Infectious coryza is an acute respiratory disease of chickens caused by Avibacterium paragallinarum. Clinical signs include decreased activity, nasal discharge, sneezing, and facial swelling. Presumptive diagnosis is based on typical clinical signs in susceptible chickens. Diagnosis is confirmed by PCR assay or bacterial culture. Early antimicrobial treatment can help infected birds recover. Prevention is based on sound management practices, including appropriate biosecurity measures and vaccination with serovars present in the local population.
Infectious coryza is an acute respiratory disease of chickens that is characterized by decreased activity, nasal discharge, sneezing, and facial swelling. It occurs worldwide. The disease apparently affects only chickens; reports in quail and pheasants likely describe a similar disease caused by a different bacterium.
In countries such as the US, infectious coryza occurs primarily in pullets and laying hens, and occasionally in broilers. It is most prevalent in commercial flocks in California and the Southeast; however, flocks in the Northeast have experienced notable outbreaks.
In resource-limited countries, infectious coryza is widespread and occurs typically in adult chickens; however, it has been reported in very young chicks (eg, 3 weeks old).
Inadequate biosecurity practices and environmental factors can contribute to the prevalence of this disease.
Infectious coryza is not a zoonotic disease.
Etiology of Infectious Coryza
The causative bacterium of infectious coryza is Avibacterium paragallinarum, a gram-negative, pleomorphic, nonmotile, catalase-negative, microaerophilic rod (see photomicrograph) that requires nicotinamide adenine dinucleotide (V factor) for culture.
Courtesy of Dr. E. Soriano-Vargas.
When A paragallinarum is cultured on blood agar with a staphylococcal nurse colony that excretes V factor, the satellite colonies appear as dewdrop shapes, growing adjacent to the nurse colony (see culture image). V factor–independent A paragallinarum strains have been reported in South Africa and Mexico.
Courtesy of Dr. E. Soriano-Vargas.
The most commonly used serotyping scheme for A paragallinarum is the Page scheme, which groups isolates into three serovars (A, B, and C) that correlate with immunotype specificity.
Epidemiology and Transmission of Infectious Coryza
Birds chronically ill with infectious coryza or healthy carrier birds are the reservoirs of infection for A paragallinarum. Chickens of all ages are susceptible; however, susceptibility increases with age. The incubation period is 1–3 days, and the disease typically lasts 2–3 weeks. The duration of illness can be longer in the presence of concurrent diseases such as mycoplasmosis.
Flocks infected with infectious coryza are a constant threat to uninfected flocks. Transmission is by direct or indirect contact, airborne droplets, and contamination of drinking water. The disease is not transmitted via eggs.
All-in all-out management has essentially eradicated infectious coryza from many commercial broiler operations in the US. Such programs move all animals of the same age at the same time, and this flow allows birds in the same enclosures to be exposed to any given pathogens at the same time. Facilities are disinfected before a new group of animals is added. Commercial farms without such flow (eg, multiple-age layer flocks) can continue to experience outbreaks of the disease.
Molecular techniques such as quantitative real-time PCR (qPCR) assay, restriction endonuclease analysis, and ribotyping have been used to trace outbreaks of infectious coryza. In addition, new typing tools are being developed to predict the serotype from targeted gene sequencing.
Clinical Findings of Infectious Coryza
In the mildest form of infectious coryza, the only clinical signs may be listlessness, a serous nasal discharge, and occasionally, slight facial swelling. With increased severity, extreme swelling of one or both infraorbital sinuses with edema of the surrounding tissues can prevent the eyes from fully opening (see facial swelling image).
Courtesy of Dr. Mohamed El-Gazzar.
In adult birds, especially males, edema due to infectious coryza can extend to the intermandibular space and wattles. The swelling usually abates in 10–14 days; however, if secondary infection occurs, it can persist for months. The extent of rales depends on the extent of infection. In Argentina, a form of the disease involving bacteremia has been reported; it is likely due to concurrent infections.
Egg production can be delayed in young pullets with infectious coryza, and severely decreased in producing hens that are affected. Affected birds can have diarrhea, and feed and water consumption usually is decreased during acute stages of the disease.
Lesions
Acute cases of infectious coryza can involve only the infraorbital sinuses, which contain copious, grayish, semifluid exudate evident on gross inspection and during histological examination (see sinusitis image). With chronicity, this exudate can become consolidated.
