Highly pathogenic influenza virus (HPAIV) H5N1 has caused mortality and morbidity in many species of domestic and wild bird. The Houbara bustard (Chlamydotis undulata macqueenii) is a solitary bird that inhabits semi-desert regions. It is known to be susceptible to avianpox, avian paramyxovirus type 1, and low-pathogenicity avian influenza H9N2. We report an outbreak of H5N1 HPAIV in Houbara bustards, which were introduced into the Kingdom of Saudi Arabia for falconry purposes. Ninety-three per cent mortality (38 out of 41 birds) in the infected Houbara bustard flock and about 62.5% mortality (10 out of 16 birds) in falcons that came in contact with these birds were observed. Pooled cloacal and tracheal swabs from Houbara bustards as well as visceral organ homogenates collected in Houbara bustards and falcons were tested by real-time reverse transcriptase-polymerase chain reaction, and virus isolation was attempted in specific pathogen free hens' eggs. The viruses isolated were characterized as HPAIV H5N1. Phylogenetic analysis of the haemagglutinating and Neuraminidase (NA) genes revealed that the viruses isolated from Houbara bustards and falcons were closely related to each other and to Kuwaiti H5N1 strains isolated in 2007. Interestingly, they were genetically distinguishable from the co-circulating A/H5N1 viruses in Kingdom of Saudi Arabia causing outbreaks in domestic birds. This case emphasizes the need for surveillance of this endangered species in its natural habitat.
The first outbreak of H5N1 highly pathogenic avian influenza (HPAI) in the Kingdom of Saudi Arabia (KSA) occurred in two "backyard" flocks of Houbara bustards and falcons in February 2007. Subsequent outbreaks were seen through the end of 2007 in "backyard" birds including native chickens, ostriches, turkeys, ducks, and peacocks. From November 2007 through January 2008, H5N1 HPAI outbreaks occurred in 19 commercial poultry premises, including two broiler breeder farms, one layer breeder farm, one ostrich farm, and 15 commercial layer farms, with approximately 4.75 million birds affected. Laboratory diagnosis of all H5N1-positive cases was conducted at the Central Veterinary Diagnostic Laboratory (CVDL) in Riyadh, Saudi Arabia. A combination of diagnostic tests was used to confirm the laboratory diagnosis. A rapid antigen-capture test and real-time reverse transcriptase-PCR (rtRT-PCR) assay on clinical and field specimens were conducted initially. Meanwhile, virus isolation in specific-pathogen-free embryonating chicken eggs was performed and was followed by hemagglutinin (HA) and hemagglutination inhibition tests, then rapid antigen-capture and rtRT-PCR tests on HA-positive allantoic fluid samples. In most HPAI cases, a complete laboratory diagnosis was made within 24-48 hr at the CVDL. Saudi Arabian government officials made immediate decisions to depopulate all H5N1-affected and nonaffected flocks within a 5-km radius area and applied quarantine zones to prevent the virus from spreading to other areas. Other control measures, such as closure of live bird markets and intensive surveillance tests on all poultry species within quarantine zones, were in place during the outbreaks. As a result, the HPAI outbreaks were quickly controlled, and no positive cases were detected after January 29, 2008. The KSA was declared free of HPAI on April 30, 2008, by the World Animal Health Organization.
The present study was conducted to monitor the persistence of Maternal Derived Antibody (MDA) in quail chicks during first five weeks of their life and its effect on the immune response to Newcastle disease virus vaccination (LaSota and Hitchner B1).The obtained results showed that, the MDA HI titers ranged from 5 to 7 (log 2) with a geometric mean of 6.2-6.4 (log 2) at the end of first week. At the end of the second week of age (day 14) the MDA HI titers were decreased with a mean titer of 5.1-5.2 (log 2). At the end of the third week, only 40% of quail chicks (4/10) showed titers more than 5 (log 2), whereas 60% of the quail chicks titers less than 4(log2) in HI test. One week later (day 28), all of the quail chicks showed titers less than 4 (log 2) in HI test. At the end of the fifth week, (day 35), the mean titer was decreased to its minimum level equal to (≤ 2.0 log 2). The obtained results revealed that, the mean value of HI antibody titers declined in the first two weeks post vaccination with (LaSota and Hitchner B1) when vaccination take place at 7 day old, whereas higher and persistence antibody response takes place when vaccination applied at 14 or 21 day old. The findings of our study suggest that the 14 th day of age is recommended as the proper time to start the first vaccination against ND in flocks of quail chicks with maternal antibodies.
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