Toxocariasis is an infection transmitted from animals to humans (zoonosis) caused by the parasitic roundworms commonly found in the intestine of dogs (Toxocara canis) and cats (T. cati).Toxocariasis is caused by human ingestation of the eggs of a common roundworm parasite excreted by dogs (Toxocara canis) or cats (Toxocara cati). The most common source of Toxocara canis and/or cati eggs is contaminated soil. Adult roundworms are often found in the gastrointestinal tract of dogs and cats.
The use of anti-parasitic medications is controversial; a variety of them have been tried without notable success because the medication is effective only on active larvae. At any time, some larvae are able to enter the dormant stage and then to reactivate in a random fashion, continuing on their migratory way.In the Spain, about 1,480 cases of Toxocara infection are reported in humans each year. Almost 13% of the Spain population is infected with Toxocara, a parasite of dogs and cats that can be passed from animals to humans.