Microsporum, Trichophyton, Malassezia, Sporothrix

Question 1

What is the most common dermatophyte of domestic animals?

Answer 1

Microsporum canis

Question 2

What forms of sporotrichosis occur in dogs?

Which is most common?

Answer 2

Cutaneous, lymphocutaneous, and disseminated

Lymphocutaneous is most common

Question 3

Describe the morphology of the genus Microsporum.

Answer 3

Hyphae are thin and smooth

Condida are large, rough, thick-walled, and have septa

Question 4

What disease patterns do members of the genus Malassezia cause in cats?

Answer 4

Otitis externa, chin acne, exfoliative erythroderma

Question 5

Why is it important to identify the species of dermatophyte causing disease?

Answer 5

Identifying the organism will help in removing the likely source of infection and prevent its spread

Question 6

What is an anthropophilic dermatophyte?

Answer 6

Dermatophyte that is a near-exclusive pathogen of humans

Question 7

How is sporotrichosis treated?

Answer 7

Itraconazole, flucytosine, amphotericin B

Oral inorganic iodides- cannot be given to cats

Question 8

True or false:

Dissemination via the lymph or blood is a serious concern with subcutaneous mycoses.

Answer 8

False. These infections rarely disseminate.

Question 9

How are Malassezia infections treated?

Answer 9

First, correct underlying conditions

Topical- nystatin, miconazole, clotrimazole

Systemic- itraconzaole or ketoconazole, plus miconazole/chlorahex shampoo

Question 10

What is a zoophilic dermatophyte?

Answer 10

A dermatophyte that is mainly an animal pathogen but can also infect humans.

Question 11

How can Derm-Duet be used as an aid to diagnose dermatophytosis?

Answer 11

Contains 2 media

Rapid Sporulating Media- promotes growth of spores and condida

Dermatophyte Test Media- will change color from yellow to red in the presence of dermatophytes

Question 12

When diagnosing dermatophytosis, what is the purpose of examining hairs under the microscope?

Answer 12

Fungal spores can be seen around the hair shaft. Some species are exothrix (spores are outside the hair shaft) and others are endothrix (spores are inside the hair shaft)

Question 13

What disease patterns do members of the genus Malassezia cause in dogs?

Answer 13

Otitis externa, seborrheic dermatitis

Question 14

What stain can be used to help diagnose dermatophytosis?

Answer 14

Lactophenol cotton blue stain

Question 15

Does the presence of Malassezia on a skin scrape or smear indicate disease?

Answer 15

Not necessarily. More than 10 yeasts/high powered field indicate infection, but it is usually present as normal microflora.

Question 16

True or false:

Humans do not have to be concerned about transmission when treating cases of sporotrichosis in animals.

Answer 16

False. Humans can contract sporotrichosis and need to take precautions when treating animals with the disease.

Question 17

How is dermatophytosis treated?

Answer 17

Topical- clip hair, use antifungals like Betadine, chlorahexidine, etc.

Systemic- ketoconazole, griseofulvin (toxic), terbinafine, lufenuron (chitin inhibitor)

Question 18

What is notable about the metabolism of dermatophytes?

Answer 18

They can use keratin as an energy source and are capable of parasitizing only keratinized epidermal structures (hair, skin, feathers, nails/claws, etc.)

Question 19

What species are susceptible to infection with Trichophyton mentagrophytes?

Answer 19

Cats, dogs, rodents, and humans

Question 20

Sporotrichosis is seen most commonly in what group of cats?

Answer 20

Outdoor cats with a history of bite or scratch wounds. Often present with draining puncture wounds.

Question 21

Describe the morphology of the genus Trichophyton.

Answer 21

Hyphae contain many microcondida

Macrocondida are smooth and thin-walled

Question 22

What is a geophilic dermatophyte?

Answer 22

A dermatophyte associated with soil.

Question 23

True or false:

If a lesion does not fluoresce under a Wood’s lamp, dermatophytosis cannot be ruled out.

Answer 23

True. Not all species will fluoresce under a Wood’s lamp.

Question 24

When preparing a skin scrape for microscopic examination, what is the purpose of adding potassium hydroxide (KOH)?

Answer 24

It removes keratinized skin cells without removing the fungi, if present. The slide can then be stained.

Question 25

How does sporotrichosis tend to manifest in horses?

Answer 25

They get hard nodules along lympathics of the legs, usually on the medial side that may ulcerate and drain

Question 26

What fungal infections are commonly associated with trauma?

Answer 26

Subcutaneous mycoses