Clinical Reviews
Fungal Testing Overview
Fungal antigens, fungal DNA, and anti-fungal antibodies can be used as non-invasive biomarkers for invasive fungal infections (IFIs). MiraVista Diagnostics (MVD) specializes in developing diagnostic tests to detect these biomarkers. These tests provide a rapid, cost-efficient alternative to invasive testing, often required otherwise to diagnose IFIs. Over the past 20 years MVD tests have revolutionized diagnosis and treatment monitoring of IFIs in animals. Use has been reported in many peer-reviewed publications. The reported diagnostic performances are found below.
Diagnostic performance of MVD fungal tests. Bolded tests are the recommended first non-invasive diagnostic test(s) to be performed.
*Blastomyces antigen test on urine is also the first-choice test for cats.
^Minimum sample volume required for testing.
#Specificity was often provided for non-fungal disease.
EIA, enzyme immunoassay; ID, immunodiffusion; LA, latex agglutination
Geographic location of enzootic invasive fungal infections (IFIs) is an important consideration. Cryptococcosis and aspergillosis, along with other invasive molds, occur anywhere in the U.S. Although infections can occur sporadically anywhere, IFIs due to dimorphic fungi (Blastomyces, Histoplasma, and Coccidioides) are found more commonly in predictable locations. The map below provides a rough estimate of enzootic regions.
Invasive fungal infections (IFIs) commonly include non-specific findings such as lethargy, anorexia, weight loss, and fever unresponsive to antibiotics. Other more specific findings are also often present and can help guide diagnostic testing. Any IFI can affect any single organ or be multi-systemic, but patterns exist.
Common anatomic locations and clinical signs of invasive fungal infections in dogs and cats.
| PATHOGEN | SPECIES AFFECTED | COMMON ORGANS INVOLVED | COMMON CLINICAL SIGNS |
|---|---|---|---|
| Blastomyces | Dog>>>Cat | Lung Lymph nodes Skin Eyes/periocular tissues Bones/joints Testicles/prostate (dog) |
Anorexia Weight loss Fever Tachypnea Cough Lameness Vision disturbance Cutaneous Lesions |
| Histoplasma | Cat>Dog | Lung Lymph node Spleen & Liver Eyes/periocular tissues Bone marrow Bone/joints (cat) GI tract (dog) |
Anorexia Weight loss Fever Tachypnea Lameness Vision disturbance Cutaneous lesions Diarrhea |
| Cryptococcus | Cat>>>Dog | Nasal cavity & sinuses Eyes & periocular tissues Lymph nodes Skin CNS Abdominal viscera (dog) |
Nasal discharge Facial deformity Cutaneous lesions Blindness CNS signs Vomiting, diarrhea (dog) |
| Coccidioides (valley fever) |
Dog>>Cat | Lung Lymph nodes Skin Eyes CNS Bones/joints |
Anorexia Weight loss Tachypnea Cough Lameness Cutaneous lesions CNS signs |
| Aspergillus (systemic) |
Dog>>>Cat | Bone/joints Vertebral end plates CNS Kidney Lymph nodes Skin Eyes Abdominal viscera |
Anorexia Weight loss Fever Lameness Vision disturbance CNS signs Cutaneous lesions PU/PD |
| Aspergillus (sinonasal) |
Dog>>Cat | Nasal cavity Sinuses Orbit CNS |
Nasal discharge Nasal depigmentation Facial deformity CNS signs |
With many available tests, choosing the best test can be challenging. In some cases, a combination of tests for a specific pathogen is preferred. For others, sequential testing might be needed. Considering the overlap of clinical findings, and enzootic areas, testing for multiple fungal pathogens is appropriate in many cases. To help simplify test selection, and treatment considerations, algorithms are provided below.
REFERENCES:
- Motschenbacher LO, Furrow E, Rendahl AK, et al. Retrospective analysis of the effects of Blastomyces antigen concentration in urine and radiographic findings on survival in dogs with blastomycosis. J Vet Intern Med 2021.
- Mourning AC, Patterson EE, Kirsch EJ, et al. Evaluation of an enzyme immunoassay for antibodies to a recombinant Blastomyces adhesin-1 repeat antigen as an aid in the diagnosis of blastomycosis in dogs. J Am Vet Med Assoc 2015;247:1133-1138.
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