15 Common Chicken Diseases: What To Know

Treating chickens can be difficult and intimidating, especially if you have no clue or idea what you’re dealing with. To help you and your flock, we’ve gathered information on some of the most common poultry illnesses.

You can use this as a reference guide to help diagnose your chickens and figure out what you can do to keep those guys alive, healthy, and layin’!

Common Chicken Diseases That You Should Know

Avian InfluenzaInfluenzavirus ADiarrhea, breathing issues, and no appetite
BotulismBotulism bacteriaTremors and paralysis
BumblefootBumblefoot bacteriaPink and callused legs
CoccidiosisParasiteDiarrhea with blood and mucus
Fowl CholeraPasteurella multocidaFever, reduced appetite, heavy breathing, mucus
Fowl PoxAvian DNA pox virusSores and respiratory issues
Infectious BronchitisAvian coronavirusLabored breathing, watery discharge from their eyes and nostrils
Infectious CoryzaBacterium Haemophilus paragallinarumFacial swelling with thick, sticky discharge thick, sticky discharge
Lymphoid LeukosisAvian leukosis virusWeakness along with comb regression, and an enlarged abdomen
Marek’s DiseaseChicken herpes virusParalysis, drooping wings, weight loss, enlarged feather follicles, and more
Mushy ChickContaminated surfacesExternal navel infection
Newcastle DiseaseParamyxovirusRunning nostrils, heavy breathing, swelling in the face, paralysis, and twisting of the neck
SalmonellosisContaminated environments or infected rodentsLethargy, puffy eyes, ruffled feathers, dehydration
Scaly LegCnemidocoptes Mutans (mites)Roughness and unevenness of the legs
Thrush Candida build-upOozy white secretion around the neck

The goal here is to highlight some of the most common poultry diseases. However, keep in mind that there are countless other diseases out there, and a veterinarian is just a phone call away.

If you have serious questions, don’t take chances, especially when other types of chicken diseases can affect humans.


Alright, let’s take a look at the list of common chicken diseases that could be affecting your birds.

1. Avian Influenza


We start with a disease that has shocked the world more than once: Avian Influenza.

More commonly known as “bird flu,” outbreaks of the disease have become alarming to humans on a global scale because of the infectious rate at which it can spread and kill off a flock – not to mention the possible transfer to humans as well.

If you suspect that your birds have the bird flu, report it to your vet immediately and ask them for assistance.


The Avian Flu is a viral disease that can survive for a very long time. It spreads through contact with an infected backyard flock or infected surfaces.

Anything from an improperly disposed-of carcass to infected rodents, equipment, and even people can all spread the disease.


Milder forms of Avian Flu can lead to tiredness, diarrhea, breathing issues, a decline in eating, and decreased egg production.

However, if the outbreak is more severe, dark red and white spots can develop on the infected chickens’ legs and combs.

Also, blood-tinged discharge from the nostrils is common and facial swelling and blue combs and/or wattles.

Is It Fatal?

Yes, Avian Influenza can be extremely deadly.

Less dangerous strains can have a relatively low mortality rate, but a large portion (half or more, depending on the source) of the birds can die during serious epidemics.


As previously mentioned, the Avian Flu is serious enough that it must be reported immediately. Even the strains from mild cases can mutate quickly and become very deadly.

To compound the issue, even if infected chickens are cared for and recover, they will continue to be infectious for a long time.

Unfortunately, the best solution is to separate the birds that carry the disease and get rid of them, as there is no effective treatment available at this time.

You can read more about the Avian Flu here.

2. Botulism


Next on the list is another worldwide sickness familiar to our collective ear: Botulism.

If you’re thinking, “wait, isn’t that when I eat something rotten and get really sick?” then you’re on the right track.


Botulism in backyard chickens is very similar in humans. When a chicken ingests something infected with Botulism bacteria, it gets really, really sick.

The bacteria can come from pond scum, maggots, plant waste, and the classic – rotting meat.

Another source is insects that have eaten from infected meat.


Tremors and paralysis are common. You may find birds unable to stand or lift its head (1).

Eventually, the paralysis can extend to breathing, at which point you can lose the animal.

Sometimes birds may just be found dead, with no evidence of struggling. There is no diarrhea or nasal discharge and no signs of injury.

