Infectious Bronchitis Virus in Broiler Chickens: Seroprevalence and Associated Risk Factors

Infectious bronchitis virus (IBV) is one of the most important viral diseases, causing considerable economic losses in the poultry industry worldwide. The present study was conducted in Algeria to investigate the seroprevalence, associated risk factors, clinical signs, and lesions of IBV disease in broiler chicken.

The study was conducted in 63 chicken farms, where three IBV vaccination protocols were used in the first protocol: A single H120 dose was administered to the chicks at 7 days of age, in the second protocol: H120 at 3 days with an MA5 booster at 14 days, and in the third protocol: H120 at 3 days with MA5 and 4/91 boosters at 14 and 35 days, respectively. A total of 2142 sera were collected and analyzed using the enzyme-linked immunosorbent assay (ELISA) test.

IBV was detected in 77.77% of broiler farms. The most common clinical signs observed were wheezing, sneezing, coughing, nasal discharge in the respiratory form, aqueous diarrhea, and dehydration in the nephropathogenic form. Lesions included tracheitis, fibrin deposition in the respiratory form, hemorrhagic nephritis, uric acid deposition at the renal, visceral, and articular level in the nephropathogenic form. Antibody titers were higher in winter compared with autumn and spring (P<0.01). Antibody titers were also higher in chickens aged >30 days, in farms with a high density, poor hygiene level, and under the first vaccination protocol, compared with chickens aged ≤30 days (P<0.01), farms with a low density (P<0.001), farms with good hygiene level (P<0.01) and those under the third vaccination protocol (P<0.01).

These findings showed a high seroprevalence of IBV in Algeria and highlight the importance of continuous surveillance and molecular characterization of persistent strains to optimize vaccination strategies against emerging variants.