摘要
Background:To monitor carrier hosts of avian influenza in Nigeria,we randomly collected cloaca swab specimens from 155 ducks at a live bird market(LBM)in Ibadan,southwest Nigeria,between July 2011 and July 2012.Methods:The samples were analyzed by real-time reverse transcription-polymerase chain reaction(RT-PCR)and virus isolation was carried out in embryonated chicken eggs.Partial sequencing of the antigenic cleavage site of the haemagglutinin(HA)gene was performed,multiple sequence alignment was carried out using ClustalW,and a phylogenetic tree was constructed using the neighbor joining method.Results:Twenty(13%)of the 155 samples were positive for avian influenza subtype H5N2 by real-time RT-PCR and three isolates were obtained from embryonated chicken eggs.Partial sequencing of the amino acid cleavage site of the HA genes of two isolates corresponded to a PQRETGL*F sequence that is common in low pathogenic avian influenza(LPAI).Phylogenetically,the HA genes of the two influenza viruses are monophyletic and clustered with H5N2 viruses detected in wild ducks from Africa.Conclusion:The occurrence of LPAI in domestic ducks in Nigeria underscores the importance of continuous surveillance and monitoring of the virus(in a country that is considered to be free of avian influenza)in order to prevent the emergence of virulent strains that may spread to commercial poultry and humans.
