A New Variant of Avian Encephalomyelitis Virus Associated with Neurologic Signs in Turkey Poults

Abstract

Avian encephalomyelitis (AE) is a disease caused by the avian encephalomyelitis virus (AEV) of the genus Tremovirus in the family Picornaviridae. Recently, cases of turkey poults showing neurological signs were submitted to the veterinary diagnostic laboratories at South Dakota State University and the University of Minnesota. The affected birds were showing nervous neurological signs such as tremors, inability to stand, torticollis, and wing drop. Clinical signs were observed by 3 weeks of age. Necropsy of birds revealed no significant gross lesions in the internal organs, including the brain. There was no significant bacterial growth in the brains. Microscopic examination of various sections of the brain revealed multifocal lymphocplasmacytic perivascular cuffs in the cerebellum and cerebral cortex. The brain samples were processed for detection and whole genome sequencing by next-generation sequencing. Three full-length polyprotein sequences (6405 nt) of AEV were assembled. All three sequences shared 99.9–100% nucleotide and 100% amino acid identities with each other. Only 77.7–78.5% of nucleotide and 90.3–92.5% of amino acid identities with AEV field strains and vaccine sequences were available in GenBank. This indicates that a new divergent variant of AEV is circulating in the field and causing AE outbreaks in the Midwest region.

Keywords

• avian encephalomyelitis
• tremovirus A1
• variant
• phylogeny