Most Common Chicken Diseases and Symptoms

Chickens are perhaps on the lead when it comes to naming animals that are best to raise and keep. They are typically low maintenance, can be free-ranged, and offer several benefits. Aside from the amusement for their fun personalities and colorful plumage, they also are great garden helpers. Not to mention, their eggs are healthy breakfast staples, and their meat healthier than red ones.

However, along with the various joys of raising chickens are terrorizing diseases. In this article, the diseases are listed under three classifications: Infectious, Respiratory, and Miscellaneous. Infectious diseases include Avian Influenza, Botulism, Fowl Cholera, Fowl Pox, Marek’s Disease, Omphalitis, and Pullorum Disease. Conversely, Respiratory Diseases are Infectious Bronchitis, Infectious Coryza, Mycoplasmosis, and Newcastle Disease. Lastly, Miscellaneous Disease has Coccidiosis and Bumblefoot.

Some of the diseases mentioned are highly fatal and contagious, even to humans. Thus, it is extremely crucial that chicken-keepers – beginners, prospecting, and experts alike – have ample knowledge about them. Although some are not treatable, prevention measures can help significantly, and they are provided in this article.

Infectious Viral/Bacterial Diseases

Avian Influenza

Avian Influenza is as popular as bird flu. Often, the disease appears suddenly and, kills the birds rapidly.


The birds, if observed early on from exposure to the disease, will exhibit the following visible indicators:

  • Diarrhea
  • Lethargy
  • Poor egg production
  • Swollen and discolored (bluish) wattles
  • Swollen face
  • Discolored or bluish combs
  • Respiratory problems
  • Dark red spots on legs and combs


There is no sound treatment for Avian Influenza. Affected birds remain carriers of the disease. They will have to be put down, and their carcass destroyed. Intense cleaning and sanitation after handling an infected bird necessary.

To prevent infection in the flock, one should limit the chickens’ exposure to potential carriers like wild birds and waterfowl. Avoiding imported flock additions should also help decrease the chances of infection.


This condition is caused by the toxic byproduct of the growth of bacteria that thrive in soils. Botulism occurs once decayed carcasses or water that contains the toxin are consumed by insects which are ingested by chickens.


Generally, botulism causes the chickens to go weak, followed by the gradual flaccid paralysis of the wings, neck, and legs. The following are specific manifestations of the disease in the birds’ body parts:

  • Limberneck
  • Loose feathers
  • Dull, sleepy eyes
  • Mucous accumulation in the mouth
  • Trembling
  • Stupor


Should an outbreak occur, one must immediately find and remove the source of the toxin. Then, visibly affected flock members should be placed in a cool, shaded area. They should be given fresh water twice every day. Also, adding a teaspoon of Epsom salts in an ounce of water should be beneficial. Also, antitoxin therapy may be administered, but it is very expensive and difficult to obtain.

Other exposed birds that do not exhibit symptoms should be handled with mild laxatives. Their feed should be mixed with Epsom salts, one pound for every 100 birds.

Fowl Cholera

This disease is caused by the organism Pasteurella multocida, which thrives in decaying carcasses and in soil. Also, it reaches the birds by contaminated water supplies or mechanically, through contaminated shoes and farming equipment. The organism, as soon as it gains entry, enters the tissues of the mouth and upper respiratory tract. 

Chicken Diseases and Symptoms


Fowl Cholera is usually observed in chickens over four months old. It can manifest itself in whether peracute or acute form. The peracute form is one in which the birds die without showing symptoms. The acute form, on the other hand, has visible symptoms more often than not.

Symptoms include the following:

  • Stupor
  • Rapid weight loss
  • Appetite loss
  • Lameness
  • Swollen wattles
  • Difficulty in breathing
  • Yellow/green liquidy diarrhea
  • Cyanosis or bluish skin discoloration

Sometimes, lesions may be present that resemble those of acute septicemic bacterial infection like those of fowl typhoid. Typically, lesions include pinpointing hemorrhages in the abdominal fat, mucous, and serous membranes. Also, birds may have a light, firm, parboiled liver, and inflammation of the upper third of the small intestine. Their spleen are likely to be enlarged and congested, and the joints, to collect creamy or solid material. Those that have twisted necks may also have a cheesy material in their cranial air spaces and in their ears.


Affected birds may be treated with drugs to be added to their feed and water. Usually, sulfa drugs and antibiotics, penicillin, shall control the disease. However, should the treatment be discontinued, the disease is likely to occur again to the bird. Affected birds also remain carriers of the disease.

For prevention, administering bacterins could be helpful, along with a strict sanitation program. The following practices comprise a good sanitation program:

  • Annual complete depopulation with definite breaks between older and replacement flock members
  • Implementation of the rodent control program
  • Constant provision of fresh and clean water
  • Regular disinfection of equipment
  • Securing the birds from wild, feral animals
  • Emptying contaminated yard or range for about three months

Fowl Pox

Fowl Pox is a type of Avian Pox, a rather slow-spreading bird disease. Its transmission is by direct or indirect contact by biting insects or sometimes by fighting. The virus gains entry through scratches or scrapes. Moreover, as a slow-spreading disease, Fowl Pox can last for several months in a flock. Perhaps the slow onset is the reason why small pox is such a common chicken disease. However, its course on an individual affected bird is about three to five weeks.


