Avian Coryza

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 particularly resistant bacterium. It is destroyed by most disinfectants, desiccation, and direct exposure to sun light. There are 3 serotypes of A. paragallinarum: A, B and C which is very important when immunizing the birds against this disease. Infectious Coryza does not present a zoonotic risk (the disease does not spread from birds to humans). In addition, human consumption of meat or eggs derived from birds contaminated with Avibacterium paragallinarum presents no risk for human health.

Clinical Signs

The most prominent clinical sign may be facial edema (swelling of the face) and conjunctivitis with nasal and ocular discharge. Wattles may also be inflamed, and the infraorbital sinuses may be distended with exudate. 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% 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 agents, such as Mycoplasma gallisepticum or E. coli

Occurrence

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 24-48 hours after experimental inoculation. Under field conditions, incubation may take an additional 24 hours. The uncomplicated disease usually runs its course in about 2 weeks.

Transmission

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. Exposure of naïve birds to 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

Isolation of the organism. This can be done by plating the samples on blood agar plates cross streaked with a Staphylococcus culture following overnight culture at 37C in anaerobiosis. Hemagglutination Inhibition and PCR are also available.

Differential Diagnosis

Coryza should be differentiated from other diseases like swollen head syndrome, fowlpox, and ornithobacterosis.

Treatment

A. paragallinarum is susceptible to several antibiotics which can be given in feed or water. Tetracyclines are commonly used for treatment.

Control

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 widespread 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 isolated from previous local outbreaks.  2 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.

References

Avian Diseases Manual 7^th edition; Diseases of poultry 13^th edition.

By Gino Lorenzoni, DVM, MS, PhD. Assistant professor, The Pennsylvania State University.

This project was supported by Agriculture and Food Research Initiative Competitive Grants (2015-68004-23132) from the USDA National Institute of Food and Agriculture