Roundworm—Toxocara: Visceral Larval Migrans or Ocular Larval Migrans is caused by Toxocara canis and cati (dog, cat and wild felid roundworms), Baylisascaris (passed by raccoons—uh. . .this one can also migrate to your brain and kill you!) and Gnathostoma. It is not the same worm that causes Toxoplasma although it has a similar name.
One thing I ask people who email me thinking they have worms is if all the worms are the same size and are they moving. If they are not, you probably don’t have worms but are seeing intestinal shreds. Here’s an example of what roundworms would look like in some dog poo. Now in pigs these worms (because they have their own species of roundworm)–can be 14 inches long. In humans the worms are so small and clear that they are difficult to see.
Symptoms include: fever, cough, skin rash diarrhea, vomiting, pneumonitis and general icky feeling. With eye involvement there may be retinoblastoma, strabismus and blindness.
Transmission is through contaminated dirt or plants and by eating undercooked and contaminated fish, meat and poultry.
Treatment is with diethylcarbamazine, albendazole, or mebendazole.
Prevention is through proper hygiene, cooking, and routine worming of pets. Cutaneous larva migrans should not be confused with visceral and ocular larva migrans, which are due to the ingestion of the eggs of the parasite Toxocara canis or Toxocara cati. Children with pica or people eating unwashed raw vegetables have the greatest risk of acquiring visceral and ocular larva migrans. Picture of Toxocara canis in a fecal sample: