Most common poultry and chicken diseases: Prevention, causes and how to treat them



In common terms, a disease is an abnormal condition that is caused by infection, basic weaknesses, or environmental stress. A disease is defined by a specific group of signs or symptoms. Diseases prevent affected animals from functioning normally.

Health is the overall condition of an animal at a given time. Disease causes this condition to weaken. This can result in poor productivity and reduced quality of the affected animals. It could even lead to the death/loss of one or all of the birds in a flock.

Diseases can be categorized by common causes, such as genetic, mechanical, toxic, and nutritional. Infectious diseases are caused by viruses, bacteria, and fungi. Parasitic diseases are caused by protozoa, worms, and external parasites such as mites and lice.

Infectious agents, commonly referred to as “germs,” move from one susceptible bird to another in order to survive. For this to occur in a flock, a sufficient number of disease-causing agents must be able to gain access to the susceptible birds. These are birds that have no immunity or other resistance against these agents or whose defense mechanisms have been reduced or overwhelmed at the time of infection.


Certain diseases have the potential to decimate a region’s poultry industry. When one of these diseases strikes, a quarantine or embargo could suddenly be placed on a region or nation. This could cause widespread economic hardship for both commercial and small flock owners. To protect their animals—and the poultry industry—flock owners must be able to identify diseases quickly to prevent them from spreading to other animals. The sooner a disease is identified and action is taken, the better.


Diseases are spread by:

– Direct contact (bird-to-bird, infected manure)

– Indirect contact (contaminated equipment, people, environment)

– Vectors (wild animals, rodents, insects)

In addition, infectious agents need a “home base,” or reservoir of the disease, to persist in an area. This reservoir could be other birds or organic matter providing life support for these agents. Disrupting the methods by which diseases are spread can greatly reduce the threat to your flock.

Behavioral Diseases

If your birds are acting aggressive, pecking other birds, or excessively plucking feathers, this could be a sign of a behavioral health problem. Overly stressed birds may begin eating eggs or revert to cannibalism under certain living conditions. To stop problems before they start, make sure your flock has adequate nutrition, isn’t overheating or overcrowding. Keep up with other general health concerns, too.

Metabolic/Nutritional Diseases

Chickens that are living in an unhealthy environment are more susceptible to metabolic and nutritional diseases. Birds can become lame, have soft bones and beaks, or have a reduction in egg production if they are not receiving proper nutrition and exercise. Most of these diseases can be easily remedied with proper care of your birds, but sometimes these symptoms can be a factor of other underlying diseases.

Infectious Diseases

Infectious poultry diseases can be viral, bacterial, or fungal and tend to be the most common since they easily spread from bird to bird. Infectious diseases can affect your birds’ intestinal, nervous, respiratory, immune, or reproductive systems, as well as their skin. If any of your birds show signs of an infectious poultry disease, it’s important to isolate the incident as much as possible and treat your birds quickly to protect your flock.

Parasitic Diseases

Parasites can live on or in your bird and are often contracted via contact with other infected birds or particular living conditions. A few types of common parasites are ticks, mites, lice, fleas, or roundworms. Most of the time you can see the parasites or their symptoms via feather damage, irritation, or even in the feces of your birds. Doing monthly checks of your birds and keeping your chickens’ enclosures clean should help avoid any parasitic poultry diseases.

What are the Most Common Diseases in Chickens?

Now that we’ve gone over the types of diseases you may encounter in your flock, we wanted to list a few of the most common specific diseases in chickens. Here are each disease’s symptoms, how to treat, and how to prevent.


– Cause: The disease is caused a virus called by Avipox virus. The disease can be transmitted from virus carrier to other poultry through wounds or spread the virus even to a nearby poultry house.

– Symptoms: Chickens develop white spots on their skin, scabby sores on their combs, white ulcers in their mouth or trachea. They also stop laying.

– Prevention and Treatment: Feed them soft food and give them a warm and dry place to try and recoup. With adequate care, there is a great chance that your birds can survive this illness. There is a vaccine that can prevent the healthy birds from contracting the disease. Else, the disease can be spread by other contaminated birds, mosquitoes and can also be contracted from the air.


– Symptoms: Just like humans, your chickens can get a cold, and it’s just as contagious. If your flock becomes infected, you’ll notice that egg production will drop, the consumption of food and water will decline, there may be a discharge from the birds’ eyes and nostrils, and you may notice labored breathing from your birds.

– How to Treat: Unfortunately, there’s not much that can be done for bronchitis. You can give your birds antibiotics for a few days to make sure no other infections happen while they’re sick, but otherwise you just have to wait it out.

– How to Prevent: Like fowl pox, there are a few types of preventative vaccinations against infectious bronchitis, but it’s not a guarantee. Having a good biosecurity method in place, as well as adequate rodent control should help keep the disease to a minimum.


– Cause: The disease is caused by a bacterium known as Hemophilus gallinarum. Outbreaks usually result from the introduction of infected or carrier birds into a flock. It can also be contracted through contaminated water and contaminated surfaces.

– Symptoms: Heads become swollen. Their eyes will literally swell shut and their combs will swell. Then a discharge will begin to flow from their eyes and noses. They will stop laying and will have moisture under their wings.

– Prevention and Treatment: There is no vaccine to stop this disease, unfortunately. Once your chickens contract this disease they should be killed and buried or burnt. If not, they will remain a carrier of the disease for life which is a risk to the rest of your flock. Keep your chickens protected from other random chickens and keep their coop and water clean to prevent the disease.


– Symptoms: This disease, also referred to as fowl paralysis, typically affects chickens between 12 and 25 weeks old. If your chick has developed tumors, has irregularly shaped pupils (typically results in blindness), or develops partial paralysis, it’s likely that they have Marek’s Disease.

– How to Treat: Since this poultry disease is a form of avian cancer, there is unfortunately not much that can be done for infected chicks. It’s also contagious since it’s a virus and is transmitted when a chicken breathes in feather dander from another infected bird. If the bird survives, it will remain a carrier of the disease for life, so it’s best to remove it from the flock early.

– How to Prevent: While this disease sounds scary, there are vaccines available. Newly hatched birds can be vaccinated for Marek’s disease to help reduce the likelihood of infection.


– Symptoms: As a respiratory disease, symptoms of Newcastle (ND) tend to appear through breathing difficulties, nasal discharge, murky eyes, and a reduction in egg laying. Sometimes birds can experience twisting in their neck and paralysis in their legs and wings. There are varying strains of this poultry disease, some of which are more lethal than others.

– How to Treat: Birds will typically recover from ND and not be carriers, but if your chicks develop the disease, they will likely not survive. As with other diseases, you can give your birds antibiotics for a few days to avoid any other bacterial infections.

– How to Prevent: Since the disease is carried by wild birds, keeping your flock vaccinated is very important. It’s also recommended to practice good sanitation since a person can infect other birds via clothing or shoes.


– Symptoms: When your chicken has loose droppings, it’s likely they have coccidiosis, a parasite that damages the gut wall of chickens. In addition to loose droppings, you may also notice bloody or watery diarrhea, weight loss, and ruffled feathers in your chickens.

– How to Treat: Since there are six species of Eimeria (the coccidiosis parasite), your bird may become immune to one kind, but contract another. You can treat this with antibiotics or other specific types of medication that will get rid of the parasite.

– How to Prevent: Keeping food areas, brooders, and coops clean and dry will help avoid the spread of coccidiosis. Using medicated starter feed for your unvaccinated chicks, or adding probiotic supplements to their food, is another way to help control this poultry disease.


– Cause: Clostridium colinum, a spore-forming bacterial rod is the cause of the disease. The infection spreads by the droppings from sick or carrier birds to healthy birds. The disease organism is very resistant to disinfectants and will persist under varying environmental conditions.

