No abstract

Between 2007 and 2014, 337 free-living red squirrels () on Jersey, Channel Islands, were examined post mortem as part of a mortality and disease surveillance scheme. Road traffic accidents (RTAs) were attributable for 50.7 per cent (171/337) of the casualties, 34.4 per cent (116/337) succumbed to diseases including fatal exudative dermatitis (FED), 7.1 per cent (24/337) to predation, 6.5 per cent (22/337) to other trauma and 1.2 per cent (4/337) to suspected poisoning. Cat predation accounted for 5 per cent (17/337) of mortalities. Pathologies were diverse and individual animals were often identified with more than one disease process. Squirrelpox virus (SQPV) particles were not detected in selected cases examined by transmission electron microscopy (TEM). Amyloid was identified in 19.3 per cent (65/337) of squirrels, often in conjunction with inflammatory lesions like hepatic capillariasis. A consistent cause of amyloid accumulation was not identified, although there was a significant association of amyloidosis with hepatic capillariasis and FED. In addition to RTAs, amyloidosis and FED have been identified as important causes of squirrel morbidity and mortality on Jersey, while the underlying aetiology and predisposing factors for these two disease complexes are presently unclear. Disease, fragmented woodlands, an increasingly suburban habitat, along with various anthropogenic factors, may jeopardise the long-term viability of this island red squirrel population.

Red squirrels (Sciurus vulgaris) found dead or dying on the Isle of Wight and the island of Jersey were suffering from exudative, ulcerative dermatitis and superficial staphylococcal pyoderma. The principal gross lesions were on the lips, eyelids and feet and showed similarities to those of squirrelpox. The histopathological lesions were also similar and, although there was no ballooning degeneration of epidermal cells, intracytoplasmic inclusions resembling those seen in poxvirus infections were present. Examination of lesions by electron microscopy failed to identify any virions, and PCR analysis for squirrelpox virus proved negative. The skin lesions also resembled those of mange, but although numerous mites were present in the fur these were mostly Dermacarus sciurinus with small numbers of Metalistrophorus pagenstecheri. The occurrence of these species on red squirrels in Britain is confirmed, but neither is pathogenic and they were not considered to have been involved in the pathogenesis of the dermatitis, the primary cause of which was not established.

Transmission electron microscopy identified adenovirus particles in 10 of 70 (14.3 per cent) samples of large intestinal content collected at postmortem examination from free-living wild red squirrels (Sciurus vulgaris) across Great Britain between 2000 and 2009. Examination was limited to cases in which an enteropathy was suspected on the basis of predetermined macroscopic criteria such as semi-solid or diarrhoeic faeces, suspected enteritis or the presence of intussusception. In most cases, meaningful histological examination of enteric tissue was not possible due to pronounced autolysis. Two (2.9 per cent) of the samples were negative for adenovirus but were found to contain rotavirus particles, a novel finding in this species.

Wildlife populations have been introduced to new areas by people for centuries, but this human-mediated movement can disrupt natural patterns of genetic structure by altering patterns of gene flow. Insular populations are particularly prone to these influences due to limited opportunities for natural dispersal onto islands. Consequently, understanding how genetic patterns develop in island populations is important, particularly given that islands are frequently havens for protected wildlife. We examined the evolutionary origins and extent of genetic structure within the introduced island population of red squirrels (Sciurus vulgaris) on the Channel Island of Jersey using mitochondrial DNA (mtDNA) control region sequence and nuclear microsatellite genotypes. Our findings reveal two different genetic origins and a genetic architecture reflective of the introductions 120 years ago. Genetic structure is marked within the maternally inherited mtDNA, indicating slow dispersal of female squirrels. However, nuclear markers detected only weak genetic structure, indicating substantially greater male dispersal. Data from both mitochondrial and nuclear markers support historic records that squirrels from England were introduced to the west of the island and those from mainland Europe to the east. Although some level of dispersal and introgression across the island between the two introductions is evident, there has not yet been sufficient gene flow to erase this historic genetic “footprint.” We also investigated if inbreeding has contributed to high observed levels of disease, but found no association. Genetic footprints of introductions can persist for considerable periods of time and beyond traditional timeframes of wildlife management.