Development and evaluation of an ELISA for the quantitation of anti-Lagenidium giganteum forma caninum antibodies in dogs.

BACKGROUND: Lagenidium giganteum forma caninum infection causes severe cutaneous and disseminated disease in dogs. Currently, diagnosis requires culture and rRNA gene sequencing. OBJECTIVE: To develop and evaluate an ELISA for quantitation of anti-L. giganteum f. caninum IgG in canine serum. ANIMALS: Sera were evaluated from 22 dogs infected with L. giganteum f. caninum, 12 dogs infected with Paralagenidium karlingii, 18 dogs infected with Pythium insidiosum, 26 dogs with nonoomycotic fungal infections or other cutaneous or systemic diseases, and 10 healthy dogs. METHODS: Antigen was prepared from a soluble mycelial extract of L. giganteum f. caninum. Optimal antigen and antibody concentrations were determined by checkerboard titration. Results were expressed as percent positivity (PP) relative to a strongly positive control serum. RESULTS: Medians and ranges for PP for each group were: L. giganteum f. caninum (73.9%, 27.9-108.9%), P. karlingii (55.0%, 21.0-90.6%), P. insidiosum (31.3%, 15.8-87.5%), nonoomycotic fungal infection or other cutaneous or systemic diseases (19.2%, 3.2-61.0%), and healthy dogs (9.9%, 7.6-24.6%). Using a PP cutoff value of 40%, sensitivity and specificity (with 95% CI) of the ELISA for detecting L. giganteum f. caninum infection in clinically affected dogs were 90.9% (72.2-97.5%) and 73.2% (60.4-83.0%), respectively. Specificity in dogs infected with P. karlingii was 41.7% (19.3-68.1%) and with P. insidiosum was 66.7% (43.8-83.7%). CONCLUSIONS AND CLINICAL IMPORTANCE: Quantitation of anti-L. giganteum f. caninum antibodies for detection of this infection in dogs has moderately high sensitivity but poor specificity, the latter because of substantial cross-reactivity with anti-P. karlingii and anti-P. insidiosum antibodies.

Clinicopathologic findings associated with Lagenidium sp. infection in 6 dogs: initial description of an emerging oomycosis.

An oomycotic pathogen in the genus Lagenidium was isolated from tissues obtained from 6 dogs with progressive cutaneous disease. Initial clinical findings in 5 dogs included multifocal cutaneous lesions, subcutaneous lesions, or both associated with regional lymphadenopathy: the 6th dog initially was presented for evaluation of mandibular lymphadenopathy. Cutaneous lesions were ulcerated, exudative regions (often with necrosis and draining tracts) or multiple firm dermal or subcutaneous nodules. Two dogs subsequently developed hemoabdomen from great vessel rupture and died acutely. Four dogs were euthanized because of progression of subcutaneous lesions or lymphadenopathy. On postmortem examination, regional granulomatous lymphadenitis was found in all 6 dogs, great vessel invasion in 3 dogs, pulmonary lesions in 2 dogs. ureteral obstruction in 1 dog, mediastinal lymphadenitis in 1 dog, and hilar lymphadenitis with invasion of the distal esophagus and trachea in 1 dog. Histologically, lesions were similar to those associated with pythiosis and zygomycosis and were characterized by severe eosinophilic granulomatous inflammation (often with numerous large multinucleated giant cells) centered around broad (7-25 micro), infrequently septate hyphae. Immunoblot analysis of the serologic response of 4 dogs to a soluble mycelial extract of Lagenidium giganteum indicated that each dog's serum recognized at least 10 different antigens of L. giganteum. Culture of infected tissues yielded rapid growth of colorless to white submerged colonies. Microscopically, mature hyphae in culture were broad (25-40 micro), segmented, and occasionally branching and produced motile laterally biflagellate zoospores in water culture. This report is the 1st description of infection caused by an oomycete other than Pythium insidiosum in any mammalian species.