Chicken Diseases And Your Backyard Flock

Chicken Diseases And Your Backyard Flock

By Jen Pitino

With the rapid and seemingly unstoppable spread of avian influenza across the United States in 2015, the containment and control of this disease is at the forefront of most North American flock owners’ minds lately. Though avian influenza currently worries many backyard chicken keepers, there is a multitude of other dangerous and deadly diseases that could strike your flock. Your flock’s health should always be the top priority, not just when crisis strikes.


When it comes to raising healthy birds, an ounce of prevention is worth a pound of cure. Many common poultry diseases are lethal to the entire flock — in some cases from the disease and in others from a legal obligation to cull an entire flock upon detection. Stringent agricultural health requirements that demand the extermination of infected flocks are designed to stop the spread of uncontrollable or otherwise already eradicated diseases.

The best methods to keep your birds free of disease may be common knowledge to most flock owners, but might not always be common practice. Good nutrition, sanitary conditions in the coop and run, and conscientious practice of biosecurity measures will protect your birds from the majority of illnesses.

A well-balanced diet and clean water is the keystone to your flocks’ well-being. All living creatures are better able to naturally defend against disease when they have strong immune systems supported by nutritious food rich in essential vitamins and nutrients.

Many diseases thrive in dirty, soiled, wet conditions. Several common poultry maladies may be spread through contact with feces. Keeping your flock’s living space (coop and run) clean, dry and free from excess droppings is essential to disease control.

Most importantly, backyard poultry keepers must be regular and consistent about practicing biosecurity procedures. The most crucial biosecurity practices that every flock owner should practice are isolation and containment.

In the context of biosecurity, “isolation and containment” simply mean keeping your flock separate and protected from potential disease hosts and contaminants. Biosecurity is best accomplished by keeping your flock must take birds off your property (e.g. to a poultry show) or you are introducing new birds to your flock, then it is crucial that you quarantine those birds that have been off your property from the rest of your flock for a set period of time (at least three to four weeks) to ensure they do not carry any diseases. Additionally, isolate your birds from disease sources by vigilantly preventing contaminants from being introduced onto your land.

Contaminants such as dirt, feces and dander are easily picked up elsewhere and brought into your yard on your clothing or body, on the bottom of shoes, car tires or even on gardening tools, chicken cages, feeders, and water containers. Keep a separate pair of garden shoes that you only wear in your own yard — and don’t let other poultry owners onto your property with soiled shoes. Furthermore, wild birds may spread some diseases, such as Avian Influenza, making containment that much more necessary.


Respiratory disease in all varieties of poultry is a common, worldwide problem. Several factors can either predispose a backyard flock to respiratory disease or exacerbate the disease once infected. These include extreme temperatures and humidity, flock density, poor coop ventilation, high levels of ammonia (from soiled litter) or dust in the coop.

Chicken respiratory infections tend to be highly contagious. In some cases, the infection may be so mild that it is unnoticed by the owner or so severe that most or all of the infected birds die in a matter of a few days. Once infected, a bird (even after recovering with the aid of medication) may be a lifelong carrier of the disease and a constant threat to uninfected birds.

The following is a chart of symptoms for some of the most common respiratory diseases found in chickens and other varieties of backyard poultry. Each respiratory disease is briefly described and discussed thereafter.


This fungal infectious disease often grows in bedding and litter (e.g. peat moss, peanut hulls, straw, peat, bark, etc.) The disease is commonly called “Brooder Pneumonia” when a hatchery is the disease source.

Affected Species:All birds, including all domestic poultry varieties.

Symptoms:Infected birds will display respiratory distress such as gasping. Feed consumption will decrease typically. Discoloration of the skin to a bluish hue is common. Nervous disorders, such as twisted necks, convulsions, or paralysis may also occur. Mortality rates can be as high as 50% in younger birds.

Transmission: This disease is spread through the inhalation of fungal spores, rather than bird-to-bird transmission.

