Final Exam Flashcards
What is the infectious particle for pythiosis?
Zoospore
What is the infectious particle for blastomycosis?
Microconidia
What is the infectious particle for zygomycetes?
Zygospore
What is the infectious particle for aspergillosis?
Conidia
What is the infectious particle for yeasts?
Chlamydoconidia
What is the infectious particle for dermatophytes?
Arthrospore
What is the infectivity of dimorphic fungi?
Highly infectious because of ability to adapt to unnatural environments once inhaled
This causes concern with presentation in necropsy
What are the primary forms of blastomycoses?
Pulmonary form Ocular form Skin lesions Bone Genitourinary
Describe the pulmonary form of blastomycoses
Does not spontaneously resolve like histoplasmosis and coccidioidomycosis
Pulmonary mycoses have indicative “snowstorm” appearance on radiographs
Describe the ocular form of blastomycoses
Usually presents as uveitis
Sometimes panophthalmitis, glaucoma, acute retinal detachment (irreversible blindness)
Describe the skin lesions form of blastomycoses
Ulcerative or granulomatous dermatitis
Usually found in animal with pulmonary form- poor prognosis
More common on face, nose, lips, limbs, feet, pads, and toes
Describe the bone form of blastomycoses
See lameness and osteolytic lesions on long bones in radiographs
Describe the genitourinary form of blastomycoses
Signs like prostatitis- hematuria and pyuria
What is the best way to make a definitive diagnosis of any fungal disease?
Infections are diagnosed by demonstrating fungus in tissues (histo), exudates or aspirates (direct microscopy) or culturing
The most useful diagnostic tool is appearance in tissues and aspirates or exudates
Which agent makes a capsule?
Cryptococcous neoformans is an encapsulated yeast
Which agents exist in the GI tract of birds and bats?
Cryptococcus neoformans
Candida
What does Histomonas look like in situ?
It is not unusual to see 20 to 40 small yeast cells growing in a single host cell
Often, the cytoplasm has shrunk away from the cell wall and a clear area is evident between the 2 dark staining areas; thus, it appears to have a capsule
What are the geographic areas for Blastomyces dermatidis?
Major endemic areas: Mississippi, Ohio River basins, and central Atlantic states
Most common systemic mycosis in dogs in Louisiana, Arkansas, and Mississippi
What are the geographic areas for Histoplasma capsulatum?
Found worldwide
Major endemic areas: Eastern US, MS River Valley basin, Great Lakes, and Northeast US
Especially common in Kentucky and Indiana
What are the geographic areas for Coccidioides immitis?
Geographically limited to Southwestern states in US
Natural habitat- soil in semi-arid areas; high temp, low humidity
Highest endemicity found in California, Arizona, and West Texas along Mexican border
Also endemic in New Mexico, Nevada, and Utah
What are the geographic locations for Sporothrix schenckii?
Occurs in nature associated with soil, wood, and vegetation
Found worldwide, but more common in tropics and the South
What are the defining features of the class Zygomycota?
Coenocytic hyphae
Produce zygospores: single, dark, thick-walled, frequently ornamented sexual spore
In tissue, they are recognized by their broad,, aseptate, hyaline, randomly branched hyphal elements
2 orders: Mucorales and Entomophthales
What is unique to Mucorales with gross identification?
Fluffy, wooly, or cottony colonies: floccose aerial mycelium
Have “heads” (sporangia) near the edge
What is unique to Entromophthales with gross identification?
Translucent/opaque leather like, folded or wrinkled growth: compact, glabrous mycelium
These colonies have forcible ejected asexually produced spores
What agents cause mycotic placentitis?
Mucor Mortierella Candida Aspergillus A variety of other molds
What causes zygomycosis?
Mucorales
What causes mycotic ruminitis in calves?
Absidia
Rhizopus
Mucor
Rhizomucor
What causes mycotic placentitia in cows?
Mucor
Mortierella
What causes subcutaenous granulomas in dogs?
Absidia
Cunninhhamella
Syncephalastrum
What does Condidiobolus cornatus cause?
