5.14 Mycology Flashcards
How are fungi classified?
mold, yeast, dimorphic
nature of mold
arial mycelia and vegetative mycelia present at both environmental and body temp
yeast nature
bacterial-like growth at both environmental and body temp
nature of dimorphic fungi
mold-like growth at environmental temp and bacterial-like growth at body temp
broad types of mycotic infection sin animals
superficial, subcutaneous, systemic
types of superifcila mycoses that i have to know
dermatophytes
malassezia pachydermatis
what is ringworm? where does it infect the body? what type of infections? what species? zoonotic?
ringworm is a superficial mycoses; dermatophyte
* Fungal parasites of keratinized epithelium of skin, hairs and nails
* Non-invasive, superficial infections (don’t grow at 37C)
* Many species partially host-adapted (anthropophilic, zoophilic)
* Zoonotic
what are the organisms that cause ringowm
a variety cause ringworm in different species;
Trichophyton:
>T. verrucosum; Cattle
>T. mentagrophytes; Broad host range
>T. equinum; Horse
Microsporum:
>M. canis; Cat, Dog
>M. nanum; Pig
>M. gypseum; Dogs
Classic ringworm lesion
Slowly expanding, circular area alopecia and desquamated epithelium (“cigarette ash”). Central hair regrowth, inflamed edge. Often multiple differently sized lesions
Ringworm: treatment
- Topical treatments (azoles, disinfectants)
- Parenteral: Griseofulvin, itraconazole, ketoconazole
Ringworm: control
- Hygiene: Isolation; treatment bedding with formalin
or washing in bleach; decontaminate environment - Vaccines for cats and cattle
Malassezia pachydermatis; what is it? what does it look like? where is it commonly found and what diseases does it cause?
Superficial mycoses:
Malassezia pachydermatis
* Pear-shaped or “footprint” shaped yeast, 3-8μm
* Common in dog’s ears, skin
* May cause otitis externa in dogs (excess wax in ears?), increasingly recognized as a cause of dermatitis
main subcutaneous mycoses that we have to know
Sporothrix schenkii
what is Sporothrix schenkii? what disease does it cause and in what animals? where is it found geographocally and what is its habitat? what tissues does it infect?
Subcutaneous mycoses:
Sporothrix schenkii
(Rose gardener’s disease)
* Sporotrichosis in horses, dogs, cats and humans
* Worldwide, more common in tropical/subtropical regions
* Habitat: rose thorns, soil, dead vegetation
* Subcutaneous nodules, lymphatics (rare lungs)
Sporothrix schenkii is a dimorphic fungi
what kind of fungi is Sporothrix schenkii?
dimorphic
“Mold in the Cold, Yeast in the Heat”
mold at 25C
yeast at 37C
what systemic mycoses do i have to know
Cryptococcus
>neoformans
>gatti
Blastomyces dermatitidis
Histoplasma capsulatum
agents of cryptococcosis?
- Cryptococcus neoformans and Cryptococcus gattii are the agents of cryptococcosis
what is Cryptococcus? what species are we concerned with and what do they cause? what type of fungi are they? what is their structure?
Systemic mycoses: Cryptococcus
* Cryptococcus neoformans and Cryptococcus
gattii are the agents of cryptococcosis
* Dimorphic fungi: yeast in vivo, encapsulated,
fast growing
C. neoformans; where is it found, who does it infect?
Bird manure especially pigeons, worldwide, disease of immunocompromised
C. gattii; where is it found, who does it infect?
More virulent; associated plant debris, esp. eucalyptus, affects healthy animals and people (West Coast, BC)
which is more virulent; C. neoformans or C. gatti?
C. gatti
Cryptococcus; what infections and lesions does it cause? in what species?
- Respiratory infection
- Skin lesions
- Neurological disease
- Cats+++, dogs, cattle, horses, sheep, goats, birds
“clown nose in cats”
Cryptococcus can cause what unique disease in cats?
clown nose
Blastomyces dermatitidis; what type of fungus is it?
Systemic mycoses: Blastomyces dermatitidis
dimorphic
“Mold in the Cold, Yeast in the Heat”
Blastomyces dermatitidis physical character
“Mold in the Cold, Yeast in the Heat”
Mycelium at 25C: Hyphae with “pear-shaped” conidia
Yeast at 37C ”thick walls”
Blastomyces dermatitidis; where is it found geographically? who is susceptible?
