Epizootiological and molecular characterization of equine influenza virus 2008 outbreak in Egypt

ABSTRACT

Equine influenza symptoms were detected in population of equines in different governorates in Egypt [Cairo, Giza, Helwan, Alexandria, Minoufia, Behaira, Assiut and Aswan] during July - August 2008. High temperature, inappetence, conjunctivitis, redness of nasal mucosa, serous to mucopurulent nasal discharge and a harsh dry cough were the most common clinical manifestations. Horses of all ages and both sexes were affected. Free movement of the infected animals and direct contact at markets and races facilitated the rapid spread of the disease. Nine suspected cases represented eight governorates were examined for equine influenza virus [EIV] where 107 nasal swabs and 107 serum samples were used for diagnosis. Real-time reverse transcription-polymerase chain reactions [rRT-PCR] assay was applied todetect the matrix [M] gene of influenza type A viruses in nasal swabs and 6 out of the 8 cases were positive. Three cases were positive by virus isolation on embryonated chicken egg inoculation and the hemagglutination test. The hemagglutination inhibition [HI] was performed to identify the isolated influenza virus using reference antisera against A/Equi-1 [H7N1] and A/Equi-2 [H3N8].In this study, full characterization of the isolated virus was carried out through molecular techniques for typing of hemagglutinin [HA] and neuraminidase [NA] genes by RT-PCR and partial sequencing of the HA gene of one isolate [A/Equine/Egypt/21 AHRI/2008[H3N8]] and the results confirmed that H3N8 virus was the causative agent of this outbreak