A chicken normally breathes with a closed beak. A chicken breathing with an open beak is either ill or under stress — perhaps from heat or anxiety. Respiratory diseases of chickens usually include additional signs, such as sneezing, coughing, wheezing, a runny nose, or sticky eyes.
Most respiratory infections are highly contagious. Some result from viruses, others from bacteria. Viruses and bacteria do not have the same treatments, so knowing the difference is important for the health of your flock. Here are six common respiratory diseases of chickens and what causes them.
Infectious bronchitis, caused by a type of coronavirus, is the most contagious disease of chickens. It starts suddenly and spreads rapidly. It results in coughing, sneezing, and rattling sounds in the throat. These signs may be obvious in older birds only at night, when they are on the roost.
This viral disease has no known cure. A vaccine is available, but works only against the strains it contains, and new strains keep developing. The only sure-fire way to get rid of infectious bronchitis is to remove the infected chickens, clean up, disinfect, and start over.
Laryngotracheitis (aka roup) is a highly contagious disease of the larynx and trachea. It results from a virus in the herpes family. It affects chickens of all ages, although illness tends to be more severe in mature chickens. In the United States most cases are mild.
The usual first sign is watery eyes, which may appear as tiny bubbles in the corner of the eye. The eyes may become swollen. The chicken may cough and sneeze, shake its head and stretch its neck while gulping for air. It may make moist respiratory sounds (gurgling, choking, rattling, whistling, or cawing). Because the bird has trouble breathing, it will be less active than usual.
Laryngotracheitis has no known treatment. Because survivors can infect other chickens, some states require culling. A vaccine is available for use where this disease is prevalent, where new chickens regularly come into an existing flock, and for exhibition chickens.
Chronic respiratory disease
Chronic respiratory disease (CRD) results from Mycoplasma gallisepticum bacteria. It is contagious, usually comes on slowly, and lasts a long time. This disease often follows an acute respiratory virus, such as infectious bronchitis. It primarily affects grown chickens, but rarely results in death. Chickens that recover usually are immune to further infection.
The first sign is weeping from one or both eyes, sometimes with minor swelling. But note that weepy eyes may also result from excessive dust, draftiness, or vitamin A deficiency.
CRD should clear up within a couple of days of treatment with erythromycin eye ointment (which, by law, requires a veterinary prescription). Left untreated, swelling increases around the eyes and they become foamy or sticky, and the chicken gasps for air. Other signs include nasal discharge with no odor, coughing, sneezing, and other respiratory sounds.
One of the most common bacterial diseases of backyard chickens is infectious coryza. This respiratory disease results from Haemophilus paragallinarum bacteria, and is particularly prevalent in California and the southeastern states. As chickens get older, they become more susceptible.
This disease can be difficult to recognize, because it resembles other respiratory diseases and often occurs in combination with them. The main signs are foul-smelling discharge from the nostrils; watery, sticky eyes; and swelling of the face. The characteristic putrid odor of the nasal discharge is a pretty good indication of coryza.
This infection spreads in respiratory droplets coughed or sneezed by infected birds. Survivors remain carriers, as may birds in the same flock that never develop any signs. Coryza therefore spreads by unknowingly bringing a carrier into a flock or to a swap meet or live bird sale.
Antibiotics, as prescribed by a veterinarian, will treat the signs but not eliminate the disease. A vaccine will prevent future outbreaks once coryza has been diagnosed.
Newcastle disease results from several strains of paramyxovirus that infect many bird species. The different paramyxovirus strains are either highly virulent (velogenic), moderately virulent (mesogenic), or mildly virulent (lentogenic). Most strains are either velogenic or lentogenic.
“Exotic Newcastle” refers to the velogenic strains as a group. It is one of the top two most devastating diseases of poultry, second only to highly pathogenic avian influenza, although the two diseases are quite similar. Fortunately velogenic forms are rare in the United States.
Lentogenic, or mild, Newcastle is quite common and not particularly serious. It can cause an infection that results in coughing, gasping, and rales, just like any other respiratory disease.
Chickens usually get better on their own with few, if any, deaths. Although a vaccine is available, there is no known treatment, other than keeping chickens warm and well fed while they recover.
Pox results from a poxvirus. It is not the same virus that causes chicken pox in humans.
In chickens, pox appears in two forms. Dry pox, the more common form, affects the skin, is usually temporary, and resolves on its own.
Wet pox is much more serious, even deadly. It typically affects mature chickens that inhale the virus from dust and dander. This respiratory disease causes yellowish curdlike bumps in the mouth and windpipe. They can accumulate until they affect the bird’s ability to breathe and swallow, causing suffocation or starvation.
Controlling this disease in pox-prone areas involves controlling mites and mosquitoes, along with annual vaccination. Exhibition chickens are also sometimes vaccinated.
For many respiratory diseases of chickens, carriers are major sources of infection. A carrier is an individual that looks healthy, even though its body harbors an infectious organism. The bird may have recovered from illness or may never have had any signs of illness. Respiratory diseases that develop carriers include chronic respiratory disease, infectious bronchitis, infectious coryza, and laryngotracheitis.
Carriers are dangerous for a backyard flock. They infect other chickens without much indication that they might be the source. A potential clue is that other chickens fall ill, while the carrier remains apparently healthy.
The older a chicken is, the more exposure it has to disease-causing organisms, and the more likely it is to be a carrier. Since growing and mature chickens accumulate levels of microbes to which chicks and young birds have not yet developed resistance, mixing together chickens of various ages from various sources is always a hazardous practice.
Sadly, eliminating many of these diseases requires destroying an entire flock, cleaning and disinfecting the facility, and leaving it vacant for a time before introducing new birds. That’s a scary enough reason to avoid respiratory diseases of chickens with careful management and good biosecurity.
And that’s today’s news from the Cackle Coop.
Gail Damerow is author of The Chicken Health Handbook, which includes details on the differences between look-alike diseases, and is the source of the above illustration of a chicken suffering from laryngotracheitis.