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Having a sick chicken is stressful enough but knowing that their illness may affect you certainly adds to the pressure of chicken care. Although not all chicken diseases can cross the species barrier, they can cross not only to humans but also to other animals. Diseases that can affect multiple species are called zoonotic diseases. The risk of these diseases is why the CDC has recently asked backyard poultry owners not to snuggle or kiss their chickens. Because we all love our chickens and probably will not stop hugging and snuggling them anytime soon, the best way to prevent catching a zoonotic disease is to prevent it from affecting your chicken in the first place. 

Avian Influenza — Avian influenza varies highly in severity. Most strains are mild and cause upper respiratory symptoms in chickens. Most commercially-raised poultry in developed countries are free of this disease, but it can be present in backyard flocks and other domestic birds. In some cases, it transmits from migratory wild birds to domestic poultry. Mostly, it is transferred from farm to farm by poor biosecurity measures. Most strains are not transmissible to humans, but mutations occur on occasion that allow this transfer. Governments in developed countries work hard to catch and extinguish these infections quickly.

Campylobacter enteritis — Campylobacter is commonly found in the intestinal tract of poultry and does not usually cause disease to the bird. However, the most common way that humans contract enteritis (intestinal inflammation) is through consumption of undercooked poultry or just from handling infected backyard poultry. It is possible for some species of Campylobacter to be transmitted through eggs either on the surface or through eating undercooked eggs.

Escherichia coli — There are different strains of E. coli, and chickens can often live symptom-free with strains in their intestines that would make you extremely ill. Always wash your hands after handling your chickens, especially before preparing food, and practice good biosecurity measures to avoid bringing it to your coop. Avian pathogenic Escherichia coli can be devastating to a flock. When a chicken is sick with E. coli, it is referred to as Colibacillosis.

Because we all love our chickens and probably will not stop hugging and snuggling them anytime soon, the best way to prevent catching a zoonotic disease is to prevent it from affecting your chicken in the first place.

Erysipelas — Rodents can bring in this bacterium, as can feces from infected birds, contaminated food (particularly cannibalism), artificial insemination, and possibly biting insects. It is often confused with E. coli, Salmonella, or Newcastle infections. There are vaccines approved for turkeys and swine, but otherwise, prevention is best done with a closed flock kept away from rodents. Erysipelas can survive in the environment for a long time, even with most sanitizing methods. In humans, it can cause an acute skin infection or become septic with endocarditis.

Listeriosis — Listeria bacterium is commonly found in the environment, especially in animal feces or decaying vegetation. This is one of the reasons why we should not use our livestock as a garbage disposal for spoiled food. Corn silage that had been stored or preserved improperly is a common source of listeria poisoning in livestock, including chickens. It can then be transmitted to humans via contact with the chicken’s droppings either in the run or possibly on an egg, not fully cooking a contaminated egg, or improperly cooked poultry.

Newcastle Disease — Newcastle has low, medium, and high virulence strains. The low virulence strains are not problematic, but the high virulence strains are what most people mean when they refer to Newcastle Disease. While it is found worldwide, the United States and Canada have virtually eliminated it in domestic poultry and keep strict importing regulations to keep it out. However, it does still occasionally make its way to domestic poultry, often through the transport of exotic pet birds. In areas where Newcastle Disease is prevalent, vaccines are a great precaution. However, in the U.S. and Canada, the best way to keep it from your flock is to keep wild birds away from your chickens and practice good biosecurity measures such as not tracking chicken poop from another farm onto yours. Chickens may have respiratory symptoms as well as neurological symptoms. The virus sheds through the air they exhale, their droppings, eggs, and even their meat. In humans, Newcastle Disease can cause conjunctivitis (pink eye).

Ringworm — Also known as Favus, ringworm is a fungal disease that spreads very easily through direct or indirect (contaminated equipment) contact. On chickens, it presents as white, powdery spots on their wattles and comb, which progresses to thickened, crusty skin on their head. This is more prevalent in humid areas or if your chickens do not get much direct sunlight. It is hard to avoid ringworm entirely, so be watchful and treat immediately to prevent spread to not only the rest of your flock but also you.

Salmonella — There are many subtypes of Salmonella, and the ones that can make your chicken sick are not the same ones that can make you sick. However, your chicken can carry the ones that make you sick without any symptoms, which is why proper food handling is vital. 

Staphylococcus — Staph bacteria are typically introduced through a wound or compromised intestinal lining. The wound could be as simple as beak or toenail trimming. It can cause a local lesion or a systemic infection. Bumblefoot and omphalitis (mushy chick disease) are commonly seen as staph infections. Still, it can cause a large variety of different symptoms such as joint inflammation, bone death, or sudden death of the chicken. Be sure that instruments are sterilized for toe and beak trimming to prevent bacteria introduction. Keep the coop and run clear of wires, splinters, and other sharp objects that can cause injury. If you treat a chicken with bumblefoot or other staph infection, wear gloves and sanitize all equipment.

Conclusion

When protecting yourself from chicken diseases that affect humans, the best protection is preventing those diseases from coming into your flock. Good biosecurity includes quarantining new birds, preventing fecal contamination from other farms or flocks, keeping contact with wild birds or rodents to a minimum, good ventilation, and cleanliness in the coop, and sanitizing all equipment that comes into contact with your chickens. Even with great biosecurity measures, chickens may still harbor diseases that can make you sick. Always wash your hands after handling your chickens and cook poultry or eggs thoroughly. 

References

• Abdul-Aziz, T. (2019, August). Listeriosis in Poultry. Retrieved from Merck Veterinary Manual.
• Backyard Poultry. (2021, January). Retrieved from Centers for Disease Control and Prevention.
• El-Gazzar, M., & Sato, Y. (2020, January). Staphylococcosis in Poultry. Retrieved from Merck Veterinary Manual.
• Lee, M. D. (2019, July). Avian Campylobacter Infection. Retrieved from Merck Veterinary Manual.
• Miller, P. J. (2014, January). Newcastle Disease in Poultry. Retrieved from Merck Veterinary Manual.
• Nolan, L. K. (2019, December). Colibacillosis in Poultry. Retrieved from Merck Veterinary Manual.
• Sato, Y., & Wakenell, P. S. (2020, May). Common Infectious Diseases in Backyard Poultry. Retrieved from Merck Veterinary Manual.
• Swayne, D. E. (2020, November). Avian Influenza. Retrieved from Merck Veterinary Manual.
• Wakenell, P. S. (2020, April). Erysipelas in Poultry. Retrieved from Merck Veterinary Manual.

Originally published in the 2021 special issue of Backyard Poultry — A Natural and Sustainable Flock — and regularly vetted for accuracy.