Infectious Coryza in Chickens and Quail: Avibacterium paragallinarum Etiology, Clinical Signs, Treatment, and Prevention
Introduction
Infectious coryza is an acute to subacute upper respiratory disease of chickens and quail caused by the bacterium Avibacterium paragallinarum (formerly Haemophilus paragallinarum). The disease is characterized by serous to mucopurulent nasal discharge, facial edema, conjunctivitis, and a marked drop in egg production in laying flocks. Although mortality is generally low in uncomplicated cases, morbidity can approach 100 percent, leading to significant economic losses in commercial poultry operations. This article provides a detailed review of the etiology, clinical presentation, diagnostic methods, therapeutic options, and prevention strategies for infectious coryza, with specific attention to both chickens and quail.
Etiology and Taxonomy
Avibacterium paragallinarum is a Gram-negative, non-motile, pleomorphic coccobacillus belonging to the family Pasteurellaceae. The bacterium is fastidious, requiring nicotinamide adenine dinucleotide (NAD, also known as V factor) for in vitro growth. It does not require hemin (X factor), which distinguishes it from Avibacterium avium and other related species. On chocolate agar or blood agar with a nurse colony (e.g., Staphylococcus), colonies appear as small, dewdrop-like, translucent growths after 24 to 48 hours of incubation in a 5 to 10 percent carbon dioxide atmosphere.
Serotyping of A. paragallinarum is based on the Page scheme, which identifies three serogroups: A, B, and C. More recently, a Kume serotyping system has been described, which further divides serogroups into serovars. Serovar diversity is important for vaccine development, as cross-protection between serogroups is incomplete. In many regions, serogroups A and C are the most prevalent, while serogroup B is less common but can cause significant disease.
Host Range and Susceptibility
The primary hosts are chickens (Gallus gallus domesticus) and Japanese quail (Coturnix japonica). Turkeys, ducks, and pigeons are generally considered resistant to natural infection. The disease is more severe in adult birds than in young chicks, and layers and breeders are particularly affected due to the negative impact on egg production. Quail are highly susceptible and may develop severe clinical signs, including sinusitis and conjunctivitis, with rapid spread through a flock.
Transmission and Pathogenesis
Transmission occurs horizontally via direct contact, aerosolized respiratory droplets, and contamination of feed, water, and fomites. The bacterium colonizes the upper respiratory tract, specifically the nasal passages, sinuses, and conjunctival mucosa. The incubation period ranges from 1 to 3 days under experimental conditions but may extend to 7 days in natural outbreaks.
The pathogenesis involves adherence to ciliated epithelial cells via fimbriae and other adhesins, followed by local inflammation and exudation. The host inflammatory response, mediated by neutrophils and macrophages, contributes to the characteristic mucopurulent discharge. In severe cases, the infection can extend to the infraorbital sinuses, causing marked facial swelling. Secondary bacterial infections, particularly with Escherichia coli or Mycoplasma gallisepticum, can exacerbate the disease and lead to airsacculitis, pneumonia, and increased mortality.
Clinical Signs
Chickens
The classic presentation of infectious coryza in chickens includes:
- Serous nasal discharge that progresses to mucopurulent, foul-smelling exudate.
- Unilateral or bilateral facial edema, particularly swelling of the periorbital region and wattles.
- Conjunctivitis with lacrimation and frothy ocular discharge.
- Sneezing, rales, and head shaking.
- Anorexia, depression, and decreased water intake.
- A sharp drop in egg production, often by 10 to 40 percent, with reduced egg quality (thin shells, pale yolks).
- In laying hens, a transient decrease in fertility and hatchability may be observed.
Mortality is typically low (less than 5 percent) unless complicated by concurrent infections or poor environmental conditions. Chronic cases may show persistent nasal discharge and sinusitis.
Quail
Infectious coryza in quail presents similarly but often with more rapid onset and higher morbidity. Clinical signs include:
- Profuse serous to purulent nasal discharge.
- Swelling of the infraorbital sinuses, causing bulging of the periorbital area.
- Conjunctivitis with ocular discharge.
- Dyspnea, open-mouth breathing, and rales.
- Ruffled feathers, lethargy, and reduced feed intake.
- Decreased egg production in laying quail.
Mortality in quail can be higher than in chickens, particularly in young birds or under stressful conditions.
Will Coryza Go Away on Its Own?
