Serological and molecular epidemiology of canine adenovirus type 1 in red foxes (Vulpes vulpes) in the United Kingdom.

David Walker,Adrian W Philbey,Jane Learmount,Barend M De C Bronsvoort,Thibaud Porphyre,Gill Hartley,Colin P Sharp,Maria J H O’Hagan,Seán A Fee,Anna L Meredith

doi:10.1038/srep36051

Abstract

Canine adenovirus type 1 (CAV-1) causes infectious canine hepatitis (ICH), a frequently fatal disease which primarily affects canids. In this study, serology (ELISA) and molecular techniques (PCR/qPCR) were utilised to investigate the exposure of free-ranging red foxes (Vulpes vulpes) to CAV-1 in the United Kingdom (UK) and to examine their role as a wildlife reservoir of infection for susceptible species. The role of canine adenovirus type 2 (CAV-2), primarily a respiratory pathogen, was also explored. In foxes with no evidence of ICH on post-mortem examination, 29 of 154 (18.8%) red foxes had inapparent infections with CAV-1, as detected by a nested PCR, in a range of samples, including liver, kidney, spleen, brain, and lung. CAV-1 was detected in the urine of three red foxes with inapparent infections. It was estimated that 302 of 469 (64.4%) red foxes were seropositive for canine adenovirus (CAV) by ELISA. CAV-2 was not detected by PCR in any red foxes examined. Additional sequence data were obtained from CAV-1 positive samples, revealing regional variations in CAV-1 sequences. It is concluded that CAV-1 is endemic in free-ranging red foxes in the UK and that many foxes have inapparent infections in a range of tissues.

Highlights

Antibodies against CAV were detected in sera from 17 of 485 (3.5%) red foxes in Germany[10] and in tissue fluid extracts from 11 of 58 (19%) red foxes in England and Scotland[7]
None of 19 foxes were positive for canine adenovirus type 1 (CAV-1) by polymerase chain reaction (PCR) in faeces and no animals were positive for canine adenovirus type 2 (CAV-2) in either faeces or urine
This study has shown that 18.8% of red foxes from across the UK, all of which were free from gross evidence of Infectious canine hepatitis (ICH) on post-mortem examination, were positive for CAV-1 sequences by PCR, consistent with inapparent infection

Summary

Introduction

Antibodies against CAV were detected in sera from 17 of 485 (3.5%) red foxes in Germany[10] and in tissue fluid extracts from 11 of 58 (19%) red foxes in England and Scotland[7]. The aim of this study was to examine the role of red foxes in the UK as a wildlife reservoir of CAV-1 and as a potential source of infection for domestic dogs. In this survey, the first in the UK to use molecular methods for the detection and sequencing of CAV-1, we investigated the epidemiology of CAV-1 in red foxes across the UK, comprising Great Britain (GB, which includes England, Scotland and Wales) and Northern Ireland (NI); the occurrence of CAV-1 in red foxes in Wales and NI has not been assessed previously. We examined whether red foxes might harbour CAV-2

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