Mycology Part 2 Flashcards by Alyssa Sorum

What is Coccidioidomycosis?

Caused by: Coccidioides immitis
C. posadasii - in TX, NM, AZ
Causes disease in animals and humans that can be inapparent to disseminated and fatal
Marked variation in susceptibility between animals

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What is the geographic distribution of Coccidioidomycosis?

Endemic areas in the US
- Southwest: CA (San Jaoquin valley, southern desert counties) Neveda, Utah, AZ, NM, TX
- Cases reported in other states too
Outside US

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What are the characteristics of Coccidioides immitis?

a dimorphic fungus
Grows in the mycelial phase in culture and soil
Grows in the yeast phase in the tissue of an infected animal
- has not yet been grown in the yeast phase in culture

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What is the prevalence of Coccidioidomycosis?

Most individuals living in endemic areas are exposed to the agent

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What is the pathogenesis of Coccidioidomycosis?

Inhalation of arthrospores which are formed in soil causes primarily a pulmonary disease
- Dogs sniffing at rodent burrows
- Wind and dust storms
Adhesins, urease, chitinase
Granulomas (may resemble tuberculosis) form in the pulmonary tissue and adjacent lymph nodes
May disseminate to liver, spleen, kidneys, and bones
Sub-cutaneous abscesses may develop with draining sinus tracts in rare cases
Yeast-like organism in tissues
- Spherules - 10-80 microns, some up to 200 microns
Spherules contain few to several hundred endospores - 2-5 microns in diameter (RBC)
- mature spherules rupture and release endospores, which infect adjacent tissues or spread to other body parts

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What are the clinical manifestation of Coccidioidomycosis?

Severe disease
- dogs, humans, primates
In cattle, swine, sheep, horses and cats, localized in the thoracic lymph nodes and/or lungs

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What are the clinical manifestations of Coccidioidomycosis in dogs?

Primarily respiratory problems due to inhalation of spores (tracking and digging/sniffing rodents burrows)
Listlessness, poor appetite, intermittent diarrhea, cough, weight loss, lameness, enlarged joints, skin lesions

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How is Coccidioidomycosis clinically diagnosed?

X-ray
Clinical signs
Demonstration of the agent
Serology - Precipitation test
Intradermal Sensitivity Test - CMI - Coccidioidin
Fluorescent Antibody test on tissue biopsy

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How is Coccidioidomycosis Diagnosed in the Laboratory?

Direct examination
- spherules in wet mounts of urine, exudates, pleural or peritoneal fluids
Cultural examination
- DTM, Sabouraud, and Mycobiotic
- Only grows in mycelial phase in culture
- Fluffy white mycelium in 2-4 weeks
- Arthrospores (alternating and barrel-shaped) become airborne very easily
  - Formalize culture before doing tease mount
  - attempt culture only in a safety glove box

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What is the Epidemiology of Coccidioidomycosis?

Survive in hot weather with little or no rainfall
Windy weather and blowing dust spreads with spores

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What is the treatment for Coccidioidomycosis?

Ketoconazole, Fluconazole, and triazole
Amphotericin B
- Very toxic, monitor kidney function closely
No vaccine

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What is Histoplasmosis?

Caused by: Histoplasma capsulatum
Primarily in pulmonary tissue or intestinal tract
- disseminated form involves spleen and liver
- Yeast cells in circulating monocytes and neutrophils
Dogs are more susceptible than other animals

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What are the general characteristics of Histoplasma capsulatum?

Dimorphic fungus
- At 25C and in the environment in the mycelial phase
- At 37C and in the animal body, the yeast phase

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What is the Geographic Distribution of Histoplasmosis?

Worldwide
Very prevalent in OH, MS, MI river valleys
Endemic in Southeast Kansas

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What is the prevalence of Histoplasmosis?

Is the most frequently diagnosed systemic fungal disease
Many in endemic areas are infected and sensitized
- few contract disease

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What is the Pathogenesis of Histoplasmosis?

Inhalation of spores (Conidia)
Development of granulomas in the lungs
- spread to other tissues of the body
Enlarged spleen, lymph nodes, and liver
Monocytes and neutrophils are infected
Adhesins for adherence to host cells

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What are the clinical manifestations of Histoplasmosis in dogs?

Chronic cough
Gradual weight loss
Diarrhea when intestinal tract affected
Irregular fever
Ascites
Lymphadenopathy

How is Histoplasmosis Diagnosed clinically?

Characteristic clinical signs
Look for yeast bodies in the monocytes and/or neutrophils from a blood smear or buffy coat smear
Intradermal sensitivity test - Histoplasmin
Serologic tests - Precipitin, Complement fixation, ELISA

How is Histoplasmosis diagnosed in the laboratory?

