Abstract

Hemorrhagic enteritis virus (HEV) is an immunosuppressive adenovirus that causes an acute clinical disease characterized by hemorrhagic gastroenteritis in 4-week-old turkeys and older. Recurrent incidence of secondary infections (e.g., systemic bacterial infections, cellulitis, and elevated mortality), may be associated with the presence of field-type HEV in Canadian turkey farms. We speculate that field-type HEV and vaccine/vaccine-like strains can be differentiated through analysis of the viral genomes, hexon genes, and the specific virulence factors (e.g., ORF1, E3, and fib knob domain). Nine out of sixteen spleens obtained from cases suspected of immunosuppression by HEV were analyzed. The limited data obtained showed that: (1) field-type HEV circulates in many non-vaccinated western Canadian flocks; (2) field-type HEV circulates in vaccinated flocks with increased recurrent bacterial infections; and (3) the existence of novel point mutations in hexon, ORF1, E3, and specially fib knob domains. This is the first publication showing the circulation of wild-type HEV in HEV-vaccinated flocks in Western Canada, and the usefulness of a novel procedure that allows whole genome sequencing of HEV directly from spleens, without passaging in cell culture or passaging in vivo. Further studies focusing more samples are required to confirm our observations and investigate possible vaccination failure.

Highlights

  • Hemorrhagic enteritis virus (HEV) or Turkey siadenovirus A, a member of the family Adenoviridae, genus Siadenovirus, is a ubiquitous poultry pathogen

  • HEV is the etiological agent of hemorrhagic enteritis (HE), a disease characterized by immunosuppression in turkeys of >4-weeks of age

  • In agreement with the later study, we showed that turkey farms with recurrent morbidities, with or without HEV vaccination, have subclinical HEV infections caused by HEV different from vaccine strains

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Summary

Introduction

Hemorrhagic enteritis virus (HEV) or Turkey siadenovirus A, a member of the family Adenoviridae, genus Siadenovirus, is a ubiquitous poultry pathogen. HEV is the etiological agent of hemorrhagic enteritis (HE), a disease characterized by immunosuppression in turkeys of >4-weeks of age. Viruses 2020, 12, 941 infection with opportunists like Escherichia coli) [6,7,8]; and (2) subclinical infection, consisting in immunosuppression and causing economical losses because of secondary bacterial infection, especially from Escherichia coli, and processing plant condemnations [7,9,10]. The immunosuppression caused by the subclinical infection increases the birds susceptibility to secondary bacterial infections which poses a problem for the judicious antibiotic use in farm animals, both being important problems for the turkey industry [11]

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