Unit 1 - Mycoses Flashcards
What causes a fungal proliferation
Treatment with antibiotics which wipes out normal bacteria microflora, decreased immune system secondary to neoplasia, corticosteroids, diabetes mellitus
What are most fungi considered
Opportunistic pathogen’s
Describe the characteristics of fungal infections
Chronic and slow progressing. Inflammatory response is granulomatous, immunity is cell mediated
What is Dermatophytosis a.k.a. ringworm
Contagious infection of keratinized skin, hair, claws. Caused by one of several species of superficial fungi, the dermatophytes
Describe the host range for ringworm
Species are host adapted, but can cross host barriers. Any animal species may contact her dermatophytosis. Particularly important in cats and is zoonotic.
What is the general age range infected with ringworm
Most commonly a disease of young animals do to immaturity of immune system
What are the risk factors for dermatophytosis
Immune deficiency. Inadequate husbandry conditions, high population density, stress, poor nutrition
Which are the breeds of cats that are predisposed to dermatophytosis
Persians and Himalayan’s
What are the most common dermatophytes of cats and dogs
Microsporum canis
Microsporum gypseum
Trichophyton mentagrophytes
Describe the dermatophytosis lesions
Circular areas of alopecia and scaling patches with central hair regrowth and inflamed edges. Often multiple lesions. Not all lesions are classic
Describe where the dermatophytosis lesions are on dogs
Face or paws
Describer where the dermatophytosis lesions are on cats
Ear pinnea and face
Why is dermatophytosis underdiagnosed in cats
Due to the variation in lesion presentation
How do you diagnose dermatophytosis
Woods lamp. Look for Applegreen florescence. Not all dermatophytes fluoresce. Fungal culture to confirm diagnosis and monitor treatment
What percentage of microsporum canis strains will flouresce a bright green color upon exposure to a uv light
50%
What materials can cause a false positive when diagnosing ringworm
Scales or dandruff and topical products which can florescence
How do you confirm that it’s a true positive when diagnosing ringworm
Bright green in hairs only. Allow the lamp five minutes to warm up
What do you do when you have fluorescing hairs in diagnosing ringworm
Sent for fungal culture. Pluck hair from edges of lesions using a sterile hemostat and submit. Or a toothbrush is vigorously combed over the lesions for 2 to 3 minutes. Wrap in plastic to submit to laboratory
Name the in clinic fungal culture method
DTM. Dermatophyte testing medium. Place hair on culture medium or inbed toothbrush. Cover plates and incubate at room temperature. Watch daily for growth.
How do you know that you have ringworm based on a culture
Look for off-white, fluffy to powdery colony with the red color change in the medium at the same time that the colony first appears. Examine them under the microscope for confirmation
How quickly does ringworm grow on culture medium
Growth happens within 7 to 14 days though plates are kept for 21 days before being deemed negative for growth
How do you perform the microscopic confirmation of ringworm
Brush a strip of clear tape over the colony. Mount tape sticky side down onto a drop of methyl blue on a microscope slide. Examine it 10 X to 40 X for typical appearance of dermatophyte macroconidia
Describe the appearance of microsporum canis generally speaking
Canoe shaped, thick walled macroconidia with terminal knobs
Describe how you would microscopically identify microsporum gypseum
Numerous thin walked macroconidia with slightly rounded proximal ends
Describe how you would microscopically identify trichiphyton mentagrophytes
Cigar shaped microconidia which may be few in number. Numerous globose microconidia . Spiral hypae might be present
How do you treat ringworm
Usually self limiting. Treatment strongly advised to accelerate recovery and minimize spread l
What does the best treatment for ringworm include
Topical, systemic and environmental treatment
How long do you do a treatment for ringworm
Continued until clinical and ideally mycologic cure is achieved, usually 8-16weeks
At what time in treatment do you repeat fungal culture for ringworm
After 2 months of treatment then once per month until 2 negative culture
Give an example of a ringworm topical treatment
Imaverol dilution with e collar.
