GI-16 lineage (624/I or Q1), there and back again: The history of one of the major threats for poultry farming of our era

Franzo, Giovanni; Cecchinato, Mattia; Tosi, Giovanni; Fiorentini, Laura; Faccin, Francesca; Tucciarone, Claudia Maria; Trogu, Tiziana; Barbieri, Ilaria; Massi, Paola; Moreno, Ana

Finally, a variation in the competitive equilibrium between GI-16 and other pathogens or IBV genotypes (including vaccine strains) could have contributed to shape this genotype epidemiology. The introduction of GI-16 in South America represented an extraordinary epidemiological success from a viral perspective, as reflected by the increase in viral population size reported in the present study and by the outstanding clinical and economic impact in those countries [39] . On the other hand, the clinical impact of this lineage in Italy was negligible in the recent years. The competition with the highly prevalent lineage GI-19 could have actually limited the potential of GI-16 in terms of prevalence and clinical relevance [20] . Additionally, the previously mentioned introduction of a combined heterologous vaccination in Italy (in South America flocks were vaccinated with Mass-based vaccines only) could have effectively protected the animals [45] , avoiding the emergence of clinical signs and related economic losses.