Systemic Mycoses Flashcards
Blastomycoses basics
Dimorphic fungus Grows in mycelial form in soil Produces infective spores Dogs, people most commonly infected Cats less commonly affected
Blasto epidemiology
Soil reservoir
Special environmental conditions required for organism survival
- Living near waterway
- Sites recently excavated
Subclinical infection uncommon
Disease reported in strictly indoor animals
Blasto distribution
NA dz
Mississippi, MO, and OH river valleys
States with highest endemnicity include IL
Blasto path
Most cases by inhalation of spores from mycelial growth in envmt
Direct inoculation into skin rare
Dissemination
- Skin, eyes, bones, LN, brain, testes, mouth, nasal passages, prostate, mammary gland, heart
Blasto risk factors
Young, large breed dogs
Sporting breeds and hounds: coonhounds, pointers, Weimeraners
Dobermans and retrievers
Proximity to waterways and exposure to excavation
Dogs 10x more susceptible than people
Blasto CS dogs
Anorexia, weight loss, cough, dyspnesa, ocular dz, lameness, skin lesions
Previous Abx therapy
Blasto PE dogs
Fever
Lymphadenopathy*
Resp: harsh, dry lung sounds, dyspnea, cough
Ocular: uveitis, chorioretinitis, retinal detachment, panophthalmitis
Skin: ulcerated and draining*
Lameness
CNS: depression, seizures, neuro deficits
Any organ
Blasto CS cats
Anorexia, fever, weight loss, lethargy, dyspnea, cough Fever Draining skin lesions Ocular lesions Respiratory signs
Blasto Dx
Cytology/histopath - Find organism - Draining skin lesion - LN aspirate - Lung aspirate - Subretinal aspirates Cytologic rxn is pyogranulomatous and includes nondegenerate N0, M0, and occasional MNGCs; may be plentiful Culture not recommended!!!
Blasto clin path
Normocytic, normochromic anemia
Leukocytosis, left shift
Hyperglobulinemia/hypoalbuminemia
Hypercalcemia
Blasto Imaging
Snowstorm chest Diffuse nodular or interstitial infiltrates Solitary nodules or masses in chest Tracheobronchial lymphadenopathy Fungal osteomyelitis
Blasto serology
Antigen detection - Urine 94% - Serum 87% - Cross reactivity with histoplasmosis - May be negative initially if illness mild - Miravista labs, Indianapolis Antibody detection - Immunodiffusion - Enzyme immunoassay
Blasto prognosis
Strong correlation between extent of lung involvement and survival
25% of dogs die, usually during first week of treatment dt respiratory failure
High urine or blood [Ag} correlates with clinical severity in dogs
Blasto treatment
Amphotericin B
Itraconazole
Fluconazole
Glucocorticoids
- To reduce inflammatory response in lung
- To avoid/manage respiratory failure
- Only after starting antifungal treatment
Blasto monitoring
Treat 4-6mo or longer Clinical response, resolution of signs Serial chest rads [Ag] declines with effective therapy - Consider stopping treatment when [Ag] <2ng/mL
Histoplasmosis basics
Dimorphic fungi
Infections documented in every continent, except Antarctica
Most prevalent in Americas, India, and southeastern Asia
Histo epidemiology
Endemic throughout temperate/subtropical areas of world
Organism isolated from soil in 31 states
Most cases occur in central US in Ohio, MO, and MS
Soil rich in bird or bat feces
Most infections subclinical
Histo pathogenesis
Infection acquired by inhalation of microconidia
Incubation period 12-16d
Microconidia convert to yeast phase in lung and reproduce by budding
Yeast phagocytized by cells of mononuclear phagocyte system and replicate further
Histo location
Infection limited to pulmonary or lymphatic/hematogenous dissemination
Organs rich in mononuclear phagocytes
Severe clinical disease if
-Dose of spores large
-Immune system of host compromised
Cellular immune system, predominately involving cytokine-mediated M0 killing will bring infection under control in most
T-cell immunity critical for clearance of organism
Histo clinical findings in cats
Very susceptible
4mo-14y
Most have disseminated disease
Non-specific C/S: weight loss, fever, anorexia, pale mm
