Abstract
BackgroundStoat (Mustela erminea) and weasel (Mustela nivalis) populations in south-west England are declining whilst polecats (Mustela putorius), absent for over a century, are increasing. Little is known about the health status of these species nationally. This study aimed at investigating respiratory disease in specimens found dead in south-west England.ResultsTrauma caused by road traffic, predator attack or being trapped was the predominant cause of death in 42 stoats, 31 weasels and 20 polecats; most were in good physical condition. Skrjabingylus nasicola was present in all species (weasels 37 %, polecats 39 %, stoats 41 %) and infected animals showed no evidence of loss of body condition. Even in carcases stored frozen L1 larvae were frequently alive and highly motile. Angiostrongylus vasorum infection was diagnosed in two stoats and one weasel: in stoats infections were patent and the lung lesions were likely of clinical significance. These are believed to be the first records of A. vasorum in small mustelids. Pleuritis and pyothorax was seen in two polecats, in one case due to a migrating grass awn. Histological examination of lungs showed granulomata in stoats (38 %), weasels (52 %) and polecats (50 %). Spherules consistent with Emmonsia spp. adiaspores were present in the granulomata of stoats (60 %), weasels (36 %) and polecats (29 %). Adiaspore diameter in all three species was similar (means: stoats 39 μm, weasels 30 μm, polecats 36 μm); these are markedly smaller than that normally recorded for E. crescens. Although they lie within the accepted range for spores of Emmonsia parva this arid-zone species is not found in Britain, thus raising a question over the identity of the fungus. Cases showing numerous granulomata but few or no adiaspores were Ziehl-Neelsen-stain negative for acid-fast bacilli and IHC negative for Mycobacterium spp. However, in some cases PCR analyses revealed mycobacteria, including Mycobacterium kumamotonense and Mycobacterium avium Complex. One stoat had numerous unidentified small organisms present centrally within granulomata.ConclusionsStoats, weasels and polecats in south-west England share several respiratory diseases, often of high prevalence, but the pathology would appear insufficient to impact on the health status of the populations and other ultimate causes of death should be investigated when examining these species.
Highlights
Stoat (Mustela erminea) and weasel (Mustela nivalis) populations in south-west England are declining whilst polecats (Mustela putorius), absent for over a century, are increasing
Evidence of Aleutian disease has been found in various mustelids in mainland Europe [15, 16] but a high antibody prevalence was recorded in feral American mink (Mustela vison) in south-east England [17], the infection has not been proven in other British small mustelids
Two conditions affecting mustelids that are well documented in Britain, as in many other countries, are adiaspiromycosis due to Emmonsia species fungi [18, 19] and upper respiratory tract infection by the nasal nematode Skrjabingylus nasicola [20, 21]
Summary
Stoat (Mustela erminea) and weasel (Mustela nivalis) populations in south-west England are declining whilst polecats (Mustela putorius), absent for over a century, are increasing. Canine distemper occurs worldwide [12] but whilst the disease has been well documented in mustelids in Europe [13] the only recorded cases in Britain were in captive stoats and weasels [14]. Evidence of Aleutian disease has been found in various mustelids in mainland Europe [15, 16] but a high antibody prevalence was recorded in feral American mink (Mustela vison) in south-east England [17], the infection has not been proven in other British small mustelids. Two conditions affecting mustelids that are well documented in Britain, as in many other countries, are adiaspiromycosis due to Emmonsia species fungi [18, 19] and upper respiratory tract infection by the nasal nematode Skrjabingylus nasicola [20, 21]
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