What is visceral larva migrans and which parasite is most commonly implicated in humans?

• A. Formation of cysts in muscles after ingestion of larvae
• B. Migration of larval worms through tissues causing eosinophilia; commonly Toxocara canis
• C. Infection of the liver by adult worms
• D. Invasion of the skin by mites

Answer: (B)

Visceral larva migrans is a tissue-mandering infection where larvae from certain roundworms migrate through various tissues in a human who is an accidental host. This migration triggers a marked eosinophilic inflammatory response and can involve organs like the liver, lungs, and sometimes the eyes or brain. The classic and most commonly implicated parasite is Toxocara canis, the dog roundworm, transmitted mainly by ingesting eggs contaminated in soil (often from dog feces). Humans don’t harbor the parasite to adulthood; the larvae wander through tissues and eventually die, producing granulomatous lesions and eosinophilia. While there are related conditions where larvae reach the eye (ocular larva migrans) or other forms with different patterns, visceral larva migrans is defined by tissue migration and systemic eosinophilia, with Toxocara canis as the typical culprit. The other options don’t fit because they describe muscle cysts from larvae (cysticercosis or trichinellosis), liver infection by adult worms, or skin invasion by mites, none of which describe this migratory larval tissue invasion.