A primer on 19 common chicken diseases and treatments

Pet chickens, from left, 99, Fonzie, Hazel, and Cashew. Photo: Elizabeth Anderson Lopez With poultry becoming popular backyard pets, you may have clients also ask you about their chickens, when they come in with their dog or cat. While clinics may not be seeing poultry as their patients, it is not a bad idea to be at least familiar with the basics of poultry medicine and be able to provide some guidance about chickens or other poultry. The term, “poultry,” refers to domestic fowl and includes not only chickens, but ducks, geese, turkey, guinea fowl, quail, and pigeon. Knowing how to perform a basic physical exam, take vitals, recognize signs in a sick bird, and cover some of the most common diseases in poultry is useful to the veterinarian or veterinary technician. Since chickens are the most common backyard pet, we will focus predominantly on this species. Basic exam and restraint tips Chickens are obviously prey animals and will flee a potential threat. There is safety in numbers, and large flocks will huddle together. Handlers approaching will notice the flock will often move when the human gets too close to their flight zone. Slowly moving the flock to a catch pen or smaller area to corner the birds will allow the person to catch a chicken with the least amount of stress. Backyard chickens, on the other hand, are typically used to more human interaction and may be somewhat easier to catch. When catching chickens, using slow and steady movements while keeping noise to a minimum is also advantageous. Placing a light cloth over the head during the exam can also sometimes keep the bird calm. With the unique anatomy of chickens, care must be taken when handling these birds. Undue pressure on the chest or keel can cause respiratory compromise and stress in the bird. Poultry should be restrained by grasping both legs between fingers and supporting the body with wings held against the body. Symptoms of stress or overheating in poultry include reddened face, comb, and wattles, as well as open-mouth breathing and panting. Signs of respiratory distress will involve gasping, extension of the neck, and a cyanotic comb and wattle. If a bird is exhibiting any of these signs, it is best to cease restraining and let the animal rest. When performing a physical exam on poultry, they should ideally be evaluated from a distance initially and observed for general demeanor and appearance. If the bird is brought into the facility, this step may not be possible, but allowing it to move freely in the exam room and observe it casually can be helpful. When ready to conduct the physical exam in a clinic, the bird can be placed on an exam table covered with a towel. The bird should be bright and alert, and interactive with its environment. Abnormal behavior would present with isolation from the flock, poor appetite, and lethargy. After capture, the bird should be examined for general appearance. Gross lesions on the body or areas of missing feathers are problematic. Beginning at the head, the bird’s comb should be prominent and brightly colored. A flaccid and pale comb is a sign of a potentially anemic bird. The comb should also not have any scabbing. The eyes should be clear without discharge or reddening. The iris should be circular around the pupil and have a reddish copper color. A gray iris with abnormal borders around the pupil can possibly indicate Marek’s disease, which will be addressed. The nostrils and the beak should also be free of any discharge. The beak should be examined for any cracking or breaks. If the bird needs to have a swab to test for upper respiratory infections, the cleft in the hard palate, called the choanal cleft, is a recommended area to sample. Like other pets, chickens can be bribed and rewarded with treats, as Mr. Blonde proves. Photo: Elizabeth Anderson Lopez Moving down the body, the breast muscle should be palpated to determine body condition of the bird. If the bone beneath can be easily palpated, this can indicate a bird that is underweight. Blistering, redness, or feather loss along the breast area can also indicate an immobile sick bird. It is worth noting that chickens do have a molting period typically in the fall that lasts several weeks. During this time, they will lose feathers and have a decrease in egg production. Feathers all over the body should lay flat and smooth in appearance. The vent, which is the opening to the cloaca, should be examined and appear pink. The mucus membrane in this area can be used to determine capillary refill time (CRT), which should be less than two seconds. CRT can also be assessed on the comb. Soiling in this area can be the result of diarrhea and the vent can also indicate evidence of ectoparasites, such as lice or mites. Next, examine the wings by gently extending them and palpate