Image Quiz: Diagnosing Dermatophytosis in Dogs & Cats

M gypseum is identified by rapid growth and a downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown appearance on the reverse or underside of the culture growth. 

In contrast, M canis is characterized by rapid growth and a downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse. 

(From Mycology Online's Microsporum)

M gypseum is identified by rapid growth and a downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown appearance on the reverse or underside of the culture growth. 

In contrast, M canis is characterized by rapid growth and a downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse. 

(From Mycology Online's Microsporum)

M gypseum is identified by rapid growth and a downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown appearance on the reverse or underside of the culture growth. 

In contrast, M canis is characterized by rapid growth and a downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse. 

(From Mycology Online's Microsporum)

M canis is characterized by rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse.

In comparison, M gypseum is identified by rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse; whereas T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

(From Mycology Online's Microsporum)

M canis is characterized by rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse.

In comparison, M gypseum is identified by rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse; whereas T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

(From Mycology Online's Microsporum)

M canis is characterized by rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse.

In comparison, M gypseum is identified by rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse; whereas T mentagrophytes is recognized by its moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

(From Mycology Online's Microsporum)

T mentagrophytes is identified by moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

M canis is characterized by its rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and M gypseum is recognized by its rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse.

(From Mycology Online's Microsporum)

T mentagrophytes is identified by moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

M canis is characterized by its rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and M gypseum is recognized by its rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse.

(From Mycology Online's Microsporum)

T mentagrophytes is identified by moderately rapid growth and powdery to granular, white to cream surface with a yellow- or red-brown reverse.

M canis is characterized by its rapid growth and downy to wooly, cream to yellow surface with a yellow to yellow-orange reverse; and M gypseum is recognized by its rapid growth and downy to powdery to granular, cream, tawny-buff, or pale cinnamon-color surface with a beige to red-brown reverse.

(From Mycology Online's Microsporum)

As shown, M canis microconidia are pear- to club-shaped but typically are absent; macroconidia are fusoid, verrucose, and thick-walled with an apex and 5 to 15 cells.

When M gypseum organisms are present microscopically, microconidia are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present, and macroconidia are multi-septate and club-shaped but often absent.

(From Mycology Online's Microsporum)

As shown, M canis microconidia are pear- to club-shaped but typically are absent; macroconidia are fusoid, verrucose, and thick-walled with an apex and 5 to 15 cells.

When M gypseum organisms are present microscopically, microconidia are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present, and macroconidia are multi-septate and club-shaped but often absent.

(From Mycology Online's Microsporum)

As shown, M canis microconidia are pear- to club-shaped but typically are absent; macroconidia are fusoid, verrucose, and thick-walled with an apex and 5 to 15 cells.

When M gypseum organisms are present microscopically, microconidia are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present, and macroconidia are multi-septate and club-shaped but often absent.

(From Mycology Online's Microsporum)

As evident in this image, macroconidia of T mentagrophytes are multi-septate and club-shaped but often absent. Spiral hyphae are often present, but difficult to observe in this image. The microconidia are rarely seen in this image as round to pyriform in shape; they are typically found in grapelike clusters. 

When M canis organisms are present microscopically, microconidia are club-shaped but typically absent; whereas macroconidia are fusiform in shape, verrucose, and thick walled with an apex and 5 to 15 cells.

Microscopically, microconidia of M gypseum are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells.

As evident in this image, macroconidia of T mentagrophytes are multi-septate and club-shaped but often absent. Spiral hyphae are often present, but difficult to observe in this image. The microconidia are rarely seen in this image as round to pyriform in shape; they are typically found in grapelike clusters. 

When M canis organisms are present microscopically, microconidia are club-shaped but typically absent; whereas macroconidia are fusiform in shape, verrucose, and thick walled with an apex and 5 to 15 cells.

Microscopically, microconidia of M gypseum are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells.

As evident in this image, macroconidia of T mentagrophytes are multi-septate and club-shaped but often absent. Spiral hyphae are often present, but difficult to observe in this image. The microconidia are rarely seen in this image as round to pyriform in shape; they are typically found in grapelike clusters. 

When M canis organisms are present microscopically, microconidia are club-shaped but typically absent; whereas macroconidia are fusiform in shape, verrucose, and thick walled with an apex and 5 to 15 cells.