Prevention and Treatments: Prevention is crucial, there is no cure for this disease. Use of high quality, dry litter and feed in addition to proper coop/brooder hygiene will help avoid introduction of this disease to your flock. If contamination is found, remove all suspected sources of the fungus and thoroughly clean and disinfect the affected coop/brooder with a germicide, and add a fungistat to the feed.

Prevalence: This disease is found worldwide.

Avian Influenza

This viral respiratory disease is also commonly called “Bird Flu.” Some strains of this disease have been transmitted to humans.

Affected Species: In virtually all species of birds, including all domestic poultry varieties.

Symptoms: Avian Influenza can be either low pathogenic or highly pathogenic. Low pathogenic symptoms include inactiveness, decreased feed consumption, respiratory distress, diarrhea and a decrease in egg production. In highly pathogenic strains of Avian Influenza, symptoms can include facial swelling, blue discoloration of comb and wattles, diarrhea, dehydration, red/white spots on legs and comb and respiratory distress. Very high mortality rates (up to 100%) in flocks infected with highly pathogenic Avian Influenza.

Transmission: This disease can be transmitted from bird-to-bird, bird contact with infected feces, as well as through exposure to contaminated materials (e.g. shoes, clothing, equipment, etc.).

Prevention and Treatments: There is no effective treatment for Avian Influenza and agricultural regulatory bodies typically require the destruction of infected flocks. Consequently, prevention through biosecurity measures and good animal husbandry are essential.

Prevalence: This disease is found worldwide.


Infectious Coryza is an acute respiratory disease caused by bacteria. It is also called “Roup” and “Cold.”

Affected Species: Chickens primarily.

Symptoms: Infected birds commonly exhibit facial swelling, diarrhea, discharge from the nostrils and eyes (to the point that eyelids may become irritated and even stick together), labored and abnormal breathing (rattle sound). Mortality rates can be as high as 50%.

Transmission: Transmission is primarily bird-to-bird, but can also be spread through airborne droplets and contaminated drinking water and/or feed. Infected flocks are a constant threat to uninfected birds.

Prevention and Treatments: Antibacterial and antibiotic medications are available to treat affected birds.

Prevalence: This disease is found worldwide.

Fowl Pox

This viral “chicken pox” (different from “chicken pox” found in humans) is a slow spreading disease causing internal canker like lesions or external wart-like lesions.

Affected Species:Found mostly in poultry – chickens, turkeys, pheasants,  quail and ducks.

Symptoms: The dry form of this disease is characterized by raised, wart-like lesions on unfeathered areas (head, legs, vent, etc.) The wet form of the disease causes canker-like lesions in the mouth, pharynx, larynx, and trachea and may cause respiratory distress. Chickens may be affected with either or both forms of fowl pox at one time.

Transmission:This disease can be transmitted bird-to-bird or by mosquitos.

Prevention and Treatments: No treatment is available, but because the disease is slow-spreading, it is possible to vaccinate other members of your flock to control the outbreak.

Prevalence:This disease is found worldwide.

Infectious Bronchitis

This is an acute, highly contagious disease with high mortality rates.

Affected Species: Chickens only.

Symptoms:Infected chickens will chirp, have watery discharge from eyes and nostrils, labored breathing or gasping in young birds. Egg production dramatically drops and egg quality is quite poor with eggshells becoming misshaped, thin or rough.

Transmission: This disease is spread through the air, feed bags, infected dead birds, infected houses, and rodents.

Prevention and Treatments:There is no specific treatment for this disease. Prevention through biosecurity measures is crucial. Vaccinations are available, but not effective for all strains of this disease.

Prevalence: This disease is found worldwide.

Infectious Laryngotracheitis

Also called “Laryngo,” this acute, highly contagious herpesvirus infection, leaves recovered birds lifelong carriers of the disease and a source of infection to susceptible birds.

Affected Species: Chickens, pheasants, peafowl and turkeys.

Symptoms: Early symptoms usually include watery eyes. Infected birds become quiet due to difficulty breathing. As the disease progresses, common symptoms include coughing, sneezing, wheezing, gurgling, shaking of the head and stretching of the neck to facilitate breathing, and spitting up of bloody “plugs” from the swollen windpipe. Many birds die from asphyxiation when tracheas become blocked by freed plugs. Mortality rates can be as high as 70% in an infected flock.

