Seals: a natural experiment in cross-species transmission, adaptation and pathogenicity of influenza A virus

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Today, we can painfully appreciate that infectious diseases from animals pose a substantial threat to human life and society. As we continue to grapple with COVID-19, experts agree that a new influenza pandemic remains a matter of 'when', not 'if'. Our ability to prevent and respond to future pandemics depends on identifying all potential sources of influenza that could spill over into humans and designing new treatments and vaccines. The biggest source of threat are livestock - poultry and pigs; these are extensively monitored and studied by global research networks already. However, an epidemic can also arise from a less expected and understood place, and seals are a prime candidate. There are three reasons why we need to study influenza in seals. First, grey seals are likely one of the largest least well-understood mammalian reservoirs of influenza, which pose a threat to both humans and wildlife. This is especially important now because grey seals in the UK are seeing an unprecedented level of population growth. Second, unlike livestock, influenza spreads freely in wild populations of grey seals without any human intervention. This offers a unique natural experiment, from which we can learn how influenza adapts to mammals over time. This will enhance our ability to predict the source and nature of future pandemics generally. Third, there are strong indications that grey seals manage to co-exist with influenza without adverse effects, while closely related harbour seals are known to suffer mass mortality events where thousands die. A comparative study of the different seal species can uncover drivers of the difference and lead us to new disease interventions. In my study, I will use swab and blood samples from wild grey and harbour seals in Scotland collected by SMRU (Sea Mammal Research Unit) at the University of St Andrews. I will also use samples from stranded seals taken to wildlife rescue centres run by the RSPCA (Royal Society for Prevention of Cruelty to Animals) and the UK government's APHA (Animal and Plant Health Agency). My aims are to understand the dynamics of influenza infections in seal populations and to identify the host factors that drive differences in disease severity. At Oxford, I will analyse the samples with cutting-edge sequencing technologies and computational biology, along with molecular methods to study wild animal biology in the lab. The project will establish a UK-wide network of collaborators from universities, specialist institutions, charities, and government agencies to address fundamental questions in biology with implications for human and wildlife health.