Disease update: Infectious coryza (Poultry Diagnostics)
(Editor’s note: Daniel Bautista is a director for Lasher Laboratory at the University of Delaware.)
Avian Coryza is a re-emerging poultry respiratory disease of chickens, mostly pullets and layers, in the Northeast United States.
It is more commonly found in commercial layers and backyard flocks in California and the Southeast, although the northeastern United States has experienced significant outbreaks in the Northeast.
Infectious Coryza has been found recently in backyard chicken flocks in Delmarva.
Presently, it has not been detected in commercial broilers, thankfully. Chickens of all ages can get sick from coryza.
Poor biosecurity, stress due to poor environment and inclement weather, and coinfection with other diseases are likely reasons for the onset and spread of the disease.
Coryza has no public health significance.
Coryza is primarily transmitted by direct bird-to-bird contact.
In addition, birds can also catch the disease by breathing airborne bacteria and consuming contaminated feed and/or water.
The disease can also be introduced when infected birds are brought into the flock.
Birds that have recovered from the disease remain carriers of the organism and may occasionally shed the bacteria during their lives.
Birds risk exposure at poultry shows, bird swaps, and live-bird sales.
Outbreaks commonly result when infected birds that are not showing any signs of the illness are brought into a healthy flock.
Infectious Coryza is an acute respiratory infection of chickens caused by the Gram-negative, non-motile bacteria Avibacterium paragallinarum (formerly called Haemophilus paragallinarum).
A. paragallinarum is not a tough bacteria to neutralize. It is destroyed by common disinfectants, dry environment, and sunlight.
Infectious Coryza does not present a zoonotic risk (the disease does not spread from birds to humans).
In addition, eating meat or eggs from birds infected with Avibacterium paragallinarum does not pose a risk for humans.
The most prominent clinical sign in chickens may be swelling of the face and watery eyes with a distinct foul-smelling mucus discharge from eyes and nose.
Wattles may also be swollen, and the sinuses around the eyes may be filled with mucus and pus.
Sneezing and coughing are frequently present, which contributes to spreading the organism.
Feed intake is decreased and layers in active production will show a sharp decrease in egg production (from 10- to 40-percent reduction).
The morbidity (proportion of affected birds) is high and is not uncommon to observe most of the birds showing disease symptoms.
However, death loss is usually low unless the disease is complicated with other disease agents, such as Infectious Bronchitis, Mycoplasma gallisepticum or E. coli.
The disease can occur in birds of any age but is more common in mature birds especially when they are stressed.
It is not uncommon for layers to become infected shortly after relocation into new cages or around peak production.
The incubation period is short, about one to two days after experimental inoculation.
Under field conditions, may take an additional day before signs become apparent.
The disease usually runs its course in about two weeks if not made worse or prolonged by environmental stress and other ongoing bacterial and viral diseases.
Birds that have recovered from the disease can harbor the bacteria for a long time (or permanently) in the absence of any clinical sign (asymptomatic carriers).
For this reason, the disease can be difficult (or impossible) to eliminate in those facilities lacking an all-in all-out practice.
Traditionally, layers are kept in multiage complexes and infectious coryza can be a challenge when bringing young pullets that have never been exposed to the organism in the past.
Infection of clean birds by birds that have been infected previously is perhaps the most common mechanism for disease transmission in regions where infectious coryza is prevalent.
The organism can spread via inhalation from aerosols or be ingested from contaminated feed or water.
Equipment moved from one house into another may also transport infective bacteria.
Diagnosis can be confirmed by isolating Avibacterium paragallinarum on blood agar plates cross-streaked with a Staphylococcus culture following overnight culture at 37C in very low-oxygen environment.
Overgrowth of other competing bacteria like E. coli is very common, and makes bacterial culture of Avibacterium difficult.
Hemagglutination Inhibition and PCR is also available.
Rapid and accurate diagnosis is now available with PCR, enabling the DNA detection of this hard-to-grow bacteria that often undetected by normal bacterial culture
Coryza should be differentiated from other common chicken diseases like Infectious Bronchitis-E. coli respiratory disease complex, Mycoplasmosis/Chronic Respiratory Disease(MG), Swollen Head Syndrome caused by Avian Pneumovirus and E. coli, Fowl Cholera, Avian Influenza, and ORT. Coinfection with Coryza by these diseases influences the severity of infection and makes exact diagnosis in the field difficult.
Enlisting the help of poultry diagnostic labs in your area is highly recommended.
Because coryza is caused by bacteria, antibiotics can be used to treat a flock.
It is important to follow the labels on any medication.
Although antibiotics can be effective in reducing clinical signs of the disease, they do not eliminate the bacteria from carriers.
If the disease is not endemic in a given area for infectious coryza, depopulation may be used to decrease the likelihood of passing the disease to future flocks. If this is not an option, avoid bringing replacement birds into the same premises while sick or recovered birds are present.
After the affected flock is removed, clean and disinfect the premises and wait at least 3 weeks before repopulating.
If the disease becomes wide-spread in a region, there are commercial bacterins (a type of vaccine made with inactivated bacteria) available.
This vaccine must match the serotype of A. paragallinarum from previous local outbreaks.
Two doses of the vaccine should be given well before the onset of lay and several weeks before moving the birds into a high-risk location.
(Editor’s note: For references and further resources on this topic, visit: https://articles.extension.org/pages/68127/infectious-coryza-in-poultry; https://www.merckvetmanual.com/poultry/infectious-coryza/overview-of-infectious-coryza-in-chickens; and https://extension.psu.edu/avian-coryza.)
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