Immune interactions and heterogeneity in transmission drives the pathogen-mediated invasion of grey squirrels in the UK

Elizabeth Howell, Andrew Ronald White, Peter W. W. Lurz, Mike Boots

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1. Mathematical models highlighted the importance of pathogen-mediated invasion, with the replacement of red squirrels by squirrelpox virus (SQPV) carrying grey squirrels in the UK, a well-known example.
2. In this study, we combine new epidemiological models, with a range of infection characteristics, with recent longitudinal field and experimental studies on the SQPV dynamics in red and grey squirrel populations to better infer the mechanistic basis of the disease interaction.
3. A key finding is that a model with either partial immunity or waning immunity and reinfection, where individuals become seropositive on the second exposure to infection, that up to now has been shown in experimental data only, can capture the key aspects of the field study observations.
4. By fitting to SQPV epidemic observations in isolated red squirrel populations, we can infer that SQPV transmission between red squirrels is significantly (4×) higher than the transmission between grey squirrels and as a result our model shows that disease-mediated replacement of red squirrels by greys is considerably more rapid than replacement in the absence of SQPV.
5. Our findings recover the key results of the previous model studies, which highlights the value of simple strategic models that are appropriate when there are limited data, but also emphasise the likely complexity of immune interactions in wildlife disease and how models can help infer disease processes from field data.
Original languageEnglish
Pages (from-to)663-675
Number of pages13
JournalJournal of Animal Ecology
Issue number6
Early online date17 Mar 2024
Publication statusPublished - Jun 2024


  • conservation
  • epidemiological modelling
  • invasive species
  • shared pathogen

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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