Microscopically, microconidia of M gypseum are abundant and club-shaped; macroconidia also are abundant and are ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells.

Microscopically these organisms demonstrate abundant, club-shaped microconidia characteristic of M gypseum. Note that macroconidia are abundant, ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

When M canis organisms are present on microscopy, microconidia are club-shaped but typically absent; macroconidia are fusoid in shape, verrucose, and thick walled with an apex and 5 to15 cells.

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present; macroconidia are multi-septate and club-shaped but often absent.

Microscopically these organisms demonstrate abundant, club-shaped microconidia characteristic of M gypseum. Note that macroconidia are abundant, ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

When M canis organisms are present on microscopy, microconidia are club-shaped but typically absent; macroconidia are fusoid in shape, verrucose, and thick walled with an apex and 5 to15 cells.

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present; macroconidia are multi-septate and club-shaped but often absent.

Microscopically these organisms demonstrate abundant, club-shaped microconidia characteristic of M gypseum. Note that macroconidia are abundant, ellipsoid to fusiform in shape, sometimes verrucose, and thin walled with 3 to 6 cells. 

When M canis organisms are present on microscopy, microconidia are club-shaped but typically absent; macroconidia are fusoid in shape, verrucose, and thick walled with an apex and 5 to15 cells.

Microscopically, T mentagrophytes microconidia are numerous, round to pyriform in shape, and found in grapelike clusters. Spiral hyphae are often present; macroconidia are multi-septate and club-shaped but often absent.

These findings reflect a positive Wood’s lamp finding of M canis organisms; note the fluorescing (blue-green or bright apple-green) of plucked hair shafts observed on this patient using magnification on the Wood’s lamp. This examination requires plug-in long-wave Wood’s lamp magnification and a darkened room (the lamp does not need to be warmed up). Wood’s lamp examination has low sensitivity for M canis and is not specific for identification of this organism.^1,5

Positive results are obtained in ≈50% of cases. Fluorescence of ectothrix spores (arthroconidia) of M canis on Wood’s lamp examination, as shown in Figure 7, would prompt collection of positive hairs for culture. Negative fluorescence does not rule out dermatophytic infection; false-positive findings are attributable to keratin, fiber, ointment, dust, and/or dander contamination.^1,5  

Histopathology and trichogram analysis provide a microscopic view of the hair shaft and helps facilitate and confirm diagnosis. The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s hair, collecting hair shafts or scale-like skin flakes for fungal culture.

These findings reflect a positive Wood’s lamp finding of M canis organisms; note the fluorescing (blue-green or bright apple-green) of plucked hair shafts observed on this patient using magnification on the Wood’s lamp. This examination requires plug-in long-wave Wood’s lamp magnification and a darkened room (the lamp does not need to be warmed up). Wood’s lamp examination has low sensitivity for M canis and is not specific for identification of this organism.^1,5

Positive results are obtained in ≈50% of cases. Fluorescence of ectothrix spores (arthroconidia) of M canis on Wood’s lamp examination, as shown in Figure 7, would prompt collection of positive hairs for culture. Negative fluorescence does not rule out dermatophytic infection; false-positive findings are attributable to keratin, fiber, ointment, dust, and/or dander contamination.^1,5  

Histopathology and trichogram analysis provide a microscopic view of the hair shaft and helps facilitate and confirm diagnosis. The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s hair, collecting hair shafts or scale-like skin flakes for fungal culture.

These findings reflect a positive Wood’s lamp finding of M canis organisms; note the fluorescing (blue-green or bright apple-green) of plucked hair shafts observed on this patient using magnification on the Wood’s lamp. This examination requires plug-in long-wave Wood’s lamp magnification and a darkened room (the lamp does not need to be warmed up). Wood’s lamp examination has low sensitivity for M canis and is not specific for identification of this organism.^1,5

Positive results are obtained in ≈50% of cases. Fluorescence of ectothrix spores (arthroconidia) of M canis on Wood’s lamp examination, as shown in Figure 7, would prompt collection of positive hairs for culture. Negative fluorescence does not rule out dermatophytic infection; false-positive findings are attributable to keratin, fiber, ointment, dust, and/or dander contamination.^1,5  

Histopathology and trichogram analysis provide a microscopic view of the hair shaft and helps facilitate and confirm diagnosis. The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s hair, collecting hair shafts or scale-like skin flakes for fungal culture.

