Visceral larval migrans in an imported dog

Siobhan O’Sullivan  

Animal Health Laboratory, University of Guelph, Guelph, ON. 

AHL Newsletter 2025;29(3):27.

A 3-year-old mixed breed dog imported as a stray from Africa presented with acute seizures and vomiting. Vomiting resulted in aspiration pneumonia and accelerated the patient’s decline. Bloodwork identified renal injury, and there were multifocal white spots on the kidneys at postmortem. Histopathology of the kidneys revealed multiple granulomas with infiltrating eosinophils and necrotic centers. Rare nematode larvae were found in the center of these granulomas, prompting the diagnosis of verminous nephritis secondary to visceral larval migrans (VLM) (Fig. 1). Migrating larvae were not seen histologically in any other organ.

VLM is an atypical cause of kidney injury in a dog, given the prevalence of deworming treatment in Ontario. Parasites implicated in VLM include nematodes such as Toxocara canis. Puppies can present with patent intestinal infections, but when eggs are ingested by older dogs or humans, larvae can develop and penetrate the intestinal mucosa and migrate through the blood, arresting in various organs. Cases of VLM are often asymptomatic, but this depends both on the organ affected, and the parasite burden. When the burden is high and/or the organ affected is vital, like the kidney, or as in cases of ocular or neural larval migrans, symptoms can be severe. In this case, it was undetermined whether seizures were secondary to kidney injury, or due to VLM that was not captured in histologic sections. The consequences for dogs and the zoonotic potential of some nematode infections underscore the importance of preventative deworming treatment.

Figure 1. Canine, kidney. A coiled larval nematode embedded in a granuloma. H&E stain.

Reference

1. Peregrine A. Roundworms in small animals. The Merck Veterinary Manual. 2025. [cited 2025 August 14]. Available from: https://www.merckvetmanual.com/digestive-system/gastrointestinal-parasites-of-small-animals/roundworms-in-small-animals