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Infectious coryza is an acute respiratory disease of
chickens characterized by nasal discharge, sneezing, and swelling of the
face under the eyes. It is found 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 the northeastern USA has recently experienced
significant outbreaks. In developing countries, the disease often is
seen in very young chicks, even as young as 3 wk old. Poor biosecurity,
poor environment, and the stress of other diseases are likely reasons
why infectious coryza is more of a problem there. The disease has no
public health significance.
Etiology
The causative bacterium is Avibacterium paragallinarum,
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 Av paragallinarum have been recovered in South Africa and Mexico. The most commonly used serotyping scheme is the Page scheme, which groups Av paragallinarum isolates into three 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.
Infectious coryza, swollen sinuses, hen
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Lesions
In acute cases, lesions may be limited to the
infraorbital sinuses. There is a copious, tenacious, grayish, semifluid
exudate. As the disease becomes chronic or other pathogens become
involved, the sinus exudate may become consolidated and turn yellowish.
Other lesions may include conjunctivitis, tracheitis, bronchitis, and
airsacculitis, particularly if other pathogens are involved. The
histopathologic response of respiratory organs consists of
disintegration and hyperplasia of mucosal and glandular epithelia and
edema with infiltration of heterophils, macrophages, and mast cells.
Diagnosis
Isolation of a gram-negative, satellitic,
catalase-negative organism from chickens in a flock with a history of a
rapidly spreading coryza is diagnostic. The catalase test is essential,
because nonpathogenic hemophilic organisms, which are catalase-positive,
are present in both healthy and diseased chickens. A PCR test that can
be used on the live chicken and that has proved superior to culture,
even in developing countries, has been developed. A real-time version of
the PCR is also available. Production of typical signs after
inoculation with nasal exudate from infected into susceptible chickens
is also reliable diagnostically. No suitable serologic test exists; a
hemagglutination-inhibition test is the best of those available.
Swelling of the face and wattles must be differentiated from that seen
in fowl cholera (see Fowl Cholera).
Other diseases that must be considered are mycoplasmosis,
laryngotracheitis, Newcastle disease, infectious bronchitis, avian
influenza, swollen head syndrome (ornithobacterosis), and vitamin A
deficiency.
While currently found only in South Africa and Mexico, the presence of a V-factor–independent Av paragallinarum must also be considered. The Av paragallinarum PCR is an ideal diagnostic tool in this situation.
Control and Treatment
Prevention is the only sound method of control.
“All-in/all-out” farm programs with sound management and isolation
methods are the best way to avoid infectious coryza. Replacements 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 are available to help prevent and control
the disease. USDA-licensed bacterins are available, and bacterins also
are produced within states for intrastate use. Bacterins also 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 should be completed ~4 wk
before infectious coryza usually breaks out on the individual farm.
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
immunize layers in endemic areas.
Because early treatment is important, water medication
is recommended immediately until medicated feed is available.
Erythromycin and oxytetracycline are usually beneficial. Several
new-generation antibiotics (eg, fluoroquinolones, macrolides) are active
against infectious coryza. Various sulfonamides,
sulfonamide-trimethoprim, and other combinations have been successful.
Antibiotic use in chickens is subject to national regulations that vary
from country to country, and use and efficacy of the various antibiotics
must be reviewed in the light of the relevant national regulations. 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 started pullets are to be reared or housed on
infected premises.
Last full review/revision August 2014 by Patrick Joseph Blackall, BSc, PhD
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