These findings reflect a positive Wood’s lamp finding of M canis organisms; note the fluorescing (blue-green or bright apple-green) of plucked hair shafts observed on this patient using magnification on the Wood’s lamp. This examination requires plug-in long-wave Wood’s lamp magnification and a darkened room (the lamp does not need to be warmed up). Wood’s lamp examination has low sensitivity for M canis and is not specific for identification of this organism.^1,5

Positive results are obtained in ≈50% of cases. Fluorescence of ectothrix spores (arthroconidia) of M canis on Wood’s lamp examination, as shown in Figure 7, would prompt collection of positive hairs for culture. Negative fluorescence does not rule out dermatophytic infection; false-positive findings are attributable to keratin, fiber, ointment, dust, and/or dander contamination.^1,5  

Histopathology and trichogram analysis provide a microscopic view of the hair shaft and helps facilitate and confirm diagnosis. The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s hair, collecting hair shafts or scale-like skin flakes for fungal culture.

This trichogram demonstrates endothrix spores (arthroconidia) of Trichophyton mentagrophytes. within the hair shaft following hair pluck with mineral oil preparation and viewed under high magnification (40×). 

Histopathology provides a microscopic view of diseased tissues or hair shafts for diagnostic purposes, allowing the clinician to assess the hair in more detail, specifically the integrity and possible disease affecting the hair follicle and surrounding tissue. 

Endothrix spores (arthroconidia) of Trichophyton spp do not fluoresce under Wood’s lamp examination,⁵ which assesses plucked hairs for fluorescence via a long-wave Wood’s lamp, a dark room, and magnification.

The MacKenzie technique involves use of a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. This technique is most commonly used in patients with large areas of ringworm infestation or to screen for carrier status.

This trichogram demonstrates endothrix spores (arthroconidia) of Trichophyton mentagrophytes. within the hair shaft following hair pluck with mineral oil preparation and viewed under high magnification (40×). 

Histopathology provides a microscopic view of diseased tissues or hair shafts for diagnostic purposes, allowing the clinician to assess the hair in more detail, specifically the integrity and possible disease affecting the hair follicle and surrounding tissue. 

Endothrix spores (arthroconidia) of Trichophyton spp do not fluoresce under Wood’s lamp examination,⁵ which assesses plucked hairs for fluorescence via a long-wave Wood’s lamp, a dark room, and magnification.

The MacKenzie technique involves use of a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. This technique is most commonly used in patients with large areas of ringworm infestation or to screen for carrier status.

This trichogram demonstrates endothrix spores (arthroconidia) of Trichophyton mentagrophytes. within the hair shaft following hair pluck with mineral oil preparation and viewed under high magnification (40×). 

Histopathology provides a microscopic view of diseased tissues or hair shafts for diagnostic purposes, allowing the clinician to assess the hair in more detail, specifically the integrity and possible disease affecting the hair follicle and surrounding tissue. 

Endothrix spores (arthroconidia) of Trichophyton spp do not fluoresce under Wood’s lamp examination,⁵ which assesses plucked hairs for fluorescence via a long-wave Wood’s lamp, a dark room, and magnification.

The MacKenzie technique involves use of a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. This technique is most commonly used in patients with large areas of ringworm infestation or to screen for carrier status.

This trichogram demonstrates endothrix spores (arthroconidia) of Trichophyton mentagrophytes. within the hair shaft following hair pluck with mineral oil preparation and viewed under high magnification (40×). 

Histopathology provides a microscopic view of diseased tissues or hair shafts for diagnostic purposes, allowing the clinician to assess the hair in more detail, specifically the integrity and possible disease affecting the hair follicle and surrounding tissue. 

Endothrix spores (arthroconidia) of Trichophyton spp do not fluoresce under Wood’s lamp examination,⁵ which assesses plucked hairs for fluorescence via a long-wave Wood’s lamp, a dark room, and magnification.

The MacKenzie technique involves use of a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. This technique is most commonly used in patients with large areas of ringworm infestation or to screen for carrier status.

This trichogram shows ectothrix spores (arthroconidia, stained blue) of M canis surrounding the hair shaft (stained brown) with 10% potassium hydroxide (KOH) preparation and Parker ink contrast dye, viewed under high magnification (100×).⁵ Trichogram is a rapid, convenient, and inexpensive method to examine the hair shaft for any structural defects, hair stage, ectoparasites, and possibly dermatophytic arthrospores and hyphae.

