Page 1515 - Clinical Small Animal Internal Medicine

165 Parasitic Skin Diseases 1453

hair follicles and sebaceous glands. This mite is slightly
VetBooks.ir narrower than D. canis. Demodex gatoi has a shortened
abdomen and spends its life cycle on the epidermal
surface. The length of the unnamed mite is between
D. cati and D. gatoi.
Demodicosis due to D. cati is typically associated with
an underlying disease or immunosuppressive therapy.
Concurrent diseases that may be present include feline
immunodeficiency virus, feline leukemia virus, diabetes
mellitus, squamous cell carcinoma in situ or other neoplastic
disorders, toxoplasmosis, systemic lupus erythematosus,
and hyperadrenocorticism. It has been reported to be
more common in the Burmese and Siamese breeds.
Demodex gatoi, unlike D. cati, is not generally associ-
ated with an underlying disease. However, it has been
identified in scrapings along with D. cati in cats positive
for feline immunodeficiency virus. This mite is more
commonly located in certain geographic areas. In the
United States, it is more often found in the south, Figure 165.6 Self‐induced, clinically noninflammatory, symmetric
especially in the Gulf of Mexico area. alopecia on the dorsum and thighs of a cat with demodicosis
Little is currently known about the unnamed Demodex caused by Demodex gatoi.
mite. The published reports have found this mite in cats
diagnosed with other concurrent illnesses or had recently ingest these mites during grooming. Therefore, scraping
recovered from illness. areas where the cat cannot groom may increase the
chances of finding mites. Fecal flotation may be another
History and Clinical Signs means of finding D. gatoi. Cellophane tape impressions
Demodex cati can cause either a localized or generalized viewed under the microscope may help to reveal the
infestation, both of which are rare. Localized demodico- mites. A negative test does not rule out this infestation so
sis is primarily located around areas on the head, includ- diagnosis in many cases may only be made based on his-
ing in the ears, causing a ceruminous otitis externa, tory and response to a therapeutic trial. The unnamed
particularly in feline immunodeficiency virus‐positive mite has been found via trichoscopy and skin scrapings.
cats. Pruritus is variable but typically not present. Other
signs include alopecia, erythema, and the presence of Therapy
scales and crusts. Generalized cases often affect the head Underlying causes leading to the development of demod-
but lesions are also found elsewhere on the body. icosis caused by D. cati should be evaluated. This disease
Presentation is similar to the localized form, but may when localized may resolve spontaneously if underlying
include hyperpigmentation. diseases have been controlled. Amitraz (Mitaban; Zoetis)
Demodicosis caused by D. gatoi is more common than at concentrations of 0.0125–0.025% applied weekly may
the disease caused by D. cati. It is contagious between help. Cats are sensitive to this product and it is not rec-
cats and pruritic. Clinical signs are typically fitting with ommended in cats with diabetes. A generally safe option
the degree of pruritus. Traumatic alopecia often results is lime sulfur applied as a 2–4% solution every week.
from the severe pruritus on the sides of the thorax, Unfortunately, therapy may need to be continued long
abdomen, and the medial aspect of the legs. Other signs term as relapses are possible. Other treatment options
include erythema, scale, excoriation, and hyperpigmen- include doramectin administered weekly at 0.6 mg/kg SC
tation. A common clinical presentation is self‐ induced, and ivermectin at 0.2–0.3 mg/kg PO daily to every other
clinically noninflammatory, symmetric alopecia day. Cats should be monitored for side‐effects such as
(Figure 165.6). Some cats can be asymptomatic carriers. neurotoxicity. The off-label use of the oral isoxazoline
fluralaner (Bravecto) for the treatment of demodicosis
Diagnosis has been reported in cats. A single oral dosage of 28 mg/kg
Skin scrapings should be performed in cases where feline resolved D. cati in one case report. No side‐effects were
demodicosis is suspected. Broad, superficial scrapings noted. Topical fluralaner, which is available for cats, may
are performed to detect D. gatoi (surface mite), whereas cause vomiting and diarrhea, decreased appetite, or
deep skin scrapings must be done to diagnose D. cati (fol- lethargy. It may also cause alopecia or crusting. While a
licular). Demodex gatoi mites are typically more difficult single topical treatment has been shown to be efficacious
to find due to their small size and low numbers as cats for the treatment of Otodectes cynotis in cats, there are