Limits...
Causes of mortality and pathological lesions observed post-mortem in red squirrels (Sciurus vulgaris) in Great Britain.

Simpson VR, Hargreaves J, Butler HM, Davison NJ, Everest DJ - BMC Vet. Res. (2013)

Bottom Line: Epidermal hyperplasia of unknown aetiology was seen in squirrels showing crusty lesions of the ear pinnae on IoW (n = 3) and Brownsea Island (n = 1), associated in two cases with cutaneous wart-like growths.Red squirrels in Britain suffer premature or unnatural mortality due to a number of conditions in addition to squirrelpox, many of which result, directly or indirectly, from human activities: road traffic trauma, pet predation, toxoplasmosis, trap injuries, rodenticide poisoning and electrocution accounted for 61% of all recorded mortality in this study.Red squirrels are also affected by several diseases of unknown aetiology which merit further research.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wildlife Veterinary Investigation Centre, Chacewater, Truro, Cornwall TR4 8 PB, UK. vic@wildlifevic.org.

ABSTRACT

Background: The red squirrel population in Great Britain has declined dramatically in recent decades, principally due to squirrelpox. Concern exists that red squirrels may become extinct nationally and, as there has been limited research in to diseases other than squirrelpox, this study aimed to identify additional causes of mortality.

Results: Post-mortem examinations on 163 red squirrels found dead on Isle of Wight (IoW) England, in Scotland and at other locations in Great Britain showed that 41.7% (n = 68) were killed by road traffic and 9.2% (n = 15) by predators, principally domestic cats and dogs. The overall male/female ratio was 1.08/1. Fleas were recorded on 34.9% of IoW squirrels and on 43.8% of Scottish squirrels but sucking lice and ixodid ticks were only seen on Scottish squirrels. Bacterial infections were significant, particularly in association with respiratory disease (n = 16); two squirrels died of Bordetella bronchiseptica bronchopneumonia. Cases of fatal exudative dermatitis (n = 5) associated with a lukM-positive clone of Staphylococcus aureus occurred only on the IoW. Toxoplasmosis (n = 12) was also confined to IoW where it was responsible for almost one tenth (9.5%) of all deaths. Hepatozoonosis was common, especially in IoW squirrels, but was not considered a primary cause of mortality. Hepatic capillariasis affected four IoW squirrels and one from Scotland. Fungal infections included oral candidiasis, adiaspiromycosis and pulmonary phaeohyphomycosis. Neoplastic conditions diagnosed were: pulmonary carcinoma, gastric spindle cell tumour, renal papillary adenoma and trichoepithelioma. Epidermal hyperplasia of unknown aetiology was seen in squirrels showing crusty lesions of the ear pinnae on IoW (n = 3) and Brownsea Island (n = 1), associated in two cases with cutaneous wart-like growths. Miscellaneous diagnoses included chylothorax, electrocution, intussusception, suspected cholecalciferol rodenticide poisoning and foetal death and mummification. No cases of squirrelpox were diagnosed.

Conclusions: Red squirrels in Britain suffer premature or unnatural mortality due to a number of conditions in addition to squirrelpox, many of which result, directly or indirectly, from human activities: road traffic trauma, pet predation, toxoplasmosis, trap injuries, rodenticide poisoning and electrocution accounted for 61% of all recorded mortality in this study. Red squirrels are also affected by several diseases of unknown aetiology which merit further research.

Show MeSH

Related in: MedlinePlus

Cutaneous wart–like lesions. A: A proliferative wart-like lesion on a digit. Several similar lesions were present elsewhere on the same squirrel. B: Histological section of the lesion shown in Figure 3A showing keratinised papilliform proliferative projections of the epidermis. H & E stain, bar = 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4225685&req=5

Figure 3: Cutaneous wart–like lesions. A: A proliferative wart-like lesion on a digit. Several similar lesions were present elsewhere on the same squirrel. B: Histological section of the lesion shown in Figure 3A showing keratinised papilliform proliferative projections of the epidermis. H & E stain, bar = 1 mm.

Mentions: Four squirrels, three from the IoW and one from Brownsea Island had gross, crusty thickening of the pinnae, sometimes with keratinised or wart-like protuberances (Figure 2A). Histologically these lesions were associated with marked epidermal papilliform hyperplasia and orthokeratotic hyperkeratosis (Figure 2B). There was variable inflammatory cell infiltration of the dermis, no evidence of primary bacterial, fungal or parasite infections and no visible epidermal inclusions. However, in one case there was serocellular crusting and pustule formation and in a second case there was an ulcerated trichoepithelioma (Figure 2B). The squirrel in the latter case died of a pulmonary carcinoma but there was no apparent cause of death for the other two. No details were available for the squirrel from Brownsea with thickened ears but in two IoW cases wart-like skin lesions were also observed elsewhere, notably on the digits (Figure 3A). One such lesion examined histologically showed heavily keratinised papilliform proliferative projections of the epidermis but no significant inflammatory change and no evidence of an infectious agent (Figure 3B).


