Systemic Fungal Infections
in Small Animals
Colleen Hock
May 12, 2010
http://atlas.arabslab.com/data/8/blasto10.gif
The Mycotic Agents
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Blastomyces dermatitidis
Histoplasma capsulatum
Coccidioides immitis
– All are dimorphic (mold and yeast forms)
– Cause primarily respiratory disease by
evasion of the host immune response
Blastomycosis
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Blastomyces dermatitidis
South east, south central, and upper
midwest near river valleys and lakes
Moist and shaded areas with increased
organic matter (soil and wood)
http://www.familyvet.com/Dogs/Fungi.html
Blastomycosis: Clinical Signs
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Dogs: Dyspnea
 Cats: Dyspnea
Anorexia
Nasal discharge
Cough
Depression
Lethargy
Lameness
Weight loss
Lymphadenopathy
Skin Lesions
+/- occular
manifestations
+/- Orchitis
**Pneumonia and weight loss are the
most common presentations**
Blastomycosis
http://veterinarymedicine.dvm360.com/vetmed/ArticleStandard/Articl
e/detail/596603
Occular blastomycosis:
Panophthalmitis
http://www.njmoldinspection.com/vetmycology/vetblastomycosis.html
Cutaneous blastomycosis:
Dermatitis
Blastomycosis: Pathogenesis
Inhale spores

Deposit in the alveoli

Acute Pulmonary Phase

Self-limiting control
of asexual reproduction

Asexual budding, not eliminated
by the immune system OR the patient
is immunocompromised
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Lymphatic and Hematogenous
Pyogranulomatous
Spread of spores
Inflammation within
the lungs

Inflammation in skin, bones, LN’s,
eyes, CNS, and/or reproductive tract
Blastomycosis: Diagnosis
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History, Clinical signs, and Diagnostic
findings
Definitive diagnosis must show the organism
Cytology: TTW, BAL, LN aspirates, fluid
from the anterior chamber of the
eye, draining tracts, prostatic
fluid, and CSF
Never Culture Blastomyces because of
danger to personnel
http://www.pharmacy-and-drugs.com/illnessessimages/blastomycosis2.jpg
Blastomycosis: Diagnosis
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Serology (AGID) is helpful if the organism
cannot be definitively diagnosed.
- Sensitivity and Specificity > 90%
Thoracic Radiographs indicated when
respiratory signs present:
- interstitial pattern
- nodular interstitial pattern/diffuse miliary
- tracheobronchial lymphadenopathy
Blastomycosis: Pyogranulomatous
Inflammation
http://www.vet.uga.edu/vpp/clerk/mordecai/index.php
Nodular Interstitial
Pattern/Diffuse Milliary Pattern
Differentials
-Lymphoma
-Fungal
pneumonia
-Pneumoconiosis
-Hematogenous
bacterial
pneumonia
-Metastases from
thyroid or
mammary
carcinoma
www.vet.uga.edu/vpp/clerk/mordecai/figure1.jpg
Blastomycosis: Fungal
Granuloma
Differentials
-Tumor metastases
-Fungal granuloma
-Parasitic granuloma
-Abscesses
-Lymphoma
-Malignant histiocytosis
-Lymphoid granulomatosis
-Cysts/Fluid filled bullae
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Fungal Osteomyelitis:
Blastomyces dermatitidis
http://cal.vet.upenn.edu/p
rojects/saortho/chapter_3
7/37mast.htm
Fungal Osteomyelitis vs. Bone Tumors

http://people.upei.ca/lpack/vetrad/VCA%20341/VCA%20
341%20Lecture%207%20Musculoskeletal%20Part%201.
ppt#362,49,Fungal Osteomyelitis

http://www.acvs.org/AnimalOwners/HealthConditions/SmallA
nimalTopics/BoneTumorsinCatsandDogs/
Blastomycosis: Treatment


Amphotercin B
- IV, nephrotoxic
- Lipid soluble form that is less toxic
Iatroconazole
- less toxic
- oral administration
- more expensive
http://www.cvs.com/CVSApp/images/health/A1055050.JPG
Histoplasmosis
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Histoplasma capsulatum
Found in soil near avian species (especially
starlings) and bats
3 forms in dogs: pulmonary, disseminated,
and subclinical
Rare and progressive in cats
http://www.familyvet.com/Dogs/Fungi.html
Histoplasmosis: Clinical
Signs

Dogs
- coughing
- dyspnea
- anorexia
- weight loss
- depression
- ascites
- ulcerated oral and/or
nasal mucosa
- anemia
- lymphadenopathy
- thrombocytopenia
- fever
- diarrhea