Describe a systemic treatment for ringworm for dogs as well as cats
Itrafunol for cats. Ketoconazole in dogs.
Describe an environmental treatment for ringworm
Disinfect environment with diluted bleach
How is ringworm transmitted
Direct contact or fomites.
What is the protocol you should follow with ringworm
Handle infected patients with gloves and wash your hands. Disinfect cages and consultation tables with diluted bleach. Remind owners of the zoonotic nature of disease
Describe malassezia pachydermatis
Pear shape yeast. Part of normal flora of ear in small quantities. Can cause otitis externa in dogs, uncommon in cats and can also cause dermatitis
What are the predisposing factors of otitis externa
Conformation, lifestyle, obstructive lesions
Describe which conformations are most susceptible to otitis externa
Cocker spaniels, basset hounds, beagles, sharpeis, english Bulldogs, chow chows, poodles
What life style factors can predispose you to otitis externa
Swimming, grooming, excessive ear care
What types of obstructive lesions can cause otitis externa
Polyps, neoplasia
How do you treat otitis externa
Topical antibacterial, Antifungal, glucocorticoid combination therapy
What is malassezia dermatitis caused by
Secondary to allergies and excessive licking.
How do you treat malassezia dermatitis
Treated topically (surolan) or systemically (itraconazole)
Describe Candida albicans
Part of the normal flora of the mouth, intestine, lower urogenital tract of animals and humans
Describe the virulence of Candida albicans
Opportunistic, can invade locally and usually causes superficial infections of skin and mucosa. Can cause systemic infections in severely immunocompromised patients
What are different examples of candida
Whitish hyperkeratitis on tongue, mouth, stomach. Diaper rash in babies. Mastitis in cows. Vaginitis in women
What is a blastomyces dermatitidis
Slow growing dimorphic fungus. Mold form in the environment and very large yeast in the body. Most common systemic mycotic infection
Describe blastomycosis
Can affect many mammalian species but occurs most often in people and dogs. Outdoor roaming dogs near waterway have increased risk. Majorly August-October
Describe the dissemination of blastomycosis
Young male hunting dog inhales spores. Spores germinate in lung to large budding yeast form, most individual resist infection. Predisposition/heavy load leads to development of chronic granulomatous pneumonia. Usually then disseminates to skin, bone, prostate, testes, eyes. Blocks capillaries and forms ulcerations.
What are the clinical signs of blastomycosis
Fever, cough, weight loss, lameness, skin ulcers, uveitis
Describe histoplasma capsulatum
Dimorphic fungus, small yeast in tissue.
Where is histoplasmosis found
Mostly in soil, especially contaminated with bird or bat droppings
How do you get histoplasmosis
Inhalation of small microconidia. Oral exposure can also result in disease. Disease may remain confined to lungs, gi tract or may become disseminated.
What does histoplasmosis cause
Granulomatous pneumonia, lymphadenopathy, colitis, emaciation
What is cryptococcosis
Dimorphic fungus with the yeast phase Being infective. The yeast is fast growing and slimy.
What does c. Neoformans var. neoformans affect
Immunocompromised individuals. Frequent in bird manure
What does c. Neoformans var. Gatti affect
More virulent, can affect healthy individuals, associated with plant debris
What are the forms of cryptococcosis
Respiratory, cutaneous, cns, ocular forms
Describe cryptococcosis in cats
Unilateral or bilateral nasal discharge, sneezing, firm swelling over bridge of nose, submandibular lymphadenopathy
What can cryptococcosis cause in cats or dogs
Multifocal neurologic signs, ocular abnormalities, cutaneous lesions
What is aspergillosis
Mold. Causes regional or disseminated infection. Dogs more commonly affect than cats.
What breeds does systemic aspergillosis affect
Middle aged German shepherd
What breeds are affected with nasal aspergillosis
Medium to large breed dogs
Describe the appearance of aspergillus fumigatus
Common grey green mold found on moldy bread, cheese and oranges.
Describe aspergillus fumigatus
Causes a wide variety of disease depending on host predisposition. Can cause chronic sinusitis in dogs, cats, horses.
