Common Poultry Diseases

Small and Backyard Flocks June 13, 2013 Print Friendly and PDF

This article describes some of the common diseases that afflict poultry, as well as symptoms and indications of different types of disease. The article begins with some general information to help clarify terms commonly used in discussions of disease.

General Information 

Terminology Used

Common Signs of Illness in Poultry

Characteristics of Healthy Birds

In order to identify signs of diseases early, it is important to be familiar with the characteristics of a healthy bird. A healthy bird displays the following traits:

  • Erect stance with head and tail elevated
  • Bright red comb and wattles
  • Filled-out face parts
  • Bright and alert eyes
  • Clean nostrils
  • Smooth, neat, clean feathers
  • Filled-out legs
  • Joints that are smooth and cool to the touch
  • Weight that is typical for the type and age of the bird
  • Powerful movements when struggling
  • Scales on the legs and feet that are clean and waxy in appearance
  • Color of the skin that is characteristic for the breed and strain of bird, as well as the age and state of production 

In addition, a healthy bird eats and drinks frequently and displays no signs of respiratory distress.

Diseases of the respiratory system

Viral Infections

Bacterial Infections

Fungal Infections

Mycoplasmal Infections

Diseases of the Nervous System

Viral Infections

Bacterial Infections

Fungal Infections

Diseases Affecting the Intestinal System

Viral Infections

Bacterial Infections


Causes of Lameness

Viral Infections

Bacterial Infections

Nutritional Conditions

Mycoplasmal Infections

Mycoplasmas are bacteria that lack a cell wall.

Mycoplasma gallisepticum

Clinical signs of infection by Mycoplasma gallisepticum include the following:

  • Coughing
  • Sneezing
  • Shaking of the head
  • Rales
  • Gasping
  • Discharge from the eyes
  • Discharge from the nose
  • Swelling of the face and/or wattles
  • Retarded growth
  • General diarrhea
  • Prostration

Mycoplasma synoviae

Clinical signs of infection by Mycoplasma synoviae include the following:

  • Sneezing
  • Shaking of the head 
  • Rales
  • Discharge from the eyes
  • Discharge from the nose 
  • Swelling of the face and/or wattles
  • Retarded growth 
  • Lameness
  • Green, watery diarrhea
  • Swollen joints

Mycoplasma meleagridis

Clinical signs of infection by Mycoplasma meleagridis include the following:

  • Coughing
  • Sneezing 
  • Rales
  • Retarded growth
  • Twisting of the head and neck (torticollis)

Diseases Affecting the Skin

Viral Infection

Bacterial Infection


Disease Affecting the Immune System

Conditions Affecting the Reproduction System

There are multiple conditions that affect the avian reproductive system.

  • Egg-bound birds are unable to expel eggs in the usual manner.
  • Prolapse in poultry occurs when the oviduct of a female bird does not retract properly after the bird lays an egg.
  • Egg peritonitis occurs when eggs are not assembled properly in a bird, and egg material fills the abdominal cavity of the bird.

Metabolic Diseases and Conditions

Poultry can suffer from a number of diseases and conditions related to metabolism.

  • Sudden death syndrome (SDS), also known as flip-over disease, is characterized by the sudden death of birds that show no clinical signs of illness. SDS is believed to be a metabolic disease related to high carbohydrate intake.
  • Ascites, also known as"'water belly," is a disease in which fluid accumulates in a bird's abdominal cavity.
  • Green muscle disease, also called deep pectoral myopathy, is a degenerative muscle disease that affects the breast tenderloin (minor pectoral muscle) deep within the breast.

For More Information

Common poultry diseases. G.D. Butcher, J.P. Jacob, and F.B. Mather, University of Florida.

Common poultry diseases in small farm flocks in Oklahoma. Stanley Vanhooser, Oklahoma State University.

Common poultry diseases. Mississippi State University.

Avian disease fact sheet. Phil Clauer, Virginia Tech.

Common diseases of chickens, turkeys and gamebirds. Julie Helm, Clemson University.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.