Fowl Pox appears as either cutaneous or dry pox or as diphtheric or wet pox. Dry pox begins as small white or cream foci, which then develop into wart-like nodules. Then, the nodules are gradually sloughed and form scabs. The scabs are signs that a bird is due for recovery. Usually, lesions are found on the featherless parts of the body, such as the comb, wattles, and eyes.

Wet pox, on the other hand, is associated with the upper respiratory tract and the oral cavity. Lesions of this type severely involve the mucous membranes. When removed, the lesions will leave an ulcerated or eroded area.

Birds that are affected by Fowl Pox will have retarded growth and poor egg production. Those that are affected orally or in the respiratory system will have difficulty breathing and eating.


The only treatment for Fowl Pox is preventive vaccination. Sometimes, even good management and sanitation will not treat and prevent its emergence.

Furthermore, vaccination is only required if the flock has a history of the disease and when there is a high mosquito population. Chicks as young as a day old may be vaccinated using one needle applicator and through the wing-web method. Replacement chickens are vaccinated as well when they are six to ten weeks old. Usually, one Fowl Pox vaccination is good for permanent immunity. Recovered birds are also already permanently immune.

Marek’s Disease

This disease is highly contagious, caused by MDV or Marek’s Disease Virus. This causes enlargement of nerves and formation of tumor in nerves, organs, muscles, and epithelial tissues.

Chicken Diseases and Symptoms


Clinical signs for Marek’s Disease are the following:

  • Paralysis of the legs, wings, and neck
  • Weight loss
  • Grey iris 
  • Irregular pupil
  • Blindness
  • Raised and roughened skin around feather follicles


There is no sound treatment for Marek’s Disease. Hence, the best way to handle infection would be to prevent it from affecting the flock. Vaccination is a fundamental strategy for the prevention and control of the infectious virus.

Omphalitis or Mushy Chick

This disease is also called Navel Ill or Yolk Sac Infection. It is caused by mixed bacterial infections that include common coliforms and Staphylococcus, Streptococcus, and Proteus species. Usually, the disease is associated with poor incubation, sanitation, and temperature regulation in brooders. Luckily, it is not transmissible among birds but is transmissible through poultry equipment to young chicks with unhealed navels.


Affected chicks usually exhibit lesions which are poorly healed navels and subcutaneous edema. Also, the abdominal muscles around the navel have a bluish discoloration. Unabsorbed yolk material has a putrid smell. Yolks are also ruptured, and peritonitis is not uncommon. Unlucky chicks may not survive within 24 hours to 5 to 7 days.

Furthermore, mushy chicks manifest themselves through the following symptoms listed below. 

  • Droopiness
  • Poor performance
  • Lack in uniformity
  • Heat-seeking behavior
  • Feed and water indifference
  • Diarrhea 


A broad spectrum of antibiotics should help relieve the chances of mortality and stunting. However, prevention of the disease is better than treatment. This should include proper management and sanitation programs in the hatchery. 

Pullorum Disease

This disease is caused by the bacterium Salmonella pullorum. It is an acute, egg transmitted disease that enters the bird through the respiratory or digestive system. Mechanically, the disease can also be transmitted through poultry equipment, incubator, brooder, coop, clothing, and shoes.

Chicken Diseases and Symptoms


Pullorum Disease is especially fatal to young chicks. In fact, they may die as soon as they are hatched without any visible indicators. Other than death, the following are symptoms of infection:

  • Droopiness
  • Ruffled feathers
  • Heat-seeking behaviors
  • Difficulty in breathing
  • Bacillary white diarrhea
  • Gross lesions


Pullorum Disease can be treated with drugs such as sulfa drugs, furazolidone, and gentamicin sulfate. However, birds will remain carriers of the disease even with the treatment. Hence, they are best not kept for egg production.

Moreover, the only sound prevention of the disease is complete eradication. The flock should be tested for pullorum, and only those that are negative should be used for egg production. Also, it helps only to buy birds that are “Pullorum Clean,” recognized by the National Poultry Improvement Plan.

Respiratory Infections

Infectious Bronchitis

Infectious Bronchitis is a disease that gets transmitted through the air. Mechanically, it reaches the birds through clothing, poultry equipment, and crates. It is not transmitted through the eggs and is less likely to survive with the absence of poultry. It can be destroyed by regular disinfectants and heat.


The disease can last between ten and fourteen days in a flock with the following symptoms:

  • Difficulty in breathing
  • Gasping
  • Sneezing
  • Rales
  • Liquid nasal discharge
  • Loss of appetite
  • Retarded growth
  • Extremely poor production
  • Small, soft-shelled, irregularly shaped eggs


The only treatment for this disease is prevention. This includes keeping high brooder temperature for chicks and vaccinating prospected egg layers. Usually, the vaccine is added to the water, but it may be applied directly on the eye or nostril.