Courtesy of Dr. Mohamed El-Gazzar.
Histopathological features of infectious coryza include edema, hyperplasia, and erosion of respiratory mucosal and glandular epithelia, as well as edema with infiltration by heterophils, macrophages, and mast cells. Other lesions can include conjunctivitis, tracheitis, bronchitis, and airsacculitis, particularly if other pathogens are involved.
Diagnosis of Infectious Coryza
Bacterial culture or PCR assay
Isolation of a gram-negative, satellitic, catalase-negative organism from chickens in a flock with history of a rapidly spreading disease is diagnostic for infectious coryza. A catalase-specific test is essential because nonpathogenic hemophilic organisms, which are catalase-positive, are present in both healthy and diseased chickens.
PCR testing of the infraorbital sinus in live flocks has been reported to provide more accurate results than bacterial culture does, including in countries with limited resources. A real-time version of the PCR assay is available.
The appearance of typical clinical signs of infectious coryza in susceptible chickens after they are inoculated with nasal exudate from infected chickens is also diagnostically reliable.
No suitable serological test exists for infectious coryza; although there is a hemagglutination inhibition test, it is not preferred over other methods.
The following are important differential diagnoses for infectious coryza:
avian metapneumovirus (swollen head syndrome)
Although currently found only in South Africa and Mexico, a V factor–independent serovar of A paragallinarum must also be considered as the cause of infectious coryza. The A paragallinarum PCR assay is an ideal diagnostic tool in this situation.
Control and Treatment of Infectious Coryza
Control: sound biosecurity practices and vaccination
Treatment: prompt antimicrobial treatment and supportive care
Prevention is the only sound method of control for infectious coryza. Sound farm management and biosecurity practices that include all-in all-out flow of animals are important disease prevention measures.
Replacement chickens should be raised on the same farm or obtained from clean flocks. If replacement pullets are to be placed on a farm that has a history of infectious coryza, bacterins/vaccines are available to help prevent and control the disease.
USDA-licensed commercially produced bacterins against infectious coryza are available, and bacterins also are produced within states for intrastate use. In addition, bacterins/vaccines are produced in many other countries. Because serovars A, B, and C are not cross-protective, it is essential that bacterins contain the serovars present in the target population.
Vaccination on individual farms should be completed between 10 and 20 weeks of age. Layers seem to be substantially protected by receiving two injections administered approximately 4 weeks apart before they are 20 weeks old. Antibodies detected by the hemagglutination inhibition test after bacterin administration do not necessarily correlate with protective immunity. Controlled exposure to live organisms also has been used to produce protective immunity in layers in endemic areas.
Because early treatment of infectious coryza is important, immediate administration of medication via drinking water is recommended until medicated feed is available.
Erythromycin and oxytetracycline are commonly used for treatment.
Various sulfonamides, including trimethoprim-sulfamethoxazole, and other drug combinations have been successful for treatment.
However, resistance to various antimicrobial classes has been documented in A paragallinarum isolates (1, 2). Furthermore, antimicrobial use in chickens is subject to national regulations that vary from country to country, and the use of antimicrobials must be reviewed in light of relevant laws. For instance, fluoroquinolones are prohibited from use in food production animals in the US.
In more severe infectious coryza outbreaks, even if treatment results in improvement, the disease can recur when medication is discontinued.
Preventive medication can be combined with a vaccination program if started pullets are to be reared or housed on infected premises.
Key Points
Infectious coryza is an upper respiratory disease of chickens that is caused by Avibacterium paragallinarum.
Diagnosis is based on bacterial culture or PCR assay.
Treatment is appropriate antimicrobials.
The main preventive strategies are all-in all-out management and sound biosecurity measures, combined with appropriate vaccination.
For More Information
Michigan State University Extension: Poultry Diseases: Infectious Coryza
PennState Extension: Avian Coryza
References
Fauziah I, Asmara W, Wahyuni AETH. Antimicrobial sensitivity of Avibacterium paragallinarum isolates from layers in the special region of Yogyakarta, Indonesia. Vet World. 2021;14(5):1124-1127. doi:10.14202/vetworld.2021.1124-1127
Cao X, Huang X, Lin Y, et al. Prevalence and genomic-based antimicrobial resistance analysis of Avibacterium paragallinarum isolates in Guangdong Province, China. Poult Sci. 2024;103(6):103751. doi:10.1016/j.psj.2024.103751
