Genetic and pathologic characteristics of infectious bursal disease viruses isolated from broiler chickens in Iran during 2014–2015

Abstract

Infectious bursal disease (IBD) virus causes a highly contagious immunosuppressive disease in chickens. A total number of 12 pooled bursal samples were collected during 2014-2015 from broiler farms in different regions of Iran. Typical macroscopical and histopathological lesions of the bursa of Fabricius were found similar to reports by other researchers. A 474-bp part of hypervariable region of VP2 (hvVP2) was sequenced and analyzed. Ten isolates had the characteristic amino acid residues of very virulent IBD (vvIBD) viruses and the other two were identified as attenuated (vaccine) strains. The vvIBD isolates had a unique G to S mutation at position 254, compared to other Iranian vvIBD isolates. Two attenuated isolates had the mutation 253Q, not found in D78 strain, creating virulent variant of vaccine strains. Degree of similarity among the studied vvIBD isolates was relatively high (97.6-100%), proposing a common ancestor for them. However, they were partly different from previous Iranian and neighbor countries' isolates (96.2-97.3% similarity to Shiraz isolate and 95.7-96.7% to Iraq and Turkey isolates). In phylogenetic analysis, the studied vvIBD isolates classified as a separate subgroup in the group of isolates from Iran and neighbor countries. More studies on genetic and antigenic characteristics of these isolates as well as probable modifications in their pathogenicity are needed to evaluate the significance of the mentioned differences.

Origin and global spreading of an ancestral lineage of the infectious bursal disease virus

“…An extensive surveillance in Turkey found that 9.5% of the strains corresponded to vvIBDV and 90.5% were vaccine‐like cIBDV (Yilmaz et al, ). A similar scenario of co‐circulation of vvIBDV and vaccine‐like strains was reported in more limited studies performed in Iran, Iraq, Pakistan, Egypt, Jordan and Kuwait (Amin & Jackwood, ; Khan et al, ; Michel & Jackwood, ; Norouzian, Farjanikish, & Hosseini, ; Samy et al, ). This epidemiological scenario provides additional support to the notion that the current spatial pattern of dIBDV strains is the result of intricate and ongoing interactions between intra‐ and inter‐continental spreading, strain replacement and local genetic differentiation.…”

“…Regarding the dIBDV strains, three main successive inter-continental migration events were detected: to vvIBDV and 90.5% were vaccine-like cIBDV (Yilmaz et al, 2019). A similar scenario of co-circulation of vvIBDV and vaccine-like strains was reported in more limited studies performed in Iran, Iraq, Pakistan, Egypt, Jordan and Kuwait (Amin & Jackwood, 2014;Khan et al, 2019;Michel & Jackwood, 2017;Norouzian, Farjanikish, & Hosseini, 2017;Samy et al, 2019).…”

Phylogeny and evolution of infectious bursal disease virus circulating in Turkish broiler flocks

“…Amongst these viruses, 97.6 to 100% similarities were found indicating the presence of a common ancestor virus circulating in Iran. However, they were partially different from previous Iranian and neighboring countries' isolates (96.2 to 97.3% similarity to Shiraz isolate and 95.7 to 96.7% to Iraq and Turkey isolates) (Norouzian et al, 2017). In a previous study performed in Turkey, classical and variant IBDVs were found by RT-PCR-RFLP method (Ture et al, 1998).…”

A review of the Infectious Bursal Disease (IBD) in Iran

“…During 2014-2015, another group of researchers collected and prepared 12 pooled bursal tissue samples, showing macroscopic lesions typical of IBD, todetect of IBDV (18). In this study, the 474 bp gene fragment from the hypervariable region of the VP2 protein coding gene was used for analysis and sequencing (18).…”

“…During 2014-2015, another group of researchers collected and prepared 12 pooled bursal tissue samples, showing macroscopic lesions typical of IBD, todetect of IBDV (18). In this study, the 474 bp gene fragment from the hypervariable region of the VP2 protein coding gene was used for analysis and sequencing (18). Ten isolates had the characteristic amino acid (AA) positions of vvIBDV viruses, and the other two isolates were identified as attenuated vaccine strains (18).…”