Histopathology is a microscopic study of diseased skin and/or hair follicles used for diagnostic purposes. 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis.^1,5 

The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. The technique is most commonly used in patients with large areas of ringworm infection or to screen for carrier status.^1,5

This trichogram shows ectothrix spores (arthroconidia, stained blue) of M canis surrounding the hair shaft (stained brown) with 10% potassium hydroxide (KOH) preparation and Parker ink contrast dye, viewed under high magnification (100×).⁵ Trichogram is a rapid, convenient, and inexpensive method to examine the hair shaft for any structural defects, hair stage, ectoparasites, and possibly dermatophytic arthrospores and hyphae.

Histopathology is a microscopic study of diseased skin and/or hair follicles used for diagnostic purposes. 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis.^1,5 

The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. The technique is most commonly used in patients with large areas of ringworm infection or to screen for carrier status.^1,5

This trichogram shows ectothrix spores (arthroconidia, stained blue) of M canis surrounding the hair shaft (stained brown) with 10% potassium hydroxide (KOH) preparation and Parker ink contrast dye, viewed under high magnification (100×).⁵ Trichogram is a rapid, convenient, and inexpensive method to examine the hair shaft for any structural defects, hair stage, ectoparasites, and possibly dermatophytic arthrospores and hyphae.

Histopathology is a microscopic study of diseased skin and/or hair follicles used for diagnostic purposes. 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis.^1,5 

The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. The technique is most commonly used in patients with large areas of ringworm infection or to screen for carrier status.^1,5

This trichogram shows ectothrix spores (arthroconidia, stained blue) of M canis surrounding the hair shaft (stained brown) with 10% potassium hydroxide (KOH) preparation and Parker ink contrast dye, viewed under high magnification (100×).⁵ Trichogram is a rapid, convenient, and inexpensive method to examine the hair shaft for any structural defects, hair stage, ectoparasites, and possibly dermatophytic arthrospores and hyphae.

Histopathology is a microscopic study of diseased skin and/or hair follicles used for diagnostic purposes. 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis.^1,5 

The MacKenzie technique involves using a sterile toothbrush to comb through an animal’s haircoat and collect hairs or scale-like skin flakes for fungal culture. The technique is most commonly used in patients with large areas of ringworm infection or to screen for carrier status.^1,5

The MacKenzie technique involves use of a sterile toothbrush to comb through the haircoat and is particularly useful in evaluating large areas of ringworm infestation or to screen for carrier status. Toothbrush bristles are pushed into DTM, or the hairs/scales are transplanted to the medium for culture.^1,5 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis. 

Histopathology and trichogram analysis provide a microscopic view of scale-like skin flakes or hair shafts for diagnostic purposes.

The MacKenzie technique involves use of a sterile toothbrush to comb through the haircoat and is particularly useful in evaluating large areas of ringworm infestation or to screen for carrier status. Toothbrush bristles are pushed into DTM, or the hairs/scales are transplanted to the medium for culture.^1,5 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis. 

Histopathology and trichogram analysis provide a microscopic view of scale-like skin flakes or hair shafts for diagnostic purposes.

The MacKenzie technique involves use of a sterile toothbrush to comb through the haircoat and is particularly useful in evaluating large areas of ringworm infestation or to screen for carrier status. Toothbrush bristles are pushed into DTM, or the hairs/scales are transplanted to the medium for culture.^1,5 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis. 

Histopathology and trichogram analysis provide a microscopic view of scale-like skin flakes or hair shafts for diagnostic purposes.

The MacKenzie technique involves use of a sterile toothbrush to comb through the haircoat and is particularly useful in evaluating large areas of ringworm infestation or to screen for carrier status. Toothbrush bristles are pushed into DTM, or the hairs/scales are transplanted to the medium for culture.^1,5 

Wood’s lamp examination involves assessing plucked hairs for fluorescence by the use of a long-wave Wood’s lamp, a dark room, and magnification. The technique is a nonspecific, poorly sensitive diagnostic test for M canis. 

Histopathology and trichogram analysis provide a microscopic view of scale-like skin flakes or hair shafts for diagnostic purposes.