DETECTION OF FIELD NEWCASTLE DISEASE VIRUS GENOTYPE VII AND INFECTIOUS BURSAL DISEASE VIRUS IN A COMMERCIAL LAYING FLOCK IN THE AKMOLA REGION

Abstract

Infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) remain important pathogens in commercial poultry production. In vaccinated flocks, molecular detection requires careful interpretation because viral genetic material may originate from either field infection or vaccine-associated signals. We investigated a mortality episode in a vaccinated commercial laying flock in the Akmola Region using reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing of selected viral genomic fragments. Five deceased laying hens were examined. NDV RNA was detected in all five birds by targeting the L gene, and sequencing supported its assignment to genotype VII and a field-associated rather than vaccine-lineage sequence. IBDV RNA was detected in two of the five birds by targeting VP2; sequencing identified a field-associated sequence most closely related to GenBank accession D00869.2.2 within the analyzed fragment. The findings demonstrate concurrent detection of genetically distinct field-associated NDV and IBDV sequences within the investigated mortality episode. Given the very small sample size and the absence of quantitative virological, serological, and detailed pathological data, the study does not establish the causal contribution of either virus to the observed production losses or mortality, nor does it demonstrate flock-level co-circulation. The results nevertheless illustrate the value of sequence-based verification when interpreting molecular detections in vaccinated poultry.