use enclosed drinkers where possible.
• Avoid leaving spilled grain on the ground.

Quarantine New Birds

Keep new chickens separate for at least 30 days before introducing them to your flock.

Watch for any signs of illness during this period.

Reduce Stress

Healthy immune systems help chickens resist disease.

Avoid:

• Overcrowding
• Poor ventilation
• Dirty housing
• Nutritional deficiencies

Provide Good Nutrition

Feed a balanced ration appropriate for the birds’ age and purpose, and ensure constant access to clean water.

Can Humans Catch Canker?

No.

Trichomonas gallinae is not considered a zoonotic parasite, meaning it does not infect humans.

However, you should always:

• Wash your hands after handling sick birds.
• Wear gloves when cleaning lesions or equipment.
• Disinfect tools and equipment after use.

These practices help prevent the spread of other poultry diseases as well.

Frequently Asked Questions

Can eggs from infected chickens be eaten?

The parasite itself does not infect people. However, if a chicken is being treated with medication, follow your veterinarian’s advice regarding egg withdrawal periods, as these vary depending on the medication used and local regulations.

How long does canker last?

With prompt treatment, improvement is often seen within several days, though full recovery can take one to two weeks or longer depending on the severity.

Will canker go away on its own?

Mild cases may appear to improve temporarily, but untreated infections often worsen. Without proper treatment, canker can become fatal.

Can recovered chickens become infected again?

Yes. Chickens can be reinfected if they are exposed to the parasite again through contaminated water, infected flock mates, or wild birds.

Download our free infographic here:

https://shegrows.koasinag.com/wp-content/uploads/2026/07/Shegrows-Canker-in-Chickens-infographic.pdf

Final Thoughts

Canker is a serious but treatable protozoal disease that affects the mouth and throat of chickens. Because it spreads through saliva, contaminated feed, and shared water sources, it can move through a flock quickly if not recognized early.

Daily observation, prompt isolation of sick birds, excellent hygiene, and veterinary guidance on treatment are the keys to protecting your flock. By reducing contact with wild birds, quarantining new arrivals, and maintaining clean feeding and watering systems, you can greatly reduce the risk of future outbreaks.