Heterobilharzia americana infection in dogs: A retrospective study of 60 cases (2010-2019).

BACKGROUND: The trematode Heterobilharzia americana (HA) causes granulomatous gastrointestinal and hepatic disease in dogs. Before 2008, diagnosis relied on saline fecal sedimentation or histopathology, and earlier reports primarily described dogs with advanced disease or cases diagnosed incidentally at necropsy. The advent of a fecal PCR test has facilitated the diagnosis of HA and provided insights into manifestations and response to treatment. OBJECTIVES: Describe the clinical findings, response to treatment, and outcome for dogs infected with HA. ANIMALS: Sixty dogs diagnosed with HA between 2010 and 2019. METHODS: Retrospective study. Medical records were searched for dogs diagnosed with HA by fecal PCR testing, identification of ova in feces, or histopathology. RESULTS: Mean age was 7.5 (±4.1) years and weight was 23.2 (±10.18) kg. Clinical signs included diarrhea (55.8%), vomiting (46.2%), and weight loss with or without anorexia (15.4%). Laboratory abnormalities included hyperglobulinemia (42.6%) and increased liver enzyme activities (30%). More than 40% of dogs had an eosinophil count >500/µL. Hypercalcemia attributable to HA was identified in only 4 dogs. Pinpoint hyperechoic foci were noted in intestines, liver, or mesenteric lymph nodes during transabdominal ultrasonography in 64.4% of dogs. Survival data was available for 34 dogs, of which 73.5% (25) were alive 6 months after diagnosis. CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperglobulinemia, high eosinophil count, and ultrasonographic evidence of visceral mineralization were suggestive of infection. Hypercalcemia was uncommon. Combination treatment with praziquantel and fenbendazole was variably effective, and 17.6% of treated dogs with known outcome died as a result of HA infection.

Sonographic findings of pinpoint hyperechoic foci in the small intestine, liver, and mesenteric lymph nodes are indicative of canine Heterobilharzia americana infection.

Canine schistosomiasis, caused by the trematode Heterobilharzia americana, can pose a diagnostic challenge due to nonspecific symptoms. The aim of this multicenter, retrospective, descriptive study was to compare the prevalence and extent of sonographic changes associated with schistosomiasis between affected and infection-free dogs. Medical records of two referral centers were searched for dogs with confirmed schistosomiasis that had undergone an abdominal ultrasound. Fifty-five cases fulfilled the inclusion criteria, and a contemporaneous control group was derived from dogs that tested negative for H. americana. Two blinded reviewers evaluated the images. The majority of Heterobilharzia-infected (further termed H-pos) dogs (82%) had ultrasonographic abnormalities in the small intestine ± liver. Abnormal layering of the small intestine was noted in 38 of 54 H-pos dogs, compared to six of 54 control dogs (P < .0001). Pinpoint hyperechoic foci were noted in the small intestinal submucosa or muscularis layers in 25 of 54 H-pos dogs, but only three controls (P < .0001). Heterogeneity of the hepatic parenchyma and pinpoint hyperechoic foci were more prevalent in H-pos dogs (65% vs 40%; P = .0213 and 44% vs 18%; P = .0068, respectively). Pinpoint hyperechoic foci within mesenteric lymph nodes were noted in seven H-pos dogs and none of the controls (P = .0128). The combination of heterogeneous small intestine wall layering and pinpoint hyperechoic foci in small intestine, liver, or mesenteric lymph nodes was the most reliable indication of infection (P = .0001; odds ratio = 36.87), with positive predictive value of 94%, yet modest sensitivity for the detection of infection (58%). Observing these sonographic features suggests schistosomiasis and should prompt further testing.