Infectious coryza (IC) is an acute upper respiratory disease of chickens caused by Avibacterium paragallinarum (previously referred to as Haemophilus paragallinarum). IC occurs worldwide. Within the United States, it is most prevalent in California and the Southeastern states.
IC usually begins abruptly, with all susceptible chickens showing signs of disease within 24-72 hours after exposure to infection. The typical symptoms are facial swelling and sinuses with a clear discharge progressively becoming foul-smelling and purulent. Roosters may have swollen wattles. There is marked conjunctivitis and lacrimation (tearing or watery eyes). Infected birds may have their eyes partially or completely closed due to the excessive eye discharge, making it difficult for them to see to eat, and drink. The disease course in uncomplicated cases of IC is usually 7-11 days. If the disease is complicated by concurrent infections it can persist for a month and longer.
Diagnosis of infectious coryza can be more complicated when it occurs alongside other pathogens.
Infectious Coryza Transmission
The main reservoirs of infection for A. paragallinarum are chronic or apparently healthy carrier birds. Once introduced into a flock, A. paragallinarum is spread rapidly via direct or indirect contact with infected birds, through ingestion of contaminated feed or water, and by aerosols. Susceptible birds exposed to infected birds may show signs of the disease within 24-72 hours. Chickens who have recovered can become carriers, shedding the bacteria when stressed.
Prevention/Treatments
Sound management practices and vaccination can help prevent infection
Prompt antimicrobial treatment with supportive care of infected birds to aid recovery
Prevention is the only sound method of control for infectious coryza. All-in/all-out flow of animals as part of sound farm management and biosecurity practices 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 are available, and bacterins also are produced within states for intrastate use. Bacterins/vaccines also are produced in many other countries. Because serovars A, B, and C are not cross-protective, bacterins must contain the serovars present in the target population.
Vaccination on individual farms should be completed ~4 weeks before infectious coryza outbreaks typically occur. 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 is important, immediate administration of medication via drinking water is recommended until medicated feed is available. Erythromycin and oxytetracycline are usually effective. Additionally, several newer-generation antimicrobials (eg, fluoroquinolones, macrolides) are active against infectious coryza. Various sulfonamides, including trimethoprim-sulfamethoxazole, and other drug combinations have been successful in treatment. Antimicrobial use in chickens is subject to national regulations that vary from country to country, and use and efficacy must be reviewed in light of relevant laws. In more severe outbreaks, although treatment may result in improvement, the disease may recur when medication is discontinued.
Preventive medication may be combined with a vaccination program if pullets are to be reared or housed on infected premises.
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