Infectious Poultry Diseases: A Quick Guide for Backyard and Farm Flocks

What are infectious poultry diseases?

Poultry—chickens, ducks, turkeys, and other birds—can be affected by diseases caused by bacteria, viruses, and fungi. These infections can spread quickly in flocks and affect animal health and farm livelihoods. Transmission happens through direct contact with infected birds, contaminated equipment, water, feed, or via wild birds and vectors.

Key pathogen types

• Viral diseases: avian influenza, Newcastle disease, infectious bronchitis, Marek's disease.
• Bacterial diseases: fowl cholera, pullorum disease.
• Other infections: fungal diseases and parasites can also influence flock health, though less common.

How diseases spread

• Direct contact between birds
• Contaminated equipment, clothing, vehicles
• Shared water or feed
• Contact with wild birds, pests, or contaminated premises

Common infectious diseases in poultry

Avian influenza

A highly contagious viral disease that can affect a wide range of birds. Signs range from sudden death and rapid drop in feed intake to respiratory symptoms and swelling of the head or wattles. In some regions, highly pathogenic strains trigger broader culling and strict movement controls. Biosecurity and vaccination decisions are guided by local authorities.

Newcastle disease

A contagious viral infection with respiratory and nervous system signs, reduced egg production, coughing, sneezing, and, in severe cases, twisted necks. Control relies on strict biosecurity and vaccination programs where permitted.

Marek's disease

A viral disease mainly affecting chickens, causing tumors and nerve signs. A vaccine is widely used, typically given to day-old chicks to reduce symptoms and mortality.

Fowl cholera

A bacterial disease that can cause sudden death and swelling. Good sanitation and vaccination can help prevent outbreaks, especially in free-range or multi-flock settings.

Infectious bronchitis

A coronavirus affecting the respiratory and reproductive tracts, leading to coughing and decreased egg production. Vaccines help reduce severity; management practices reduce spread.

Pullorum disease

A Salmonella infection primarily affecting chicks, often transmitted from parent stock. Eradication programs, sanitation, and careful broodstock management are common in commercial flocks; backyard flocks should seek veterinary guidance.

Signs and impacts

Common signs include sudden death, drooping wings, ruffled feathers, coughing or sneezing, nasal discharge, reduced growth, poor weight gain, and lower egg production. Outbreaks can cause significant economic losses for smallholders and farms through mortality, culling, and trade restrictions.

Prevention and biosecurity

On-farm practices:

• Limit visitors; wear clean clothes and boots; disinfect gear.
• Separate new or sick birds; quarantine introductions.
• Clean, disinfect, and manage water and feed sources; control pests.
• Maintain a clean coop, good ventilation, and dry litter.

Vaccination and testing:

• Follow a veterinarian-guided vaccination schedule appropriate for the region and species.
• Monitor flocks for unusual mortality or signs; conduct diagnostic testing when needed.

What to do if you suspect an outbreak

• Immediately isolate sick or dead birds from the rest of the flock.
• Restrict movement of birds, equipment, and people in and out of the area.
• Contact a local veterinarian, agricultural extension service, or animal health authority for guidance and reporting requirements.

Resources

Local veterinary services and agricultural authorities provide region-specific guidance on testing, vaccination, and reporting. If you keep poultry, establishing a relationship with a veterinarian or extension agent is a key step in preparedness.