IVRA Pythiosis Mylene Auger, DVM, DACVR Animages, Longueuil, QC, Canada Pythiosis (Pythium insidiosumIVRA) ▪ Aquatic pathogen in class Oomycetes ▪ Fungal -like microbes but differ from true fungi – Produce motile, flagellate zoospores – Have cell walls that contain cellulose and β -glucan but not chitin – Resemble algae more than fungi ▪ Infective stage thought to be aquatic zoospores – Released into warm water environments – Possess strong tropism for plant tissue and mammalian open skin – Encysts in damaged skin or GI mucosa – No evidence of transmission between hosts Pythiosis (Pythium insidiosumIVRA) ▪ Mostly reported in Gulf Coast states – Increasingly recognized in many other states ▪ Most common in young, large-breed, male dogs – History of exposure to warm, freshwater habitats – Typically immunocompetent and otherwise healthy animals ▪ Has also been reported in numerous other species – Including cats, horses, sheep, humans, a California bird, and zoo-captive animals including camels, big cats, and bears Pythiosis (Pythium insidiosumIVRA) ▪ Clinical Findings – Cutaneous or GI lesions ▪ Rarely both in same patient ▪ Systemic dissemination is rare ▪ In dogs, GI more frequent – Cutaneous pythiosis ▪ Nonhealing wounds or invasive masses ▪ Lymphadenomegaly often extension of infection (rather than reactive lymphadenopathy) Pythiosis (Pythium insidiosumIVRA) ▪ Clinical Findings – GI pythiosis ▪ Severe segmental transmural thickening of stomach, small intestine, colon or rectum – Inflammation often centered on submucosa ▪ Mucosal ulceration possible ▪ Can extend through serosa and infiltrate mesentery ▪ Esophagus/pharyngeal region (rare) ▪ Mesenteric lymphadenopathy common ▪ May extend from GI tract to adjacent tissues ▪ Clinical signs: – Weight loss, vomiting, diarrhea, hematochezia Pythiosis (Pythium insidiosumIVRA) ▪ Reported ultrasound findings (9 dogs) (Graham 2000) – Stomach, duodenum, descending colon most common – Majority had circumferential lesions – Variable degree of wall thickening (5 mm – 20 mm) ▪ In all dogs, regions of loss of normal wall layering Case Example - Lola Radiographs IVRA There is an approximately 10.0 cm (L) ×6.0 cm (W) soft tissue opaque, homogenous mass within the right caudal ventral abdomen. The adjacent serosal margin detail is mildly mottled. Differential diagnoses include a non-organ associated mass such as an abscess or gossypyboma with associated focal peritonitis, or a small intestinal mass of benign or malignant etiology. Case Example - Lola Ultrasound IVRA 2.4 cm Jejunal mass transverse Ultrasound confirms a circumferential hypoechoic jejunal mass with complete loss of wall layering Case Example - Lola Ultrasound IVRA The mesenteric, colic and medial iliac lymph nodes are enlarged, rounded, some with irregular margination, and heterogeneous. Case Example - Duke Radiographs IVRA The distal aspect of the descending colon at the pelvic inlet is mildly narrowed and changes appearance between views. There is the impression of a soft tissue opaque mass within the caudal abdomen, within the plane of the descending colon. There is moderate smooth periosteal proliferation along the ventral aspect of the sacrum and mildly at the ventral first caudal vertebra. The appearance of the colon is consistent with the reported colitis. The colonic narrowing at the pelvic inlet is suggestive of intramural infiltrative disease. Impression of a soft tissue mass within the caudal abdomen may represent lymphadenopathy, a colonic mass and/or concurrent summation of soft tissues. Smooth periosteal proliferation at the sacrum and first caudal vertebra could represent metastatic disease or reactive periostitis (spondylitis). Duke