Genetic characterization of very virulent infectious bursal disease viruses from Latin America

Very virulent infectious bursal disease viruses (vvIBDVs) were detected in phenol inactivated bursal samples obtained from Brazil, the Dominican Republic, and Venezuela. After nucleotide sequence analysis of the hypervariable region of VP2 gene, the vvIBDVs from Brazil and Venezuela exhibited all of the 14 nucleotide changes that are conserved in the European UK-661 and most other vvIBDV strains. However, the vvIBDV from the Dominican Republic presented 11 nucleotide changes that are conserved in vvIBDV strains. After phylogenetic analysis, the Latin American strains were found to be related to other vvIBDV strains from Europe, Asia, and Africa. However, Brazilian and Dominican vvIBDVs clustered in two separate subgroups, while the vvIBDVs from Venezuela were closely related to other strains from other parts of the world. By deduced amino acid sequence, the three conserved amino acid residues in vvIBDV strains (222 Ala, 256 Ile, and 294 Ile) were confirmed in the Latin American viruses, and one amino acid change (300 Ala) was unique to all vvIBDVs from the Dominican Republic. The occurrence of this change in the Dominican vvIBDVs may have an impact in their antigenic makeup. Results of this study indicate that the vvIBDVs detected in Latin America are genetically similar to IBDV strains from other parts of the world. However, vvIBDVs from Venezuela were more similar to the vvIBDV strains from Europe and Asia. Of all the samples analyzed, vvIBDVs from Brazil and the Dominican Republic exhibited more genetic changes. These changes may have emerged as a result of the different management practices and environmental conditions present in each particular geographic area.     

Molecular and phenotypic characterization of infectious bursal disease virus isolates

Two infectious bursal disease viruses (IBDVs 1174 and V1) were isolated from IBDV-vaccinated broiler flocks in California and Georgia. These flocks had a history of subclinical immunosuppression. These isolates are commonly used in IBDV progeny challenge studies at Auburn, AL, as well as vaccine manufacturer's vaccine efficacy studies, because they come from populated poultry-producing states, and are requested by poultry veterinarians from those states. Nested polymerase chain reaction (PCR) generated viral genome products for sequencing. A 491-bp segment from the VP2 gene, covering the hypervariable region, from each isolate was analyzed and compared with previously sequenced isolates. Sequence analysis showed that they were more closely related to the Delaware (Del) E antigenic variant than they are to the Animal Health Plant Inspection Service (APHIS) standard, both at the nucleotide level (96%, 97%) and at the amino acid level (94%, 97%). Both isolates had the glutamine to lysine shift in amino acid 249 which has been reported to be critical in binding the virus neutralizing Mab B69. Phenotypic studies showed that both isolates produced rapid atrophy of the bursae and weight loss, without the edematous bursal phase, in 2-wk-old commercial broilers having antibody against IBDV. A progeny challenge study showed both isolates produced more atrophy of the bursae (less percentage of protection) than the Del E isolate. Molecular and phenotypic data of these important IBDV isolates help in the improved detection and control of this continually changing and important viral pathogen of chickens.     

Diversity of genome segment B from infectious bursal disease viruses in the United States

Several phylogenetic lineages of the infectious bursal disease virus (IBDV) genome segment B have been identified. Although this genome segment has been shown to contribute to virulence, little is known about the genetic lineages that exist in the United States. The nucleotide genome segment B sequences of 67 IBDV strains collected from 2002 to 2011 in the United States were examined. Although they were from nine different states, a majority (47) of these viruses were from California. A 722-base pair region near the 5' end of genome segment B, starting at nucleotide 168 and ending at 889, was examined and compared to sequences available in GenBank. The nucleotide sequence alignment revealed that mutations were frequently observed and that they were uniformly spaced throughout the region. When the predicted amino acids were aligned, amino acids at positions 145, 146, and 147 were found to change frequently. Six different amino acid triplets were observed and the very virulent (vv) IBDV strains (based on presence of vvIBDV genome segment A sequence) all had the triplet T145, D146, and N147. None of the non-vvIBDV strains had this TDN triplet. Phylogenetic analysis of the 67 nucleotide sequences revealed four significant genome segment B lineages among the U.S. viruses. One of these included the genome segment B typically found in vvIBDV and three contained non-vvIBDV genome segment B sequences. When the available sequences in GenBank were added to the analysis, two additional lineages were observed that did not contain U.S. viruses; one included viruses from China and the other contained viruses from the Ivory Coast. Although the samples tested do not represent all poultry producing regions in the United States, serotype 1 viruses from states outside California all belonged to one genome segment B lineage. The other three lineages observed in the United States were populated with viruses exclusively found in California, except the serotype 2 lineage, where the type strain was a serotype 2 virus from Ohio. The data provide further evidence for the importance of genome segment B identification during routine molecular diagnosis of all IBDV strains.     

