First case of fatal Aleutian disease documented in a striped skunk in Quebec
Last August, an adult male skunk (Mephitis mephitis) with severe lethargy was euthanized and submitted for analysis to CWHC-Quebec. The specimen was in very good body condition and the only abnormality detected on gross examination was the presence of dried secretions around the eyes and nostrils. The histological examination revealed lesions of tubulointerstitial nephritis, membranous glomerulonephritis, as well as nonsuppurative meningoencephalitis. The lesions of encephalitis could account for the lethargy observed. Although moderate, the renal lesions appear to be significant enough to have an impact on renal function (probable chronic renal failure).
These lesions are highly suggestive of Aleutian disease and the presence of the virus was confirmed by molecular analysis (PCR). Neither rabies virus nor distemper virus were detected by the DRIT method and PCR, respectively. This is the first case of Aleutian disease in skunks diagnosed in our laboratory.
Caused by a parvovirus, the Aleutian disease is an important threat for mink farms where it is responsible for epidemics causing significant economic losses. It takes its name from its first victim, the mink with the Aleutian coat colour gene, in which the virus was discovered in 1956, but it also affects mink with other color variants. It has also been reported in domestic ferret, river otter and striped skunk. The presence of antibodies against this virus has also been detected in other species of wild carnivores such as foxes and raccoons. The description of clinical signs likely caused by this virus in two mink farmers suggests that in rare cases this virus can cause disease in humans (Jepsen et al, 2009). In wild skunks, Aleutian disease is recognized as an emerging disease in Canada and California (United States); the presence of the virus (exposure and / or infection) has already been documented in Ontario, Nova Scotia, British Columbia, California, Georgia, and recently in Minnesota (Giannitti et al, 2018). The different molecular studies conducted in wild striped skunks show a high prevalence of carriers for this virus; 32% (14/40) in Ontario and 86% (30/35) in British Columbia. However, the infection seems subclinical in most individuals, suggesting these animals might primarily act as asymptomatic carriers (Britton et al, 2017; Canuti et al, 2017). It is also possible that in some cases the infection was detected before signs of disease became evident (Canuti et al, 2017).
The virus in question belongs to the family Parvoviridae and the genus amdoparvovirus. The genus is subdivided into four species (Carnivore amdoparvovirus 1-4). It is the Carnivore amdoparvovirus 1 species that cause Aleutian disease. A new genus, Carnivore amdoparvovirus 5, has recently been proposed to classify circulating virus in wild skunks (Canuti et al, 2017). Aleutian disease virus is highly contagious and is transmitted vertically or horizontally through direct and indirect contact with blood, urine, feces and saliva. Aerosol transmission may also occur (Britton et al 2017, according to Hunter 1996). The duration of the clinical course varies according to the species and breed: a few months in Aleutian minks and up to two years in ferrets and minks with other color variants. Chronic infection results in a high production of IgG (hypergammaglobulinemia) and immune complexes that are deposited on the basement membranes and cause arteritis, glomerulonephritis and systemic lymphoplasmocytic inflammation. The lesions observed are variable; lesions often found in skunks include lymphoplasmocytic hepatitis and nephritis (but not necessarily glomerulonephritis) as well as brain lesions such as neuronal degeneration or nonsuppurative meningoencephalitis (Williams et al, 2018, Britton et al 2017, LaDouceur et al. al, 2015; Allender et al 2008; Pennick et al, 2007). In this individual, the lesions were highly suggestive of Aleutian disease. However, this is not always the case and some authors suggest that infection should be suspected in any striped skunk with interstitial nephritis, glomerulonephritis, and/or multisystemic lymphoplasmacytic lesions involving the kidneys, heart, brain, liver, and lungs. (LaDouceur et al, 2015).
Marion Jalenques et Stéphane Lair, RCSF-Québec
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