Canine and feline demodicosis - Veterinary Medicine
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Canine and feline demodicosis
You know demodectic mange frequently occurs in dogs. Now it appears to be more common in cats than previously thought, and new species have been discovered. Find out the latest on diagnosing and treating this frustrating skin disease.



Figure 12. An adult Demodex cati mite (50X).
Cats have two recognized species of Demodex mites. Microscopically, Demodex cati is similar in appearance to the canine mite D. canis (Figure 12).32 Likewise, it lives in the hair follicle. Although difficult to find, D. cati may be seen in clinically healthy cats as part of the normal cutaneous flora.

Figure 13. An adult Demodex gatoi mite (100X).
The short-bodied cat Demodex mite is Demodex gatoi. Like D. cornei in dogs, it resides in the stratum corneum layer of the epidermis. Demodex gatoi is about 55% shorter than the average length of D. cati and has a rounded opisthosoma (tail) (Figure 13).33,34 This species is considered potentially contagious to other cats.

Clinical signs

Figure 14. Scaling on the dorsum of a cat with Demodex gatoi infection.
Clinical signs of feline demodicosis secondary to D. cati infection are generally similar to those of canine demodicosis secondary to D. canis infection. Alopecia, erythema, crusting, and ceruminous otic discharge can all occur with D. cati infection. Pruritus may or may not be present. Clinical demodicosis due to D. cati infection in cats is often related to mite overgrowth secondary to an underlying systemic disease or immunosuppression.35,36

Figure 15. Patchy alopecia on the forelimb of a cat with Demodex gatoi infection.
Cats with demodicosis secondary to D. gatoi infection typically present for evaluation of moderate to severe pruritus. Self-induced alopecia secondary to overgrooming may be noted. We have especially noted scaling on the dorsum and self-induced alopecia on the forelimbs of cats with D. gatoi infection (Figures 14 & 15). Clinical signs of D. gatoi infection are indistinguishable from those of cats with allergic or psychogenic dermatologic conditions. Demodex gatoi infection caused pruritus in multiple cats in one household and, thus, may be contagious between cats.37 While this mite was initially reported to have a geographic focus in the southern United States, unpublished reports of D. gatoi infection occurring in other areas of the country exist. Consider D. gatoi infection a differential diagnosis in any pruritic cat.

Cats with feline demodicosis can be coinfected with both species of Demodex mites, and, in one such case, a cat had feline immunodeficiency virus (FIV) infection.38 Clinical signs included alopecia, pruritus, crusting, scaling, erythema, and papules.

Conduct a full physical examination, obtain a careful patient history, and perform laboratory tests (complete blood count, serum chemistry profile, microscopic fecal examination, feline leukemia virus and FIV testing) in all cats with demodicosis. Just as in dogs, both systemic and topical immunosuppressive therapies can trigger demodicosis in cats, especially in cases involving D. cati. Obtain a thorough drug history with special attention to glucocorticoid use from the client.


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