Scaly face in the budgerigar is considered pathognomonic for knemidocoptiasis. A diagnosis is usually easily confirmed by
identifying the mites on a skin scraping under the microscope. With a small scalpel or a spatula, carefully obtain a small
sample of keratinized debris, scales, and crusts from the affected area. Then place the sample onto a slide premoistened with
a drop of mineral oil. For birds with thickened leg scales, gently remove a loose leg scale, and examine the underside with
a magnifying lens. Interfering with the base of any large crusts on passerines can result in hemorrhage and should be performed
carefully. Occasionally, you can directly see adult mites in honeycomb tunnels with a high-quality operating microscope.
The mites are recognized by their globoid shape and stubby legs that barely extend beyond the body's lateral margins.23
Knemidocoptes species mites are sexually dimorphous. Adult females are large and round (up to 0.5 mm in diameter), with short legs and
no stalks on the ends of the legs. The smaller male has long, unjointed stalks with pretarsi (resembling those of Sarcoptes species) on each leg (Figures 1 & 6A). Larvae have stalked pretarsi, and nymphs lack stalks. Compared with Sarcoptes and Notoedres species, Knemidocoptes species lack scales and spines on the dorsal surface. Their tarsal segments have clawlike structures and tactile hairs instead
of pediculated suckers. Look for larvae, nymphs, and adult mites; female mites are found more commonly than males. Also, mite
feces and shed nymphal skins may be seen in heavy infestations.
Occasionally, biopsy or tissue samples obtained at necropsy and submitted for histologic examination will yield more mites.
Mites cause papillomatous proliferation of the epidermis (acanthosis) and cystic degeneration of the feather follicles. Both
orthokeratotic and parakeratotic hyperkeratosis are seen and contribute to superficial keratin sloughing. Mites are seen within
all layers of the stratum corneum in heavy infestations, as demonstrated in the histologic sections in Figures 4A-4C.10,19,24
Rarely, mites will not be identified on cytologic or histologic examination in birds with classic lesions. In those cases,
a positive response to treatment confirms the diagnosis.