Sinusitis
Nasopharyngitis
Upper respiratory disease
What does Basidiobolus ranarum cuase?
Subcutaneous mycosis
Which agent is inhibited by cycloheximide?
Zygomycetes
Which agent is sensitive to cyclohemiide?
Cryptococcus
What is the diagnostic test for crypto?
Direct examination of smears from exudaes with India Ink will show yeasts cells surrounded by large capsule
Culture can be done on blood agar or SDA, but inhibit by cylcoheximide
Immunodiagnosis can be done by direct agglutination of circulating capsular antigen in a latex bead test
What are the reservoirs of Microsporum canis?
Zoophilic: animals are hosts and reservoirs
What are the reservoirs of Microsporum gypseum?
Geophilic: Soil is reservoir
What are the reservoirs of Trichophyton mentagrophytes?
Ubiquitous: found in many moist, dark, environemtns
What are the reservoirs of Epidermophyton flocculosum?
Anthropophilic: only found on humans
Which animals amplify Sporothrix so that when they introduce it back into the environment it causes false zoonosis?
Cats
What kind of tissues are invaded with dermatophytes?
Hair and skin
How far down do dermatophytes go into the hair follicle?
The grow down the side of the hair follicle and attach hair during anagen stage –> grow down to Adamson’s fringe
Which dermatophytes occur in cattle?
Trichophyton verrucosum
Which dermatophytes occur in horses?
Microsporum canis M. gypseum Trichophyton metagrophytes T. equinum T. verrucosum
What is the result of sexual reproduction?
Spores
What is the result of asexual reproduction?
Conidia
What does teleomorph produce?
Meispore (spore formed via sexual reproduction resulting from meiosis; type of spore varies by phylum)
What does anamorph produce?
Mitospore (spore formed via asexual reproduction resulting from mitosis; commonly called a conidium or sporangiospore)
What class of Basidiomycetes are mushrooms and toadstools classified as?
Hymenomycetes
What is mushroom poisoning caused by?
Aminita
Lepiota
Coprinus
Psilocybe
What is the quickest, easiest, and most reliable way to ID fungi?
Histopathology
Cytology
Culture
What dyes are used to stain dermatophytes?
PAS stain: hyphae stain bright red and are easily seen
What dyes are used to stain cryptococcus?
India ink will show yeast cells surrounded by a large capsule
What dyes are used to stain Blastomyces?
Stains can be used, but not usually necessary
Adding 10% KOH to specimen is helpful
What dyes are used to stain Histoplasma?
H&E can be used, but PAS is more specific of all fungi
What dyes are used to stain coccidioides?
10% KOH
What dyes are used to stain sporotrichosis?
PAS or methenamine silve stains
What is arthroconidium?
An asexual spore formed by the breaking up of a hypha at the point of septation
The resulting cell may be recetangular or barrel shaped and thick or thin walled depending on genus
What is asexual reproduction?
Reproduction in an organism by division or redistribution of nuclei but without nuclear fusion (imperfect state)
What is blastoconidium?
Conidium formed by budding along hypha, pseudohypa, or single cell as in the yeasts
What is budding?
Process of asexual reproduction
New cell develops as a smaller outgrowth from the older parent cell
Characteristic of yeasts or yeast-like fungi
What is a capsule?
Colorless. transparent, nucopolysaccharide sheath on the wall of a cell
What is chlamydoconidium?
Conidium that is thick walled and contains stored food enabling it to function as a survival propagule
It may be located at the end of the hypha (terminal) or inserted along the hypha (intercalary)- singly or in chains
Greated in diameter than the hypha on which it is born
Unlike other conidia, doesn’t readily separate from the hypha
What is a germ tube?
Tubelike outgrowth from a conidium or spore- the beginning of a hypha
What is glabrous?
Smooth, without serial hyphae
What is a host?
Animal or plant that supports a parasite
What is hyaline?
Clear, transparent, colorless
What is a hypha?
Tubular or threadlike structure of a fungus
Many together compose mycelium
What is macroconidium?
Larger of the two type of conidia in fungi that produce both large and small conidia
Usually multicelled, but can be single celled
What is microconidium?