Transmission: An airborne disease spread bird-to-bird. The disease can also be spread through contamination (e.g. clothing, shoes, tires, etc.)

Prevention and Treatments: Biosecurity measures are the best means in the prevention of this disease. Vaccination is available, but mass vaccination is not recommended for large operations. Affected coops and runs should be cleaned, disinfected and left empty for at least three weeks to eliminate active Infectious Laryngotracheitis virus. Incinerate all dead infected birds.

Prevalence: Found in most areas of the United States and in several other countries.

Mycoplasma Gallisepticum

Many backyard flocks carry Mycoplasma Gallisepticum. This respiratory disease often weakens the affected bird’s immune system making such birds susceptible to other diseases. Infected birds remain lifelong carriers of this disease and are a constant threat to susceptible birds.

Affected Species: Chickens, turkeys, pigeons, ducks and peafowl

Symptoms: Symptoms vary between species of birds. Chickens, if there are any visible symptoms, commonly display sticky discharge from their nostrils, foamy discharge in and around eyes, swollen sinuses, sneezing and abnormal breathing sounds (rattle).

Transmission: This disease may spread bird-to-bird and also to offspring through the egg. Contamination may also transmit this disease.

Prevention and Treatments: The disease can be controlled with the use of antibiotics, but not cured. Because infected birds remain carriers for life of the disease, eradication is often considered the best control method. Vigilant biosecurity measures are important for the prevention of this non-curable illness.

Prevalence: This disease is found worldwide.

Mycoplasma Synoviae

This disease has significantly decreased in the United States due to National Poultry Improvement Plan control programs implemented for chicken and turkey breeders.

Affected Species: Chickens and turkeys only.

Symptoms: Infected birds may display lameness, lethargy, swollen joints, stilted gait and respiratory distress. Weight loss and the formation of breast blister may also be signs of the disease. Severely infected birds commonly suffer from greenish diarrhea.

Transmission: This disease is transmitted bird-to-bird and through airborne transmission. Embryos may be infected via the egg by infected breeders.

Prevention and Treatments: Several antibiotics are effective, though recovery is slow. Eradication of infected flocks is considered the best and surest method to control this disease.

Prevalence: This disease is found worldwide.


In addition to the many respiratory diseases that can afflict a backyard flock, there are many non-respiratory diseases just as virulent and lethal to your birds. The following chart lists symptoms for some of the most common nonrespiratory poultry diseases, particularly for chickens. A brief description of each of these non-respiratory diseases is also provided below.


The ingestion of microscopic protozoa (called “Coccidia”) causes this illness. There are eleven species of Coccidia of varying virulence which affect chickens. Virtually all poultry carry at least some Coccidia. The amount of ingested oocysts (the spore stage of Coccidia lifecycle found in the earth) coupled with the severity of the particular Coccidia strain contracted will determine whether the bird simply is an unwitting host or succumbs to this disease.

Affected Species: Chickens, Turkeys, Ducks, Geese, pheasants and wild birds.

Symptoms: The most common symptom of this illness is bloody diarrhea. Decreased feed and water consumption, droopiness, lethargy, weight loss, and decreased egg production are other common signs of Coccidiosis.

Transmission: Coccidiosis can be spread bird-to-bird, through contact with feces and also through contamination.

Prevention and Treatments: Newly born chicks can be vaccinated for this disease or fed medicated chick feed (treated with a coccidiostat) for the first four months of their lives to prevent this illness. However, it is crucial to not use both vaccine and medicated feed as this will negate the any protection . Additionally, biosecurity is important as oocysts contamination is easy and can introduce a different strain of Coccidiosis that your flock is not immune to. Prevalence: This disease is found worldwide.

Fowl Cholera

This contagious, bacterial disease affects wild and domesticated birds worldwide. Fowl Cholera usually has a sudden onset with high mortality rates in the infected. Affected Species: Primarily chickens and turkeys, though all species of domesticated fowl may be affected.

