Epidemiological Surveillance of Influenza Virus Matrix Gene in Pigs, in Lagos, Nigeria, 2015-2016

Abstract The co-infection of different influenza A virus enable viral gene re-assortments especially in pigs that serve as mixing vessel with the possibility of emergence of novel subtypes. Such re-assortants pose serious public health threat, as epitomised by the emergence of pandemic influenza in 2009. In Nigeria, there is mixture of animal species and highly populated densities that can increase the risk of influenza virus endemicity, genetic reshuffling and emergence of future pandemic influenza viruses. Thus, this study was aimed at determining influenza virus disease burden in pigs. This study was a cross sectional molecular surveillance of influenza virus. A total of 194 pig nasal samples from reported cases and randomly sampled were collected from pig farms in Ojo and Ikorodu in Lagos State between October, 2015 and April, 2016. The samples were investigated for the presence of influenza virus matrix gene by Reverse Transcriptase Polymerase Chain Reaction and detected by gel electrophoresis. P-values were calculated using Chi-square and Fisher’s exact tests. The result showed that 25 (12.9%) samples were positive for influenza A virus, out of which, 20 (80%) were samples from Ojo while 5 (20%) were samples from Ikorodu. Epidemiological parameters for the sampled locations, methods either as reported case or randomised, and sex compared were significant at 95% confidence interval. This study determined influenza viral burden in pigs with a molecular prevalence of 12.9% to influenza A. It further confirmed the sub-clinical and clinical circulation of Influenza A virus in pigs in Ojo and Ikorodu in Lagos. Therefore, the detection of influenza A virus in commercial pigs in Nigeria accentuates the importance of continuous surveillance and monitoring of the virus in order to prevent the advent of virulent strains that may spread to Pig-handlers and the community at large.