Smaller of 2 types of conidia in fungi that produce both large and small conidia
Usually single celled
Usually round, ovoid, pear shaped, or club shaped
What is mold?
Fungus composed of filaments that generally form a colony that’s fuzzy, powdery, woolly, velvety, or relatively smooth
What is monomorphic?
Fungi that have the same type of morph in culture at 25030 deg. C and 35-37
What is mycelium?
Mat of intertwined hyphae that constitutes the colony of a fungus
What is mycology?
Study of fungi
What is mycosis?
Disease produced by a fungus
What is pseudohyphae?
Chains of cells formed by budding that resemble true hyphae when elongated
Differ from true hyphae because they are constricted at the septa forming branches that begin with a septation; also by having terminal cells smaller than the other cells
Do you culture a dimorph in a practice setting or in a lab?
No, you do not want to
Which fungi are dimorphs?
Blastomyces dermatidis
Histoplasma capsulatum
Coccidioides immitis
Sporothrix schenchkii
What agents are associated with Nasopharangitis in the horse?
Condidiobolus cornatus typically infects mucocutaneous sites to produce sinusitis nasopharyngitis or upper respiratory disease in horses
What dermatophytes cause 99% of ringworm cases in dogs and cats?
Microsporum canis (98% in cats, 70% in dogs) M. gypseum (20% in dogs) Trichophyton mentagrophytes (10% in dogs)
What infection can dermatophytes cause?
Onychomycosis
What are cryptococcus infections most common in?
Cats
What tends to become involved with cryptococcus?
CNS
Eye involvement is common: chorioretinitis and blindness
What is the pathogenicity of cyptococcus often associated with?
The aniphagocytic and immunosuppressive capsule
What diseases are common with cryptococcus?
Mastitis characterized by gross swelling, induration, and gradual changes in secretions
Ulcerative lesions of the nose, mouth, sinuses, and pharyn
What are the disease associations with Candidia?
Candidiasis (thrush) in birds
Systemic candidiasis in feedlot cattle and piglets
Cutaneous candidiasis in dogs and cats
Opportunistic candidiasis in mastitis, abortion, and rumenitis
Describe candidiasis in birds
Lesions involve the mouth, crop, proventriculus, and gizzard- consisting of white circular patches or white elongated areas along the folds of mucosa.
Epizootics in young birds have high mortality.
Describe systemic candidiasis in feedlot cattle
Dyspnea, pneumonia, nasal discharge, wasting
Describe systemic candidiasis in piglets
Pseudomembrane on the tongue, esophagus, and stomach causing vomiting and rapid wasting
What is the disease association with Malasseia pachydermitis?
Chronic otitis externa and pododermatitis of dogs
What are the disease associations with Aspergillis in avian species?
Diffuse infection of their air sacs
Diffuse pneumonic form
Nodular pneumonic form know as brooder pneumonia
What are the disease associations with Aspergillis in cattle?
Uterine, placental, or fetal skin infections may result in abortion
Mastitis can occur by intra-mammary inoculation
What are the disease associations with Aspergillis in equine?
Abortions and gutteral pouch infection
Eye infections, keratomycosis can be very serious
What are the disease associations with Aspergillis in dogs?
Nasal aspergillosis
Systemic aspergillosis caused by A. terris in Iga deficient GSD
Osteomyelitis is a common finding
What are the disease associations with Aspergillis in penguins?
Pneumonia in captive birds housed inadequately
What can interal aspergillosis occur in?
Calves, foals, and cats
What is chytridiomycetes associated with?
Epidermal changes
Morbidity and mortality in wild and captive anurans
Cutaneous chytridiomycosis
What are the diseases associated with zygomycetes Conidiobolus and Basidiobolus??
Entomophthorales subcutaneous zygomycosis (Entomophthoromycosis)
What do mucorales cause?
subcutaneous and systemic zygomycosis (Mucormycosis)
What is Blastomycosis chronic disease characterized by?
Suppurative and granulomatous lesions
What is the primary site of Blastomycosis?
