Poultry diseases are a major concern for poultry farmers and the poultry industry as a whole. Diseases can cause high mortality rates in flocks, leading to significant economic losses. Maintaining flock health is crucial for sustainable poultry production. Here we will look at 13 of the most common poultry diseases that affect chickens, turkeys, and other domesticated birds.
1. Avian Influenza
Avian influenza (AI), commonly known as bird flu, is a contagious viral infection caused by influenza type A viruses. AI viruses can infect chickens, turkeys, pheasants, quail, ducks, geese, and guinea fowl. AI spreads quickly and has a high mortality rate in poultry flocks. The most highly pathogenic AI viruses, such as H5N1 and H7N9, cause severe clinical signs and death rates over 90% in just a few days. Lower pathogenicity viruses cause milder symptoms but can mutate into highly pathogenic strains.
Transmission occurs through direct contact with infected birds or contact with contaminated equipment and materials. Wild aquatic birds can also carry AI viruses without showing signs and spread it to domestic poultry. AI outbreaks have led to the culling of tens of millions of birds globally. There are no treatments for AI, so control relies on quarantine, disinfection, and preventing contact with wild birds.
2. Infectious Laryngotracheitis
Infectious laryngotracheitis (ILT) is a respiratory disease in chickens, pheasants, and peafowl caused by gallid herpesvirus 1. It is characterized by inflammation of the trachea, larynx, and upper respiratory tract. Infected birds develop coughing, sneezing, nasal discharge, and difficulty breathing. Severe cases lead to suffocation. ILT spreads via direct contact and inhalation of dust or dander carrying the virus. Outbreaks tend to occur when birds are confined together in high densities.
Mortality rate is low (less than 10%) but morbidity can be high. Recovered birds become lifelong carriers. ILT virus can survive for months in the environment. Biosecurity, vaccination, and isolation of infected birds are key control measures. There are several ILT vaccines available to help prevent outbreaks.
3. Infectious Bursal Disease (Gumboro)
Infectious bursal disease (IBD), also called Gumboro disease, is an acute, highly contagious viral infection of young chickens. The IBD virus targets developing B lymphocytes in the bursa of Fabricius, causing severe immunosuppression. Infections occur from 3-6 weeks of age. Chicks huddle, become lethargic and develop watery diarrhea. Mortality varies from 0-50% in susceptible flocks.
The IBD virus spreads through direct contact or exposure to contaminated equipment, shoes, clothing, and feed. Recovered birds remain lifelong carriers. Strict biosecurity and vaccination help control IBD. Inactivated and live attenuated vaccines are available. All replacement pullets and broilers should be vaccinated against IBD.
4. Marek’s Disease
Marek’s disease is a lymphoproliferative disease of domestic chickens caused by an oncogenic herpesvirus. It affects birds between 12-25 weeks of age. The virus targets lymphocytes, causing tumors in nerves, organs, and tissues throughout the body. Infected birds develop paralysis, weight loss, enlarged nerves, and irregular feathering. Mortality ranges from 10-70% in unvaccinated flocks.
Transmission occurs through direct contact between birds and through dander, dust, and feathers carrying the virus. It spreads rapidly through the air in poultry houses. All chickens are vaccinated against Marek’s disease at the hatchery. Biosecurity and ventilation control are also critical. There is no treatment once birds display symptoms.
5. Newcastle Disease
Newcastle disease (ND) is a contagious viral disease affecting the respiratory, nervous and digestive systems of birds. All species of birds are susceptible to infection, but it is most damaging in domestic poultry. Newcastle disease virus (NDV) causes coughing, sneezing, nasal discharge, and swelling around the eyes. GI signs like greenish, watery diarrhea are also common.
Highly virulent strains of NDV result in sudden death with nearly 100% mortality in unvaccinated flocks. Low virulent strains produce milder symptoms. The virus spreads through direct contact with bodily fluids or exposure to contaminated equipment, shoes, clothing, and feed. Vaccination, biosecurity, and rapid detection are key for controlling ND outbreaks.
6. Infectious Coryza
Infectious coryza is an acute upper respiratory disease of chickens caused by the bacterium Avibacterium paragallinarum. Signs include nasal discharge, facial swelling, and conjunctivitis. Infected chickens become anorexic and egg production drops sharply. Morbidity can reach 100%, although mortality is low (1-4%).
Infectious coryza spreads through direct contact and aerosol transmission. Recovered birds become lifelong carriers. Vaccines are available to help control the disease. Strict biosecurity, all-in/all-out production, and prompt treatment of outbreaks are recommended. Excellent sanitation and disinfection helps eliminate the bacteria from the premises.
7. Fowl Cholera
Fowl cholera is a bacterial disease caused by Pasteurella multocida that affects chickens, turkeys, and wild birds. In acute cases, birds develop severe respiratory distress and die rapidly from septicemia. Chronic cases result in localized infections in joints and internal organs. Morbidity varies from 10-100% with mortality of 10-80% in acute outbreaks.
