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A bone marrow infection caused by Phialosimplex caninus was diagnosed in a seven-year-old female spayed Cocker Spaniel that was receiving prednisone for autoimmune hemolytic anemia. Histopathologic examination of a bone marrow core biopsy revealed clusters of oval to round yeast-like cells of varying shape and size and occasional irregular hyphae. Culture of a bone marrow aspirate sample yielded a mould initially suggestive of Paecilomyces inflatus or Sagenomella species but later determined to be P. caninus. The dog was treated with itraconazole and amphotericin B, and prednisone was continued at the lowest dose needed to control the hemolytic anemia. The patient died after 18 months of treatment. This is the first detailed clinical report of infection caused by P. caninus, a newly described fungus associated with disseminated disease in dogs.

Pythiosis is a life-threatening infectious disease of both humans and animals living in Asia, Americas, Africa, and parts of Australia and New Zealand. The etiologic pathogen is the fungus-like organism Pythium insidiosum The disease has high mortality and morbidity rates. Use of antifungal drugs are ineffective against P. insidiosum, leaving radical surgery the main treatment option. Prompt treatment leads to better prognosis of affected individuals, and could be achieved by early and accurate diagnosis. Since pythiosis has been increasingly reported worldwide, there is a need for a rapid, user-friendly, and efficient test that facilitates the diagnosis of the disease. This study aims to develop an immunochromatographic test (ICT), using the bacterial protein A/G, to detect anti-P. insidiosum IgGs in humans and animals, and compare its diagnostic performance with the established ELISA. Eighty-five serum samples from 28 patients, 24 dogs, 12 horses, 12 rabbits, and 9 cattle with pythiosis, and 143 serum samples from 80 human and 63 animal subjects in a healthy condition, with thalassemia, or with other fungal infections, were recruited for assay evaluation. Detection specificities of ELISA and ICT were 100.0%. While the detection sensitivity of ELISA was 98.8%, that of ICT was 90.6%. Most pythiosis sera, that were falsely read negative by ICT, were weakly positive by ELISA. In conclusion, a protein A/G-based ICT is a rapid, user-friendly, and efficient assay for serodiagnosis of pythiosis in humans and animals. Compared to ELISA, ICT has an equivalent detection specificity and a slightly lower detection sensitivity.

Medical therapy for pythiosis is hampered by a lack of efficacious drugs. The present report describes a case of canine gastrointestinal pythiosis in which lesions were resolved through the administration of itraconazole, terbinafine, and the agricultural fungicide mefenoxam. No substantial adverse effects occurred in association with administration of the latter compound. Additional studies are needed to evaluate the pharmacokinetics of mefenoxam and to further assess its tolerability and potential efficacy for the treatment of pythiosis in dogs.