Lecture 20 11/14/23

Question 1

What are the characteristics of dermatophytes?

Answer 1

-fungal parasites of keratinized epithelium
-cause non-invasive superficial infections
-host-adapted
-zoonotic
-highly contagious
-predisposed in young and/or malnourished
-infection promoted by high humidity and low UV light

Question 2

What are the different dermatophyte types, based on main reservoir?

Answer 2

-anthropophilic (humans)
-zoophilic (animal)
-geophilic (soil/environment)

Question 3

What are the common dermatophytes and their host range?

Answer 3

-Microsporum canis (cats, dogs, humans)
-Trichophyton mentagrophytes (broad)
-Trichophyton verrucosum (cattle)

Question 4

What is the classic ringworm lesion?

Answer 4

-circular area of alopecia
-central hair regrowth
-inflamed edge

Question 5

Which species are a major asymptomatic carrier of ringworm?

Answer 5

cats

Question 6

What are kerion lesions?

Answer 6

localized or generalized folliculitis with or without furunculosis, caused by dermatophytes

Question 7

Which disease is caused by Microsporum gallinae?

Answer 7

avian ringworm/favus

Question 8

How can ringworm be diagnosed?

Answer 8

-Woods lamp/detection of fluorescence
-culture of skin/nail tissue
-wet mount of plucked parasitized hairs
-dermatophyte test medium

Question 9

Where should samples for ringworm tests be collected?

Answer 9

the periphery of the lesion

Question 10

What are the two possible dermatophyte locations, in relation to the hair follicle?

Answer 10

-ectothrix/outside follicle
-endothrix/inside follicle

Question 11

How is ringworm treated?

Answer 11

-azols
-natamycin
-terbinafine
-griseofulvin
-environmental washes/sprays to prevent reinfection

Question 12

How is ringworm controlled?

Answer 12

-hygiene
-isolation
-environmental decontamination
-clipping hair around lesions
-discard bedding
-disinfect grooming equipment
-vaccines

Question 13

Which human dermatophyte diseases are seen in humans?

Answer 13

-athlete’s foot
-jock itch
-tinea

Question 14

How can ringworm outbreaks be prevented in shelters?

Answer 14

-examinations at admission
-using Wood’s lamps/culture
-using isolation facilities
-PPE
-topical treatment for exposed but test-negative animals
-oral/topical for test-positive animals
-post-treatment testing
-cleaning and disinfection

Question 15

What are Malassezia sp.?

Answer 15

lipophilic yeasts often seen as commensals

Question 16

Which Malassezia sp. is of importance?

Answer 16

M. pachydermatis

Question 17

What are the characteristics of Malassezia pachydermatis?

Answer 17

-thick-walled
-bottle-shaped
-small and lipophilic
-cause otitis externa in dogs
-cause of dermatitis

Question 18

What are the characteristics of Candida albicans?

Answer 18

-normal flora of mouth, intestine and lower urogenital tract
-gram-positive
-reversibly transitions from single-cell form to psuedohyphal/hyphal forms
-produces germ tubes in serum

Question 19

What are the characteristics of C. albicans disease?

Answer 19

-opportunistic
-superficial skin and mucosa infections
-causes thrush (white/yellow hyperkeratotic lesions)
-predisposed by antibiotic treatment, immunosuppression, and moisture
-can cause mastitis, vaginitis, and diaper rash
-systemic infections possible

Question 20

What are the characteristics of C. albicans diagnosis, treatment, and control?

Answer 20

-diagnosed through staining/direct demonstration or culture
-preventing predisposition important
-treated with local or systemic antifungals
-possible to do susceptibility testing

Question 21

What are the characteristics of Cryptococcus sp.?

Answer 21

-large round/oval yeast
-budding
-mucopolysaccharide capsule is important virulence factor
-common in cats; CNS manifestations
-gelatinous masses/polyps with minimal inflammation
-granulomas
-opportunistic

Question 22

How are Cryptococcus sp. diagnosed?

Answer 22

-microscopic detection of encapsulated yeast
-fungal culture
-test for capsular antigen in serum or CSF

Question 23

How are Cryptococcus sp. treated?

Answer 23

-long term treatment until serum antigen is neg. or clinical signs resolve for one month
-amphotericin B, flucytosine, azoles
-surgical mass removal

Question 24

How are Cryptococcus sp. prevented?

Answer 24

avoiding areas with high conc. of bird droppings or lots of disturbances
-cleaning/disinfecting bird habitats