Question
Visceral larva migrans
Answer
Visceral Larva Migrans (VLM) is caused most commonly by animal roundworm larvae — Toxocara canis (dog roundworm) and Toxocara cati (cat roundworm) — in which humans (typically young children, via geophagia/pica or contact with contaminated soil/dog faeces) are an accidental, aberrant host unable to complete the parasite’s normal life cycle to maturity.
Pathogenesis: ingested embryonated eggs hatch in the intestine, releasing larvae that, unable to mature to adult worms in this aberrant host, disseminate via the bloodstream to various organs — liver (hepatomegaly), lungs (cough, wheeze, eosinophilic pneumonitis), and, importantly, the eye (ocular larva migrans), where larval migration/death provokes a granulomatous inflammatory reaction that can mimic retinoblastoma, a serious diagnostic pitfall in children.
Laboratory findings: marked peripheral eosinophilia and hypergammaglobulinaemia are characteristic; diagnosis is largely serological (ELISA for Toxocara antibody), since larvae are rarely recovered directly; biopsy of an affected organ occasionally demonstrates the larva histologically.
Treatment: albendazole/mebendazole combined with corticosteroids for significant inflammatory/ocular involvement.
Prevention: avoiding contact with soil/sand contaminated by dog/cat faeces, hand hygiene, avoiding pica, and regular deworming of pet animals.