Fungi in Vet Med

fungus growing in any vertebrate tissue regardless of immune status that is able to survive and disperse at any life stage

primary infection

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TF all primary fungal infections are dimorphic

T

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ability of a fungus to exist in different morphologies (such as yeast or hyphae) depending on environmental changes

dimorphism

non-pathogenic fungal infections with low virulence that are ubiquitous in the environment and have a preferred habitat independent of a living host

opportunistic infection (secondary pathogen)

fungal infections that are most often acquired in immunocompromised individuals or via accidental penetration of intact skin barriers (i.e. trauma, wounds)

opportunistic infection

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disease manifestations with opportunistic fungal infection?

Cutaneous

Subcutaneous

Systemic

most important opportunistic fungal infections in vet med?

aspergillus spp.

cryptococcus spp.

characteristics of fungi that cause primary invasive fungal infections?

-thermally dimorphic

-able to escape from the host

-require a vertebrate host for their life cycle

-saprobic filamentous molds

-usually isolated from soil in specific geographic areas

how are primary invasive fungal infections usually transmitted?

inhalation of airborne conidia or cutaneous inoculation

are primary invasive fungal infections usually zoonotic?

no

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disease manifestations of primary invasive fungal infections include

pneumonia or disseminated systemic disease from the lungs

what are the most important primary fungal pathogens in vet med?

Blastomyces dermatidis

Coccidioides immitis

Histoplasma capsulatum

Sporothrix schenchkii

what is the body's most important defense against primary fungal infection?

cell-mediated immunity

what must a primary invasive fungal infection do first once it enters the body?

transform into yeast via thermal dimorphism

what are ways by which primary invasive fungal infections evade the immune system?

Thermal dimorphism

Capsules

Adhesion factors

Trojan horse w/in phagocytic cells

Pigment

what kind of inflammatory response do dimorphic/primary fungi cause?

granulomatous to pyogranulomatous

where does dimorphic/primary yeast transformation and budding occur in the body?

lungs

how do dimorphic/primary yeast spread throughout the body?

hematogenous and lymphatic spread

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diagnostics that can be used for dimorphic fungal infection?

-Direct microscopic examination (cytology)

-Histopath

-Culture

-Serology

-PCR

do opportunistic fungal infections cause infection in healthy patients?

no

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? fungal infections are more often associated with cutaneous and subcutaneous inoculation

opportunistic

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why is diagnosis of fungal infection challenging?

-methods lack of sensitivity/specificity

-can take a long time to yield a results

most dimorphic fungi can be diagnosed via

cytology

when collecting samples for cytology, collect additional samples aseptically for

fungal culture and susceptibility

what samples can be collected for fungal cytology?

-aspirates of masses

-cytocentrifugation of urine, BALf, CSF

-conjunctival brushings

impression smears of ulcerated lesions

be careful when interpreting cytology of ? due to contamination/colonization with fungal spores

nasal swabs

diagnostic method that provides the best samples for definitive diagnosis when less invasive tests are not available or cytology is non-diagnostic

biopsy/histopath

fungal elements on histopath are predominantly found at what part of the lesion?

necrotic centre of lesions

peripheral biopsies are often abundant in ? leading to a non-diagnostic or misdiagnosed biopsy

inflammatory tissue

what should you request from the lab if you suspect fungal infection?

PAS and GMS stains

a ? biopsy must be obtained for histopathology

representative

"gold standard" for diagnosis of certain fungal infections that allows for identification of the specific etiological agent and susceptibility testing

fungal culture

If you send out a culture for a suspect dimorphic fungi, what should you do first?

alert the lab in advance to prevent infection to laboratory workers

limitations of fungal culture?

Slow growing

Low sensitivity

Invasive procedure to obtain samples

TF breakpoints for antifungal susceptibility are well developed in human and veterinary medicine

F

lacking in vet med

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disadvantage of serologic testing for fungal infections?

-does not reflect severity of disease

-negative serology does not exclude disease in acute phase

-positive titers does not confirm presence of disease

antibody titers increases do not occur when infection persists beyond ?

1-2 months

interpret all positive serology titers less than ? along with clinical signs

<1:16

fungal antigen testing is reliant on ? being shed into body fluids during infection

fungal polysacchargides/proteins

in endemic areas, use other diagnostics such as ? along with serology to confirm diagnosis

culture

cytology

histopath

immunoassays for antigen detection are constructed based upon antibodies that are raised against ?

shed antigens

advantages of serologic antigen testing?

-minimally invasive collection because antigens are present in several body fluids

-positive results when negative fungal culture

-positive results reduce need for fungal culture

disadvantages of serologic antigen testing?

-low sensitivity/specificity

-negative tests don't exclude fungal infection

-sensitivity dependent on disease type and test timing

limitations of PCR?

-contamination

-previous treatment leads to false negatives

-false negatives can occur from inadequate amount of DNA

extracellular yeast with a thick, refractile, double contoured wall and broad based budding that likes to live near water and is endemic to eastern US and north florida

blastomycosis dermatitidis

why don't all animals get blastomycosis dermatitidis?

resident soil organisms destroy it

is blastomycosis dermatitidis contagious?

no

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blastomycosis dermatitidis causes what kind of disease?

localized pulmonary or disseminated disease

what animals are most commonly affected by blastomycosis dermatitidis?

