Evaluation of some local inactivated avian influenza vaccines in comparison to imported ones

Abstract

Avian influenza (AI) is highly contagious notafiable viral disease affecting several species of birds likes chickens, turkeys, quails, guinea fowls as well as pet and wild birds. This disease is caused by influenza virus type (A) which is a member of family orthomyxoviridea (Lamb and Krug, 1996).

AI viruses are segmented, negative sense RNA virus. The AI genomes has

8 different gene segments which encodes at least 10 different viral proteins .The structural protein divided into surface proteins (heamagglutinin (HA), neuraminidase (NA) and membrane ion channel protein) and internal protein (nucleoprotein, matrix protein and polymerase 1 and 2, while nonstructural protein (NS) includes two additional NS1 and NS2 protein (O'Neill et al. 1998 ).

Avian influenza viruses are further subtyped based on the antigenic properties of their surface glycoproteins, heamagglutinin (HA) into 16 subtypes (H1-H16) and neuraminidase (NA) into 9 subtypes (N1-N9) (Fouchier et al. 2005). The HA glycoprotein plays a major role in pathogenicity and immunigenicity of AI virus infections and is the critical component of AI vaccines. The AI virus are further characterized by genetic sequencing and pathogencity testing of the virus in chickens into high pathogenic avian influenza viruses (HPAI) and low pathogenic avian influenza viruses (LPAI)(OIE, 2008).

HPAI cause severe disease in domestic poultry which spread rapidly resulting in high mortality rates (up to 100% within 48 hrs)(Check, 2006). While, The LPAI have been associated with subclinical infection or produces a mild disease with respiratory signs , depression and egg production problems (Cattoli et al. 2004). In field outbreaks, only viruses of the H5 and H7 subtypes have been known to be classified as HPAI virus.