Cats
- weight loss
- lethargy
- fever (fluctuant)
http://cat.uab.cat/Publications/2005/SEP05/starlings.jpg
Histoplasmosis: Pathogenesis
Inhale or ingest
microconidia or hyhae

Conversion to yeast within the host

Yeasts engulfed by macrophages
and they replicate intracellularly

Immune system is
overwhelmed

Hematogenous and
Lymphatic spread

Clear infection
Histoplasmosis: Diagnosis

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Cytology: exudates, TTW, FNA (LN’s),
and Bone Marrow
Histopathology
Serology
Blood smear
http://www.google.ca/imgres?imgurl=http://www.vet.uga.edu/vpp/cler
k/edison/Fig4ADJ
Histoplasmosis: Diagnosis


Radiographs:
- pulmonary interstitial pattern with
miliary or nodular infiltrates
- Abdomen: hepatomegaly, splenomegaly, and
ascites
- Gastogram: Barium highlights thickening of the
intestinal wall and mucosa
- Abdominal Ultrasound for gi thickening
- Bone: osteolysis with periosteal proliferation
Endemic areas: may see patients with calcification
in the thorax or abdomen secondary to persistence
of the organism
Histoplasmosis
http://www.vet.uga.edu/vpp/clerk/edison/Fig4ADJ.jpg
Histoplasmosis
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51108.htm
Histoplasmosis
http://www.vet.uga.edu/vpp/clerk/edison/index.php
Histoplasmosis: Fungal
osteomyelitis
http://cal.vet.upenn.edu/projects/saortho/c
hapter_37/37F8.jpg
Histoplasmosis: Treatment

Iatroconazole: lower toxicity
http://www.my-online-pharmacy.net/i/products/sporanox.jpg
Coccidiomycosis
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Coccidioides immitis
Soil in arid or semi-arid regions
Virulent reputation
Epidemics after rainy season followed by a
drought
http://www.familyvet.com/Dogs/Fungi.html
Coccidiomycosis: Clinical Signs

Dogs
- dyspnea
- anorexia
- cough
- weight loss
- lameness
- draining tracts
- abscesses
- lymphadenopathy
- meningitis


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Signs can range from
flu-like symptoms to
severe pneumonia
when pulmonary tissue
involved
Can see extensive
damage to bones,
joints, skin, and CNS
when dissemination
occurs
Fatal when
immunocompromised
Coccidiomycosis: Pathogenesis
Inhalation of infective
arthroconidia

Deposition in the lung

Microenvironment induces
endosporulation

Endospores released

Removed by
mononuclear cells

Subclinical or clearance of organisms

Immunocompromised patients

Extensive lung
damage

Dissemination
Coccidiomycosis: Diagnosis



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Cytology: exudate, TTW, LN or bone
biopsy
Wet mount with 10% KOH
- endospores 2-5 um
- spherules 10-100 um
- mycelial form= dangerous
Serology
Radiographs: Thorax and bones
Coccidiomycosis: wet mount
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51104.htm
Coccidiomycosis
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51104.htm
Coccidiomycosis: Fungal
osteomyelitis
http://www.familyvet.com/Dogs/Fungi.html
Coccidiomycosis: fungal
osteomyelitis
http://cal.vet.upenn.edu/projects/saortho/chapter_37/37mast.htm
Coccidiomycosis: Treatment


Ketoconazole: helps to prevent
dissemination
Iatroconazole
www.amercianvetonline.com
References
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http://www.vet.uga.edu/vpp/clerk/mordecai/index.php
http://www.familyvet.com/Dogs/Fungi.html
http://cal.vet.upenn.edu/projects/saortho/chapter_37/37mast.htm
http://www.acvs.org/AnimalOwners/HealthConditions/SmallAnimalTopics/Bon
eTumorsinCatsandDogs/
http://www.pharmacy-and-drugs.com/illnessessimages/blastomycosis2.jpg
http://veterinarymedicine.dvm360.com/vetmed/ArticleStandard/Article/detail/
596603
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51108.htm
http://www.vet.uga.edu/vpp/clerk/edison/Fig4ADJ.jpg
http://www.vet.uga.edu/vpp/clerk/edison/index.php
http://cal.vet.upenn.edu/projects/saortho/chapter_37/37F8.jpg
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/51104.htm
http://www.vet.uga.edu/vpp/clerk/edison/index
Songer, J.G., & Post, K.W. (2003). Veterinary Microbiology. St Louis: Elsevier.
http://www.acvs.org/AnimalOwners/HealthConditions/SmallAnimalTopics/Bon
eTumorsinCatsandDogs/
http://people.upei.ca/lpack/vetrad/VCA%20341/VCA%20341%20Lecture%20
7%20Musculoskeletal%20Part%201.ppt#362,49,Fungal Osteomyelitis