A common question among poultry producers is whether infectious coryza will resolve without intervention. In some mild cases, the disease may appear to self-limit over 2 to 3 weeks, but birds often remain carriers and shed the bacterium intermittently. Without treatment, the infection tends to become chronic, with persistent nasal discharge and periodic flare-ups. Furthermore, untreated flocks suffer prolonged production losses and increased susceptibility to secondary infections. Therefore, reliance on spontaneous recovery is not recommended. Active intervention with antibiotics and supportive care is the standard approach.
Diagnosis
A definitive diagnosis of infectious coryza requires isolation and identification of A. paragallinarum or detection of its nucleic acid. Differential diagnoses include avian influenza, Newcastle disease, avian pneumovirus infection, mycoplasmosis, fowl cholera, and vitamin A deficiency.
Sample Collection
Swabs of the nasal cavity, infraorbital sinuses, or conjunctival sac should be collected from acutely affected birds. Postmortem samples include sinus exudate and tracheal mucosa. Samples should be placed in transport medium (e.g., Amies with charcoal) and kept cool but not frozen.
Bacterial Culture and Identification
Samples are streaked onto chocolate agar or blood agar with a Staphylococcus nurse colony to provide V factor. Plates are incubated at 37 degrees Celsius in 5 to 10 percent CO2 for 24 to 48 hours. Suspect colonies are small, grayish, and translucent. Identification is confirmed by Gram stain (Gram-negative pleomorphic rods), oxidase positivity, catalase negativity, and requirement for NAD but not hemin. Biochemical profiles can be generated using commercial identification systems, though these may have limited accuracy for Avibacterium species.
Molecular Detection
Polymerase chain reaction (PCR) assays targeting the hagA gene or 16S rRNA gene are highly sensitive and specific for A. paragallinarum. Real-time PCR can provide rapid results and is particularly useful for detecting carrier birds or confirming infection in flocks with atypical signs. PCR is preferred over culture for chronic or treated cases where bacterial viability is reduced.
Serology
Serological tests, including hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA), are available for detecting antibodies against A. paragallinarum. These tests are useful for flock-level surveillance and vaccine response monitoring but are not recommended for individual diagnosis due to variable sensitivity and cross-reactivity.
Diagnostic Workflow
The following Mermaid diagram illustrates a recommended diagnostic workflow for suspected infectious coryza outbreaks.
flowchart TD
A[Clinical Signs: Nasal discharge, facial edema, egg drop], > B{Collect samples}
B, > C[Nasal or sinus swabs from acute cases]
C, > D[Transport in Amies medium, 4 degrees C]
D, > E[Laboratory processing]
E, > F[PCR for A. paragallinarum]
E, > G[Culture on chocolate agar + nurse colony]
F, > H[Positive: Confirm diagnosis]
F, > I[Negative: Consider differentials]
G, > J[Colony morphology and Gram stain]
J, > K[Biochemical identification]
K, > L[Serotyping if needed]
H, > M[Report and treatment plan]
I, > N[Test for Mycoplasma, Pasteurella, viruses]
Treatment
Antibiotic Therapy
Antibiotic treatment is the cornerstone of managing infectious coryza. The goal is to reduce clinical signs, limit production losses, and decrease bacterial shedding. However, antibiotics do not eliminate the carrier state, and relapses can occur after treatment cessation.
Commonly used antibiotics include:
- Tetracyclines: Oxytetracycline or chlortetracycline administered in feed or water at 200 to 400 g per ton of feed or 10 to 20 mg per kg body weight for 5 to 7 days.
- Sulfonamides: Sulfadimethoxine or sulfamethazine in water at 0.05 to 0.1 percent for 3 to 5 days.
- Macrolides: Tylosin or tilmicosin in water at 10 to 20 mg per kg body weight for 3 to 5 days.
- Fluoroquinolones: Enrofloxacin or norfloxacin in water at 5 to 10 mg per kg body weight for 3 to 5 days (use restricted in some regions due to regulatory concerns).
- Penicillins: Amoxicillin or ampicillin in water at 10 to 20 mg per kg body weight for 5 days.
Antimicrobial susceptibility testing is recommended to guide therapy, as resistance to tetracyclines and sulfonamides has been reported. Treatment should be initiated early in the outbreak for optimal efficacy.
Supportive Care
Supportive measures include improving ventilation, reducing stocking density, providing clean water and feed, and minimizing stress. Anti-inflammatory drugs (e.g., meloxicam) may be used to reduce facial swelling and improve feed intake, though their use in poultry is off-label in many jurisdictions.