Is It Fatal?

Unfortunately, yes. So when it shows up, it’s not fun. 

But the good news is that while Botulism shows up on most lists of diseases (as it’s an intense one to deal with), it is fairly uncommon when compared to other conditions.


Birds sick with Botulism can be given antitoxins from the vet, although they can be expensive. 

Another good idea is to get rid of the source! Whether it’s pond scum or the dead carcass over there, get it out of here!

If you’re interested in learning more about Botulism in chickens, check out this article.

3. Bumblefoot


Another interesting one for us humans to relate to, Bumblefoot is a chicken’s version of a staph infection in their leg (hence the “foot” part…)


This bacteria, which comes from the soil, can appear especially after a heavy rain disrupts any stagnant water in the chicken’s environment.

Usually, an injury on the leg allows the bacteria to enter and infect.


True to its name, a bird with Bumblefoot has some pretty gnarly-looking legs. They become pink and callused and can eventually end up covered in sores.

If left untreated, eventually, the whole foot turns dark blue or even black, becoming swollen and distorted.

Is It Fatal?

No, unless you just leave the infection to fester. This one is fairly easy to keep from becoming morbid.


Antibiotics are effective. Dietary change and even surgery are options as well. It’s a good idea to ask a vet on this one!

Here is a good source for more information on Bumblefoot in chickens.

4. Coccidiosis


While the name alone is a bit challenging, that’s just the beginning of the trouble.

This parasitic disease will literally turn your stomach, or more accurately, your chicken’s stomach. It shows up, like many parasitic diseases, in overcrowded and unsanitary environments.


Coccidiosis is a chicken disease that invades the bird’s intestinal tract.

The parasite is ingested from the chicken’s environment in its egg form and then reproduces, at which point more eggs leave through the chicken’s feces.

This, of course, leads to a vicious cycle in which eggs are littered around the environment, making it quite contagious (if you’re looking for further information, check out this article on Coccidiosis).


The Coccidiosis parasites can create a huge amount of gut damage, leading to things like diarrhea with blood and mucus and losing weight.

Ruffled feathers and listless activity are also symptoms that something is going on inside.

Is It Fatal?

Generally no, although severe cases can be.

More dangerous is that Coccidiosis weakens a chicken, making them susceptible to other diseases while battling with the parasite.


There are quite a few ways to deal with Coccidiosis. You can get an anticoccidial agent like amprolium or toltrazuril, while antibiotics can be an option if secondary infections occur.

A gentler alternative is using an essential oil like thyme, tea tree, or clove.

Easy preventatives include vaccinating the backyard chickens and keeping the coop clean and dry.

Because the parasite becomes infectious in wet or humid environments, it is a good idea to keep the entire coop clean and the area around feeders and waterers.

This can help prevent any future outbreaks.

5. Fowl Cholera


Here we run into one of the granddaddies of chicken illnesses.

First diagnosed over a century ago, fowl cholera can be a doozy. It can also be one of the more serious diseases in winter when chickens are closer together.


This one is another bacterial illness that can spread from things like rats, possums, and other rodents and wildfowl that stop in for a visit.


When the outbreak is serious, the first symptom you might run into is death.

However, keep your eyes peeled for other symptoms of this disease, including fever, reduced appetite, heavy breathing, mucus from the mouth, diarrhea, and ruffled feathers.

Weight loss can be another sign, as well as the bird losing the ability to walk. Signs of nearing death include swollen joints and feet as well as abscessed wattles.

Is It Fatal?

As implied by the first symptom, yes.

This one can be intense, as the symptom list is long and ugly, leaving plenty of openings for the grim reaper’s icy grip.


While there are antibiotics available, this is one of those sad cases where even if the bird recovers, it’s still a carrier.

However, preventative treatments exist, including vaccinations to keep the sickness from spreading to the rest of the chickens.

Really, though, keeping those pesky rodents out is the best long-term preventative you can find.

You can get some more info on this illness here (the first one under Nonrespiratory Bacterial Diseases

6. Fowl Pox


Also known as chicken pox (much more reasonable use of the title, in our opinion), this chicken disease is a viral infection that can cause a good deal of harm to a flock.

Note: this is not the same illness in humans.


