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Vet. Sci. 2018, 5(2), 49; https://doi.org/10.3390/vetsci5020049

Field Efficacy of an Attenuated Infectious Bronchitis Variant 2 Virus Vaccine in Commercial Broiler Chickens

1
Department of Toxicology and Forensic Medicine, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt
2
Poultry Diseases Department, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef 65211, Egypt
3
Reference Laboratory for Veterinary Quality Control on Poultry Production (NLQP), Animal Health Research Institute, P.O. Box 264, Dokki, Giza 12618, Egypt
4
Avian and Rabbit Medicine Department, Faculty of Veterinary Medicine, Suez Canal University, Ismailia 41522, Egypt
5
Poultry Disease Department, Faculty of Veterinary Medicine, Aswan University, Aswan 81528, Egypt
6
Middle East for Veterinary Vaccine Company, Second Industrial Area, El-Salihya El-Gededa, El-Sharkia 44671, Egypt
7
Microbiology Department, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt
*
Authors to whom correspondence should be addressed.
Received: 3 April 2018 / Revised: 25 April 2018 / Accepted: 2 May 2018 / Published: 9 May 2018
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Abstract

Egyptian poultry suffer from frequent respiratory disease outbreaks associated with Infectious Bronchitis Virus (IBV) variant 2 strains (Egy/VarII). Different vaccination programs using imported vaccines have failed to protect the flocks from field challenge. Recent studies confirmed a successful protection using homologous strains as live attenuated vaccines. In this study, a newly developed live attenuated IB-VAR2 vaccine representing the GI-23 Middle East IBV lineage was evaluated in day-old commercial broilers in an IBV-endemic area. A commercial broiler flock was vaccinated with the IB-VAR2 vaccine at day-old age followed by IB-H120 at day 16. The vaccinated flock was monitored on a weekly basis till the slaughter age. The health status and growth performance were monitored, and selected viral pathogen real-time RT-PCR (rRT-PCR) detection was conducted on a weekly basis. Finally, the flock was compared to a nearby farm with only the classical IB-H120 vaccination program. Results showed that the IB-VAR2 vaccine was tolerable in day-old broiler chicks. The IBV virus rRT-PCR detection was limited to the trachea as compared to its nephropathogenic parent virus. Respiratory disease problems and high mortalities were reported in the IB-H120-only vaccinated flock. An exposure to a wild-type Egy/VarII strain was confirmed in both flocks as indicated by partial IBV S1 gene sequence. Even though the IB-VAR2-vaccinated flock performance was better than the flock that received only IB-H120, the IBV ELISA (enzyme-linked immunosorbent assay) and log2 Haemagglutination inhibition (HI) antibody mean titers remained high (3128 ± 2713 and ≥9 log2, respectively) until the 28th day of age. The current study demonstrates the safety and effectiveness of IB-VAR2 as a live attenuated vaccine in day-old commercial broilers. Also, the combination of IB-VAR2 and classical IBV vaccines confers a broader protective immune response against IBV in endemic areas. View Full-Text
Keywords: IBV; attenuated vaccine; infectious bronchitis virus; Middle East; variant 2 IBV; attenuated vaccine; infectious bronchitis virus; Middle East; variant 2
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Elhady, M.A.; Ali, A.; Kilany, W.H.; Elfeil, W.K.; Ibrahim, H.; Nabil, A.; Samir, A.; El Sayed, M. Field Efficacy of an Attenuated Infectious Bronchitis Variant 2 Virus Vaccine in Commercial Broiler Chickens. Vet. Sci. 2018, 5, 49.

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