Chicken Diseases: The Complete List (And How To Treat Them)

Chickens and chicks can suffer from a variety of diseases.

The effects of these diseases can range from a temporary upset with no long-term effects, to long term issues with health and egg laying.

Because many of these chicken diseases are contagious you should isolate them as soon as you suspect something may be wrong.

In this article we will discuss ten of the most common diseases and explain how to identify them, what causes them and how to treat them…

10. Bumblefoot

Bumblefoot Chicken

This is probably one of the most common problems with backyard chickens.

Bumblefoot is caused by an infection in the sole of their foot and is usually caused by a small cut or splinter that goes unnoticed. The infection starts under the skin and causes a cyst like structure.

The top of the cyst that is visible is usually black and hard.

You may notice your hen limping or favoring one foot when she walks or roosts.

Unfortunately bumblefoot can cause a lot of pain if left untreated.

The good news is that it is easy to treat.

You should start by washing her foot and removing all the dirt before starting treatment.

To do this you will need a bowl or container big enough to cover their foot in water. Fill the container with Epsom salts and warm water then stand the chicken in the water for around ten minutes. The skin should be soft and if you are lucky the bumble will be ready to pull out. Wear some protective gloves since the staphylococcus infection can also infect humans and use a pair of tweezers to try and remove the black scab.

If it won’t come off then do not force it. Just put your chicken back into the footbath for a further ten minutes. Most bumbles will pop out after two or three soakings.

The bumble will look somewhat round like a pea and should come out in one piece. The wound should not bleed much, but it may ooze a little at the edges.

You should fill the hole with plain Neosporin and place a gauze pad over it. You can also spray the entire sole of their foot with Theracyn or Vetericyn to make sure the area is clean.

Let the foot air dry then wrap well with vet-wrap or similar and tape into place.

You can read Simple Ways To Treat Bumblefoot In Chickens for more guidance.

9. Coccidiosis

Coccidiosis is more of a disease for chicks, but adult chickens can suffer from it too.

It has been reported as the number one killer of brooder chicks.

To help prevent this infection with your chicks you can either give them medicated starter crumble or have them vaccinated by the hatchery.

If you do not meditate against Coccidiosis then your chicks may look and act fine one day and the next be very ill indeed. Symptoms include:

  • Lethargy and weakness.
  • Diarrhea.
  • Decreased appetite and not drinking water.
  • Pale skin and combs.
  • Ruffled feathers.
  • Weight loss (in older chickens).

If you notice these symptoms and your chicks have not been vaccinated then you should start them on a medicated feed.

Make sure to isolate the sick chicks from the healthy ones – you can use a chicken crate for isolation.

The only way to confirm a diagnosis of coccidiosis is by a fecal float test. Coccidiosis is one of those chicken diseases in which brooder cleanliness is vitally important because it is spread through chicken poop. Of course, ventilation and adequate space are also equally important.

When introducing your new chicks to the world make sure the areas that they are going to be in are as poop free as you can get them. Chicks will gradually build up their own immunity to coccidiosis slowly and by eight weeks or so they should have a fairly robust immunity.

Any chicken that survives coccidiosis tends not to recover 100%.

They may not lay eggs as well as before and will likely be susceptible to other problems such as respiratory issues.

8. Mycoplasma (Bulgy eye)

Mycoplasma is a fairly common occurrence in backyard flocks across the US.

There are two main types: M. gallisepticum and M. synoviae.

There is little practical difference between them and they are both long term chronic diseases.

Common symptoms include respiratory symptoms such as nasal discharge, sneezing, foamy eye discharge, bubbles in the eye and swollen sinuses.

This is where the name bulgy eye comes from.

Mycoplasma can spread from chicken to chicken and even transferred through infected material on boots/gloves or equipment. It can also be transmitted through the egg, so you should avoid raising chicks from infected hens. Once the disease has been diagnosed by a veterinarian, symptoms can be managed with antibiotics but there is no cure and chickens remain lifelong carriers.

Your main task will be to care for the chickens and manage their symptoms.

Unfortunately one of the long-term effects of the disease is a reduction in egg laying too.

7. Fowlpox

Fowlpox comes in two forms: wet and dry.

Because they are both caused by a virus there is no cure.

Once the acute infection has passed, the virus remains dormant in their body (similar to human chickenpox virus). During times of high stress or compromised immunity, you may see an outbreak of pox again.

Dry fowlpox is the least of the twin evils. It usually affects the face, wattles, comb and possibly the legs of the hen, occasionally the vent or any place where there are no feathers. The lesions or pox start out by looking like spots of ash on the unfeathered areas, these will slowly turn into raised yellowish blisters/bumps and then slowly blacken and scab over and eventually drop off.

During the course of the disease (two to four weeks) it will resolve itself.

Wet fowlpox is more worrisome because the lesions can form inside the mouth and possibly down the larynx into the trachea and digestive tract.

These lesions look like plaques or canker sores in the mouth.

Treatment of pox is supportive.

With dry pox you can treat the scabs with a dilute iodine solution and an antibiotic ointment.

Wet pox should be seen by a veterinarian because of the risk of respiratory problems. They may prescribe an antibiotic to prevent secondary infections occurring.

Prevention is of course the preferred choice here.

It is spread by biting insects, particularly mosquitoes, so try to eradicate mosquitoes and biting flies from the area. Cleanliness in the coop is essential to prevent further infections from occurring.

Life Cycle Of A Chicken

6. Infectious Bronchitis

This disease is viral so there are no helpful antibiotics you can use.

Although your veterinarian may prescribe them to treat any secondary infections.

Infectious Bronchitis will come over your chickens fairly quick (within 24 – 48 hours). With uncomplicated cases it will typically last for around seven days.

