27 Wednesday March 2019
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Overview of Infectious Coryza in PoultryInfectious coryza is an acute respiratory disease of chickens characterized by nasal discharge, sneezing, and swelling of the face under the eyes. It is distributed worldwide. The disease is seen only in chickens; reports of the disease in quail and pheasants probably describe a similar disease that is caused by a different etiologic agent.

In developed countries such as the USA, the disease is seen primarily in pullets and layers and occasionally in broilers. In the USA, it is most prevalent in commercial flocks in California and the southeast, although northeastern USA has experienced significant outbreaks. In developing countries, the disease often is seen in very young chicks, even as young as 3 wk of age. Poor biosecurity, poor environment, and the stress of other diseases are probably the main reasons why infectious coryza is more of a problem in developing countries. The disease has no public health significance.

Etiology

The causative bacterium, Avibacterium (Haemophilus) paragallinarum is a gram-negative, pleomorphic, nonmotile, catalase-negative, microaerophilic rod that requires nicotinamide adenine dinucleotide (V-factor) for in vitro growth. When grown on blood agar with a staphylococcal nurse colony that excretes the V-factor, the satellite colonies appear as dewdrops, growing adjacent to the nurse colony. V-factor-independent A paragallinarum have been recovered in South Africa and Mexico. The most commonly used serotyping scheme is the Page scheme, which groups A paragallinarum isolates into 3 serovars (A, B, and C) that correlate with immunotype specificity.

Epidemiology and Transmission

Chronically ill or healthy carrier birds are the reservoir of infection. Chickens of all ages are susceptible, but susceptibility increases with age. The incubation period is 1–3 days, and the disease duration is usually 2–3 wk. Under field conditions, the duration may be longer in the presence of concurrent diseases, eg, mycoplasmosis.

 Infected flocks are a constant threat to uninfected flocks. Transmission is by direct contact, airborne droplets, and contamination of drinking water. "All-in/all-out" management has essentially eradicated infectious coryza from many commercial poultry establishments in the USA. Commercial farms that have multiple-age flocks tend to perpetuate the disease. Egg transmission does not occur. Molecular techniques such as restriction endonuclease analysis and ribotyping have been used to trace outbreaks of infectious coryza.

Clinical Findings

In the mildest form of the disease, the only signs may be depression, a serous nasal discharge, and occasionally slight facial swelling. In the more severe form, there is severe swelling of one or both infraorbital sinuses with edema of the surrounding tissue, which may close one or both eyes. In adult birds, especially males, the edema may extend to the intermandibular space and wattles. The swelling usually abates in 10–14 days; however, if secondary infection occurs, swelling can persist for months. There may be varying degrees of rales depending on the extent of infection. In Argentina, a septicemic form of the disease has been reported, probably due to concurrent infections. Egg production may be delayed in young pullets and severely reduced in producing hens. Birds may have diarrhea, and feed and water consumption usually is decreased during acute stages of the disease.