Page 1513 - Clinical Small Animal Internal Medicine

165 Parasitic Skin Diseases 1451

and fistulous tracts are also present on paws when furun- clinical signs suggestive of demodicosis, consider this
VetBooks.ir culosis develops (Figure 165.4). finding important. This scenario is typically encountered
Demodex cornei mites have been found in demodicosis
in cases of juvenile, localized demodicosis.
caused by D. canis, suggesting that these mites are a mor-
Similar technique should be applied when D. injai
phologic variant of D. canis and not a separate species. infestation is suspected; however, mites can be harder to
Demodex injai typically manifests with dorsal and find because they are present in small numbers and often
occasionally facial seborrhea oleosa (Figure 165.5). In in sebaceous glands, making their extrusion difficult.
these areas, hypotrichosis is present. Pruritus may also Superficial scrapings should be adequate for D. cornei
be noted. but mites are typically not easy to find.
Trichoscopy may also reveal mites in severe cases of
Diagnosis demodicosis caused by D. canis. Various hairs are plucked
Diagnosis of D. canis infestation involves performing from affected areas, placed in mineral oil on a glass slide
multiple deep skin scrapings. As mites live in the hair and covered with a cover slip before microscopic evalua-
follicles and sebaceous glands, the lesional area is tion. These may or may not be positive in affected dogs.
squeezed before scraping in an attempt to extrude the Acetate tape impressions of affected squeezed skin have
mites. The scraping should be deep enough that capillary recently been shown to reveal mites in 100% of samples.
bleeding occurs. Multiple adult mites and/or immature Mites can also be found on cytology of exudate collected
forms are diagnostic. Mites should be easy to find if skin from draining tract lesions. Mites may also be identified
scrapings are performed adequately. If only a few mites using a zinc sulfate centrifugal fecal flotation technique. It
are found after multiple skin scrapings in an animal with is important to emphasize that sensitivity of these tests is
generally lower than that of deep skin scrapes adequately
performed. Biopsy may be needed in Chinese shar‐peis or
dogs with fibrotic lesions especially affecting the paws.
Mites can be found in the stratum corneum, hair follicles,
and on occasion the sebaceous glands. Inflammation
may present as an interface mural folliculitis, nodular
dermatitis, or a suppurative folliculitis and furunculosis.

Therapy
Affected dogs should be treated with appropriate sys-
temic antibiotics, if indicated. Supportive care may be
needed in severe cases. Underlying disease processes
should be addressed. Localized cases are typically self‐
limiting and resolve without treatment in about 6–8
weeks. Generalized cases should be treated for one
Figure 165.4 Feet of a dog with juvenile‐onset generalized month beyond two negative consecutive skin scrapings.
demodicosis caused by Demodex canis. Multiple tracts draining Skin scrapings are recommended monthly to assess
serosanguineous exudate correspond to areas of furunculosis. progress. Numbers of live versus dead mites and their life
stages can help assess response to therapy.
The most effective treatments are amitraz, macrocyclic
lactones, and isoxazolines. The only treatment currently
licensed in the United States is amitraz. Labeled treat-
ment is a 0.025% amitraz (Mitaban®; Zoetis) solution used
as a dip every 14 days. Variations of this therapy protocol,
such as weekly applications at 0.025%, 0.05%, 0.075% or
0.1%, can be considered for more difficult cases. Removal
of follicular debris, crusts, and hair that prevents penetra-
tion of the solution into the hair follicle is an important
part of this treatment regimen; therefore, medium to long
hair coats should be clipped and crusts removed prior to
dipping. This chemical is a monoamine oxidase inhibitor
as well as an alpha‐2‐adrenergic agonist. Potential side‐
effects include lethargy, ataxia, vomiting and diarrhea,
Figure 165.5 Excessive oil along the dorsum of a West Highland polyuria and polydipsia, bradycardia, depression, and
white terrier with demodicosis caused by Demodex injai. hyperglycemia. The person providing treatment should