Will Coryza Go Away on Its Own? Revisited
As noted, untreated infectious coryza may appear to resolve in some birds, but the infection persists at the flock level. Carrier birds continue to shed the bacterium, leading to recurrent outbreaks. Therefore, antibiotic therapy is strongly advised to shorten the clinical course and reduce economic impact.
Prevention
Vaccination
Vaccination is a key component of infectious coryza control. Both inactivated (bacterin) and live attenuated vaccines are available. Bacterins are typically administered subcutaneously or intramuscularly to pullets at 8 to 12 weeks of age, with a booster at 16 to 18 weeks. Vaccines are formulated to include the predominant serogroups (A, B, C) present in the region.
Vaccination reduces the severity of clinical signs and egg production losses but does not prevent infection or the carrier state. In quail, vaccine efficacy data are limited, but some producers use chicken-derived bacterins off-label with variable results.
Biosecurity
Strict biosecurity measures are essential to prevent introduction and spread of A. paragallinarum. Key practices include:
- All-in/all-out flock management with thorough cleaning and disinfection between cycles.
- Quarantine of new birds for at least 30 days.
- Restriction of visitor access and use of dedicated footwear and clothing.
- Rodent and wild bird control to prevent mechanical transmission.
- Disinfection of equipment, vehicles, and feed delivery systems.
- Use of footbaths with appropriate disinfectants (e.g., quaternary ammonium compounds, chlorhexidine).
Eradication
Eradication of infectious coryza from a flock is difficult due to the carrier state. Depopulation followed by thorough cleaning, disinfection, and a downtime period of 2 to 4 weeks is the most reliable method. In multi-age facilities, eradication is rarely achieved, and management focuses on vaccination and biosecurity to minimize clinical disease.
Infectious Coryza in Quail: Special Considerations
Quail are highly susceptible to A. paragallinarum and often develop more severe clinical signs than chickens. Outbreaks in quail flocks can result in high morbidity and mortality, particularly in young birds. Treatment protocols are similar to those for chickens, but dose adjustments may be necessary due to smaller body size and metabolic differences. Vaccination is less commonly practiced in quail, and biosecurity is the primary preventive measure. Quail should not be housed with or near chickens to prevent cross-species transmission.
Economic Impact
The economic impact of infectious coryza stems from reduced egg production, increased mortality in severe cases, costs of treatment and vaccination, and trade restrictions. In layer flocks, a 10 to 40 percent drop in egg production can persist for 2 to 4 weeks, with partial recovery thereafter. Broiler breeders may experience reduced hatchability. The cost of antibiotic therapy and labor for treatment adds to the financial burden.
Public Health Significance
Avibacterium paragallinarum is not considered a zoonotic pathogen. There are no documented cases of human infection, and the bacterium is not transmitted to humans through handling of infected birds or consumption of poultry products. Therefore, infectious coryza is of veterinary and economic concern only.
Conclusion
Infectious coryza remains a significant respiratory disease of chickens and quail worldwide. The causative agent, Avibacterium paragallinarum, is a fastidious Gram-negative bacterium that causes acute upper respiratory signs and marked egg production losses. Diagnosis relies on culture and PCR, while treatment with appropriate antibiotics reduces clinical severity but does not eliminate the carrier state. Prevention through vaccination and rigorous biosecurity is essential for long-term control. Quail are particularly susceptible and require tailored management strategies. Understanding the etiology, clinical presentation, and control measures is critical for veterinary practitioners and poultry producers to mitigate the impact of this disease.
References
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Bragg, R. R., & Albertyn, J. (2008). A review of the epidemiology, pathogenesis, and control of infectious coryza in chickens. World's Poultry Science Journal, 64(4), 497-508.
Page, L. A. (1962). Haemophilus infections in chickens. I. Characteristics of 12 Haemophilus isolates recovered from diseased chickens. American Journal of Veterinary Research, 23, 85-95.
Kume, K., Sawata, A., & Nakai, T. (1983). Serologic classification of Haemophilus paragallinarum with a hemagglutinin system. Journal of Clinical Microbiology, 17(6), 958-964.
Blackall, P. J., & Soriano-Vargas, E. (2013). Infectious coryza. In D. E. Swayne, J. R. Glisson, L. R. McDougald, L. K. Nolan, D. L. Suarez, & V. L. Nair (Eds.), Diseases of Poultry (13th ed., pp. 789-803). Wiley-Blackwell.