Infectious Coryza

Often, this disease affects semi-mature or adult chickens. It is caused by the bacterium Haemophilus gallinarum. The very common chicken disease spreads by direct contact with a carrier bird, through the air, or through contaminated water.


Symptoms for Infectious Coryza are visible as early as three days after exposure. These include the following:

  • Edematous swollen eyes and wattles
  • Swollen sinuses
  • Nasal discharge
  • Liquid eye discharge
  • Loss of appetite
  • Poor egg production


The disease can be treated with drugs. However, it does not get eliminated totally. Affected birds remain carriers for long periods.

To reduce the symptoms, sulfadimethoxine or sulfathiazole may be added in the feed or water. Erythromycin may also be administered in the drinking water.

For prevention, carrier birds should be separated from the flock. Chicken-keepers should also only ever introduce new birds that are obtained from known sources. Should there be an outbreak, complete depopulation may be necessary. A thorough cleaning or disinfecting shall follow.


Generally, Mycoplasmosis is a collective term for a variety of infectious diseases caused by mycoplasmas. These infectious diseases include Chronic Respiratory Disease (CRD), Air Sac Syndrome, and Infectious Sinusitis.

Chicken Diseases and Symptoms

Mycoplasmosis is egg transmitted. However, other than that, it can also be spread by direct contact with the carrier, through the air, and mechanically through poultry equipment.


Mycoplasmosis symptoms include, but are not limited to, the following:

  • Sneezing
  • Foamy discharge from nose and sometimes eyes
  • Clear, watery eye discharge
  • Coughing 
  • Raspy breathing
  • Swollen eyes 
  • Sinuses


All mycoplasmas can be eradicated by a broad spectrum of antibiotics. Vaccines for specific mycoplasmas are available as well. For prevention, good biosecurity, sunlight, and disinfection should be critical.

Newcastle Disease

This is a highly contagious common chicken disease that gets transmitted through the air within a relative distance. Also, it spreads by contaminated poultry equipment, clothing, and shoes. It lasts no longer than thirty days and can be totally eliminated.


Frequently, the symptoms of Newcastle disease are similar to those of other respiratory diseases such as the following:

  • Nasal discharge
  • Mucous accumulation in the trachea
  • Cloudy air sacs
  • Cloudy corneas
  • Casts or plugs in the lungs’ air passages

This common chicken disease is particularly bad in, young chicken that often exhibit difficulty in breathing, gasping, and sneezing for ten to fourteen days. Then, nervous disorders develop, including paralysis of wings and legs. Limber neck may also be visible as the head is drawn over the back or down between the legs.

Adult birds rarely develop nervous disorders. However, egg layers will have a rapid drop in egg production for about four weeks or longer. Eggs during this period are small, soft-shelled, irregularly shaped, and off-colored.


The only treatment for Newcastle Disease is prevention. This includes recommended vaccinations such as B1 and La Sota types. The vaccines may be applied directly into the nostrils or eyes or added to drinking water.

Seven to ten days old, chicks may already be vaccinated. Egg layers, on the other hand, are normally vaccinated at least thrice. This should be on their seventh day, fourth week, and the fourth month.

Miscellaneous Infections


This disease is caused by parasitic organisms, coccididal protozoan parasites of the phylum Apicomplexa. These organisms damage the intestines of the host, causing loss of production and even death.

Chicken Diseases and Symptoms


Common clinical signs of Coccidiosis include the following:

  • Bloody diarrhea 
  • Rapid weight loss 
  • Severe loss of egg production


Anticoccidial medication prescribed by the vet is effective in killing the parasites in the gut of the chickens. Also, vaccines are very common for prevention.

Bumble foot

Last in this list of common chicken diseases is bumble foot; a condition caused by the chickens’ constant digging and scratching in the garden or yard. They gain cuts out of the habits which are susceptible to infection.


A visible indication of bumblefoot is swelling of the foot. Sometimes, the infection even rises up to the leg, also causing it to swell.


Bumblefoot can easily be treated by performing surgery. Failure to do so might cause the infection to take over the infected chicken and possibly kill it. There is no sure prevention for bumblefoot, but it helps to wash, and disinfect observed cuts immediately.

Related Questions

Are humans safe from chicken diseases?

Some chicken disease may be contagious to humans; for instance, avian influenza or bird flu. Thus, it is very important that one is properly equipped when handling the affected bird. Many diseases can also be transmitted to humans by ingestion, respiration, and ingestion. Therefore, it is imperative that no one ever eats butchered, previously sick chickens. Dead animals should be disposed of by burying or by burning.

Do chickens develop behavioral diseases?

Chickens do develop a behavioral disease. Many people diagnose Cannibalism or aggressive pecking to some birds. Naturally, pecking is a result of investigative behaviors and of establishing social order. This then escalates to severe aggressiveness, which results in death. Potentially, the behavior may spread throughout the flock as a learned behavior. Extremely difficult to treat, cannibalism can be prevented by good husbandry, minimizing stressors, and properly regulating light and ventilation.

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Eni Gordove

is a freelance writer that covers several niches like digital marketing, book publishing and marketing, travel, home improvements, and backyard gardening and farming. Also, she's a strong advocate of eco-farming and home gardening.

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