Abstract
Invasive species have been cited as major causes of population extinctions in several animal and plant classes worldwide. The North American grey squirrel (Sciurus carolinensis) has a major detrimental effect on native red squirrel (Sciurus vulgaris) populations across Britain and Ireland, in part because it can be a reservoir host for the deadly squirrelpox virus (SQPV). Whilst various researchers have investigated the epizootiology of SQPV disease in grey squirrels and have modelled the consequent effects on red squirrel populations, less work has examined morphological and physiological characteristics that might make individual grey squirrels more susceptible to contracting SQPV. The current study investigated the putative relationships between morphology, parasitism, and SQPV exposure in grey squirrels. We found geographical, sex, and morphological differences in SQPV seroprevalence. In particular, larger animals, those with wide zygomatic arch widths (ZAW), males with large testes, and individuals with concurrent nematode and/or coccidial infections had an increased seroprevalence of SQPV. In addition, males with larger spleens, particularly those with narrow ZAW, were more likely to be exposed to SQPV. Overall these results show that there is variation in SQPV seroprevalence in grey squirrels and that, consequently, certain individual, or populations of, grey squirrels might be more responsible for transmitting SQPV to native red squirrel populations.
Highlights
There is a strong link between infectious disease and biodiversity because individual success, survival, and, the viability of entire host populations depend upon interactions with external pathogens [1]
We determined whether individuals with higher parasite burdens were more likely to be exposed to squirrelpox virus (SQPV); whether males in general and, whether those with larger testes were more likely to be seropositive for SQPV; and whether there were any links between spleen size, zygomatic arch widths (ZAW), and SQPV exposure
Small males with a narrow ZAW were more likely to be exposed to SQPV than larger males with wide ZAW
Summary
There is a strong link between infectious disease and biodiversity because individual success, survival, and, the viability of entire host populations depend upon interactions with external pathogens [1]. Virulent pathogens may result in the rapid death of their host and initiate subsequent host population decline [7], whereas others can persist as low-grade chronic infections that are mediated immunologically [8]. Chronically diseased animals can be ‘‘carriers’’ within an ecosystem, potentially transmitting infection to other individuals [9]. The arrival of novel pathogens and/or infected hosts/vectors into a geographical area where the resident species were not previously exposed could facilitate disease transmission [10]. Diseases in resident individuals may present as acute rather than chronic [11]
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