for obvious fractures or injuries. Legs and feet should be bright yellow with smooth scales. Some breeds do have darker colored legs that are grey or olive in appearance. (Some breeds have gray or olive-colored legs. Pale or reddened legs can indicate disease. Disheveling of the scales can be a sign of scaley mites. Toes should be examined for string or wire, which can inhibit blood flow to the area, as well as swelling, which can indicate bumblefoot. Vital signs are not typically a routine portion of a physical exam in chickens; however, they can be measured if needed. Temperature can be measured by inserting a thermometer into the vent or cloaca. Respiratory rate can often be difficult to obtain and is usually easier to calculate if the bird is in respiratory distress, displaying open-beak breathing with tongue movements. The heart rate can be measured by listening with a stethoscope and counting the rate for 15 seconds and multiplying by four to get the per-minute count. Vital signs chart courtesy the author. Common poultry diseases Newcastle. Newcastle disease is a zoonotic viral disease affecting all types of birds. Humans will typically present with a mild conjunctivitis. Chickens’ clinical signs include a raspy chirp in chicks, as well as watery discharge from nostrils, dyspnea, swelling of the face, and limb paralysis. When the virus has affected the central nervous system, the chicken will present with a twisting of the neck. Adults will also show decreased food and water consumption, and decreased egg production. Since it is a viral disease, treatment involves mostly supportive care. Antibiotics can prevent secondary bacterial infections. Chicks will also benefit by raising the brooding temperature by 5 F. Since the virus is transmitted by aerosol and contaminated sources, good sanitation and biosecurity program, and vaccination can help with preventing outbreaks. Fowl pox. The virus that causes fowl pox can affect many species of birds. The virus is transmitted by mosquitos. There are two forms of the disease, and birds can be affected by both at the same time. Clinical signs of the dry form are wart or pox-like lesions on areas without feathers such as the legs, comb, and head. These will scab over and heal in about two weeks. The lesions heal in about two weeks. Chicks may also be affected and have poor growth and appear unkempt. Hens may show a decrease in egg production. With the wet form, the lesions form in the mouth, trachea, larynx and pharynx. The lesions can cause obstruction of the respiratory tracts. The disease is rather slow to spread, so a vaccination protocol can be established to prevent further outbreaks. A good mosquito eradication program should be implemented, as well. With the disease being viral, there is no other treatment besides supportive care. Infectious bronchitis. This extremely contagious viral disease affects all ages; however, the severity of the disease will depend on the age, presence of concurrent illnesses, environmental housing factors, and overall health of the bird. Typically, with all birds, inappetence and decrease in water consumption will occur, as well as dyspnea. In layers, egg production will decrease. Discharge from nostrils and eyes will also be present. The virus, which is airborne, as well as from contaminated fomites, can also be transmitted to the egg, which inevitably will not hatch. Antibiotics may be administered to prevent secondary bacterial infections and raising the brooding temperature by 5 F can help decrease losses. There is a vaccine available, and establishing a good biosecurity program can help prevent outbreaks. Avian influenza. AI can be classified as either mild or highly pathogenic. Clinical signs of the mild form include lethargy, poor appetite, respiratory issues, and diarrhea. The highly pathogenic form, however, causes severe dyspnea, facial swelling, cyanosis, and discoloration of the legs and combs. The virus can be spread easily from other infected birds, contaminated fomites, and insects. It can also thrive in the environment for a significant period of time. Administration of antibiotics to prevent secondary bacterial infections, along with supportive care, can reduce mortalities. Birds that recover can continue to spread the virus. There is a vaccine available. but must be administered with a special permit. Destruction of the entire exposed flock is recommended to prevent further spread, and any suspected case must be reported to state authorities. This chicken has an eye ulcer and swollen globe. Photo: Ann Wortinger Infectious coryza. This disease is caused by bacteria, Avibacterium paragallinarum. Clinical signs include swelling of the face, diarrhea, fetid discharge from nostrils and eyes, dyspnea, and rales heard during respiration. The disease is typically transmitted by direct contact, and