(02-11) Fungal Skin Disease: Dermatophytosis - Dogs and Cats

Question 1

Is Dermatophysis a self limiting condition?

Answer 1

yes - but it may take months to resolve spontaneously

Question 2

Is it zoonotic?

Answer 2

yep

Question 3

what organisms account for most cases of dermatophytosis in cats and dogs?

Answer 3

Zoophilic (e.g. Microsporum canis, T. mentagrophytes) and geophylic (e.g. Microsporum
gypseum)

Question 4

Most cases of dermatophytosis in animals will be associated with what?

Answer 4

an ectothrix parasitism

Question 5

Dermatophytosis is over diagnosed.

Answer 5

d

Question 6

What accounts for at least 80% of the isolates in cats and dogs?

Answer 6

Microsporum canis

Question 7

what animals are predisposed to infection?

Answer 7

Very young and old or immunosuppressed

Question 8

The main modes of transmission include what?

Answer 8

direct contact with infected host, fomite, or
contaminated environment.

(Remember! Fungal spores can remain viable in the environment for years)
(Remember! Asymptomatic carries (especially cats) can serve as reservoir of infection)

Question 9

Well-adapted species (e.g. Microsporum canis) will typically induce how much inflammation?

Less well-adapted species (e.g. Microsporum gypseum) will induce how much inflammation?

inflammation helps reduce what?

Incubation periods vary from what to what?

Answer 9

minimal

marked (which will cause more discomfort to the animal but may help reduce the duration of the infection)

Inflammation helps reduce the course of infection.

4 to 40 days

Question 10

what is most important for the animal’s protection against infection

Answer 10

Cell – mediated immunity

Question 11

Clinical signs are quite variable

Answer 11

d

Question 12

Most cases that look like ringworm in dogs will be caused by what?

Answer 12

staphylococcal pyoderma.
(Epidermal
collarette lesions mimic the classic ringworm lesion (patch of alopecia characterized by broken
stubby hair, scaling, and mild erythema).)

Question 13

what is a nodular lesion resulting from the severe inflammatory reaction induced by rupture of the
hair follicle and the presence of the fungus in the dermis?

It is induced by organisms which are what?

Answer 13

Kerion is a nodular lesion resulting from the severe inflammatory reaction induced by rupture of the
hair follicle and the presence of the fungus in the dermis

not well adapted to the dog and cat skin (e.g. Microsporum gypseum).

Question 14

what is a rare condition caused by the dermatophyte infection of the keratin at the nail and nail bed?

Answer 14

Onychomycosis (It can be difficult to diagnose and also difficult to manage) (Usually other parts of the body are also involved)

Question 15

Most cases in cats are associated with what signs?

Pruritus can be present but, it is rare.

What are characterized by subcutaneous nodules with draining tracts with or
without grains due to dermatophyte infection of the dermis and subcutaneous tissue. It is
most commonly seen in Persians

Answer 15

alopecia, crusting and scaling localized to the head and ears.

Pseudomycetomas

Question 16

what % Microsporum canis strains fluoresce under the wood’s lamp

Only the what fluoresces with the Wood’s lamp

Answer 16

50% (Therefore, negative results do not rule out dermatophytosis)

hair shaft

Question 17

A negative direct examination does not rule out dermatophytosis!

Accurate sample collection increases your chances to find the organisms

Pluck the abnormal hairs (broken) located within the lesion but close to the periphery of the
lesion.

Samples can be visualized using 10% KOH or simply mineral oil (if not a lot of scales present)

Look for spores and/or hyphae parasitizing the outside of the hair shaft (ectothrix).

Answer 17

d

Question 18

what is the most reliable diagnostic test for dermatophytosis?

Use the same technique previously described to collect samples for direct examination.
However, do a dry scraping (do not put water or oil on your scalpel blade)

MacKenzie toothbrush technique should be used to collect hair samples from what?

Keep media at room temperature and examine it daily! In the presence of dermatophyte organisms the change in color of the media occurs when?

In cases of contaminants the color in media will
occur when?

Dermatophytic colonies are white or light tan in color; saprophytic colonies are usually
pigmented (green, black).

Examine all colonies under the microscope for the characteristic features of the fungal
macroconidia

Answer 18

Fungal culture (DTM, Sabouraud’s or RSM media can be used)

asympomatic cats

before the colony growth or simultaneously and typically occurs within first week

after the colony growth and typically after 10 to 14 days. (However, it may take up to 3 weeks before any growth can be seen. So, wait at least 3 weeks
before giving a negative result)

Question 19

1. Never spot treat cats as the sole therapy! Remember they can be health carriers.
2. Clip the affected area and surroundings every time you are using topical therapy.
3. What is a good adjuvant therapy for cases associated with multiple lesions?
4. What have been shown to have better effect than the other topical products?

Answer 19

3. Whole body dip

4. Lime sulfur and enilconazole

Question 20

1. What should always be considered in the management of feline dermatophytosis?
2. Griseofulvin, itraconazole, terbinafine or ketoconazole can be selected.
3. Remember! Cats can develop bone marrow suppression with what?
4. FIV cats are more
   susceptible. Perform a CBC every 7 to 14 days. Cats are very sensitive to the side effects of
   ketoconazole.
5. Itraconazole is fairly safe in cats and it is more efficacious than ketoconazole
6. Be sure to treat until when?
7. Usually, a minimum of how long is necessary to obtain cure.

Answer 20

1. Systemic therapy
2. griseofulvin
3. l at least one (ideally two) negative culture is obtained!
4. 8 weeks

Question 21

1. Always recommend treating what?
2. Under ideal environmental conditions, fungal spores can survive in the environment for how long?
3. Always recommend vacuum cleaning
4. The environment can be treated with bleach (1:10 dilution) or enilconazole
5.  Change heating and air conditioning filters.
6. Clean vents.

Answer 21

1. treating the environment!

2. more than 1 year!