Skin Scraping From a Cat
and haired regions. The fluorescence of the hairs was
suggestive of a dermatophyte infection. Dermatophy-
tosis was confirmed 6 days later with a positive fungal
culture. Microsporum canis was the isolated dermato-
phyte. Both topical and systemic treatments were initi-
ated. These consisted of weekly lime sulfur dips (Lym-
Dyp, 4 oz diluted with 1 gallon of water) and ultramicro-
size griseofulvin (Fulvicin P/G) therapy at 64 mg (10
mg/kg) PO twice daily with food for 1 month. A fungal
culture rechecked 27 days after the initial presentation
was negative. At this time, the cat appeared clinically
healthy.
Discussion
Figure 3. Skin scraping from a cat with Microsporum canis infec-
tion. Numerous small arthrospores are adherent to the squamous
epithelial cells as well as free in the background. Wright-Giemsa,
ϫ330.
Dermatophytosis is a common infectious and some-
times zoonotic disease involving the superficial layers of
the skin, hairs, and claws; keratin provides the primary
1
nutritional source for these fungi. Microsporum and Tri-
chophyton are the genera of dermatophytes that are most
2
often associated with animal infections. In cats, approx-
3
imately 98% of infections are attributed to M canis. Cats
seem to be the natural reservoir of this organism.
Transmission occurs via direct contact with infected ani-
mals or contact with fungal material on fomites. Rarely
4
does transmission occur from humans to cats. Also, cats
may be asymptomatic carriers of M canis, making this a
notable source of infection to other animals and
5
humans. This is important when one considers that
approximately 50% of humans exposed to clinically
6
affected and carrier cats develop skin lesions.
Cat populations at risk for developing infection
include kittens, cats with immunosuppressive diseases
such as feline leukemia virus and feline immunodefi-
ciency virus infections, cats being administered anti-
inflammatory or immunosuppressive drugs, cats with
genetic susceptibility such as the long-haired breeds,
cats infested with ectoparasites, and cats cohabiting in
large cat populations (ie, animal shelters, pet stores, cat-
Figure 4. A septate hypha along the surface of a hair shaft from a
cat with Microsporum canis infection. Wright-Giemsa, ϫ330.
Cytologic Interpretation
The smears consisted of moderate numbers of hair
shafts, squamous epithelial cells, and RBCs. Numerous
round to elongated (approximately 2-4 µm in diameter)
dark purple fungal spores surrounded by a thin, clear
halo were observed aggregated along the outside of sev-
eral of the hair shafts, adhered to the squamous epithe-
lial cell surface and scattered free in the background of
the smear (Figures 2 and 3). A few septate hyphae were
present along the hair shaft (Figure 4). The cytologic
diagnosis was a fungal infection compatible with der-
matophytosis.
7
teries, cat shows, and multiple-cat households).
Skin lesions of feline dermatophytosis frequently
do not have the classical ringworm appearance as is seen
in dogs and humans and often present a variable clini-
cal picture. Therefore, dermatophytosis should be con-
sidered in the differential diagnoses for any feline der-
8
matopathy. Typical lesions are nonpruritic, unifocal to
mutifocal areas of alopecia with mild to moderate crust-
ing and scaling often on the head, face, and forelimbs.
Other presentations include multiple areas of brittle
and broken hairs with minimal alopecia, folliculitis, and
Additional Test Results
4
rarely furunculosis or granuloma formation. Disease
At the time of the skin scraping, the Wood’s lamp exam-
ination demonstrated green fluorescent hairs on the
inner aspect of the pinna along the line of the hairless
results when arthrospores are able to penetrate the stra-
tum corneum or hair cuticle secondary to a small defect
in the intact epithelium, a depressed or underdeveloped
Page 14
Veterinary Clinical Pathology
Vol. 31 / No. 1 / 2002
Milas