Ultrasound 11/20/2017 IVRA Mesenteric LN Left MILN Descending colon longitudinal There is progressive thickening of the wall of the descending colon from orad to aborad which becomes progressively markedly thickened caudally, measuring up to approximately 1 cm in thickness. This thickening is associated with loss of the normal pattern of wall layering with ill-defined hypoechoic extensions into the adjacent mesentery. Multiple abdominal lymph nodes are enlarged and hypoechoic. Pythiosis (Pythium insidiosumIVRA) ▪ Atypical presentations ▪ Prostatic pythiosis without primary GI lesions (Kepler 2019) ▪ Bronchocentric pythiosis with marked tracheobronchial lymphadenopathy (Jaeger 2002) – No cutaneous or GI disease – Previously reported in one horse, a captive jaguar and an outbreak in sheep Pythiosis (Pythium insidiosumIVRA) ▪ Diagnosis – Cytology ▪ Can establish presumptive diagnosis ▪ Often pyogranulomatous, suppurative or eosinophilic inflammation (or combination) ▪ May see wide, poorly septate, branching hyphal elements Duke 283176 Pythiosis (Pythium insidiosumIVRA) ▪ Diagnosis – Culture – Serologic testing ▪ ELISA: high sensitivity/specificity for antibody detection – Useful for monitoring response to therapy – Marked decrease in antibody levels 2-3 months following successful resection of affected tissues – Remain high if recurrence or incomplete excision ▪ Western blot: high sensitivity/specificity for antigen detection ▪ Molecular assays – PCR: high specificity Pythiosis (Pythium insidiosumIVRA) ▪ Treatment – Aggressive surgical excision – Mesenteric lymphadenomegaly almost always present ▪ P. insidiosum hyphae often absent in enlarged mesenteric nodes ▪ Intraoperative biopsy for prognostic information – Combination therapy Terbinafine/Itraconazole ▪ At least 2-3 months post-op – Pythium vaccine ▪ Successful treatment of cutaneous granulomas in horses and vasculitis in people ▪ Efficacy of vaccine in dogs appears to be poor Pythiosis (Pythium insidiosumIVRA) ▪ Prognosis (GI pythiosis) – Poor to grave prognosis – Few (<10) reported cases of survival in the literature ▪ Some with medical management alone ▪ Some with combination marginal or radical surgery and medical management References IVRA • Berryessa NA, Marks SL, Pesavento PA, et al. Gastrointestinal pythiosis in 10 dogs from California. Journal of veterinary internal medicine 2008;22:1065-1069. • Dycus DL, Fisher C, Butler R. Surgical and Medical Treatment of Pyloric and Duodenal Pythiosis in a Dog. JAAHA. 2015;51:385-391. • Fujimori, Mahyumi, et al. Pythium insidiosum colitis in a dog: treatment and clinical outcome. Ciencia Rural, vol. 46, no. 3, 2016, p. 526 • Graham JP, Newell SM, Roberts GD, et al. Ultrasonographic features of canine gastrointestinal pythiosis. Vet Radiol Ultrasound 2000;41:273-277. • Greene, C. Infectious diseases of the dog and cat (4th ed.). 2012, St. Louis, Mo.: Elsevier/Saunders. • Helman RG, Oliver J, 3rd. Pythiosis of the digestive tract in dogs from Oklahoma. JAAHA. 1999;35:111-114. • Jaeger GH, Rotstein DS, Law JM. Prostatic pythiosis in a dog. Journal of veterinary internal medicine 2002;16:598- 602. • Kepler D, Cole R, Lee-Fowler T, et al. Pulmonary pythiosis in a canine patient. Vet Radiol Ultrasound 2019;60:E20- 23. • Mendoza et al., Journal of Clinical Microbiology, Vol. 31, No. 11, Nov. 1993, p. 2967-2973 • Mendoza, Leonel, and Raquel Vilela. “The Mammalian Pathogenic Oomycetes.” Current Fungal Infection Reports, vol. 7, no. 3, 2013, pp. 198–208 • Pereira DI, Botton SA, Azevedo MI, et al. Canine gastrointestinal pythiosis treatment by combined antifungal and immunotherapy and review of published studies. Mycopathologia 2013;176:309-315..