A re-evaluation of known and potential pathogens in canine and feline infectious respiratory disease



Afonso, MM
(2019) A re-evaluation of known and potential pathogens in canine and feline infectious respiratory disease. PhD thesis, University of Liverpool.

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Abstract

Respiratory infections represent an important and frequent cause of disease in cats and dogs worldwide. Many pathogens have been associated with feline (FIRD) and canine infectious respiratory disease (CIRD) including feline calicivirus (FCV) and herpesvirus (FeHV-1) in cats and canine distemper virus (CDV), parainfluenza virus (CPiV), adenovirus type 2 (CAV-2), herpesvirus (CHV) and Bordetella bronchiseptica in dogs. All these pathogens are currently included in either core or non-core vaccines, leading to a reduction in overall disease burden. Despite widespread use of vaccines, disease is still present at significant levels. In dogs, several new pathogens, potentially associated with respiratory disease, have recently emerged including canine respiratory coronavirus (CRCoV) and canine pneumovirus (CnPnV). In cats, it has been theorised that the high rates of evolution of viruses such as FCV may lead to a reduction of vaccine efficacy. Finally, even though respiratory disease of suspected infectious origin is frequent, the culprit often remains unidentified. This thesis aims to build understanding of canine and feline infectious respiratory disease epidemiology, re-evaluate the roles of known and suspected pathogens in this syndrome and to aid in informing the development of new disease prevention strategies. During a cross-sectional study across 6 European countries, samples were collected from 1521 veterinary practice attending cats. The prevalence of FCV in this population was 9.2%. Phylogenetic analysis of these field isolates showed high viral variability with a radial phylogeny. In vitro viral neutralisation suggested that antibodies raised to the FCV-F9 vaccine strain (which has been widely in use for decades) are still broadly cross-reactive to contemporary field isolates. A retrospective serosurvey of 200 canine and 179 feline samples screened for influenza A and B viruses suggested that UK dogs and cats have been rarely exposed to influenza viruses in recent years with only 1.5% of canine samples being seropositive for equine H3N8 and 0.56% of feline samples being seropositive to human pandemic 2009 H1N1. Two case control studies were conducted in British veterinary practices in order to re-appraise the role of known and potential upper respiratory pathogens in pet dogs and cats. In the feline study, FCV was detected in 21.1% of cases and 4.7% controls. FeHV-1 was detected in 10.5% cases and 1.6% controls. Bordetella bronchiseptica was identified in 5.3% cases and 9.4% controls. Finally, 65.8% cases and 48.8% controls were positive for M. felis. In the canine study, CRCoV was identified in 6.1% of cases, CnPnV in 4.4% cases and 1.2% controls, M.cynos in 4.4% cases and 2.3% controls, and B.bronchiseptica in 6.7% cases and 20.7% controls. No samples tested positive for CAV-2, CPiV, CHV, CDV, influenza A, Streptococcus equi subsp. zooepidemicus or C.felis. A cross-sectional sampling of dogs and cats was conducted in four British shelters with one of these also taking part in a 10-week longitudinal study. FCV, FeHV-1 and M. felis were detected in 7.4%, 4.6% and 16.8% feline samples. Cross-sectional dog samples tested negative for all pathogens included in the study. In the longitudinal study, M. felis was the most frequently encountered microorganism followed by FCV in cats. In dogs, CnPnV was identified during two weeks that coincided with reports of canine respiratory disease by members of the shelter staff. Together, findings confirm the importance of CIRD and FIRD as multifactorial syndromes in both pet and unowned shelter populations where pathogen shedding is often observed without clinical signs. In FIRD, FCV is reaffirmed as a majorly important disease causing pathogen. Finally, where CIRD is concerned, findings suggest that recently emerged pathogens such as CRCoV are of increasing importance in this syndrome whereas classic pathogens seem to be less and less present, likely due to widespread vaccination.

Item Type: Thesis (PhD)
Divisions: Faculty of Health and Life Sciences
Depositing User: Symplectic Admin
Date Deposited: 07 Jan 2020 10:43
Last Modified: 03 Oct 2021 07:11
DOI: 10.17638/03059917
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3059917