Causes of mortality and pathological lesions observed post-mortem in red squirrels (Sciurus vulgaris) in Great Britain.

Simpson VR, Hargreaves J, Butler HM, Davison NJ, Everest DJ - BMC Vet. Res. (2013)

Cutaneous wart–like lesions. A: A proliferative wart-like lesion on a digit. Several similar lesions were present elsewhere on the same squirrel. B: Histological section of the lesion shown in Figure 3A showing keratinised papilliform proliferative projections of the epidermis. H & E stain, bar = 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225685&req=5

Figure 3: Cutaneous wart–like lesions. A: A proliferative wart-like lesion on a digit. Several similar lesions were present elsewhere on the same squirrel. B: Histological section of the lesion shown in Figure 3A showing keratinised papilliform proliferative projections of the epidermis. H & E stain, bar = 1 mm.
Mentions: Four squirrels, three from the IoW and one from Brownsea Island had gross, crusty thickening of the pinnae, sometimes with keratinised or wart-like protuberances (Figure 2A). Histologically these lesions were associated with marked epidermal papilliform hyperplasia and orthokeratotic hyperkeratosis (Figure 2B). There was variable inflammatory cell infiltration of the dermis, no evidence of primary bacterial, fungal or parasite infections and no visible epidermal inclusions. However, in one case there was serocellular crusting and pustule formation and in a second case there was an ulcerated trichoepithelioma (Figure 2B). The squirrel in the latter case died of a pulmonary carcinoma but there was no apparent cause of death for the other two. No details were available for the squirrel from Brownsea with thickened ears but in two IoW cases wart-like skin lesions were also observed elsewhere, notably on the digits (Figure 3A). One such lesion examined histologically showed heavily keratinised papilliform proliferative projections of the epidermis but no significant inflammatory change and no evidence of an infectious agent (Figure 3B).

Bottom Line: Epidermal hyperplasia of unknown aetiology was seen in squirrels showing crusty lesions of the ear pinnae on IoW (n = 3) and Brownsea Island (n = 1), associated in two cases with cutaneous wart-like growths.Red squirrels in Britain suffer premature or unnatural mortality due to a number of conditions in addition to squirrelpox, many of which result, directly or indirectly, from human activities: road traffic trauma, pet predation, toxoplasmosis, trap injuries, rodenticide poisoning and electrocution accounted for 61% of all recorded mortality in this study.Red squirrels are also affected by several diseases of unknown aetiology which merit further research.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wildlife Veterinary Investigation Centre, Chacewater, Truro, Cornwall TR4 8 PB, UK. vic@wildlifevic.org.

ABSTRACT

Background: The red squirrel population in Great Britain has declined dramatically in recent decades, principally due to squirrelpox. Concern exists that red squirrels may become extinct nationally and, as there has been limited research in to diseases other than squirrelpox, this study aimed to identify additional causes of mortality.

Results: Post-mortem examinations on 163 red squirrels found dead on Isle of Wight (IoW) England, in Scotland and at other locations in Great Britain showed that 41.7% (n = 68) were killed by road traffic and 9.2% (n = 15) by predators, principally domestic cats and dogs. The overall male/female ratio was 1.08/1. Fleas were recorded on 34.9% of IoW squirrels and on 43.8% of Scottish squirrels but sucking lice and ixodid ticks were only seen on Scottish squirrels. Bacterial infections were significant, particularly in association with respiratory disease (n = 16); two squirrels died of Bordetella bronchiseptica bronchopneumonia. Cases of fatal exudative dermatitis (n = 5) associated with a lukM-positive clone of Staphylococcus aureus occurred only on the IoW. Toxoplasmosis (n = 12) was also confined to IoW where it was responsible for almost one tenth (9.5%) of all deaths. Hepatozoonosis was common, especially in IoW squirrels, but was not considered a primary cause of mortality. Hepatic capillariasis affected four IoW squirrels and one from Scotland. Fungal infections included oral candidiasis, adiaspiromycosis and pulmonary phaeohyphomycosis. Neoplastic conditions diagnosed were: pulmonary carcinoma, gastric spindle cell tumour, renal papillary adenoma and trichoepithelioma. Epidermal hyperplasia of unknown aetiology was seen in squirrels showing crusty lesions of the ear pinnae on IoW (n = 3) and Brownsea Island (n = 1), associated in two cases with cutaneous wart-like growths. Miscellaneous diagnoses included chylothorax, electrocution, intussusception, suspected cholecalciferol rodenticide poisoning and foetal death and mummification. No cases of squirrelpox were diagnosed.

Conclusions: Red squirrels in Britain suffer premature or unnatural mortality due to a number of conditions in addition to squirrelpox, many of which result, directly or indirectly, from human activities: road traffic trauma, pet predation, toxoplasmosis, trap injuries, rodenticide poisoning and electrocution accounted for 61% of all recorded mortality in this study. Red squirrels are also affected by several diseases of unknown aetiology which merit further research.

Show MeSH
Related in: MedlinePlus