– Symptoms: Birds with the acute form may die suddenly while in good flesh, whereas more chronically affected birds become listless, have ruffled feathers, whitish watery diarrhoea, and develop a humped-up posture. Infected birds usually die in an extremely emaciated condition.

– Prevention and Treatment: Seek professional advice if you suspect infection. Bacitracin and penicillin are the most effective drugs in the treatment and prevention of this disease. If bacitracin is used, incorporate in the feed at levels up to 200 grams per ton of feed. Addition of bacitracin to the water at the rate of one teaspoon per gallon aids in controlling an outbreak of the disease. Either method of administering bacitracin will control the disease within two weeks unless a bacitracin-resistant strain of the disease organism is present. Penicillin is also used to treat the disease if bacitracin is not effective.


– Cause: It is a disease caused by the ingestion of a toxin produced by the Clostridium botulinum bacterium. All domestic fowl and most wild birds are susceptible to the toxin’s effects. If your chickens have contracted this disease it means that there has been some type of dead meat left near their food and water which contaminated it.

– Symptoms: Chickens begin to have progressing tremors. The tremors will progress into total body paralysis which includes their breathing. You will also notice their feathers will be easy to pull out and death usually occurs within a few hours.

– Prevention and Treatment: There is an antitoxin that can be acquired from a vet. If you notice the disease early enough you can mix 1 teaspoon of Epsom salts with 30mils of warm water. Administer to the birds by dropper once daily. This disease is avoidable as long as you keep your chickens in a clean environment and clean up any dead carcass from around their environment.


– Cause: The causative organism of fowl cholera is Pasteurella multocida. Fowl Cholera can be contracted from wild animals or food and water that has been contaminated by this bacteria.

– Symptoms: Birds begin to have a greenish or yellowish diarrhoea and obvious joint pain. They also struggle to breathe and have a darkened head or wattle.

– Prevention and Treatment: There is no real treatment. If by some chance your chicken survives, it will still always be a carrier of the disease. So it is usually better to put them down and destroy their carcass to prevent the spread. There is a vaccine, however, for your chickens to prevent the disease.


– Cause: It is a fungal disease caused by the yeast Candida albicans.

– Symptoms: A white oozy substance inside their crop. The chicken will appear lethargic and have a crusty vent area. And their feathers will look ruffled.It is important to mention that thrush is a fungal disease. This means it can be contracted if you allow your chickens to eat moulded feed or other moulded food. And they can also contract the disease from contaminated water or surfaces.

– Prevention and Treatment: Though there is no vaccine, it can be treated by an anti-fungal medicine that you can get from your local vet. Be sure to remove the bad food and clean their water container as well.


– Cause: This disease is acquired the chicken wound on the foot gets infected. The chicken may accidentally cut its foot on something; when digging in the garden, scratching around in mulch, and so many other ways.

– Symptoms: This infected wound swells up the leg.

– Prevention and Treatment: Bumblefoot can happen very easily and it is not much you can do to prevent besides just keep a close eye on your chickens’ feet. If you find out a cut on the foot, wash and disinfect it to prevent the disease from setting up.


– Cause: Also known as the bird flu, It was one of my initial fears of owning chickens because all you hear about on the news is how people get sick with bird flu from their chickens. However, after knowing the symptoms you’ll be able to put that fear to rest. You need to know how to act quickly if you are afraid your backyard birds have come in contact with it.

– Symptoms: The signs include respiratory troubles and birds will stop laying. They develop diarrhoea. There may be swelling in the chicken’s face and that their comb and wattle discoloured or turned blue. They may even develop dark red spots on their legs and combs.

– Prevention and Treatment: There is no vaccine and the chickens infected will always be carriers. Wild animals can even carry the disease from bird to bird. Once your birds get this disease, they need to be put down and the carcass burnt or buried. You need to sanitize all areas that the birds were, before introducing a new flock. Take great caution because this disease can make humans sick.