Lecture 20 11/14/23 Flashcards
What are the characteristics of dermatophytes?
-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
What are the different dermatophyte types, based on main reservoir?
-anthropophilic (humans)
-zoophilic (animal)
-geophilic (soil/environment)
What are the common dermatophytes and their host range?
-Microsporum canis (cats, dogs, humans)
-Trichophyton mentagrophytes (broad)
-Trichophyton verrucosum (cattle)
What is the classic ringworm lesion?
-circular area of alopecia
-central hair regrowth
-inflamed edge
Which species are a major asymptomatic carrier of ringworm?
cats
What are kerion lesions?
localized or generalized folliculitis with or without furunculosis, caused by dermatophytes
Which disease is caused by Microsporum gallinae?
avian ringworm/favus
How can ringworm be diagnosed?
-Woods lamp/detection of fluorescence
-culture of skin/nail tissue
-wet mount of plucked parasitized hairs
-dermatophyte test medium
Where should samples for ringworm tests be collected?
the periphery of the lesion
What are the two possible dermatophyte locations, in relation to the hair follicle?
-ectothrix/outside follicle
-endothrix/inside follicle
How is ringworm treated?
-azols
-natamycin
-terbinafine
-griseofulvin
-environmental washes/sprays to prevent reinfection
How is ringworm controlled?
-hygiene
-isolation
-environmental decontamination
-clipping hair around lesions
-discard bedding
-disinfect grooming equipment
-vaccines
Which human dermatophyte diseases are seen in humans?
-athlete’s foot
-jock itch
-tinea
How can ringworm outbreaks be prevented in shelters?
-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
What are Malassezia sp.?
lipophilic yeasts often seen as commensals
Which Malassezia sp. is of importance?
M. pachydermatis
What are the characteristics of Malassezia pachydermatis?
-thick-walled
-bottle-shaped
-small and lipophilic
-cause otitis externa in dogs
-cause of dermatitis
What are the characteristics of Candida albicans?
-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
What are the characteristics of C. albicans disease?
-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
What are the characteristics of C. albicans diagnosis, treatment, and control?
-diagnosed through staining/direct demonstration or culture
-preventing predisposition important
-treated with local or systemic antifungals
-possible to do susceptibility testing
What are the characteristics of Cryptococcus sp.?
-large round/oval yeast
-budding
-mucopolysaccharide capsule is important virulence factor
-common in cats; CNS manifestations
-gelatinous masses/polyps with minimal inflammation
-granulomas
-opportunistic
How are Cryptococcus sp. diagnosed?
-microscopic detection of encapsulated yeast
-fungal culture
-test for capsular antigen in serum or CSF
How are Cryptococcus sp. treated?
-long term treatment until serum antigen is neg. or clinical signs resolve for one month
-amphotericin B, flucytosine, azoles
-surgical mass removal
How are Cryptococcus sp. prevented?
avoiding areas with high conc. of bird droppings or lots of disturbances
-cleaning/disinfecting bird habitats
