Surveillance for low pathogenic avian influenza viruses in live-bird markets in Oyo and Ogun States, Nigeria

ObjectiveTo conduct sero-epidemiological and virological surveillance for lowly pathogenic avian influenza virus (LPAIV) in apparently healthy birds slaughtered at live-bird markets (LBMs) in Southwestern Nigeria.MethodsA competitive ELISA was used for detecting avian influenza virus-specific antibodies in 491 chicken sera obtained from five LBMs in Oyo and Ogun States, Nigeria while haemagglutination inhibiting antibodies against LPAIVs were detected using H5N2, H7N1 and H9N2 subtype-specific antigens. Suspensions prepared from 400 cloacal swabs were inoculated into 9-day-old embryonated chicken eggs and harvested allantoic fluids were tested for the presence of haemagglutinating agents.ResultsAn overall avian influenza virus antibody prevalence of 10.4% (51/491) was obtained with mean percentage inhibition of 61.0 (95% confidence interval: 58.2-63.8) and geometric mean of 60.3 (95% confidence interval: 57.7-62.9). Whereas no LPAIV H7N1 antibodies were detected, 47.1% and 52.9% seroprevalence were obtained for H5N2 and H9N2 viruses respectively. Virus isolation in embryonated eggs was unsuccessful.ConclusionsConsidering the propensity of LPAIVs for mutation into high pathogenicity strains, detection of LPAIV H5N2 and H9N2 antibodies in these chickens is of public health significance and warrants continuous surveillance. Interventions to reduce market-based disease transmission including routine cleaning and disinfection, wearing of protective clothing and gloves, and periodic market rest days are advocated in Nigerian LBMs.