A molecular epidemiology study based on VP2 gene sequences reveals that a new genotype of infectious bursal disease virus is dominantly prevalent in Italy.
A distinctive infectious bursal disease (IBD) virus genotype (ITA) was detected in IBD-live vaccinated broilers in Italy without clinical signs of IBD. It was isolated in specific-pathogen-free eggs and molecularly characterized in the hypervariable region of the virus protein (VP) 2. Phylogenetic analysis showed that ITA strains clustered separately from other homologous reference sequences of IBDVs, either classical or very virulent, retrieved from GenBank or previously reported in Italy, and from vaccine strains. The new genotype shows peculiar molecular characteristics in key positions of the VP2 hypervariable region, which affect charged or potentially glycosylated amino acids virtually associated with important changes in virus properties. Characterization of 41 IBDV strains detected in Italy between 2013 and 2014 showed that ITA is emergent in densely populated poultry areas of Italy, being 68% of the IBDV detections made during routine diagnostic activity over a two-year period, in spite of the immunity induced by large-scale vaccination. Four very virulent strains (DV86) and one classical strain (HPR2), together with eight vaccine strains, were also detected. The currently available epidemiological and clinical data do not allow the degree of pathogenicity of the ITA genotype to be defined. Only in vivo experimental pathogenicity studies conducted in secure isolation conditions, through the evaluation of clinical signs and macro/microscopic lesions, will clarify conclusively the virulence of the new Italian genotype.
a Department of Veterinary Medical Sciences , University of Bologna , Ozzano dell'Emilia (BO) , Italy.
Caterina
C
Lupini
b Tre Valli Laboratory , San Michele Extra (VR) , Italy.
Davide
D
Giovanardi
b Tre Valli Laboratory , San Michele Extra (VR) , Italy.
Patrizia
P
Pesente
a Department of Veterinary Medical Sciences , University of Bologna , Ozzano dell'Emilia (BO) , Italy.
Michela
M
Bonci
a Department of Veterinary Medical Sciences , University of Bologna , Ozzano dell'Emilia (BO) , Italy.
Viviana
V
Felice
b Tre Valli Laboratory , San Michele Extra (VR) , Italy.
Giulia
G
Rossi
c Agricola TreValli , Quinto di Valpantena (VR) , Italy.
Emilio
E
Morandini
d Department of Animal Medicine, Production and Health , University of Padua , Legnaro (PD) , Italy.
Mattia
M
Cecchinato
a Department of Veterinary Medical Sciences , University of Bologna , Ozzano dell'Emilia (BO) , Italy.
Elena
E
Catelli
D000595:Amino Acid Sequence; D000818:Animals; D018175:Birnaviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D002645:Chickens / Q000821:virology*; D005260:Female; D005838:Genotype; D007243:Infectious bursal disease virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D007558:Italy / Q000453:epidemiology; D008137:Longitudinal Studies; D017720:Molecular Epidemiology; D010063:Ovum; D010802:Phylogeny; D011201:Poultry Diseases / Q000453:epidemiology* / Q000821:virology; D015995:Prevalence; D016415:Sequence Alignment / Q000662:veterinary; D017422:Sequence Analysis, DNA / Q000662:veterinary; D013047:Specific Pathogen-Free Organisms; D015678:Viral Structural Proteins / Q000235:genetics*; D014774:Virulence
C082513:VP2 protein, infectious bursal disease virus; D015678:Viral Structural Proteins
Gumboro disease; Infectious bursal disease virus; broiler; molecolar characterization; phylogenetic analysis