Avian Gyrovirus 2 and Avirulent Newcastle Disease Virus Coinfection in a Chicken Flock with Neurologic Symptoms and High Mortalities

A disease with severe neurologic symptoms caused 100% mortality in a small broiler operation in the Gauteng Province, South Africa in late March 2013. Routine diagnostic PCR testing failed to identify a possible cause of the outbreak; thus, samples were submitted for virus isolation, serology, and bacteriology. An avirulent Newcastle disease virus (NDV) strain isolated was identified as a V4-like genotype 1 strain, by DNA sequencing, with a cleavage site of 112GKQGR↓L117. Real-time reverse transcription PCR identified NDV in the brain but not in cecal tonsils or pooled tracheas, spleens, lungs, and livers. A random amplification deep sequencing of a transcriptome library generated from pooled tissues produced 927,966 paired-end reads. A contig of 2,309 nucleotides was identified as a near-complete avian gyrovirus 2 (AGV2) genome. This is the first report on the African continent of AGV2, which has been reported in southern Brazil, the Netherlands, and Hong Kong thus far. A real-time PCR for AGV2 only detected the virus in the brain but not in cecal tonsils or pooled tracheas, spleens, lungs, and livers. Sequence reads also mapped to the genomes of mycoplasma, Escherichia coli, avian leukosis virus subtype J, and Marek's disease virus but excluded influenza A virus, Ornithobacterium rhinotracheale, avian rhinotracheitis virus, avian encephalomyelitis virus, and West Nile virus. Air sac swabs were positive on bacterial culture for E. coli. The possibility of a synergistic pathogenic effect between avirulent NDV and AGV2 requires further investigation. Coinfección entre el gyrovirus aviar 2 y el virus de la enfermedad de Newcastle avirulento en una parvada de pollo de engorde con signos neurológicos y alta mortalidad. Una enfermedad con signos neurológicos graves causó una mortalidad del 100 % en una operación pequeña de pollos de engorde en la provincia de Gauteng, en Sudáfrica a finales de marzo del 2013. Las pruebas rutinarias de diagnóstico por PCR no lograron identificar una posible causa del brote, por lo que las muestras fueron sometidas al aislamiento viral, serología y bacteriología. Se aisló e identificó un virus de la enfermedad de Newcastle no virulento (NDV) como una cepa similar al genotipo 1 V4, por secuenciación de ADN, en el sitio de disociación 112GKQGR ↓ L117. Mediante un método de transcripción reversa y PCR en tiempo real se identificó la presencia del virus de Newcastle en el cerebro, pero no en las tonsilas cecales o en las muestras agr