Surveillance and Characterisation of the Humoral Immune Response to SARS-CoV-2 in UK Companion Animals during the COVID-19 Pandemic

Bayne Tyson, Grace (2025) Surveillance and Characterisation of the Humoral Immune Response to SARS-CoV-2 in UK Companion Animals during the COVID-19 Pandemic. PhD thesis, University of Glasgow.

Abstract

The 2019 emergence of SARS-CoV-2, the causative agent of the COVID-19 pandemic, resulted in a global public health crisis. The virus is believed to have emerged from bats, via an intermediate animal species into the human population. This significant spillover has laid bare the significant gaps in the scientific community’s understanding of coronaviruses and the surveillance of viruses in animal species. Although SARS-CoV-2 can be considered primarily as a human pathogen, it has been shown to infect a diverse range of animal species, including white-tailed deer, mink and companion animals such as cats and dogs. These animal infections have resulted in severe pathologies in numerous cases, as well as rare instances of animal-to-human transmission.

In human diagnostics, reverse transcription polymerase chain reaction (RT-PCR) testing has been the gold standard for identifying active SARS-CoV-2 infections throughout the pandemic. RT-qPCR can also be used to identify SARS-CoV-2 animal infections. This thesis outlines a series of SARS-CoV-2 RT-qPCR-confirmed cases in domestic cats, demonstrating a range of clinical manifestations and outcomes. The occurrence of severe and sometimes fatal infections in both cats and dogs not only raises concerns for animal health, but also for public health, given the close contact between pets and humans and previously documented cases of SARS-CoV-2 zoonosis.

RT-qPCR’s utility in animals is limited by challenges in detecting asymptomatic or transient infections. As such, this thesis details the development of an enzyme-linked immunosorbent assay (ELISA) to be used alongside a pseudotype virus neutralisation assay (PVNA), to detect previous exposure to SARS-CoV-2 in companion animal populations. These assays were used in combination to test 5847 residual diagnostic feline samples, finding a neutralising antibody seroprevalence of 4.8%, alongside an ELISA seroprevalence of 13.7%. This large non-neutralising response is likely driven by the production of antibodies against viral epitopes that are not conducive to virus neutralisation, suggesting a complex humoral immune profile in cats following natural infection. Additionally, several demographic risk factors for SARS-CoV-2 seropositivity were identified in cats, including age and breed.

A companion serosurvey in dogs, comprising a smaller sample size, demonstrated a comparable overall seroprevalence (4.3% neutralising and 14.3% seropositive on ELISA) but notably lower antibody titres, indicating a weaker humoral immune response relative to cats. Analysis of immune responses in both species showed variant-dependent patterns of antibody neutralisation, which implied the existence of at least two distinct SARS-CoV-2 serotypes.

A small serosurvey was also conducted on pre-pandemic raccoon dog sera, uncovering evidence of antibodies against an unknown Betacoronavirus that were capable of cross-neutralising multiple SARS-CoV-2 variants. This finding provides insight into the potential role of raccoon dogs as hosts of coronaviruses with zoonotic potential and underscores the importance of expanded viral surveillance in wildlife.

The findings outlined in this thesis emphasise the importance of adopting a One Health approach to pandemic preparedness, integrating human, animal, and ecosystem health research to provide a comprehensive understanding of coronavirus transmission and evolution. The data presented also highlight the requirement for enhanced surveillance of coronavirus infections in companion animals, bats, raccoon dogs, and other wildlife to better characterise the Coronaviridae family and identify potential emerging threats. This knowledge is essential for the understanding of the origins of human coronaviruses like SARS-CoV-2, as well as for informing vaccine strategies, veterinary diagnostics and public health messaging.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QL Zoology; Q Science > QR Microbiology > QR355 Virology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Supervisor's Name: Weir, Professor Willie, Hosie, Professor Margaret, Williett, Professor Brian and Murcia, Professor Pablo
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85635
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 02 Dec 2025 14:57
• Last Modified: 02 Dec 2025 15:21
• Thesis DOI: 10.5525/gla.thesis.85635
• URI: https://theses.gla.ac.uk/id/eprint/85635

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