Antigenic relationship of non-serotype 1 turkey infectious bursal disease viruses from the United States and United Kingdom

Cross-neutralization tests showed that non-serotype 1 infectious bursal disease viruses originating from turkeys in the United States and the United Kingdom belong to the same serotype. It is proposed that this serotype be designated serotype 2.     

Persistence of infectious bursal disease virus in New Zealand commercial egg layer flocks

Extract

After the discovery of infectious bursal disease (IBD) in New Zealand poultry flocks in November 1993, serological surveys of most commercial layer, broiler and breeder flocks were carried out. In January 1994, it was reported that a total of 34 infected farms had been detected⁽¹⁾.     

Counter immunoelectroosmophoresis in the diagnosis of infectious bursal disease of poultry

Summary Infectious bursal disease virus antigen was detected in the bursa of Fabricius of infected birds by the use of the counter immunoelectroosmophoresis technique. Eight suspected outbreaks were confirmed in this way and 82 out of 89 bursal samples submitted for laboratory confirmation were positive. The test was also suitable for the detection of antibody to infectious bursal disease virus in sera of infected birds. Precipitin lines were visible within 30 min as compared with 18 to 24 h with the Ouchterlony agar gel precipitation test. Counter immunoelectroosmophoresis is recommended for rapid confirmation of infectious bursal disease of poultry.

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Resumen Mediante el empléo de la técnica de contra inmunoelectroosmoforesis, se detectó antigeno viral en la bolsa de Fabricio de aves infectadas con Gumboro. Se confirmaron ocho brotes sospechosos mediante la técnica, y 82 de 89 muestras tomadas de bolsas sospechosas y analizadas en el laboratorio fueron positivas. La prueba tambien fue útil para la detección de anticuerpos de Gumboro en el suero de animales infectados. Las lineas de precipitación fueron visibles a los 30 minutos en comparación a las 18 a 24 horas necesarias para leer la prueba de Ouchterlony. Se recomienda la contra inmunoelectroosmoforesis para el diagnóstico de la enfermedad de Gumboro en aves.

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Résumé L'antigène du virus de la bursite infectieuse aviaire a été détecté dans les bourses de Fabricius d'oiseaux infectés en utilisant la technique de contre immuno-électro-osmo-phorèse. Huit foyers suspects ont été confirmés dans cette manière et, sur 89 prèlevements de bourses soumis pour confirmation de diagnostic au laboratoire, 82 ont été trouvés positifs. Le test est indiqué pour la détection d'anticorps anti-virus de la bursite infectieuse aviaire dans les sérums d'oiseaux infectés. Des lignes de précipitation sont visibles dans les trente minutes alors qu'elles n'apparaissent qu'en 18–24 heures avec le test d'Ouchterlony en gélose. La contre immuno-électro-osmo-phorèse est recommandée pour une confirmation rapide de la bursite infectieuse aviaire.

     

Isolation and characterization of attenuated plaque variants of infectious bursal disease virus

Attenuated plaque variants were obtained from infectious bursal disease virus adapted to chick embryo cell cultures. The large plaque (Lp) clone and the small plaque (Sp) clone formed homogeneous plaques about 5 and 1 mm in diameter, respectively. Neutralization tests indicated that these clones differed little from their parent strain in antigenicity. Sp clones showed a retarded growth rate in chick embryo cell cultures as compared with Lp clones. The clones were significantly less pathogenic for chick embryos than the parent strain, although Lp clones were more pathogenic than Sp clones, and they were much less pathogenic for 1-day-old chicks and 28-day-old chickens. Both clones had immunizing potency in 28-day-old chickens, although the Lp clone had a somewhat higher potency than the Sp clone. These findings suggest the Lp and Sp clones, in particular the Lp clones, to be useful as live virus vaccine strains.     

Infectious bursal disease virus variant from commercial Leghorn pullets

An infectious bursal disease virus (IBDV) was isolated from 39-to-43-day-old commercial leghorn pullets suspected of having infectious bursal disease (IBD). These chickens had been vaccinated with a commercial live IBDV vaccine at 28 and 35 days of age. An isolate designated IN was recovered using specific-pathogen-free (SPF) chickens and the BGM-70 established cell line. Experimental studies using SPF chickens vaccinated with either inactivated vaccines made from the vaccine strain used in the problem flock or a standard-type vaccine indicated no protection against the IN isolate. However, two variants and another standard-type vaccine induced protection against the IN isolate. Cross-neutralization tests indicated that the IN isolate differed antigenically from commercial vaccine strains and was related to the variant IBDV strains recently isolated from broilers. To our knowledge, this is the first report of a variant IBDV recovered from commercial layer chickens in the United States.