Feline dermatophytosis: aspects pertinent to disease management in single and multiple cat situations

Abstract

Practical relevance: Dermatophytosis (ringworm) is a superficial fungal skin disease of cats that, depending on the geographic region and practice caseload, may be encountered uncommonly through to commonly. This is a self-curing disease in an immunocompetent cat.

Global importance: Dermatophytosis is prevalent worldwide and is one of a number of zoonotic skin diseases that cat owners are at risk of contracting.

Clinical challenges: Dermatophytosis causes non-specific signs of hair loss, erythema and scaling, making it a differential diagnosis for many skin diseases of cats. The fact that this disease is infectious and contagious, and does not have any one classic clinical presentation, makes knowledge of diagnostic tools important in detection. The veterinarian's role is in early disease recognition and institution of appropriate therapy to hasten resolution of the disease.

Aim: The focus of this article is to provide an update and review of the most pertinent aspects that may be helpful in the management of dermatophytosis in any single or multiple cat situation.

Evidence base: Where appropriate, evidence from the literature is used to supplement a summary of the author's clinical experience and research in feline dermatophytosis.

Figure 1

Focal lesion of dermatophytosis on an otherwise healthy cat. Courtesy of Dr Rebecca Stuntebeck

Figure 2

Generalized dermatophytosis in a kitten with malnutrition, diarrhea and upper respiratory infection

Figure 3

Ear of a cat with dermatophytosis. Note the limited lesion extent observed in room light (a) versus how, under Wood’s lamp examination (b), the extent of the lesions is highlighted. Images courtesy of Dr Alana Canupp

Figure 4

Wood’s lamps. (a) Small compact model and (b) model with built-in magnification

Figure 5

Using a Wood’s lamp to locate hairs for microscopic examination

Figure 6

Microscopy of Wood’s lamp positive hairs mounted in mineral oil. Infected hairs are wider and paler than normal hairs (arrow). x10 magnification

Figure 7

Inoculating plates ‘upside down’ over a disinfectant wipe minimizes contamination

Figure 8

Fungal culture plate from a cat under treatment. Note the lack of growth in the center and the ring of growth on the margins. The plate was inoculated starting at the center and working outwards in a centrifugal direction. The pattern of growth reflects the fact that the toothbrush bristles had residual deposits of antifungal rinse on them

Figure 9

The best way to examine cultures daily is to hold them up to the light to look for evidence of growth. It is not necessary to open plates except to obtain samples