-large breed, young, male, sporting dogs overrepresented

-less common in cats

clinical signs associated with blastomycosis dermatitidis infection in dogs?

fever

lymphadenopathy

harsh lung sounds

skin lesions

ocular lesions

cough

weight loss

clinical signs associated with blastomycosis dermatitidis infection in cats?

similar to dogs

GI disease

urinary tract disease

cavity effusions

best diagnostic tests for blastomycosis dermatitidis?

Blasto cell wall galactomannan quantitative antigen test

Cytology

Histopathology

thoracic radiographs are abnormal in ?% of patients with blastomycosis dermatitidis and histoplasma capsulatum

85%

bone lesions associated with blastomycosis dermatitidis and histoplasma capsulatum?

lytic with periosteal reaction surrounding and soft tissue swelling

treatment of choice for blastomycosis dermatitidis?

itraconazole

contraindication for itraconazole use?

CNS disease

pathologic intracellular small yeast with a thick, retractile, double contoured wall and broad based budding

histoplasma capsulatum

histoplasma capsulatum are seen in what type of cell?

alveolar macrophages

primary reservoir of histoplasma capsulatum?

Decaying soil, bat, and bird guano + potting soil

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geographic distribution of histoplasma capsulatum be found?

worldwide

hyperendemic areas for histoplasma capsulatum?

Mississippi river valley

Missouri river valley

Ohio river valley

Mid-atlantic states

Latin America

SE asia/india

are dogs or cats more susceptible to histoplasma capsulatum?

cats

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most common clinical sign of histoplasma capsulatum in dogs?

large bowel diarrhea

how is histoplasma capsulatum best diagnosed?

H. capsulatum antigen test

Cytology

Histopathology

imaging findings associated with histoplasma capsulatum?

-Diffuse/miliary/nodular interstitial pattern

-Hilar lymphadenopathy

-Hepato/splenomegaly

-Effusion

-Thickened/irregular colon

-GI Lymphadenomegaly

-Lytic bone lesions with periosteal reaction and soft tissue sweeling

unique cytology sample for histoplasma capsulatum?

rectal scrape

unique cytology sample for blastomycosis dermatidis?

ocular fluid

treatment of choice for histoplasma capsulatum?

itraconazole

general timeline for histoplasma and blastomycosis treatment ?

at least 60-90 days or continue for at least 1-2 months past resolution of measurable signs - whichever is longer

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poor prognostic indicators for blasto?

CNS involvement

Severe pulmonary disease

poor prognostic indicators for histoplasmosis?

disseminated infection

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histoplasmosis prognosis is excellent with

only pulmonary involvement

anti-fungal resistance is more common with blasto or histo?

histoplasma capsulatum

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what percentage of patients with blastomycosis dermatitidis are cured?

50-75%

soil bourne fungus with alternating barrel-shapped arhrospores and a large, double walled spherule form that contains multiple endospores

coccidioides immitis

where is coccidioides immitis found in the world?

-dry, warm climates

-southwest US

when is infection by coccidioides immitis most likely to occur?

when soil is disrupted

subclinical infection is ? with coccidioides immitis

common

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most common clinical signs of coccidioides immitis ?

respiratory signs within 1-3 weeks then disseminated disease within 4 months

best diagnostics for coccidioides immitis ?

Antibody testing

Fungal culture

Cytology

Histopathology

imaging findings associated with coccidioides immitis?

-Diffuse interstitial pulmonary pattern

-Hilar lymphadenopathy

-Pleural effusion

-Heart effacement

-More proliferative bone lesions

1st line treatment for coccidioides immitis?

Itraconazole

Surgerical removal if possible (e.g. amputation, enucleation etc.)

medical therapy should persist ? past resolution of measurable signs with coccidioides immitis

1-2 months

prognosis of coccidioides immitis depends on

degree of dissemination

zoonotic and worldwide primary fungal infection known as "rose gardener's disease" that affects dogs and cats

sporotrichosis

how is sporotrichosis transmitted?

-Cutaneous/subcutaneou inoculation through trauma

-Inhalation

is sporotrichosis more common in dogs or cats?

cats

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most common form of sporotrichosis characterized by non-painful ulcerative lesions with draining tracts on the nose/eyelids/pinnae and regional lymphadenomegaly

cutaneous

how is sporotrichosis diagnosed?

Cytology

Culture

Histopathology

sporotrichosis treatment?

16-80 weeks of itraconazole +/- potassium iodide

sporotrichosis prognosis?

good but relapse is common

which of the primary fungal infections is/are zoonotic?

sporotrichosis

opportunistic and ubiquitous saprophytic fungal infection that is distributed worldwide and causes nasal or disseminated disease

aspergillosis

aspergillosis most commonly affects what animals?

immunocompromised and german shepherds

most consistent clinical findings for aspergillosis?

vertebral pain

paraparesis

paraplegia

lameness with swelling and draining tracts

kidney disease

how is aspergillosis diagnosed?

Aspergillus galactomannan antigen

PCR

Cytology

Urine sediment (visualize fungal hyphae)

Histopathology

imaging findings consistent with aspergillosis?

diskospondylitis

osteomyelitis

thoracic lymphadenomegaly

kidney pelvic dilation/lesions

splenic nodules or prior infarction

lymphadenopathy

aspergillosis prognosis?

poor - static disease with life long treatment rather than cure is more common

there are few ? tests for diagnosis of sinonasal aspergillosis

specific

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first line diagnostics for sinonasal aspergillosis?

antibody serology

nasal CT

nasal biopsy

fungal culture