Demodex mite infection is commonly reported in the dog, but less common in the cat. When feline demodicosis is diagnosed an underlying cause should be sought as it has been associated with serious disease such feline leukaemia, cancer and diabetes.
Mac Kneipp BVSc MANZCVS October, 2014
Feline demodicosis is caused by three mites; Demodex gatoi, Demodex cati, and an unnamed demodex (Moriello, et al., 2013; Miller, et al., 2013). Identifying which mite(s) is involved is important because they cause different clinical diseases (Chesney, 1988; Tater & Patterson, 2008; Saari, et al., 2009) D. gatoi diagnosis may require multiple superficial skin-scrapings or trial treatment of affected and in-contact cats. D. cati is more likely to be diagnosed by large-area, deep skin-scrapings (Tater & Patterson, 2008). D.gatoi-associated intensely pruritic dermatitis has been compared to other superficial manges, like sarcoptes (Wilkinson, 1983), whilst D. cati causes lifelong follicular demodicosis like canine Demodex canis.
D. gatoi-associated dermatitis is an emerging contagious skin disease (Saari, et al., 2009), history and examination of in-contact cats is important (Morris, 1996).
D. cati-associated dermatitis can be localized, generalized or ceruminous otitis externa (Scott, 1980). Localized demodicosis often involves the face (Beale, 2012). Two cases were reported on the muzzle of cats treated with inhalant glucocorticoids (Bizikova, 2014). History of medications, particularly glucocorticoid use, is relevant (Tater & Patterson, 2008). Demodex cati is a “classic” follicular-dwelling demodex with infestation starting when the neonate is suckled (Nutting, 1984). The mite can be considered part of the natural feline skin microfauna, having evolved to be immunologically recognized as ‘self’ (Chesney,1989). There is little or no reaction or pruritus (Beale, 2012). Some question whether D cati alone causes clinical disease (Chesney,1989). If dermatitis occurs an investigation of factors that alter the host’s immune system is warranted (L Medleau, 1988). D. cati has been described as an “opportunist dermatosis associated with internal disease” (Muller, 2004).
The search for underlying factors may be more rewarding in feline demodicosis than in canine demodicosis and “history, clinical and laboratory examinations should be directed to this possibility” (Chesney, 1989). D. cati mange has been associated with; feline immunodeficiency virus (J A Neel, 2007), feline leukaemia virus (Guaguere, 1993), neoplasia (Guaguere, et al., 1999) (Johnstone, 2002), cutaneous xanthoma (Vogelnest, 2001), systemic lupus erythematosus (L Medleau, 1988), toxoplasma (Guaguere, et al., 1999), diabetes mellitus (S D White, 1987) and hyperadrenocorticism (Muller, 2004).
In some cases of generalized D. cati demodicosis no underlying disease is found (Miller, et al., 2013; Beale, 2012).
A diagnosis of D gatoi contagious mange warrants examination of in-contact cats. A diagnosis of D cati demodicosis warrants a careful review for concurrent disease or immunosuppressants; physical examination, thorough history and laboratory tests (complete blood count, serum chemistry, faecal examination, feline leukaemia and FIV testing) as a minimum.
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