Prevalence and complete genome characterization of turkey picobirnaviruses

The “light turkey syndrome” (LTS), in which birds weigh less than their standard breed character at the marketing time, is believed to be a consequence of viral enteritis at an early age (3-5 weeks) from which the birds never fully recover. In a previously published study, we collected fecal pools from 2, 3, 5 and 8 week old turkey poults (80 pools from LTS farms and 40 from non-LTS farms) and examined them for the presence of astro-, rota-, reo-, and coronaviruses. To determine the presence of additional enteric viruses, we analyzed a fecal pool by Illumina sequencing and found picobirnavirus (PBV). Segments 1 and 2 of this virus shared 45.8% aa and 60.9-64.5% aa identity with genogroup I of human PBV, respectively. Primers based on RNA-dependent RNA polymerase and capsid genes were designed for detection and molecular characterization of PBVs in the 120 fecal pools described above. From LTS farms, 39 of 80 (48.8%) pools were PBV positive while 23 of 40 (57.5%) were positive from non-LTS farms. The phylogenetic analysis of 15 randomly selected strains divided them into four subgroups within genogroup I (subgroups 1A-D). Nine strains were in subgroup IA showing 69.9-76.4% nt identity with human PBV GI strainVS111 from the Netherlands. Strains in subgroup IB (n = 2) had 91.4-91.7% nt identity with chicken PBV GI strain AVE 42v1 from Brazil. Two strains in subgroup IC had 72.3-74.2% nt identity with chicken PBV strain AVE 71v3 from Brazil. In subgroup ID, two strains showed 72.4-81.8% nt identity with chicken PBV GI strain AVE 57v2 from Brazil. Subgroup IC and ID were the most divergent. Five of the 15 strains were typed using capsid gene primers. They showed 32.6-33.4% nt and 39.5-41.3% aa identity with VS10 human PBV strain. These results indicate co-circulation of divergent strains of PBVs among Minnesota turkeys.