Cutaneous pythiosis in two dogs from Wisconsin, USA

BackgroundPythium insidiosum is an oomycete that causes cutaneous lesions or infiltrative gastrointestinal disease in dogs, cats, humans, horses and other mammals, primarily in tropical and subtropical climates. Hypothesis/ObjectivesWe report the clinicopathological findings associated with cutaneous pythiosis in two dogs from a Northern temperate climate zone. AnimalsA 3-year-old intact male Chesapeake Bay retriever was presented with an ulcerated soft-tissue swelling over the left eye. A 4-year-old spayed female German shepherd dog was presented with a soft-tissue swelling overlying the right hock. Both dogs lived in northern latitudes (between 43 and 45 degrees N) and neither had travelled outside of Wisconsin or Michigan's upper peninsula, USA. MethodsHistopathological examination and culture of affected tissues on specialized media, serology for anti-P.insidiosum antibodies, P.insidiosum-specific PCR and ribosomal RNA gene sequencing were carried out. ResultsHistopathological examination revealed pyogranulomatous and eosinophilic inflammation associated with wide, poorly septate hyphae. Conclusions and clinical importanceEven clinicians who practice in temperate climates should consider pythiosis as a differential diagnosis for young to middle-aged adult dogs presented with ulcerated cutaneous nodules or infiltrative gastrointestinal disease.