Infectious coryza:

Synonym: Fowl coryza

• It is an acute, respiratory disease of chickens caused by bacterium of genus Haemophilus or Avibacterium.
• Disease is characterized by swelling of face, and discharge from the eyes and nostrils.
• Infectious coryza causes greatest economic losses from poor growth in chickens and reduced egg production in layers.

Etiology:

• Haemophilus paragallinarum
• Avibacterium paragallinarum
• It is gram -ve, pleomorphic, non-motile, catalase negative, microaerophilic rod.
• It is delicate bacterium which dies quickly outside the bird; survival outside body of poultry in farm is not more than 48 hours.
• It occurs in 3 serotypes; A, B and C. presence of serotype B has not been confirmed so far.

Epidemiology:

• Disease occurs worldwide and extremely common in India, both in broiler and layer.
• Fowl cholera was the dominant one with 18.48% incidence in poultry industry on a study conducted in Chitwan district.
• Chickens of all age group are highly susceptible and mature birds are more at risk.
• Occurrence of disease is higher in chickens farming in intensive system.
• Disease is often seen during flock’s peak egg laying season and when birds are in stress condition.
• Outbreaks are more frequent during fall and winter season.
• Outbreaks of infectious coryza in broiler farm in Alabama causes 69.8% condemnation of birds due to severe air sacculitis.
• In a study of 10 outbreaks of coryza in Morocco, it was found that there is 40% drop in egg production and mortality ranging from 0.7-10%.

Transmission:

• Clinically affected and carrier birds are the main sources of infection.
• Infection spread through ingestion of contaminated food and water by nasal discharge.
• Infection also spreads through nasal discharge through aerosol over short distance.
• Direct contact with affected birds
• It donot transmits vertically.

Pathogenesis:

Clinical Findings:

• Incubation period is 1-3 days after contact infection
• Sneezing, mucus-like nasal discharge and ocular discharge
• Swelling of face (facial oedema)
• In severe cases, marked conjunctivitis with closed eyes, swollen wattles and difficulty in breathing
• Decreased in feed and water consumption.
• Decrease in egg production in layer birds
• If complicated with other infection, disease becomes severe and prolonged.

PM Findings:

• Inflammation of nasal passage and infraorbital sinus characterized by presence of mucus, pus or fibrin.
• Conjunctivitis characterized by presence of mucus, pus or fibrin.
• Swelling of face and wattle due to accumulation of fluid under skin is prominent.
• Upper trachea may be involved but lungs and air sacs are only affected in complicated cases.

Diagnosis:

• Based on history of spreading; rapid spread with acute nature
• Based on clinical findings
• Based on PM findings
• Isolation of organism from tracheal swabs on blood agar plates.
• HI test can be done but not suitable compared to other diagnostic methods.
• PCR provides more accurate results.

Differential Diagnosis:

1. Fowl cholera:

• Disease is more septicemic than fowl coryza.
• Wattles are swollen, nasal discharge is foul smelling
• Necrotic foci in liver, sudden death

2. Mycoplasmosis:

• Disease is chronic in nature and low mortality
• Swelling of face is less acute
• Swollen sinuses, rales, coughing is evident

3. Colibacillosis:

• Air sacculitis is present
• Pericarditis and perihepatitis is constant feature in colibacillosis
• It usually occurs secondary to viral or mycoplasma infection.

4. Staphylococcosis:

• It may cause swelling around head/comb with abscess
• Arthritis, septicemia

5. New Castle Disease (ND):

• Along with respiratory signs, nervous signs are also present in ND
• Greenish diarrhea, high mortality
• Hemorrhages in proventriculus/cecal tonsils.

6. Infectious bronchitis (IB):

• Sneezing, rales, watery eyes, drop in egg production, wrinkled eggshells.
• Usually no foul odor, affects all ages.

7. Vitamin A deficiency:

• Keratinization of respiratory epithelium, ocular discharge, white plaques in oropharynx.

8. Aspergillosis:

• No facial swelling is present.
• Dyspnea, nodules in lung/air sac is evident.

Treatment:

• Various sulphonamides and antibiotics are useful in treating the disease.
• Tetracyclines, enrofloxacin, norfloxacin, sulphonamide-trimethoprim may be used.
• Erythromycin and OTC are two commonly used antibiotics for 5-7 days. However, disease is not completely removed but help in reducing outbreaks and clincal signs.
• Sulfadimethoxine @0.05% in drinking water for 3-5 days
• Oxytetracycline @1g/L in drinking water for 3-5 days
• Doxycycline @10-20 mg/kg, b.wt. PO, for 5 days
• Enrofloxacin @10mg/kg, BW, orally for 3-5 days.
• Erythromycin @ 25-50 mg/kg, b.wt. orally for 3-5 days
• Tylosin in drinking water @ 0.5-1g/L for 3-5 days.
• Supportive therapy includes electrolytes in DW to correct dehydration, multivitamin supplement in water.

Control Measures:

• All recovered birds remain carrier of disease. So, culling of carrier birds from flock is effective in controlling disease.
• Infected birds should be depopulated from house.
• New birds should be quarantined before introducing into poultry house.
• Frequent turning and changing of poultry litter is essential.
• Equipment used in poultry houses such as feeder, drinker should be cleaned properly and disinfected with appropriate disinfectants.
• Houses should be sprayed with disinfectants to kill organism present in environment.
• After cleaning and disinfection, poultry houses should be kept vacant for 2-3 weeks before restocking with new birds.
• All in and all out method of poultry farming should be adopted to prevent cross contamination.
• Vaccination of birds with killed vaccine protects birds. It is given SC at age of 16 weeks of age. Two injections at interval of 3-4 weeks before outbreak is recommended.