Fowl Pox spreads from direct contact between birds and can spread through scabs that have fallen off, skin that has been scraped, breathing, and even through a bird’s eyes.

Mosquitoes who have fed on infected birds can also spread the disease.


There are two kinds of Fowl Pox.

The “dry form” comes with warty, raised spots on featherless areas of the infected chicken. The sores can take a couple of weeks to heal and lead to slowed growth, lethargic behavior, and fewer eggs.

The “wet form” comes with actual pox in the mouth and throat. These look a lot like canker sores and can cause respiratory issues if they’re serious enough.

Either form can come separately or work in concert together to wreak havoc on a brood.

You can learn more about Fowl Pox here.

Is It Fatal?

Not generally, unless the pox leads to secondary infections.


There is no known treatment available, but it spreads slowly, you should conduct preventative measures.

This gives you the option to vaccinate the rest of the chickens if desired.

7. Infectious Bronchitis


Another one to add to our list of respiratory diseases, this incredibly contagious viral disease plagues chickens in particular, rather than birds in general.


As mentioned above, this one is very infectious and can be spurred on by factors like the flock’s age and the living environment.

The virus can spread through many transmissions, including feed bags, dead birds, infected coops, and those good-for-nothing rodents. But most commonly, it can spread via the air.


Chickens with Infectious Bronchitis will eat and drink less and develop a watery discharge from their eyes and nostrils. They will begin to have heavy and labored breathing. They can also lay fewer eggs.

However, while this is a common symptom we’ve seen multiple times before, often chickens who have contracted Infectious Bronchitis never recover to previous egg production levels. Their egg whites can become more watery.

Is It Fatal?

Generally not.

While it can lead to secondary infections, most adult chickens can recover. However, chicks are highly at risk and can have high mortality rates.


Once again, there is little to do once your chickens already have the virus besides taking good, rehabilitative care of them.

However, if they are still chicks, you can raise their environment’s temperature by a few degrees and give them a mash to help them eat easier.

Regular cleaning of your coop and vaccination can help manage and prevent this infectious chicken disease from spreading.

Vaccines are available to prevent contracting the disease, but it must be given early on in life (within the first 15 weeks) as eventually, it will stop the hen from laying eggs. If you want to learn the other reasons why chickens stop laying eggs, read here.

If you think you’re battling with Infectious Bronchitis or another respiratory illness, here is some more information to help make the diagnosis.

#8. Infectious Coryza


Similar in many ways to Infectious Bronchitis (scroll down for a comparison of the two), Infectious Coryza is a bacteria-driven respiratory infection.


Most often, Infectious Coryza transmits merely when two birds make contact, although airborne transmission is another possibility.

Chickens who have recovered can carry the disease as well, so be careful when introducing a new chicken into your flock.


One of the ways to tell Infectious Coryza from Infectious Bronchitis is that Coryza usually involves facial swelling accompanied by a thick, sticky discharge from the eyes and nostrils.

This can sometimes become so intense that the eyes stick shut.

Another stand-out about Infectious Coryza is that the chickens just plain stink.

I know, I know, chickens always stink, but if things smell worse than normal, you might be dealing with more than just the chicken’s bachelor-scented lifestyle.

Is It Fatal?

Yes, but mortality rates tend to stay pretty low, at around 20%.

It can get up around 50% at times, but either way, even recovered chickens are left weakened and susceptible to secondary diseases and infections.


This is a bacterial infection, so antibiotics and antibacterials are both options. As always, though, there can be restrictions and both should be used on animals with care.

Consult a vet!

Here’s a bit more information on Infectious Coryza.

9. Lymphoid Leukosis


This is one of the sadder, more intense diseases on the list.

It is a viral, tumor-forming disease that targets the organs of adult birds in particular.


Carriers are infected for life and can pass on the virus through direct contact and eggs.

Unfortunately, it is very hard to know when this is happening, as so much of the damage takes place inside before exterior symptoms reveal what’s going on.


As is so often the case, infected birds may take longer to produce eggs.

However, beyond that, weakness can gradually increase along with comb regression, an enlarged abdomen, and a loss of appetite along with emaciation.

If greenish diarrhea develops, it is a sign that the bird is terminal.

Is It Fatal?

Not surprisingly, this one is a yes.