Symptoms: The outbreak of this disease is quite acute and dead birds may be the first sign of infection. Other symptoms of Fowl Cholera may include fever, discharge from mouth, ruffled feathers, diarrhea, labored breathing, and reduced feed consumption. If the disease progresses (without killing the infected) additional symptoms commonly exhibited include weight loss, lameness, abnormal breathing sounds (rattle) are commonly seen as well as abscessed wattles, and swollen joints and foot pads in chronic cases.

Transmission: Bird-to-bird (within the flock and with wild birds), contact with infected animals of other species (e.g. rodents, etc.) as well as through contamination.

Prevention and Treatments: Vigilant biosecurity measures and rodent control are important to preventing outbreaks of this disease. Sulfa drugs, vaccinations or both can be used to stop the mortality associated with an outbreak of this disease. Antibiotics can also be used, though this treatment requires higher levels and long term medication use to stop the outbreak.

Prevalence: This disease is found worldwide.

Infectious Bursal Disease

This highly contagious disease, which is also called “Gumboro,” was first discovered in Gumboro, Delaware in 1962. Very young chicks are particularly susceptible to this disease and the results of infection are highly dependent on the age and breed of chicken as well as the virulence of the viral strain.

Affected Species: Chickens

Symptoms: Rapid onset of this disease is typical with a sudden drop in feed and water consumption as well as listlessness, ruffled feathers, watery droppings and soiling of feathers surrounding the vent and infected chicks may sit in a hunched position.

Transmission: This virus may be spread through the air by dust particles, through bird-to-bird contact, feces and also through contamination (clothing, shoes, tires, equipment, etc.). Dead birds should be incinerated.

Prevention and Treatments: Vigilant biosecurity measures are crucial to the prevention of this disease as there are no specific treatments for it other than vaccination. Medications (e.g. antibiotics, etc.) have little to no effect.

Prevalence: This disease is found in domestic chickens worldwide.

Lymphoid Leukosis

Chickens infected with this virus become carriers for life of the disease.

Affected Species: Primarily Chickens.

Symptoms: This virus has a long incubation period and is typically not noticed until birds are 16 weeks or older. Infected birds will suffer internal lesions and tumor. External symptoms include progressive weakness and more emaciation. Combs will become smaller and abdomens become enlarged. Birds dying from this disease will suffer greenish diarrhea in the terminal stages of this disease.

Transmission: This virus may be spread through bird-to-bird contact, to offspring through the egg and also through contamination.

Prevention and Treatments: There are no treatments for this disease. Consequently, vigilant biosecurity measures are crucial to prevent introducing this virus to a flock. Eradication of infected birds is considered the most effective control for this disease.

Prevalence: This disease is found worldwide.

Marek’s Disease

This deadly alphaherpesvirus contagion is considered one of the most widespread avian diseases worldwide — it is found in virtually every flock, everywhere.

Affected Species: Primarily chickens, though also found in turkeys.

Symptoms: This disease is a type of avian cancer. If not vaccinated, infected chickens can develop tumors in nerves and vital internal organs causing lameness, loss of coordination, labored breathing, blindness and paralysis. In terminal stages of the disease, affected birds become emaciated, experience greenish diarrhea and develop pale and scaly combs.

Transmission: This highly contagious disease is transmitted through the air, by feather dander and litter dust as well as by feces and saliva.

Prevention and Treatments: There is no treatment for this disease, though the vaccination for newly hatched chicks will prevent tumor formation though the bird will remain infected. Infected birds are lifelong carriers of the virus and thus a constant threat to susceptible birds.

Prevalence: This disease is found worldwide.


Though this is not an exhaustive list of all common poultry diseases milling around in the world, it is also not a reason to be deterred from starting your own backyard flock. Proper, conscientious animal husbandry and straightforward biosecurity practices are generally sufficient protection for the average backyard flock keeper to raise healthy and happy birds.


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8. Jackson, Richard. “The Chicken Vet Talks about Respiratory Disease in Chickens.” Poultry Keeper RSS. problems/respiratory-disease-in-chickens.

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