RESUMEN
The infectious bronchitis virus (IBV) is still one of the major respiratory viral pathogens of chickens. The IBV infection resulted in a wide range of clinical syndromes in the affected chickens, including respiratory, renal, gonads affections as well as generalized infections. Despite the intensive application of various commercial vaccines against the virus, many outbreaks are still reported in chickens worldwide. Several studies reported the circulation of several strains and genotypes of the IBV in eastern Saudi Arabia. The main goal of the current study was to isolate some of the circulating strains of IBV and assess its ability to reproduce the IBV infections in the challenge birds. Another objective was to monitor the immune status of the infected chickens during the course of this study. To achieve these goals, we used some filed IBV isolates retrieved from an outbreak in a broiler chicken farm in eastern Saudi Arabia in 2014. A total of 220-day-old chickens (110 Ross and 110 native Saudi breed chickens), twenty birds per each group, were used in this study. The chickens in some groups received some IBV vaccines on day one of the experiment, and some are boosted on day 19. All birds were challenged on day 28 of the experiment. Our results showed mild IBV signs in the non-vaccinated control group of chickens; however, the vaccinated chickens did not show any signs of IBV infections. Meanwhile, both the vaccinated and the none- vaccinated birds seroconverted to the IBV as shown by the ELISA results. In conclusion, the response of the IBV infected birds is mainly driven by the vaccination plans they received as a prime-boost regime. Further studies are required for a better understanding of the dynamics of IBV infection in native Saudi chickens.
RESUMEN
Rabbit hemorrhagic disease is an acute fatal highly contagious viral infectious disease that causes high losses among rabbitries. The disease was first reported in China in 1984 and later on in Saudi Arabia in 1996. The aim of this study was to investigate the emergence and pathogenicity of new rabbit hemorrhagic disease virus (RHDV) strains in Saudi Arabia. The pathogenicity was confirmed by inoculation in susceptible rabbits. Three RHDV strains were detected by reverse transcriptase polymerase chain reaction (RT-PCR) using primers targeting VP60 capsid protein gene in infected rabbitries during 2012 and 2013. These strains clustered into two genetically distinct genogroups related to year of isolation (G2 and G3). All new Saudi Arabia viruses clustered with the European strains, while the old strains clustered with strains from China and America. Based on amino acids and nucleotide sequences, the Saudi Arabia strains (RHD/1/SA/2012, RHD/2/SA/2012, and RHD/3/SA /2013) had high identity with Mexico89, Ca11-ITA, and 00-13,FRA virus; on the other hand, there was a relatively high identity with Bahrain strain. The evolutionary relationship of Saudi RHDVs strains revealed significant nucleotides and amino acid substitutions in hypervariable region E, suggesting the emergence of new RHDVs circulating in Saudi Arabia rabbitries. These antigenic changes represented by the antigenic index might be a potential cause of vaccination failure and raises the need to review the vaccination strategies against RHD.