Transmission occurs through contact with carrier birds or exposure to contaminated feed, water, litter, and equipment. Wild birds and rodents can introduce it to flocks. Strict biosecurity and sanitation are essential for prevention and control. Antibiotic treatment may help, but losses can be high once the disease breaks out. Commercial vaccines are available but efficacy is limited.
8. Infectious Bronchitis
Infectious bronchitis (IB) is a highly contagious respiratory disease of chickens caused by an influenza type A virus. Signs include coughing, sneezing, tracheal rales, and nasal discharge. In laying hens, IB also causes a temporary drop in egg production and poor egg quality. Morbidity approaches 100%, but mortality is low except in chicks.
The IB virus spreads rapidly via aerosol and dust. It can also spread on contaminated equipment, shoes, and clothing. All replacement pullets should be vaccinated against IB to prevent respiratory disease and egg production problems. Biosecurity and ventilation control are critical. There is no treatment for birds showing symptoms.
9. Mycoplasmosis
Mycoplasmosis refers to any respiratory disease caused by Mycoplasma bacteria such as M. gallisepticum and M. synoviae. Infected birds develop sinusitis, coughing, sneezing, and ocular and nasal discharge. In turkeys, the disease can spread systemically causing airsacculitis. Egg production and hatchability decline severely in affected breeder flocks.
Mycoplasma spread through direct contact between birds and via aerosols. Treatment with antibiotics may help contain outbreaks but does not clear the infection. Once birds are infected, they remain lifelong carriers. Control relies on maintaining Mycoplasma-free flocks through testing, biosecurity, eradication of positive flocks, and vaccination where necessary.
10. Necrotic Enteritis
Necrotic enteritis is an acute clostridial disease caused by Clostridium perfringens type A and type C. It affects broiler chickens aged 2-6 weeks, causing diarrhea, reduced growth rates and sudden death. Intestinal damage is the result of potent toxins releases by C. perfringens as it proliferates in the small intestine.
The C. perfringens bacterium is transmitted from bird to bird through the fecal-oral route. Disease outbreaks are often associated with predisposing factors like coccidiosis, feed changes, and overcrowding. Antibiotic treatment and vaccination help control outbreaks. Maintaining proper gut health is also key to prevention.
11. Ulcerative Enteritis
Ulcerative enteritis is a bacterial disease of chickens and turkeys caused by Clostridium colinum. The disease affects young birds 1-6 weeks old, causing watery diarrhea, weight loss, appetite loss, and increased mortality. Ulcers and inflammatory lesions develop in the small intestine resulting in reduced nutrient absorption.
C. colinum is transmitted through the fecal-oral route. Outbreaks are often associated with coccidiosis or dietary changes. The bacteria can persist in litter and housing between flocks. Antibiotic treatment may help control mortality. Strict biosecurity, competitive exclusion products, and litter management can help prevent ulcerative enteritis.
12. Pullorum Disease
Pullorum disease is a systemic infection of poultry caused by the bacterium Salmonella Pullorum. Signs include white diarrhea, anorexia, weakness, dehydration and high mortality in chicks and poults. In mature birds, decreased egg production may be the only sign.
S. pullorum is transmitted both vertically from infected breeders to eggs, as well as horizontally through contact with carrier birds. Sanitation, biosecurity and testing breeding flocks helps eliminate this disease. Commercial poultry breeding flocks are monitored closely and culled if found positive for S. pullorum.
13. Colibacillosis
Colibacillosis refers to a bacterial disease caused by avian pathogenic E. coli (APEC). It is characterized by systemic or localized infections leading to various signs: respiratory disease, swollen head syndrome, diarrhea, salpingitis, and mortality. Both broilers and layers are affected.
APEC is spread by the fecal-oral route or through contaminated dust and water. Inhalation of contaminated dust allows it to colonize the respiratory tract. Colibacillosis often occurs secondary to viral or mycoplasma infections that damage the immune system and mucosal barriers. Antibiotic therapy and improved hygiene help control problems.
Summary
Maintaining healthy, productive poultry flocks requires an understanding and vigilance against common diseases. Viral infections like avian influenza, Newcastle disease, and infectious bronchitis tend to spread rapidly and cause high morbidity. Bacterial diseases often lead to enteritis or systemic infections. Mycoplasmosis, in particular, has a severe long-term impact through declines in egg production.
Biosecurity, all-in/all-out production, vaccination, prompt treatment, and excellent sanitation are collectively vital for disease prevention. Testing breeders and isolating infected birds limits the spread and impact of contagious poultry diseases. By staying informed about diseases prevailing in the area, poultry producers can implement cost-effective, customized disease control programs.