RNAscope: a novel method for the detection of Heterobilharzia americana ova in canine liver

Canine schistosomiasis caused by Heterobilharzia americana can lead to severe morbidity and eventual mortality, in part due to the deposition of fluke ova in the liver and gastrointestinal tract, which promotes an influx of peri-ova inflammatory cells. Although fluke eggs can be identified in H&E-stained histologic sections, cases exist in which only fragments of the ova persist, or the egg is obscured by inflammatory infiltrates, which can confound definitive histologic diagnosis. Unfortunately, antibodies specific to Heterobilharzia are not commercially available for immunohistochemical labeling. Therefore, we aimed to use an RNA in situ hybridization strategy to fluorescently label Heterobilharzia ova. Using the H. americana 18S rRNA sequence, we developed an RNA probe and validated its performance on archival formalin-fixed, paraffin-embedded canine tissue. A positive signal was observed for all identifiable ova, fragmented and whole. Use of this methodology could aid understanding of the pathogenesis of H. americana infection in dogs. This technique augments standard diagnostic methodology, enabling spatial colocalization of fluke ova and inflammatory infiltrates when using fluorescent techniques.

Other Schistosomatoidea and Diplostomoidea

Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis (schistosomiasis) affecting more than 200 million people in tropical and subtropical countries, and infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The "Aporocotylidae" sensu lato are pathogenic in fish, "Spirorchiidae" sensu lato in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in mollusks and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.

Schistosomatoidea and Diplostomoidea

Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis affecting more than 200 million people in tropical and subtropical countries, infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The Aporocotylidae are pathogenic in fish, Spirorchiidae in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in molluscs and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive, but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.

Geographical differences in survival of dogs with non-Hodgkin lymphoma treated with a CHOP based chemotherapy protocol

BACKGROUND

In humans geographical differences in the incidence and presentation of various cancers have been reported. However, much of this information has not been collected in veterinary oncology.

AIM

The purpose of this study was to determine if a geographic difference in progression free survival exists for dogs with lymphoma treated within the US.

MATERIALS AND METHODS

Medical records of 775 cases of canine lymphoma from 3 US regions (west, south and north), treated with CHOP chemotherapy, were retrospectively evaluated. Cases were collected from referral institutions and were required to have received at least one doxorubicin treatment and have follow up information regarding time to progression.

RESULTS

Significant differences in sex (p = 0.05), weight (p = 0.049), stage (p < 0.001), immunophenotype (p = <0.001), and number of doxorubicin doses (p = 0.001) were seen between regions. Upon univariate analysis, progression free survival (PFS) differed by region (p = 0.006), stage (p = 0.009), sub-stage (p = 0.0005), and immunophenotype (p = 0.001). A multivariable Cox regression model showed that dogs in the western region had a significantly shorter PFS when compared to the south and east.

CONCLUSION

PFS was significantly affected by stage, sub-stage and phenotype.

Distribution and characterization of Heterobilharzia americana in dogs in Texas

Heterobilharzia americana is a trematode parasite (family Schistosomatidae) that infects a wide range of wild mammalian hosts. Canine cases have been reported in the Gulf coast and south Atlantic states, Kansas, and Oklahoma. A total of 238 canine H. americana cases in Texas were retrospectively collected for a period of approximately 22 years from case records at the Texas Veterinary Medical Diagnostic Laboratory and the Veterinary Medical Teaching Hospital pathology service, diagnostic parasitology service, and Gastrointestinal Laboratory at Texas A&M University College of Veterinary Medicine. Of these cases, 26 patients had 1-2 repeat positive tests for a total of 268 positive tests (26 biopsies, 39 necropsies, 160 fecal examinations, and 43 PCR). Multiple dogs were infected in 12 households. Cases were distributed primarily in the eastern region of Texas in 42 of 254 counties. Cases were seen as far west as Kerr county and in counties bordering Oklahoma, Louisiana, Mexico, and the Gulf of Mexico. The median dog age was 5.6 years (2.7 months to 17.2 years) and the median weight was 20.5 kg (1-61.6 kg). All American Kennel Club (AKC) breed groups were represented (n=186): crossbred (20%), herding (17.8%), sporting (16.1%), toy (10.8%), hounds (10.8%), working (10.1%), terrier (8.5%), non-sporting (4.9%), and miscellaneous (1%). No seasonal pattern of diagnosis was apparent. Clinical signs reported (n=90) were diarrhea (67%), weight loss (38%), anorexia/hyporexia (27%), vomiting (22%), hematochezia (20%), lethargy (17%), polyuria/polydipsia (6%), and collapse (3%). In 39 necropsy cases, trematode eggs were identified by histopathology in the small intestine (84%), liver (84%), large intestine (39%), pancreas (35%), lung (9%), lymph node (8%), spleen (4%), and stomach (3%). Adult parasites were identified histologically in four cases. Granulomatous inflammation associated with the eggs was the most commonly reported histopathologic change. Other changes reported were fibrosis, pigment in macrophages, and organ mineralization. Glomerulonephritis was identified in four cases. Of 20 necropsy cases where death was attributable to H. americana infection, only one case was diagnosed ante mortem. Eleven of these dogs were examined by a veterinarian but H. americana was included as a differential diagnosis in only two cases. Reported differential diagnoses included ethylene glycol toxicity, cholecalciferol toxicity, lymphoma, and pancreatitis. These data indicate that this parasite is more widely distributed and more common than is generally recognized. Increased awareness may aid in more diagnoses and timely therapy.