*Circumstantial evidence of mutation from human strain
*Circumstantial evidence of mutation from human strain
−
*Migrating [[Parasitic infections#Ascaris suum|ascarids]] thought to precipitate the disease, reservoir of infection in earthworms containing infected lungworm larvae
+
*Migrating [[Respiratory Parasitic Infections - Pathology#Ascaris suum|ascarids]] thought to precipitate the disease, reservoir of infection in earthworms containing infected lungworm larvae