Common Diseases of Pet and Backyard Chickens

Over the past several decades, chickens have become a popular bird to keep as both a pet and a supplier of fresh eggs. It is important that all chicken owner have a general understanding of what diseases affect chickens and, where possible, how they can be prevented.

Chicken diseases are quite different from diseases that affect other species of pet birds.

• Viral diseases that affect chickens are vastly different than those that affect pet parrots.
• Since most chickens are housed outdoors, they may suffer traumatic wounds from predators (e.g., foxes, coyotes, raccoons, dogs, hawks, weasels, ferrets, rats, or mice) or be bitten by insects that pass along Fowl Pox virus. 
• Improper ground coverage or perching material will often lead to sores on the undersides of the feet called bumblefoot. 
• Chickens are notorious for picking at shiny objects and so they are prone to ingesting objects that may contain lead or zinc, which in turn causes a “heavy metal toxicity”. 
• Like many pets that have exposure to outdoor ground surfaces, chickens may often succumb to intestinal parasites.

What viral diseases do chicken get?

The two most common diseases affecting chickens are Marek's disease virus and avian leukosis virus. 

Marek's disease virus is a type of herpes virus. Symptoms of Marek's disease in a bird may range from lameness due to infection involving the sciatic nerve, to reproductive tract tumors in female chickens, to tumors inside the abdominal cavity. Clinical signs of Marek's disease may include a fluid distension of the abdomen (referred to as “water belly”) or a firm swelling that many owners assume is egg binding but actually is a thickened, diseased oviduct that will require surgical attention to resolve. Most chickens affected by Marek's disease will be very thin and have a pale comb and/or wattles.

Avian leukosis virus, a retrovirus, is also referred to as lymphoid leukosis virus. This virus usually produces tumors in the abdominal organs (liver, spleen, reproductive tract), but also may just produce small nodules/tumors on the surfaces of many abdominal organs. Tumors in the bone marrow are common with the leukosis virus.

Both Marek's disease virus and avian leukosis virus are transmitted by contact from other infected birds. Not all infected birds are symptomatic (carrier status), making it difficult to separate visibly sick birds from non-affected birds. Leukosis virus may be transmitted through the egg by an infected hen.

Avian influenza virus and Newcastle disease virus can both be deadly for chickens and can both be highly contagious to other chickens nearby, as well as other types of birds in the vicinity.

All sudden death occurrences in chickens should be reported to your local veterinarian and a necropsy performed to rule out these two diseases.

What do I do if my chicken gets attacked?

Chickens often present to veterinary hospitals with a wide array of injuries from predators such as those mentioned above. With these injuries, there is generally exposed tissue, missing skin, and sometimes broken bones. Immediate attention by a veterinarian familiar with birds is essential for a positive outcome. 

Wound cleansing is essential to remove dirt and broken pieces of feathers stuck to exposed muscle tissue. Surgery may be required to suture exposed muscle and/or bone tissue. X-rays (radiographs) may be required to identify broken bones. Your veterinarian will most likely send your chicken home with antibiotics and anti-inflammatory medications to protect against infection and help with pain relief.

Is pox virus deadly for chickens?

Chickens affected by fowl pox have circular, crusty scabs on exposed skin surfaces around the head and feet. Pox virus is spread by biting flies and mosquitoes. Pox lesions on the head often involve the comb and/or wattles, but severe cases involve the corners of the mouth and eyelids, making it difficult for the chicken to see or eat. The wet form, also known as the diptheroid form, causes large plaques to form in the oral cavity, trachea, esophagus or crop. 

"Pox virus is spread by biting flies and mosquitoes."

As with chicken pox in humans – do not remove the scabs. Any damage or manipulation of the affected areas will cause the pox virus to spread to adjacent areas. There is no treatment for fowl pox. Good nutrition and prevention of the spread to other chickens is essential. The diptheroid form may be life threatening if the diseased tissue becomes infected with bacteria or the chicken has difficulty eating or seeing due to swelling caused by the pox lesions.

What causes Bumblefoot?

Bumblefoot is a well known disease that starts with inflammation of the foot pads on one or both feet and may advance to deep abscess formation within the foot pad(s). Bumblefoot lesions start in conditions where the bird is housed on hard ground/rocks/pebbles/cement or has improper perching surfaces in their roost. Perches/roosts should be made of smooth wood, tree branches, or soft rubber-like material. 

The process usually starts as a pressure sore that becomes inflamed and swollen, causing a certain degree of lameness. If the tissue gets damaged or the swelling forms a scab and the swollen tissue becomes infected, then an abscess forms that will require surgery to resolve.

How can I tell if my chicken has eaten a metal containing zinc or lead?

Any symptom that involves a neurological imbalance should raise concern that your chicken may have ingested a toxic metal. The common signs generally involve head tilt, wobbly gait, stumbling, unwillingness to move around or, in an advanced state, seizures.

Birds with these symptoms should receive immediate attention from a veterinarian. X-rays will be recommended to see if there is visual evidence of metal (washers, screws, wire, pieces of costume jewelry) in the ventriculus (gizzard). A blood sample must be sent to a reference lab for analysis to confirm that the metal seen on X-rays is toxic (lead or zinc). If the metal object seen on X-rays is the shape of a coin, testing for copper may be advised as well. Pennies made before 1982 were 92% copper.

What types of intestinal parasites can chickens get?

Chickens may be infected with a wide array of intestinal parasites: some they may get from their immediate flock or parents, and some they may acquire from contact with the ground, which has exposure to other fowl species and mammals that harbor intestinal parasites. Since all chickens tend to peck around their indoor and outdoor ground surfaces, exposure to feces from other birds is the main source of intestinal parasites. 

• Coccidia are microscopic parasites that are passed from one infected bird to another by fecal to oral transmission. Coccidia infect the cells of the intestine and can become a life-threatening disease if not treated promptly. 
• Ascarids (roundworms) and capillaria are common helminths (worm-like parasites) that cause illness in chickens. These parasites are acquired by contact with the ground/soil that is contaminated with eggs of the parasite that have been passed in fecal droppings. Both parasites cause lethargy, diarrhea, weight loss and, in severe cases, death. 
• Gapeworms are helminths that infect the trachea (windpipe) of chickens and other fowl species. It causes the chicken to cough, spit up mucus, and/or leave their mouth agape (open) to breath.

Microscopic examination of a fresh fecal sample by an avian veterinarian will help identify which type of parasite is present and in what numbers. Treatment depends on what parasite is present, how severe the infection is, and how many birds are exposed.