infected birds that recover are carriers for life. Treatment includes antibiotics, but will not eliminate the bacteria in carrier birds. A vaccine is available and recommended at facilities that have had outbreaks. Infectious laryngotracheitis. LT (also called croup) is a highly contagious herpesvirus infection that presents initially with watery eyes. The virus causes a thick exudate that can block the trachea. Birds will shake heads, cough, and sneeze to try and force out the exudate. Birds can also be seen extending head and neck to open up airway in what is called “pump handle breathing.” Death from asphyxiation is common. Respiratory sounds may also be heard with gurgling or wheezing. A vaccine is available, and antibiotics may be given to prevent secondary bacterial infections. Birds that survive are also carriers for life. Aspergillosis. This fungal disease causes acute illness in young birds and chronic issues in older ones. Young birds will have severe dyspnea, as well as inappetence. Mature birds will also have dyspnea and cyanosis. When the toxin from the fungus affects the nervous system, the birds may have a twisted neck appearance or seizures. The fungus is commonly found in bedding and nesting materials. Having good ventilation and spraying bedding with an antifungal can help eliminate dispersement of fungal spores. Adding a fungistat to food or water for three days can help prevent spread. This fungus is also zoonotic and presents a risk to immunocompromised and geriatric poultry handlers. Marek’s disease. This virus causes systemic tumors in the chicken. Clinical signs will vary depending on the location of the tumors, but often the central nervous system, kidney, eyes liver, muscles, and skin are affected. Typical symptoms include inappetence, lethargy, unthriftiness, dyspnea, weight loss, and diarrhea. There is no treatment, and birds are immediately euthanized and the carcass is condemned. There is a vaccination to prevent tumor formation in chicks, but it will not prevent infection by the virus. Fowl cholera. This is caused by the bacteria, Pasteurella multocida. Clinical signs include diarrhea, dyspnea, inappetence, disheveled feathers, nasal discharge, and fever. As the disease progresses and becomes chronic, birds may be lame from infections in the joints and feet, as well as abscesses in the wattles and weight loss. Sulfa drugs are recommended for treatment in conjunction with a vaccine to stop the outbreak. Staphylococcus. This bacterial infection, also known as bumblefoot, causes three types of illness in the chicken. The septic form causes symptoms such as lethargy, inappetence, fever, diarrhea, swollen joints, and reluctance to move. The arthritic form appears after the septicemia and birds continue to be reluctant to move and also blistering of the breast due to continual sitting. The third form of bumblefoot occurs when the Staphylococcus bacteria causes a localized infection in the foot due to injury. The affected area will swell and the bird is lame. Treatment involves antibiotics that can be administered in the food or water for five days. A chicken with bumblefoot. Photo: Getty images Pullorum. Also known as bacillary white diarrhea, or BWD, is a bacterial disease caused by Salmonella pullorum. This diseases often presents as a high mortality of chicks and another wave of deaths about a week later. Clinical signs include diarrhea, dyspnea, white feces, lethargy, and pasted vent. Chicks that survive have stunted growth and are poor doers. They will also become asymptomatic carriers. The bacteria will become localized infection in the ovary and spread from hen to chick. Treatment can involve sulfonamides to reduce mortality, but will not eradicate the bacteria from the flock. Eradication of the entire infected and exposed flocks is required by law. Ectoparasites and their risks Scaley mite. Also known as Knemidokoptes mutans, this mite, as the name implies, burrows under the scales of the legs on the chicken. Severe cases can impact the blood flow to the feet and toes causing necrosis. Topical treatment of petroleum jelly or a safe oil-based topical will suffocate and kill the mites. As with other ectoparasites, treatment of the environment is vital in controlling the infestation. Birds that have legs deformed by mites should not be shown. Scaley mites can cause very visible damage; treating the bird and its environment is key. Photo: Ann Wortinger Red mite or Dermanyssus gallinae. This is an opportunistic ectoparasite that takes blood meals from chickens at night while they are roosting. These nocturnal mites will reside during the day in dark areas of the chicken’s housing unitm particularly in cracks and crevices. Severe infestations will result in anemia. Treatment involves not just application of an insecticide on the bird, but also strict application