Because this disease is highly infectious your entire flock will catch it.

Symptoms include:

  • Coughing
  • Rales (clicking or bubbling noises when they breath)
  • Watery or foamy eye discharge
  • Sneezing

This disease will also impact egg laying. The production of eggs can drop by up to 70% and the eggs may appear wrinkly with watery albumin.

Any treatment you give them will be supportive in nature. Make sure they get good amounts of protein, vitamin/electrolytes supplements and plenty of fresh air and sunshine. There is a vaccine against IBV but it is usually only given to commercial flocks and not backyard flocks.

5. Marek’s Disease

Marek’s Disease is another fairly common disease found in backyard flocks.

It is caused by the Herpes virus and causes lots of problems for the infected chicken.

Interestingly though it can range from benign to highly virulent in strength. Some birds in the flock may be affected whereas others will not.

Although Marek’s has a high mortality rate, it is not always a death sentence.

Symptoms can be quite varied and include paralysis, decreased weight, grey or irregular eyes and rough, raised skin around the follicles. It is more commonly associated with younger chickens but can still impact older chickens particularly if they are highly stressed.

There is a vaccine available and chicks should be inoculated as soon as they hatch.

If your hen does catch Marek’s then they will likely not live a long life, but with a little extra attention they can have a full life.

Marek's Disease

4. Vent Gleet

Yes, this is as yucky as it sounds.

This is a fungal infection of the cloaca (vent) area.

You may first notice a whitish discharge from their vent and perhaps some reddened and irritated skin, mucky butts and a yeasty smell.

Vent Gleet is caused by mucky water, dirty living conditions or eating moldy or spoiled food.

First of all you need to bathe the area to remove all the poop from the area and clean the feathers and skin.

If the skin looks very inflamed then you can apply a topical antifungal cream or powder to the area. You will need to repeat the treatments daily until the white discharge stops. Make sure to give your chickens probiotics to help prevent a reoccurrence.

3. Sour Crop

Sour Crop

Sour crop happens when the crop becomes overloaded.

A chicken’s crop is simply an expandable storage pouch where food is kept before it is processed.

There can be several causes of sour crop. In the springtime the most usual reason is eating long tough grass after the winter diet. Other causes include: a slow emptying crop, huge worm load, infection, antibiotics, moldy food or odd diets.

When the hen goes to roost at night her crop is full – this food will be digested overnight. If she wakes up in the morning and her crop is still full then she has a problem.

Here is the easiest way to check her for sour crop:

  • Feel her crop in the morning. If it is flat then you have no problem, but if full or partially full there is a problem.
  • Hold her chest up to your ear. Can you hear gurgling noises? If yes, you have a problem.
  • Lastly, sniff her breath. If it smells sour or yeasty then you have a problem.

She will need to be isolated for treatment.

The first twelve hours she should have nothing to eat or drink. You will need to massage her crop every couple of hours if you can.

For the next twelve hours she can have clear water only. Make sure to continue with the massage.

The following day, if the crop is flat then she can have two or three small meals during the day (scrambled egg, pellets with a little plain yoghurt) and water. Keep her on this diet for two or three days until you are sure the problem is resolved.

2. Brooder Pneumonia (Aspergillosis)

This occurs mainly in brooding chicks or sometimes in hatching eggs.

It is a fungal infection that thrives in warm and moist environments.

When hatching or brooding chicks it is important to be scrupulous in your housekeeping. Use fresh bedding and fresh feed.

The signs of brooder pneumonia can be as follows:

  • Respiratory (gasping)
  • Loss of appetite
  • Emaciation
  • Conjunctivitis
  • Sleepiness

It is spread in the air or within contaminated materials such as feed.

You need to make sure the brooder is clean and well ventilated.

Infected chicks will start to exhibit signs after three days or so. If you act quickly you may be able to save many of them but there is a high mortality associated with aspergillosis. Occasionally an egg in the incubator will be infected and explode, releasing thousands of spores into the incubator. If at all possible, the remaining eggs should be removed while the incubator is thoroughly cleaned out.

1. Infectious Coryza

Coryza can be mild or severe in nature.

This is a disease which demonstrates the need for quarantine and hygiene.

The most likely places to get a coryza infection are poultry shows, swap meets and bird markets.

If you do buy chickens from these places then you will need to quarantine them for an absolute minimum of fourteen days (thirty days is better).

The onset of the disease is quick and symptoms will show within three days.

You can try isolating infected chickens, but it is likely all the flock will be affected. It is a disease with high morbidity but low mortality.

In mild cases your chickens can have nothing more than an occasional sneeze or beak discharge.

With more severe cases there can be swollen wattles, sneezing, respiratory difficulty and decreased appetite. Older and weaker chickens can even succumb to the disease.

If you suspect your flock has Coryza you should consult with your veterinarian for the appropriate treatment.


Just remember that I am not a vet and hold no qualifications in animal care other than many years of experience raising chickens.

If you have an acutely ill bird your best resource is your local vet and not Facebook.

However many of these problems can be dealt with at home without the need for a veterinary consultation.

Some diseases (such as Marek’s or Mycoplasma) are sadly quite widespread among backyard flocks and others (such as brooder pneumonia) are thankfully quite uncommon.

For a deeper understanding of some of these chicken diseases then make sure to follow the links to other articles on the website.

Chris Lesley Bio Picture
Chris Lesley has been Raising Chickens for over 20 years and is a fourth generation chicken keeper. She can remember being a young child when her grandad first taught her how to hold and care for chickens. She also holds a certificate in Animal Behavior and Welfare and is interested in backyard chicken health and care.

1 Comment

  1. my chicken just seem to be
    tired but she she drinks she eats she get a lot of fresh air her pen is clean and none of the other chicken seem to be affected.

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