Gulls as a host for both gamma and deltacoronaviruses

The coronaviruses (CoV) are ubiquitous pathogens found in wide variety of hosts that constantly pose a threat to human and animal health as a result of their enormous capacity to generate genetic changes. Constant monitoring of virus reservoirs can constitute an early-warning tool and control the spread and evolution of the virus. Coronaviruses are common in wild birds, globally, and birds of the Charadriiformes in particular have been demonstrated to be carriers of delta- (dCoV) and gammacoronaviruses (gCoV). In this paper, we present the genetic characterisation of five CoV strains from black-headed (Chroicocephalus ridibundus) and common (Larus canus) gulls. Whole genome sequence analysis showed high similarity of detected dCoV in gulls to previously identified strains from falcon, houbara, pigeon and gulls from Asia (UAE, China). However, phylogenetic analysis revealed bifurcation within a common branch. Furthermore, the accumulation of numerous amino acid changes within the S-protein was demonstrated, indicating further evolution of dCoV within a single gull host. In turn, phylogenetic analysis for the most of the structural and non-structural genes of identified gCoV confirmed that the strain belongs to the duck coronavirus 2714 (DuCoV2714) species within Igacovirus subgenera, while for the spike protein it forms a separate branch not closely related to any gCoV species known to date. The current study provides new and significant insights into the evolution and diversification of circulating coronaviruses in members of Laridae family.