Once Lymphoid Leukosis reaches a point where it can be detected, many birds already have tumors on their organs and may die within weeks.


There is currently no known treatment.

Once a bird is diagnosed, do not let them reproduce or contact other birds to prevent spreading the disease further.

Once again, here is a bit more info if you think this might be a problem and want to pursue a more detailed self-diagnosis.

10. Marek’s Disease


Similar to Lymphoid Leukosis, Marek’s Disease is another one of the nastier types of illnesses.

A bane to younger chicks, in particular, this tumor-driven virus affects the nervous system.


While it does not spread directly from parent to egg, it is highly contagious.

It transmits through the air via chicken dander/dust and can lie dormant in a seemingly healthy host for as long as a year.


Lameness, paralysis, drooping wings, weight loss, enlarged feather follicles, paleness, loss of appetite, blindness, and reddened, bloody looking shanks (lower legs) can all be symptoms that something is going on.

Is It Fatal?

Yes. It has a very high death rate.


You can only vaccinate against Marek’s Disease before tumors develop.

But even then, the vaccine is only good for preventing the tumors themselves. Even vaccinated chickens can still be carriers.

If you’re interested in learning some more information on this one, you can find it here.

11. Mushy Chick


What a charming name… for a sad and grotesque bird disease (who comes up with these?).

Officially known as Omphalitis, “Mushy Chick” is a disease that infects new chicks shortly after hatching.


When a chick is born, its navel needs to heal. (2)

The likelihood of omphalitis developing is much higher in a batch of eggs that includes bangers, or if the hatcher baskets are not thoroughly cleaned and disinfected prior to transfer.

However, in the short time between hatching and healing, the navel can become infected if it comes in contact with a dirty environment, such as soiled eggs, unclean hatching boxes, etc., which can lead to infection.


External navel infection is the obvious one. 

Others include abnormally large, unused yolk sacs, very bad smelling peritonitis (a swelling infection of the abdomen), seeping out of the navel, edema in the lower skin of the chick, dehydration, and even blood poisoning.

Is It Fatal?

Sadly, this one is fatal, with most infected chicks dying within a few days.


While there is little you can do other than comfort the infected chicks, some sources claim that antibiotics can give the chick a chance at recovery – although this is a long shot.

Either way, make sure to keep them away from the rest of the flock to avoid contamination of other chicks.

Prevention can be easily attained by keeping your hatchery clean – one of the many rules of raising healthy chicks and creating a good environment for them. You can also give your chickens vitamins and a vaccine to boost their immune system.

More information on Mushy Chick disease can be found here.

12. Newcastle Disease


Next on our list of diseases in chickens (and another poultry respiratory disease), this viral infection attacks the nervous system and can vary in its intensity.


This disease can spread short distances through the air, but it is more likely to be transmitted through contaminated “outsiders.”

Wild birds, dirty equipment, and your own shoes can all spread the infection.


Depending on how bad the case is, chickens can have wheezing, running nostrils, heavy breathing, swelling in the face, paralysis, trembling, and twisting of the neck, like this:

Other typical symptoms include eating and drinking less and a decrease in the number of eggs.

Is It Fatal?

Yes. Once again, the intensity factor can affect the numbers quite a bit, but mortality rates for Newcastle Disease can be as low as 10% and as high as 80%!


There isn’t treatment at this point, so the virus must be left to run its course.

However, this is a serious enough disease that, at least in the U.S., you report it if you suspect your chickenshas the disease.

Separate the animal to prevent the disease from spreading, and give them plenty of TLC while recovering. One possible solution is to provide them with Vitamin A.​​​​ 

Also, keep an eye out for secondary infections, which can usually be combated with antibiotics.

Vaccines are available to help prevent any future outbreaks as well.

Here is a good source for further information if needed!

13. Salmonellosis


This bacterial disease can show up in various forms, including Arizonosis, Pullorum disease, fowl typhoid, and paratyphoid (see the breakdown here).

It is also more dangerous during cold seasons when chickens live in close quarters due to the weather.


Unfortunately, this one can spread vertically (from parent to child) and horizontally (between adult chickens).

The latter can come in many forms, including an infected coop, food, boots and hands, rodents, bugs, and the addition of new birds to the flock.