Lung. It can stay localized or disseminate to other organs
What are the disease ascscoations with histoplasmosis?
Most have slight or no clinical illness.
Lesions don’t develop in the lung or intestine.
Most common in people and dogs- occasionally cats.
Primary site of infection- lung.
GI form may develop too.
What are the disease associations with coccidiomycosis?
Mainly people dogs, and cats infected.
Most virulent of all fungal pathogens.
Benign, inapparent, or mildly severe URTI- usually resolves rapidly.
Primary infection- 1-3 weeks after exposure.
Rarely- disease is acute or chronic, severe, disseminating, fatal mycosis
Most common in dogs involving bones, meninges, joints, subcutaneous, and cutaneous tissues
Such involvement is characterized by burrowing abscesses
May become characterized by formation of nodules or granulomas.
What is the disease associated with sporotrichosis?
Subacute or chronic disease in which lesions are confined to the skin and SQ tissues as nodules or granulomas- which may spread in a line along lymphatics and often ulcerate and srain (seropurulent)
Most common in dog, cat, horse, and people.
“Cigar bodies” in tissues
What does pythiosis cause?
Granulomatous inflammatory response
What are the characteristics of pythiosis?
Purulent outer coat of eosinophils and neutrophils forms around the developing and enlarging kunkers.
Predominance of eosinophils in granulomas is the predominant histo characteristic.
What is the ingectious particle of pythium?
Zoospore
What does pythium do in the host? Know the pathogeneis and know the names associated with those structures
Pythium is in the water and reproduces asexually as zoospores. The zoospores (motile, biflagellated spores) are ingested by horse or dog. Zoospore comes into contact with mucosa of GI tract and can damage tissue or pass through mucosa and invade lymphatics. OR the zoospore can enter into a small cut/wound on limb of animal and invade the soft tissue. Once it germinates, it causes a granulomatous inflammatory response.
Which fungi get in the eyes of animals?
Pythium
Blastomyces
Aspergillis
Cryptococcus
What is brooder pneumonia in chickens?
The nodular pneumonic form of aspergillosis
What is the mechanism of action of allyalimines (terbinafine)?
Inhibits ergosterol biosynthesis via inhibition of squalene epoxidase. Squalene eposidase is an enzyme part of the fungal sterol synthesis pathway that creates the need for sterols which are required for fungal cell membrane
What is the mechanism of antimetabolites (flucytosine)?
Inhibits fungal protein synthesis by replacing uracil with 5-flurouracil in fungal RNA. Also inhibits thymidylate synthetase which is a fancy way of saying it inhibits fungal DNA synthesis too.
What is the mechanism of action of azoles (fluconazole)?
It inhibits cytochrome P450 14a-demethylase (P45014DM) which is used in the sterol biosynthesis pathway and makes lanosterol to become ergosterol
What is the mechanism of actions of glucan synthesis inhibitors (capsofungin)?
Blocks synthesis of a major fungal cell wall component, 1-3-beta-D-glucan- this is really nice because animals do not have this receptor so little risk.
What is the mechanism of action of polyenes (amphotericin B)?
Binds to sterols (usually ergosterol) and disrupts osmotic integrity of the fungal membrane.
What is the mechanism of action of Griseofulvin?
Inhibits fungal mitosis by disrupting the mitotic spindle through interaction with polymerized microtubules
What is an example of allylamines?
Terbinafine
What is an example of antimetabolites?
Flucytosine
What are examples of azoles?
Fluconazole
Ketoconazole
Itraconazole
What are examples of glucan synthesis inhibitors?
Caspofungin
Micafungin
Anidulafungin
What is an example of polyenes?
Amphotericin B
What is an example of miscellaneous systemic agents?
Griseofulvin
What is the difference between fungi and pythiums?
Pythium cell membranes do not contain ergosterol, but its staining and morphology characteristics still resemble fungi.
What is the treatment of pythium?
Since Pythium does not share the same cell wall characteristics of fungi, antifungal chemotherapy agents do not work.
Surgical removal of infected area is treatment of choice
Which fungal disease is associated with piglets?
Systemic candidiasis in piglets
