Antigen and Antibody Testing for the Diagnosis of Blastomycosis in Dogs

Abstract

Background: Early diagnosis and treatment are associated with an improved prognosis in blastomycosis. The diagnosis of blastomycosis may be missed by cytology, histopathology, culture, or serology. An enzyme immunoassay (EIA) for detection of Blastomyces dermatitidis galactomannan antigen in body fluids has been used for rapid diagnosis of blastomycosis in humans.Hypothesis: Measurement of Blastomyces antigen in urine or serum by the MVista Blastomyces antigen EIA is more sensitive than measurement of anti-Blastomyces antibodies for diagnosis of blastomycosis in dogs.Methods: Serum and urine samples from 46 dogs with confirmed blastomycosis were tested for Blastomyces antigen and serum was tested for anti-Blastomyces antibodies.Results: The sensitivity for the detection of antigen in urine was 93.5% and it was 87.0% in serum. The sensitivity of antibody detection by agar gel immunodiffusion (AGID) was 17.4% and it was 76.1% by EIA. Antigen and antibody decreased during itraconazole treatment.Conclusions and Clinical Importance: Antigen detection is a more sensitive test for diagnosis of blastomycosis than antibody testing by AGID, the only commercially available method. Antigen concentrations decreased with treatment.

Serum and UrineBlastomycesAntigen Concentrations as Markers of Clinical Remission in Dogs Treated for Systemic Blastomycosis

“…This is consistent with case reports in humans11, 12 and in a retrospective study in dogs, using an older version of the same assay 8. In our study, serum antigen concentrations had a sensitivity of only 18% for active disease during treatment, as assessed 2–4 months into treatment.…”

“…Similar to prior reports in people and dogs,7, 8, 9, 10 we found urine Blastomyces antigen to be highly sensitive for the diagnosis of blastomycosis (100% sensitivity in this population). The sensitivity for serum antigen test was also quite high (about 90%), which is similar to previous reports (87%) 8. The magnitude of urinary antigen concentration at diagnosis was modestly correlated with time to clinical remission, which suggests that dogs with higher urinary antigen concentrations may require longer duration of treatment.…”

“…In the absence of organism identification, diagnosis has been accomplished historically through a combination of clinical signs, radiographic findings, and serum antibodies 2, 4, 5, 6. Recently an antigen test has been developed, which detects a cell wall galactomannan, and has been found to have a high degree of both sensitivity and specificity for the diagnosis of blastomycosis in dogs and humans 7, 8, 9, 10. Although both urine and serum can be assayed to evaluate the presence of Blastomyces antigen, urine antigen measurement appears to have an increased sensitivity relative to serum antigen for the diagnosis of blastomycosis in dogs 8…”

Antigen Detection in Canine Blastomycosis: Comparison of Different Antibody-Antigen Combinations in Two Competitive ELISAs

“…If the disease is not diagnosed or goes untreated while in the lungs it may become invasive and disseminate to other organs and possibly to the central nervous system where fatal meningitis may develop [2][3][4][5][6]. In dogs a B. dermatitidis infection may disseminate to the eyes, bones, skin or lymph nodes and produce an immune response directed against the yeast phase antigens [7,8]. Blastomycosis, as well as other systemic mycoses, are termed "emerging fungal threats" since they can not only infect individuals with normal immune systems, but also are a cause for concern in hosts with deficiency diseases that compromise the immune system; therefore, a prompt diagnosis and treatment is important to the survival of the patient [2,5,6].…”

Comparison of antibody detection with <i>Blastomycesdermatitidis</i> yeast lysate antigens in serum specimens from immunized rabbits and infected dogs

“…Current culture methods may be effective, but very time consuming. Therefore researchers have focused on the development of immunodiagnostic assays in attempts to provide improved methods for the clinical diagnosis of blastomycosis in humans and animals [2,10,11,[14][15][16][17][18]. Our laboratory has developed various B. dermatitidisyeast phase lysate preparations and utilized these antigens in the ELISA for the detection of antibodies in serum specimens from immunized or infected animals [10,11,13,15].…”