Mycology Flashcards
What are some key facts surrounding fungi?
- Eukaryotic
- widely distributed in the environment
- can be commensals
- grow aerobically
What are the four main groups of fungi?
- Ascomycetes
- Basidiomycetes
- Zygomycetes
- Deuteromycetes
What is the name of the fungi of most veterinary importance?
Deuteromycetes
(usually only asexual reproduction)
What are the two main morphological forms of fungus?
- Filamentous
- Yeast
3.Some can take on both forms (this is dependent on the environment)
When may a fungus be in its spore phase?
When the fungus is in the environment
with decreased temperatures
More Oxygen and more Nutrients
When may a fungus germinate into yeast?
When in a host, this is where it reproduces through budding
What are two examples of fungi that can change shape/ size in order to survive in the environment?
Dimorphic fungi
* Candida albicans
* Histoplasma
What is a dimorphic fungus?
Switches between Yeast and Filamentous
What are three mechanisms involved in fungal production?
- Tissue invasion (mycosis)
- Toxin Production (mycotoxicosis)
- Induction of hypersensitivity (this is rare in domestic animals)
What are the two types of mycosis that fungi can cause?
- Superficial (mucous membranes + subcut)
- Systemic (usually in the respiratory or GIT)
What are the three types of dermatophytes?
- Zoophillic (obligate pathogens that mainly effect animals and people)
- Anthropophillic (obligate pathogens that only infects humans)
- Geophillic (they occur naturally in the soil with decomposing hair/ feathers)
Where does dermatophysis most commonly invade?
superficial keratinised structures (skin, hair claws)
the transmission is via direct or indirect contact with spores
What are the four most common dermatophytosis (ringworm) fungi?
- Microsporum canis
- Trichophyton mentagrophytes
- T.Verrucosum
- M.gypseum
How long does it take Dermatophytosis spores to germinate on the skin?
They germinate on the skin within 6 hours
What clinical signs will dermatophytosis cause?
- Alopecia
- Dermatitis
- epidermal hyperplasia
- hyperkeratosis
- secondary bacterial infections
What is the most common Aspergillus species?
A.Fumigatus
What kind of pathogen is A.fumigatus?
respiratory pathogen acquired by spore inhalation
usually found in poor quality bedding and compost heaps
What does aspergillosis cause in poultry?
Yellow nodules in the lungs/ airsacs and elsewhere = causes gasping, emaciation and death
What does aspergillosis cause in the guttural pouch mycosis of horses?
epistaxis, nasal discharge, dysphagia, laryngeal hemiplegia
What are the clinical signs of nasal aspergillosis in dogs?
sanguinopurulent nasal discharge,
sneezing, epistaxis
What are the three yeast species of importance?
- Candida
- Cryptococcus
- Malassezia
What are the key facts about candida albicans?
- Commensal of the GIT and urogenital tracts
- In a yeast form but then becomes a hyphal form in the body
- Overgrowth is what causes the clinical signs (e.g thrush, stomatitis, enteritis)
- White discharge, plaque, itching, erythema
What are the key facts about cryptococcus neoformans?
- Opportunistic infections
- Bird droppings are the most common source
- Cells are inhaled in contaminated dust
- Cryptococcosis is rare and usually relates to the nasal cavity or the skin
- Granuloma formation
- there are sporadic cases in dogs and cats
What are the key facts about Malassezia pachydermatis?
Very common commensal
they like areas rich in sebaceous glands e.g the ear canal, lip folds, interdigital skin
Most common in dogs
Overgrowth causes clinical signs
has a characteristic appearance under the microscope (like a snowman)
What are the two most common presentations of malassezia pachydermatitis?
- Canine seborrheic dermatitis- itching erythema, smelly greasy, exudate, hair matting
- Canine otitis externa- dark pungent discharge, swollen red ear canal, intense itching
What is histoplasma commonly associated with?
soil contaminated with bird/ bat droppings
spores usally enter the host via the respiratory route
granulomatous lesions form which mimic TB in humans
What are the two types of histoplasma?
- H. capsulatum
- H. farcimosum (epizootic lymphangitis)
How are mycotoxins produced?
Produced by toxigenic fungi on crops, pasture and stored feed under certain conditions (moisture, temp, O2 levels)
Many are heat stable (processing cant remove them) and are ingested by animals
What are two examples of mycotoxins?
- Afltatoxins, produced by aspergillus flavus
- Ergotamine produced by claviceps purpurea (which can cause ergotism)
Name 6 ways you could diagnose a fungal disease
- Hair Pluck/ Skin scrapings
- Biopsy
- Woods lamp
- Culture
- Microscopy
- PCR
What are the four main classes of drug you can use to treat fungal diseases?
- Allylamines
- Azoles
- Echinocandins
- Polyenes
ergosterol is the primary target of most anti-fungal drugs
