Respiratory signs, diarrhea, lameness, and sudden changes in laying can have many causes. This guide introduces eleven important poultry diseases and conditions so you can recognize a problem and describe it accurately. It is not a way to diagnose a flock from one symptom or choose medication without examination.
First decide whether this is urgent
Sudden unexplained deaths, several sick birds, breathing difficulty, severe weakness, swelling or discoloration of the head, or neurological signs warrant prompt contact with a poultry veterinarian or animal-health authority. Stop moving birds or sharing equipment while you obtain advice. In the United States, USDA’s Defend the Flock guidance explains how to recognize and report suspicious illness.
1. Fowl pox
Dry pox can produce crusted lesions on unfeathered skin; wet pox involves lesions in the mouth or upper respiratory tract and can interfere with breathing or eating. It is a poultry viral disease, not human chickenpox. An apparently similar lesion can have another cause. Ask about diagnosis, supportive care, mosquito control, and whether vaccination fits the flock’s risk.
2. Coccidiosis
Coccidiosis is caused by Eimeria protozoa that damage the intestine. Young birds may become depressed, eat less, grow poorly, or pass abnormal droppings; blood is possible but is not present in every case. It needs an appropriate anticoccidial plan, not an assumption that a general wormer or antibiotic will fix it. MSD’s coccidiosis reference discusses diagnosis and control.
3. Fowl cholera
This is a bacterial disease caused by Pasteurella multocida. It can involve sudden deaths or more persistent signs such as swollen joints and wattles. Color of droppings is not a reliable diagnostic test. Treatment and flock-management decisions require veterinary guidance; do not assume that every affected bird must be treated or euthanized solely from a symptom list. See the veterinary overview of fowl cholera.
4. Avian influenza
Avian influenza is viral, and signs vary with the strain and birds affected. Respiratory, digestive, reproductive, and neurological changes or sudden death may occur. A suspected outbreak is an animal-health reporting issue, not a home-remedy project. Follow the authority’s instructions about testing, movement, handling, and protection; do not dispose of birds or resume movement based on an online checklist.
5. Infectious bronchitis
This contagious viral infection can cause respiratory signs and changes in egg production or quality. Some strains also affect the kidneys. Antibiotics do not cure the virus, although a vet may treat a secondary bacterial problem. MSD’s infectious-bronchitis reference distinguishes those issues. The sneezing guide covers useful observations before an examination.
6. Infectious coryza
Facial swelling, nasal discharge, and reduced laying can be associated with this bacterial disease, but overlap with other illnesses. Recovered birds may remain carriers. Veterinary treatment and biosecurity decisions matter; vaccination availability and usefulness depend on the situation. It is incorrect to say that no vaccine exists or that every case has the same outcome. See the infectious-coryza reference.
7. Marek’s disease
Marek’s is caused by a herpesvirus and can affect nerves, eyes, organs, and the immune system. Paralysis alone does not confirm it. There is no treatment that cures the infection; vaccination is preventive and does not make infected birds incapable of shedding virus. The Marek’s guide explains vaccination, diagnosis, and why a clean-looking coop is not sufficient protection.
8. Newcastle disease
Newcastle disease is viral, not bacterial. Signs can include respiratory trouble, abnormal droppings, neurological changes, and reduced laying, with severity depending on the virus and flock. Virulent Newcastle disease requires official investigation in many jurisdictions. Do not prescribe antibiotics as treatment for the virus or assume that a surviving bird is safe to move.
9. Botulism
Botulism results from toxin exposure and may cause progressive weakness or flaccid paralysis. Rotting material, carcasses, contaminated feed, and associated maggots can be involved. An affected bird needs urgent professional advice. Remove access to suspect material without exposing other animals; do not force Epsom-salt mixtures into a weak chicken.
10. Bumblefoot
Bumblefoot is inflammation and damage of the foot pad, sometimes with deep infection. Look for lameness, swelling, or a scab, but do not cut into the foot yourself. Address footing, litter, and pressure as well as the wound. The bumblefoot guide covers inspection and when veterinary care is needed.
11. Omphalitis, sometimes called mushy chick disease
An infected or poorly healed navel can be associated with weakness, abdominal changes, and early chick losses. Incubation hygiene and conditions matter, but an affected batch needs assessment rather than a promise that one drug cures every case. Keep records of hatch dates, incubator conditions, and losses; review incubation management and early chick care.
Build prevention around the flock, not a universal medicine list
Use a quarantine and introduction plan for incoming birds, protect feed and water from wild birds and rodents, clean equipment between groups, and keep age-appropriate records. Discuss vaccination with the hatchery and vet before chicks arrive. Follow separate guidance for external mites and internal worms rather than treating all parasites alike. Good care reduces risk, but it does not rule out infectious disease.