Dyspnea, tachypnea, and abnormal lung sounds in more than 1/2 affected cats
Histo CS cats
Peripheral/visceral lymphadenopathy***
Hepatomegaly/splenomegaly
Ocular lesions: conjunctivitis, granulomatous blepharitis, chorioretinitis, retinal detachment, and optic neuritis
Bone lesions with soft-tissue swelling and lameness
Skin infrequently affected with nodular/ulcerated lesions
Rare CS: oral ulcers, nasal polyps, vomiting, diarrhea
Histo clinical findings dogs
2mo-14y
Most dogs <4y
Pointers, Weimaraners, and Brittany Spaniels overrepresented
Inappetence, weight loss, fever
Unresponsive to therapy***
Some signs confined to resp tract
- Dyspnea, coughing, abnormal lung sounds
Histo CS dogs
Most signs result from disseminated histoplasmosis with GI involvement
- Large bowel diarrhea with tenesmus, mucus, and fresh blood
Pale mm dt blood loss or bone marrow involvement
Small bowel involvement can produce voluminous, watery stool with PLE
Hepatomegaly/splenomegaly, icterus, ascites, visceral lymphadenopathy
Histo cytology
Rectal scrapings BAL Bone marrow LN Liver aspirates Lung aspirates Peritoneal/pleural effusions Granulomatous lesions
Histo other Dx
Fungal Isolation - not recommended
Ag detection
Miravista labs, Indianapolis
FIND THE ORGANISM
Histo Tx
Itraconazole “standard of care”
Fluconazole
Amphotericin B
Coccidiomycosis basics
Valley fever, San Joaquin Valley fever, desert fever, cocci
Dimorphic fungi, immitis and posadasii
Occurs in most mammalian species, but most cases people and dogs
Coccidiosis epidemiology
Cocci endemic to hot, semi-arid southwestern US, northern Mexico, and Central America
- California, southern Arizona, southern New Mexico, western Texas, southern Nevada, and Utah
Coccidioides immitis in California
Coccidioides posadasii in Arizona
More coccidiosis epidemiology
Grows in soil as mycelia with barrel-shaped arthroconidia
Dormant in mycelial phase during drought
Rain causes germination of arthroconidia and production of mycelia
Infection occurs most often during dry weather following heavy rainfall when arthrospores are dispersed
Cases described in people and animals that have travelled to endemic areas
Coccidioides pathogenesis
Time for C&S 2 or more weeks Sites for dissemination - dogs - Bone, joints, LN, heart/pericardium, brain, eyes, testes, skin and SQ, spleen, liver, and kidney Sites for dissemination - cats - Skin
Coccidioides risk factors for dogs
Young (<6y) Large breed (>22kg) Outdoor, working, sporting dogs Boxers, Doberman pinschers, pointers, Australian Shepherds, Beagles, Scottish terriers
Coccidioides risk factors for cats
No breed predisposition apparent
More common in middle-aged cats
Neither FeLV nor FIV appears to predispose to feline cocci
Host response to coccidiosis
Cell mediated immunity is the key mechanism of defense
- CMI required for resolution
- Prevents against dissemination
Antibody production
- Not believed to play significant role in recovery
- Most useful as a marker of infection
People who have recovered considered immune for life
Subclinical infections common in dogs
- 70% of cases in one prospective study
Relapse is common in dogs and cats
Duration of immunity in dogs and cats?
Coccidioides CS in dogs
Fever Cough Anorexia Lethargy Primary pulmonary: -Chronic, dry, or moist cough -Fever, weight loss, anorexia, lethargy Cough dt lung involvement or tracheal/bronchial constrictiondt hilar lymphadenopathy Disseminated - Lameness dt osteomyelitis (most common form in dogs) - Draining tracts in skin - Regional lymphadenopathy - Ocular signs - CNS signs: Seizures, ataxia, behavioral changes, coma - Heart, pericardium
Coccidioides Dx
Clinical suspicion Travel history*** PE Imaging CBC/serum biochem Cytology/histopath/culture Serology
Coccidioides Dx challenges
Diverse clinical presentations in both dogs and cats
Better diagnostic tools for clinicians
- Organism typically difficult to isolate
- Clinicians often have to rely on serology
- Must differentiate exposure from active infection
- Future of antigen testing
