Coronaviruses (CoVs) are a large group of enveloped viruses with a single-strand RNA genome, which continuously circulate in mammals and birds and pose a threat to livestock, companion animals, and humans. CoVs harboured by avian species are classified to the genera gamma- and deltacoronaviruses. Within the gamma-CoVs the main representative is avian coronavirus, a taxonomic name which includes the highly contagious infectious bronchitis viruses (IBVs) in chickens and similar viruses infecting other domestic birds such as turkeys, guinea fowls, or quails. Additionally, IBVs have been detected in healthy wild birds, demonstrating that they may act as the vector between domestic and free-living birds. Moreover, CoVs other than IBVs, are identified in wild birds, which suggests that wild birds play a key role in the epidemiology of other gammaCoVs and deltaCoVs. Development of molecular techniques has significantly improved knowledge of the prevalence of CoVs in avian species. The methods adopted in monitoring studies of CoVs in different avian species are mainly based on detection of conservative regions within the viral replicase, nucleocapsid genes, and 3’UTR or 5’UTR. The purpose of this review is to summarise recent discoveries in the areas of epidemiology and diagnosis of CoVs in avian species and to understand the role of wild birds in the virus distribution.

Ever since infectious bursal disease (IBD) was recognised in Nigeria over forty years ago, it continues to pose a threat to poultry production with limited information on the likely role of other avian species especially those raised in close proximity with chickens. For this study, blood samples were obtained from184 unvaccinated apparently healthy birds comprised of Japanese quails (63) andindigenous chickens (60) on smallholdings as well as pigeons (61) in a live-bird market in Osun and Oyo states, southwest Nigeria.Sera from these birds were analysed for IBD virus antibodies using a commercial ELISA kit. Overall, 69 (37.5%) sera were positive for IBDV with 52.8% (65/184) and 6.6% (4/184)from birds on smallholdings and live-bird market, respectively. These findings indicate that these birds were sub-clinically infected and could serve as reservoirs shedding the virus into the environment and perhaps, corroborate the suggestion that the inability to effectively control or eradicate the disease from poultry flocks in Nigeria may be due to limited information on the contributions of other avian species other than chicken in the spread of IBD virus.