to all areas the bird resides in. Due to the lifecycle of the mite, retreatment must be completed every four to seven days. Northern fowl mite. Ornithonyssus sylviarum is one of the most common ectoparasites of chickens. This mite takes blood meals, and heavy infestations can cause severe anemia. The mites are very small and difficult to see with the naked eye. Signs of an infestation may include appearance of eggs or black spots of fecal material around the vent. All birds in the flock should be treated for mites. Topical insecticides approved for use in poultry will kill the mites but treatment should also include all areas the birds reside. Lice. There are two types of lice the afflict chickens. The chicken body louse or Menacanthus stramineus, and the shaft louse Menopon gallinae are the two most common. Poultry lice feed on dead skin, scales, and feathers. Birds will have damaged feathers and look unthrifty. Topical approved insecticides are recommended, as well as comprehensive treatment of the facility. Endoparasites and their signs Given that approved anthelmintics are limited in poultry, it is recommended to check the United States Food and Drug Administration (FDA) Approved Animal Drug Products list or appropriate drug reference. Round worms. Common roundworms include Ascaris sp, and Capillaria species. These worms typically affect the GI tract or trachea causing damage to their respective organs. Clinical signs of most roundworm infections include poor doer, lethargy, inappetence, and decrease in egg production. Cecal worms. Also known as Heterakis gallinarum, they do not usually cause clinical signs in their host, however, they carry a protozoa (Histomonas melegridis) that can cause disease in turkeys. It is recommended to treat the chickens for prevention if these species are housed together. Coccidia. Coccidia protozoa are parasites that cause diarrhea and malnutrition in the bird. Birds are most susceptible at a young age; immunity to the parasite develops as the bird ages. Clinical signs include watery to bloody diarrhea, lethargy, weight loss, and inappetence. There is a vaccine available that is administered to young chicks, and a good biosecurity program is recommended for prevention. Coccidiostats may be given, and medicated feed can also help develop immunity. Many people are finding the joy of raising poultry in their backyards for the purpose of being able to have fresh eggs or raising for meat purposes later on. With the potential for zoonotic or health hazards, being able to educate owners on things to watch out for and pitfalls to avoid, the veterinarian or veterinary technician can be a helpful advocate in this undertaking. Some veterinary staff may even decide to raise these amazing and fun birds in their own backyards! Jennifer Serling, CVT, RVT, VTES, BVSc, is a credentialed technician with more than 30 years of experience in both small and large animal practices. She has been a veterinary technician educator since 2007. She currently works for Appalachian State University as the assistant director of the Bachelors of Veterinary Technology program. Serling is a nationally known speaker as well as the author of several veterinary technology textbooks. She is the current president of the Association of Veterinary Technician Educators (AVTE). Serling resides in Tucson, Ariz., with her two boys: her cat and her favorite child, a golden retriever named Daffy. Resources 1. Animal Behavior and Restraint: Poultry. https://www.cfsph.iastate.edu/Emergency-Response/Just-in-Time/08-Animal-Behavior-Restraint-Poultry-HANDOUT.pdf 2. Serling, J. Large animal medicine and nursing for veterinary technicians. 2021. Minneapolis, MN: Bluedoor. 3. Performing a Physical Exam on a Chicken. Ohioline.osu.edu. https://ohioline.osu.edu/factsheet/vme-20 4. Internal Parasites of Poultry – Small and backyard poultry. https://poultry.extension.org/articles/poultry-health/internal-parasites-of-poultry/ 5. Physical Examination of Backyard Poultry. Exotic and Laboratory Animals. 6. Merck Veterinary Manual. Retrieved October 3, 2022. https://www.merckvetmanual.com/exotic-and-laboratory-animals/backyard-poultry/physical-examination-of-backyard-poultry 7. Common Infectious Diseases in Backyard Poultry. Exotic and Laboratory Animals. Merck Veterinary Manual. https://www.merckvetmanual.com/exotic-and-laboratory-animals/backyard-poultry/common-infectious-diseases-in-backyard-poultry 8. External Parasites of Poultry – Small and backyard poultry. Retrieved October 3, 2022. https://poultry.extension.org/articles/poultry-health/external-parasites-of-poultry/

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A primer on 19 common chicken diseases and treatments

A look at viruses, bacteria, ectoparasites, endoparasites, and other poultry ailments

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