- Blastomyces dermatitidis
- Acidic soil and organic material
- Distribution appears to be growing
- Also occurs in Europe, Asia and Africa
- Dogs are 10x more susceptible to blastomycosis than humans
- Occasionally affect other mammals
Blastomyces dermatitidis lesions
Primary lesions in lungs with metastases to skin and other organs
Blastomyces dermatitidis: transmission and pathogenesis
mold form survives in organic materials or acidic soils
-conidia are inhlanes by dog or humans
> Dimorphic change to yeast form in lung of host
Yeast are very resistant to killing by leukocytes => pneumonia
Immunosuppression (e.g., lymphopenia) may promote dissemination to skin, bone, lymph nodes, eye or other organs
Canine blastomycosis lesions in dog
Diffuse interstitial nodular pneumonia
Eye lesions (e.g., uveitis) are present in up to 40% of cases
Cross-section of infected lung - note the massive influx of inflammatory cells and how little oxygen could be transported in this lung
Skin lesions (e.g., onchyomycosis – B. dermatitidis infection of toe nail)
B. dermatitidis ulcerative dermatitis near face - may be seen in 20-50% of cases
B. dermatitidis ulcerations on planum nasale
Blastomycosis in humans; type of disease, transmission, lesions, treatment and prognosis
- Respiratory disease usually apparent
- It cannot be spread among humans and dogs
- Skin granulomas are seen (chronic inflammation)
- May be confused with skin cancer
- Need to diagnose and aggressively treat
- Can be fatal if left untreated
Histoplasma capsulatum; what is it? what type of fungi?
Systemic mycoses:
Histoplasma capsulatum
“Mold in the Cold, Yeast in the Heat”
mold: Hyphae and macroconidia/microconidia
Histoplasma capsulatum; what species infected? zoonotic? carriers?
- Dogs, cats and humans (zoonotic!!!)
- Organism does not infect birds, but they are carriers!
- Bats can contract histoplasmosis and spread disease
Histoplasma capsulatum lesions?
- Primary lesions in lungs with dissemination to intestines and other organs
Histoplasmosis is found where geographically?
is endemic in Mississippi and Ohio River valleys and some tropical areas
Histoplasma capsulatum: transmission/ pathogenesis
H. capsulatum mold form lives in top layer of soil
containing infected bird or bat guano
> Microconidia are released and are inhaled by animals, humans
Microconidia convert to yeast form in the lung of an animal and infect alveolar macrophages
H. capsulatum inside macrophages disseminates throughout the body
Histoplasmosis in dogs; what disease? what clinical signs? what about cats?
Histoplasmosis in dogs
Respiratory disease
* Clinical signs often mild, if apparent at all
* Serious respiratory disease only in a small percent of dogs
* H. capsulatum disseminates to other tissues in dogs
> could see emaciation due to malabsoption form histoplasma capsulatum enteritis
could see enlarged mesenteric lymph nodes in dog with disseminated histoplasmosis
- Cats are also highly susceptible
Coccidioides immitis; what type of fungi
“Mold in the Cold, Yeast in the Heat”
dimorphic
Coccidioides immitis found in what species? primary lesions?
- Dogs, horses, cats, humans
- Primary lesions in lungs and secondary in bones
Coccidioides immitis found where geographically?
- Endemic areas
- New Mexico, Texas, California, Arizona
- Known as “Valley fever”
- Northern Mexico, Central America, Argentina
Coccidioides immitis ecology
- soil of low elevation, deserts
- Hot summers, cold winters
Coccidioidomycosis - Life Cycle
Mold form
* Hyphae fragment to form arthroconidia which become airborne and inhaled
* As few as 10 inhaled arthroconidia can produce disease
“Yeast-like form
* Arthroconidia transform into spherules inside the lung of host
NO YEAST FORMATION! IT IS A SPHERULE!
spherules mature and rupture, releaseing many small apherules in host
Coccidioidomycosis - Canine symptoms
Coccidioidomycosis - Canine
Most dogs are asymptomatic (95%) Some show signs of pneumonia
* High Fever
* Lethargy, inappetence
* Dry, harsh cough
> May be confused with kennel cough
(B. bronchiseptica)
Pneumonia may lead to dissemination! (5% of cases)
– Osteomyelitis
what type os fungus lead to systemic infections with primary lesions in lungs?
blastomyces (dimorphic)
coccidiodes (mold and SPHERULE)
histoplasma (dimorphic)
what type of fungus leads to subcutaneous and lymphatic lesions?
sporothrix
