Coronaviruses in Avian Species – Review with Focus on Epidemiology and Diagnosis in Wild Birds

Milek, Justyna; Blicharz-Domanska, Katarzyna

The main representative of the Gammacoronavirus genus is avian coronavirus. This taxonomic name includes IBV which causes a highly contagious disease of chickens, and genetically similar viruses isolated from other domestic galliformes: turkey coronavirus (TCoV), responsible for turkey enteritis, and the more recently detected guinea fowl coronavirus (GfCoV), the aetiological factor of fulminating disease in this species (2, 6, 27) . Analogous viruses were also detected in pheasants, peafowl, and quails, but also in nongalliformes, namely Columbiformes, Pelecaniformes, Ciconiiformes, Psittaciformes, and Anseriformes (12, 13, 22, 24, 30) . There are plenty of IBV variants with divergent molecular and biological properties. Due to the lack of a clear method for IBV classification, new rules based on the spike gene fragment (S1) sequence were recently proposed. It distinguished and named 32 lineages, categorised into six genotypes (GI to GVI) (42) . The difference between other members of the avian coronavirus family, namely TCoV and GfCoV, is also in the S gene structure. Interestingly, all other regions of the genome were found to be similar to IBV, suggesting that they come from the same ancestor (2, 27) . In 2008, surprising information about a new gammaCoV species from the white beluga whale appeared, which challenged the prevailing opinion of the specificity of gammaCoVs only to birds (32) . Further studies identified another coronavirus in ducks in 2015 whose genome fulfilled the official ICTV criteria required to distinguish a new species in the Gammacoronavirus genus. ICTV approval is still awaited for this new species designation (54) .