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Cheyletiellosis 155

CONTAGION AND ZOONOSIS ○ If pruritus is present, DDx includes ecto-
• Cheyletiella spp mites are very contagious parasites (e.g., lice, fleas, scabies), hypersen-
VetBooks.ir • Cheyletiellosis is a zoonotic disease; humans food), pyoderma, and fungal infections Diseases and Disorders
sitivities (e.g., flea bites, atopic dermatitis,
and not host specific; they transfer readily
among dogs, cats, and rabbits.
(e.g., Malassezia, dermatophytosis).
are at risk if exposed to an infested pet
ectoparasites (e.g., lice, flea infestation,
(whether or not overt clinical signs are • In cats, DDx includes dermatophytosis,
present in the pet). otodectic mange), and hypersensitivities
(e.g., flea bites, food, environmental).
Clinical Presentation • In humans, the pruritic erythematous papular
HISTORY, CHIEF COMPLAINT eruption (papular urticaria) induced by a
Reason for presentation can be any combination hypersensitivity reaction to Cheyletiella mites
of scaling, pruritus, or zoonosis. is often indistinguishable from other zoonotic
(e.g., fleas, Sarcoptes spp, Dermanyssus spp) or
PHYSICAL EXAM FINDINGS nonzoonotic (e.g., harvest mites, straw itch
• Scaling (“dandruff”) noted primarily over mites, bedbugs) arthropod bite reactions.
the dorsum and neck and/or
• Mild to intense pruritus or overgrooming Initial Database
in cats and/or • Confirmation relies on collecting and
• Dorsal erythema, papules, and crusting noted identifying the mite or its eggs. Occasionally
occasionally, particularly in cats (“miliary they may be difficult to recover, especially in
dermatitis”) adult cats, because of cats’ grooming habits.
• Among the exfoliated epidermal cells, Chey- • Mites and eggs can be harvested using
letiella mites can be seen moving, hence the adhesive acetate tape (transparent Scotch
name “walking dandruff.” The term should tape) preparations, superficial skin scrapings, CHEYLETIELLOSIS Microscopic view of adult
not be overinterpreted; the mites are much flea combing, fecal flotation, or by collecting Cheyletiella mite. (Copyright Dr. Manon Paradis.)
smaller than skin scales, and a pet has to be scales dislodged when rubbing/petting the
very still to enable the clinician to see the animal’s back.
subtle movement of mites carrying scales • The epidermal debris is examined directly alternative in dogs but should never be
and/or the mites themselves. with a magnifying lens or is put on a glass used in collies or related breeds carrying the
• Some pets not noted by the owner to have slide, mixed with mineral oil, covered with a MDR1/ABCB1-Δ mutation (p. 638). The
clinical signs are presented for evaluation cover slip, and examined with a microscope injectable product (Ivomec 1% injection for
because of suspected zoonotic lesions in a at low power. cattle and swine) is usually given (0.3 mg/kg
human in contact with the animal. q 7 days PO or q 14 days SQ for 6-8 weeks).
Advanced or Confirmatory Testing The 0.5% alcohol-based pour-on ivermectin
Etiology and Pathophysiology Therapeutic trials with reliable acaricides are formulation (Ivomec Pour-On for cattle) is
• Cheyletiella is a relatively large mite essential to confirm or rule out cheyletiellosis also effective and practical when applied
(0.4 mm) with prominent hooklike mouth in pruritic or scaling animals with negative topically to the interscapular skin (0.5 mg/
parts. It lives on the skin surface and feeds samplings, as well as when a human in contact kg q 14 days for 3-4 treatments).
on surface debris and exudates. These has a pruritic papular eruption evocative of • Milbemycin oxime (Interceptor), albeit more
mites form pseudotunnels in the surface skin lesions caused by zoonotic arthropod bite expensive, is also effective (2 mg/kg PO q
keratin. reactions. 3-7 days for 6-9 doses).
• The mite eggs, smaller than lice eggs, are ○ Although not documented, isoxazoline
loosely attached to hair shafts. TREATMENT drugs are also likely to be effective.
• The entire life cycle is completed on the host
within ≈3 weeks. Treatment Overview Possible Complications
• Although adult mites may survive in the • The goal of treatment is to thoroughly eradi- In collies and other herding breeds, the MDR1/
environment for 10 days, eggs are shed into cate the mites. All affected and in-contact ABCB1-Δ mutation can cause intoxication with
the environment with the pet’s hair and may animals should be treated with an appropriate commonly recommended dosages of ivermectin
be an important source of reinfestation acaricide regardless of presence or absence or other off-label macrocyclic lactones (p. 638).
beyond those 10 days. of clinical signs.
• All suspected cheyletiellosis cases should PROGNOSIS & OUTCOME
DIAGNOSIS be treated even if the parasite has not been
isolated. • Prognosis with appropriate treatment is
Diagnostic Overview • Environmental treatment may be required excellent.
The diagnosis is suspected from the history and in severe cases. • In humans, the zoonotic infestation is tran-
clinical signs, potentially including zoonotic • Traditional topical acaricides (lime sulfur, sient, with resolution of the pruritic papular
lesions in humans. Demonstration of mites amitraz, organophosphates) have been largely eruption when the mites are eradicated from
or eggs under the microscope is confirmatory. replaced by off-label macrocyclic lactones. the animals.
Differential Diagnosis Acute General Treatment PEARLS & CONSIDERATIONS
• In dogs, differential diagnosis (DDx) depends • Selamectin (Revolution/Stronghold) and
on the clinical presentation. moxidectin/imidacloprid (Advantage Multi/ Comments
○ If only scaling is present, DDx includes Advocate) are not approved for the treatment • Infested animals may show no clinical signs.
ectoparasites (e.g., fleas, lice, Demodex), of cheyletiellosis but appear effective when • Cheyletiellosis is possible even if there is
intestinal parasitism, poor nutrition, applied topically every 2-4 weeks for 2 months. only one animal with clinical signs among
cornification disorders (e.g., ichthyosis, • Off-label ivermectin remains a treatment a household full of pets without any clinical
sebaceous adenitis). option in cats and can still be a therapeutic signs.

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