Highly pathogenic H5N1 avian influenza virus epidemic in Egypt

AuszugEmergence of the highly pathogenic avian influenza virus (HPAIV) of the H5N1 subtype in Egypt in mid-February 2006 caused magnificent losses in the poultry industry and was considered a potential threat to public health. Since late 2007, there is increasing evidence that stable lineages of H5N1 viruses are being established in chickens and humans in Egypt despite the blanket vaccination policy in all poultry sectors. Presence of the virus under immune pressure in vaccinated birds accelerated the mutation rate of the virus to escape from the repertoire of immune response. Existence of deleterious mutations in the primers and probe specific sites resulted in loss of sensitivity of the currently recommended real time reverse transcription polymerase chain reaction (RT-qPCR) by the World Organization of Animal Health “OIE” (Slomka et al., 2007) targeting the H5 gene. Furthermore, and recently, there are two different H5N1 sublineages co-circulating in Egypt referred to as variant 2.2.1 strains isolated from vaccinated poultry and classic or proper 2.2.1 strains usually isolated from backyard birds and accidently transmitted to humans (WHO, 2011a). Development of sensitive and specific RT-qPCR to detect and differentiate between those sublineages is of epidemiological concern and will improve the early detection and subsequently the control of the disease in poultry. Increase in incidence of H5N1 outbreaks in vaccinated poultry in Egypt criticized the effectiveness of the current used vaccines to protect birds in the face of antigenic variation of the virus and increased the demand for testing a new vaccination regime and the development of new vaccines (Peyre et al., 2009; Hafez et al., 2010). Moreover, transfer of maternal antibodies from vaccinated breeders to their offspring might impair the efficiency of the vaccines. Studies described in this dissertation were planned to improve the diagnosis of the virus, as a first step in the control of the disease, and to evaluate a commonly used commercial vaccine to protect birds against currently circulating field virus. To achieve this aim the following studies have been conducted: 1. Development of modified H5 RT-qPCR oligonucleotides for detection of divergent HPAIV H5N1 in Egypt. 2. Development of new multiplex RT-qPCR for detection and differentiation of HPAIV H5N1 classic and variant viruses currently co-circulating in Egypt. 3. Effect of multiple dose vaccination of broiler breeder chickens with an H5N2 vaccine against challenge with classic and variant HPAIV H5N1 viruses of clade 2.2.1. 4. Study the influence of maternal immunity on infection and/or vaccination of one day old chicks against infection with Egyptian HPAIV H5N1