Direct examination
- Look for yeast cells in biopsy material
- Look for yeast cells in feces
- Tissue impression smears of liver, spleen, lung
Culture:
- On Mycobiotic
  - At 25C Mycelial phase
  - at 37C Yeast phase
- Blood sample or buffy coat
- Tease Mount only after formalizing the culture
- Conidia with cocklebur appearance - in the mycelial phase

What is the epidemiology of Histoplasmosis?

Fungus in mycelial phase in the soil
Requires very high nitrogen content and low pH in order to survive
Frequently found in areas where wild birds roost or in bat caves because of an abundance of fecal material
Infection acquired by inhalation o spores

What is the treatment for Histoplasmosis?

Ketoconizole
Itraconazole
Miconazole
Fluconazole
Amphotericin B
- Renal toxicity

What is Blastomycosis?

Caused by: Blastomyces dermatitidis
Granulomatous and suppurative disease
Primary pulmonary lesions which may disseminate to other organs such as skin, eye, and bone
Dogs most susceptible

What are the general characteristics of Blastomyces dermatitidis?

Diphasic fungus
Budding yeast cells (figure 8) in tissue and when grown at 37C in culture
Mycelial phase in soil and when grown at 25C in culture

What is the prevalence of Blastomycosis?

Most cases reported in dogs
Cats and horses are also susceptible

What is the pathogenesis of Blastomycosis?

* Primary pulmonary infection due to inhalation of spores * Adhesin

What are the Clinical Manifestation of Blastomycosis?

* Eye lesions * Enlarged Thoracic lymph nodes * lymphadenopathy * Bone and skin lesions may develop * In disseminated disease, lesions throughout the body * Granulomatous and suppurative * Signs: * **Cough and dyspnea** * **Skin furuncles** (small abscesses) large abscesses, and may ulcer

How is Blastomycosis Diagnosed?

* Clinical: * Respiratory disease, differentiate from Nocardiosis and Actinomycosis * Blastomycin skin test * Precipitin test * Laboratory: * Direct Examination: * Large budding (Figure 8) yeast cells in exudate or tissue * Yeast cells are thick-walled and 5-30 microns in diameter * Not capsulated * Cultural Examination: * Mycobiotic Agar * Grow Slow (10-14 days) * Hold for 30 days before discarding as negative * Mycelial phase 25C * Characteristic conidia, 3-4 microns in diameter, smooth * Non-pathogenic fungi may have similar appearance, but do not convert to yeast phase at 37 C * Yeast phase at 37 C on blood agar

What is the Epidemiology of Blastomycosis?

* Saprophyte in the soil * Infection by inhalation of conidia

How is Blastomycosis treated?

* Ketoconazole * Itraconazole (drug of choice) * Amphotericin-B

What is cryptococcosis?

* Caused by: *Cryptococcus neoformans* * Causes subacute to chronic granulomatous disease * In dogs and cats: * pulmonary disease, central nervous system involvement in some cases * Localized infections or oral and nasal mucosa * In Cattle: * mastitis * In horses: * Nasal granulomas -with discharge and respiratory distress * CNS - A somewhat bland lesion with little inflammatory response

What is cryptococcosis?

What is *Cryptococcus neoformans?*

* Causes Cryptococcosis * Yeast-like fungus * only seen in the yeast phase * unable to produce mycelial phase in culture * Has a very thick capsule

What is the Geographic distribution of cryptococcosis?

* Worldwide * Associated with pigeon droppings * likes high nitrogen * low pH for survival

What is the pathogenesis of Cryptococcosis?

* Primarily by inhalation of the blastospores * Capsule, lipases, melanin

What are the clinical manifestations of Cryptococcosis in Dogs and Cats?

* Pulmonary infections * Mediastinal and bronchial lymph nodes * Granulomas of the oral and pharyngeal mucosa * Granulomas of the nasal cavity and adjacent structures * Invasion of the bone on rare occasions * Eventually goes to the CNS

What are the clinical manifestations of Cryptococcosis in horses?

* Most cases nasal granulomas * lesions on the lips * CNS

What are the clinical manifestations of Cryptococcosis in cattle?

* Mastitis

How is Cryptococcosis diagnosed?

* Laboratory: * Direct Examination * Spinal fluid, milk, tissue biopsy impression, et * India ink wet mount - Negative staining * Look under microscope for **yeast cells with thick capsule** * Cultural examination: * Grow on Sabouraud Dextrose agar or BHI * Biochemical tests are of no value * **API system - commercial test kit** * **4 antigenic types** based on capsular polysaccharide

What is the epidemiology of Cryptococcosis?

* Ubiquitous organism, isolated from a wide variety of locations: * Surface of fruit * Pigeon droppings * Healthy human skin * air conditioners at KSU * bat feces * Butter * Grass * Insects * Milk * Soil * Humans who come down with cryptococcosis have a history of association with pigeons. Pigeons carry the organism in their digestive tracts, does not cause disease

How is Cryptococcosis treated?

* Fluconazole and Itraconazole are drug of choice * Amphotericin-B - Toxicity * 5-Fluorocytosine