Feline Demodicosis

Question 1

Feline Demodicosis

Answer 1

D. cati and D. gatoi
Skin scrape (superficial), may be negative if cat grooming
Differentials: psychogenic alopecia, atopy, food hypersensitivity, feline scabies, contact dermatitis, flea bite hypersensitivity
Tx with Revolution Plus (lyme sulfur no longer available), oral ivermectin

Question 2

Demodex cati

Answer 2

D. Cati similar to D. Canis, ova slim and oval and all immature life stages narrower in D. Cati than D. Canis, can be localized or generalized
Localized rare: eyelids, periocular, head, or neck, or ceremonious otitis external (FIV+)
Variably pruritic with patchy alopecia, erythema, scaling, and crusting
Localized is self-limiting and responds to tx with lime sulfur, pyrethrum-containing ear meds, or amitraz in mineral oil (1:9)
Generalized is rare and not as severe as dogs, more common in Siamese and Burmese
Lesions primarily face and head but may be on neck, trunk, and limbs
Circumscribed to diffuse areas of alopecia, scaling, erythema, hyperpigmentation, and crusting, some generalized; Pruritus variable but can be intense
Co-infection with D. Gatoi or other unnamed species reported
Generalized usually associated with underlying dz: DM, FeLV, SLE, HAC, FIV, or SCC in situ
Occ no underlying cause, but be aware of poss association with systemic dz
Histo: varying degrees of perifolliculitis and folliculitis, with mites in hair follicles
Unless resolve underlying dz, only controlled not cured, lime sulfur or amitraz dips weekly but relapse expected, possibly oral ivermectin (0.3mg/kg), weekly SQ doramectin (0.6mg/kg)

Question 3

Demodex gatoi

Answer 3

Taxonomically related to D. Criceti (epidermal pits in stratum corneum of hamsters)
Shorter and have broad, blunted abdomens
Superficially located, only inhabit stratum corneum
In non pruritic cats skin scrapings have numerous mites and ova (rapid reproduction), small and translucent and easily overlooked
Pruritic cats no mites may be seen, especially in those that lick their skin, contact housemate can be scraped b/c contagious or therapeutic trial
More prevalent and regionalized than cati, contagious but not all exposed will harbor mite or show pruritus, typically sudden onset, but history may suggest harboring mite for longer, intensity of pruritus and poor response to steroids may indicate hypersensitivity to the mite

Question 4

Demodex gatoi diagnosis

Answer 4

Traumatic alopecia most commonly lateral thorax, ventral and lateral abdomen, and medial aspects of all 4 legs, exposed skin may be erythematous and scaly or hyper pigmented, pending chronicity and intensity of pruritus
Histo: minimal inflammation, epidermis may be irregularly acanthotic and hyperkeratotic, mites in stratum corneum, no mites found in hair follicles
Differentials: all feline dermatoses associated with excessive grooming, psychogenic alopecia, atopy, food hypersensitivity, feline scabies, contact dermatitis, and fleabite hypersensitivity
Mite can be difficult to find on cats that groom excessively, short therapeutic trial recommended if suspected (pos response after 3 treatments)
Do not respond to spot-application products, need weekly lime sulfur or amitraz (125-250ppm), 6 or more needed, EOD ivermectin may be effective
Contagious and harbor asymptomatically, all contact cats need simultaneous treatment

Question 5

Dermatophytosis and anagen effluvium

Answer 5

Young animals with actively growing hairs (sudden illness causing disruption of hair cycle)

Question 6

Differentials:

Answer 6

Dermatophytosis
Nodoedres