5.14 Mycology

Question 1

How are fungi classified?

Answer 1

mold, yeast, dimorphic

Question 2

nature of mold

Answer 2

arial mycelia and vegetative mycelia present at both environmental and body temp

Question 3

yeast nature

Answer 3

bacterial-like growth at both environmental and body temp

Question 4

nature of dimorphic fungi

Answer 4

mold-like growth at environmental temp and bacterial-like growth at body temp

Question 5

broad types of mycotic infection sin animals

Answer 5

superficial, subcutaneous, systemic

Question 6

types of superifcila mycoses that i have to know

Answer 6

dermatophytes
malassezia pachydermatis

Question 7

what is ringworm? where does it infect the body? what type of infections? what species? zoonotic?

Answer 7

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

Question 8

what are the organisms that cause ringowm

Answer 8

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

Question 9

Classic ringworm lesion

Answer 9

Slowly expanding, circular area alopecia and desquamated epithelium (“cigarette ash”). Central hair regrowth, inflamed edge. Often multiple differently sized lesions

Question 10

Ringworm: treatment

Answer 10

• Topical treatments (azoles, disinfectants)
• Parenteral: Griseofulvin, itraconazole, ketoconazole

Question 11

Ringworm: control

Answer 11

• Hygiene: Isolation; treatment bedding with formalin
  or washing in bleach; decontaminate environment
• Vaccines for cats and cattle

Question 12

Malassezia pachydermatis; what is it? what does it look like? where is it commonly found and what diseases does it cause?

Answer 12

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

Question 13

main subcutaneous mycoses that we have to know

Answer 13

Sporothrix schenkii

Question 14

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?

Answer 14

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

Question 15

what kind of fungi is Sporothrix schenkii?

Answer 15

dimorphic
“Mold in the Cold, Yeast in the Heat”
mold at 25C
yeast at 37C

Question 16

what systemic mycoses do i have to know

Answer 16

Cryptococcus
>neoformans
>gatti

Blastomyces dermatitidis

Histoplasma capsulatum

Question 17

agents of cryptococcosis?

Answer 17

• Cryptococcus neoformans and Cryptococcus gattii are the agents of cryptococcosis

Question 18

what is Cryptococcus? what species are we concerned with and what do they cause? what type of fungi are they? what is their structure?

Answer 18

Systemic mycoses: Cryptococcus
* Cryptococcus neoformans and Cryptococcus
gattii are the agents of cryptococcosis
* Dimorphic fungi: yeast in vivo, encapsulated,
fast growing

Question 19

C. neoformans; where is it found, who does it infect?

Answer 19

Bird manure especially pigeons, worldwide, disease of immunocompromised

Question 20

C. gattii; where is it found, who does it infect?

Answer 20

More virulent; associated plant debris, esp. eucalyptus, affects healthy animals and people (West Coast, BC)

Question 21

which is more virulent; C. neoformans or C. gatti?

Answer 21

C. gatti

Question 22

Cryptococcus; what infections and lesions does it cause? in what species?

Answer 22

• Respiratory infection
• Skin lesions
• Neurological disease
• Cats+++, dogs, cattle, horses, sheep, goats, birds

“clown nose in cats”

Question 23

Cryptococcus can cause what unique disease in cats?

Answer 23

clown nose

Question 24

Blastomyces dermatitidis; what type of fungus is it?

Answer 24

Systemic mycoses: Blastomyces dermatitidis
dimorphic
“Mold in the Cold, Yeast in the Heat”

Question 25

Blastomyces dermatitidis physical character

Answer 25

“Mold in the Cold, Yeast in the Heat” Mycelium at 25C: Hyphae with “pear-shaped” conidia Yeast at 37C ”thick walls”

Question 26

Blastomyces dermatitidis; where is it found geographically? who is susceptible?

Answer 26

* 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

Question 27

Blastomyces dermatitidis lesions

Answer 27

Primary lesions in lungs with metastases to skin and other organs

Question 28

Blastomyces dermatitidis: transmission and pathogenesis

Answer 28

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

Question 29

Canine blastomycosis lesions in dog

Answer 29

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

Question 30

Blastomycosis in humans; type of disease, transmission, lesions, treatment and prognosis

Answer 30

* 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

Question 31

Histoplasma capsulatum; what is it? what type of fungi?

Answer 31

Systemic mycoses: Histoplasma capsulatum “Mold in the Cold, Yeast in the Heat” mold: Hyphae and macroconidia/microconidia

Question 32

Histoplasma capsulatum; what species infected? zoonotic? carriers?

Answer 32

* Dogs, cats and humans (zoonotic!!!) * Organism does not infect birds, but they are carriers! * Bats can contract histoplasmosis and spread disease

Question 33

Histoplasma capsulatum lesions?

Answer 33

* Primary lesions in lungs with dissemination to intestines and other organs

Question 34

Histoplasmosis is found where geographically?

Answer 34

is endemic in Mississippi and Ohio River valleys and some tropical areas

Question 35

Histoplasma capsulatum: transmission/ pathogenesis

Answer 35

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

Question 36

Histoplasmosis in dogs; what disease? what clinical signs? what about cats?

Answer 36

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

Question 37

Coccidioides immitis; what type of fungi

Answer 37

“Mold in the Cold, Yeast in the Heat” dimorphic

Question 38

Coccidioides immitis found in what species? primary lesions?

Answer 38

* Dogs, horses, cats, humans * Primary lesions in lungs and secondary in bones

Question 39

Coccidioides immitis found where geographically?

Answer 39

* Endemic areas * New Mexico, Texas, California, Arizona * Known as “Valley fever” * Northern Mexico, Central America, Argentina

Question 40

Coccidioides immitis ecology

Answer 40

* soil of low elevation, deserts * Hot summers, cold winters

Question 41

Coccidioidomycosis - Life Cycle

Answer 41

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

Question 42

Coccidioidomycosis - Canine symptoms

Answer 42

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

Question 43

what type os fungus lead to systemic infections with primary lesions in lungs?

Answer 43

blastomyces (dimorphic) coccidiodes (mold and SPHERULE) histoplasma (dimorphic)

Question 44

what type of fungus leads to subcutaneous and lymphatic lesions?

Answer 44

sporothrix