Chicken Diseases

Whether you are a farmer or a homeowner with backyard chickens, you know that chickens are loyal, intelligent, enjoyable to watch and efficient producers of eggs. Proper feeding and a regimen for disease control are necessary to keep your chickens in good health. There are a variety of diseases which affect chickens, all of which fall into one of four categories: metabolic/nutritional, infectious, parasitic and behavioral.

  1. Nutritional/Metabolic Diseases

    • Nutritional and metabolic diseases are the result of abnormal metabolic activity. They can be caused by poor nutrition, genetics or poor nutrient absorption. Included in this category are the following diseases:

      Fatty liver syndrome is characterized by rapid beak growth, obesity, black dots on the toenails and beak, abnormal coloration in the feathers, abnormal bleeding and an enlarged liver.

      Slipped tendon (also called perosis) is characterized by weakness and deformity in the legs.

      Cage layer fatigue and rickets are caused by nutritional imbalance or deficiencies (particularly of phosphorus, vitamin D3 and calcium). Both conditions are characterized by bowed legs and decreased ability to walk.

    Infectious Diseases

    • Infectious diseases are of particular concern since they are usually contagious and can sometimes be spread from chickens to other living things. This includes:

      Avian influenza is a virus which is very contagious and usually fatal in chickens. It is also known as virus H5N1 and is spread by contact with the emissions from infected chickens.

      Avian encephalomyelitis is another virus which affects the central nervous system. It is characterized by symptoms like tremors, loss of coordination and decreased egg production.

      Chicken anemia virus (also known as CAV) is a worldwide condition which affects the immune system, leaving the infected chicken more vulnerable to contracting additional illnesses. Symptoms include bleeding, sudden death, anorexia, depression and anemia.

    Parasitic Diseases

    • Parasites are organisms which attach (either internally or externally) on a host. Some of the parasitic diseases affecting chickens include:

      Coccidiosis is caused by a parasite which destroys its host's (the chicken) gastrointestinal tract (GI tract). This leads to diminished egg production and death.

      Cryptosporidiosis is caused by a parasite which can infect other species, including humans. Symptoms include respiratory disease and disease of the GI tract.

      Lice and mites are external parasites which can survive on the skin and/or feathers. Symptoms include change in feather condition, itching, nervousness and anemia.

      Toxoplasmosis infections are more common in backyard chickens than those raised commercially. Symptoms include decreased egg production, weight loss, diminished appetite, diarrhea, trembling, loss of coordination, twisted neck and blindness.

    Behavioral Diseases

    • Behavioral diseases like cannibalism often lead to the injury of both the chicken suffering from it and the other chickens living with it. A certain amount of pecking is normal. This condition is characterized by escalated pecking behavior and even to a point where chickens will peck one another to death. The behavior is a learned behavior and can spread throughout the flock.

    Considerations

    • There are other poultry diseases not listed here. If you are concerned about the health of your chicken or if you think your chicken may be suffering from a disease, talk to your veterinarian to get detailed advice.