Spirocercosis in red fox (Vulpes vulpes) in a natural reserve located in a meso-Mediterranean area

CHARACTERIZATION OF LESIONS INDUCED BY SPIROCERCA VULPIS (SPIRURIDAE: SPIROCERCIDAE) IN RED FOXES (VULPES VULPES)

Spirocerca lupi infection in dogs (Canis domesticus) is associated with esophageal lesions that may evolve to a neoplastic stage in the form of esophageal sarcoma. In the red fox (Vulpes vulpes) infected with the closely related Spirocerca vulpis, similar lesions may occur in the stomach, but neoplastic forms have not been reported. We characterize Spirocerca vulpis-induced lesions in the fox, using pathology and immunohistochemical (IHC) techniques. Seventy-one out of 163 Spirocerca vulpis-positive red foxes were selected and subjected to histopathological study. Lesions were classified as patchy or diffuse. Ten patchy and 10 diffuse lesion samples were studied using three IHC markers (CD68, CD3, and CD79α for macrophages, T lymphocytes, and B lymphocytes, respectively) and H&E stain for neutrophils and eosinophils. Intensity of necrosis, hemorrhages, and the presence of collagen was also analyzed. Of the S. vulpis-positive red foxes, 96.9% had S. vulpis nodules localized in the gastric area (wall and/or omentum), and 3.1% had nodules in the small intestine. All the samples had a moderate to severe lymphoplasmacytic infiltrate. Mild eosinophil infiltration was observed in both types of lesions, while neutrophil infiltration was significatively higher in the patchy than in the diffuse lesions. Fibrosis with mature collagen fibers was also predominant in the patchy lesions along with the presence of T lymphocytes and macrophages. Both the patchy and diffuse patterns had very few B lymphocytes. These findings suggest that the diffuse form is an earlier stage of the lesion, which eventually evolves into patchy forms. Neoplastic forms were not seen. Although more studies are necessary, this study describes the lesions, characterizes the inflammatory infiltrates, and establishes a possible evolution of the different pathological forms of S. vulpis infection in the red fox.

Ultrasonography is insensitive but specific for detecting aortic wall abnormalities in dogs infected with Spirocerca lupi

BACKGROUND

Spirocercosis is caused by the nematode Spirocerca lupi (S lupi). The disease mainly affects dogs and is typically diagnosed by oesophagoscopy or faecal examination; however, these diagnostic tests may deliver false negative results during the migration phase of the nematode. The aim of the present prospective study was to evaluate whether ultrasonography could detect abnormalities in the abdominal aorta, celiac artery, and gastric wall structure as a diagnostic aid to detect S lupi infection in dogs.

METHODS

Oesophagoscopy and a focused abdominal ultrasound scan were performed in 40 dogs that presented to the Koret School of Veterinary Medicine Teaching Hospital, Hebrew University of Jerusalem, with gastrointestinal complaints. Ultrasonography scan findings of 20 dogs with oesophageal nodules, indicating S lupi infection (study group), were compared with those of 20 control dogs.

RESULTS

Vascular wall irregularity was significantly more common in the study group than in the control group (9/20 v 1/20, respectively; P=0.008).

CONCLUSION

Ultrasonographic evaluation of the abdominal aorta, celiac artery, and gastric wall structure is not a sensitive diagnostic marker for spirocercosis in dogs. However, the presence of vascular wall irregularity of the abdominal aorta or celiac artery might indicate S lupi migration.

Occurrence, prevalence, and explanatory environmental variables of Spirocerca vulpis infestation in the foxes of western Spain

The main aim of this study was to not only establish the prevalence of the recently described Spirocerca vulpis parasite in the wild-life cycle of carnivores in western Spain but to also elaborate a model to explain the risk of infestation based on 16 topo-climatic and habitat variables. During the period from June 2016 to November 2017, 1644 carcasses of red foxes (Vulpes vulpes) and another 105 wild mammals, legally hunted or killed in car accidents, were analyzed. Parasitic nodules of Spirocerca were found in 6% of the foxes, and the molecular analyses established a homology of our samples with the species S. vulpis. There were no differences in the occurrence of the infestation between sexes, but there were differences in terms of age, such that infestation was proportionally more frequent among young individuals. In terms of temporality, a higher percentage of positive cases was observed during the late-autumn and winter months, especially between December and February. This study provides new data on the factors that predispose S. vulpis infection in the red fox. Model results indicate that a spatial pattern exists in the occurrence and prevalence of this species in the studied area (higher probabilities to the west), and that this pattern seems to mainly be associated with topo-climatic variables.