Chickens infected with the bacteria can show signs of lethargy, puffy eyes, ruffled feathers, dehydration, lowered egg production, white, chalky diarrhea, and pasty vents.

Is It Fatal?

Yes. This one can be deadly.


Probiotics in a supplement form or even yogurt can help fight off the infection.

In addition, to help prevent further outbreaks, clean up the coop and take measures to keep bugs and rodents out and the food and water clean from contamination.

Winter can be harsh, and in cold conditions, your chickens are susceptible to disease if they don’t have adequate water or a healthy environment. You may want to check out our articles on How Cold Is Too Cold For Chickens, and How To Keep Your Chicken Water From Freezing for some top tips and recommendations! 

14. Scaly Leg


This one is a basic infection with a simple (and gross) cause: mites.

It’s true. Mites exist. They’re an unfortunate part of life. And in the case of Scaly Leg, it can cause a lot of issues.


Mites burrow down into the chicken’s skin, causing particularly bad damage to their legs and feet.

The mites spread from contact between the chicken and rodents, wildfowl, or other animals.

It can be hard to see initially, as the mites are too small to see with the naked eye, but the symptoms can be a quick indicator of what’s going on.


Roughness and unevenness, and straight-up deterioration of the skin’s legs and feet are obvious signs of Scaly Leg.

Is It Fatal?

No. Although if left untreated, secondary infections can be a danger.


There are plenty of options available.

You can suffocate the mites with topical ointments like vegetable oil, olive oil, coconut oil, and even petroleum jelly.

Diatomaceous earth is a good option as well. You can also use Ivermectin, but please consult a vet before you do.

If you think you’re dealing with Scaly Leg and need more information, you can find it here.

15. Thrush


Last but not least, we come to Thrush, or Candidiasis as it is officially called. Much the same as the infection seen in humans, Thrush is a fungal disease that can come from a number of sources.


Thrush can be transmitted through moldy feed, water, or other contaminated surfaces.

The long-term use of antibiotics can also make chickens more susceptible to the fungal disease.


An oozy white secretion between the neck and the body is common, as well as overeating, lethargy, ruffled feathers, and a crusty vent area.

Is It Fatal?

Not particularly. As with all diseases, if symptoms go unchecked it can become dangerous, but this one is pretty easy to address.


Feeding probiotics as a supplement or in a form like yogurt can be very helpful, and an antifungal medication from the vet is a quick and effective solution as well.

Obviously, removing the source of the mold is also imperative, as the fungus can otherwise be re-ingested.

Here is a great follow up source for dealing with fungal infections like Thrush (second down on the list!)

Wrapping Things Up

Having the right information on the types of poultry diseases can help you diagnose what your flock is suffering from. Also, remember to call the vet if things are looking serious!

Now that you’ve got the rundown on what your chicken is dealing with, you can go help out your flock!

But before you do, please share this post!

And let us know in the comments below what your chickens were diagnosed with and what you did to treat poultry diseases.


Chicken diseases that you can prevent include the New Castle Disease, infectious bronchitis, fowl pox, and more. If your chickens are not vaccinated yet, you can consult your veterinarian for a suitable vaccination program. If you are planning to get new birds, you should get them from reputable farms or hatcheries. Ask for vaccine certifications, if possible.

You should immediately take your chickens to a vet if you noticed any signs of lethargy, ruffled feathers, diarrhea, and other symptoms that would suggest that your bird is unhealthy. Waiting too long can cause the spread of the illness to the rest of your flock, especially when the sick chicken is infected with a highly contagious disease.

Yes, a vaccinated chicken with Marek’s disease can pass the illness to unvaccinated birds. If you bring a new chicken into an infected flock, it will most likely get the disease too. Fortunately, this deadly chicken disease is preventable by having your birds, young and adult, vaccinated. Since it takes at least a week for the vaccine to kick in, you will need to isolate your chickens to the infected hen.

  1. Botulism in chickens, ducks and other poultry. Retrieved from: https://nt.gov.au/__data/assets/pdf_file/0010/233569/botulism-in-chickens-ducks-and-others.pdf
  2. Preventing omphalitis to reduce first week mortality. Retrieved from: https://nt.gov.au/__data/assets/pdf_file/0010/233569/botulism-in-chickens-ducks-and-others.pdf
List Of Chicken Diseases

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