Toxocariasis is a zoonotic disease caused by parasitizing of larvae of roundworms belonging to the genus Toxocara in humans with concomitant damage to eyes and internal organs. The disease is (...)
Toxocariasis is a zoonotic disease caused by parasitizing of larvae of roundworms belonging to the genus Toxocara in humans with concomitant damage to eyes and internal organs. The disease is widespread in all countries and often affects children. Several species of this genus are known, and the majority of studies have shown the role Toxocara canis (worms affecting mainly dogs) and to a lesser extent Toxocara cati (affects mainly cats) in human disease.
The sources of human infestation are mainly dogs that contaminate the soil with eggs of Toxocara excreting them with their faeces. The rate of dog infection with this helminth is about 15-50%, but in some areas it reaches 90%. Since mature forms are not formed in the human body infected people cannot be the source of Toxocara.
Humans are infected with toxocaras by ingestion of eggs with food or water contaminated with animal faeces, as well as by direct contact with infected animals. Larvae emerging from eggs migrate through the intestinal wall into the bloodstream and enter various organs and tissues where they encapsulate and maintaining long-term biological activity cause the larval form of the disease. While migrating within the human body, the larvae injure tissues causing necrosis and inflammatory processes.
Clinical symptoms of toxocariasis depend on the location and intensity of the parasite invasion. In the clinical course of the disease two forms of invasion are distinguishable: visceral syndrome of "migrating larvae” (visceral larva migrans) and ocular toxocariasis (ocular larva migrans). Visceral toxocariasis manifests itself with a recurrent fever lasting for several weeks or even months. Enlargement of individual lymph nodes and diseases effecting the respiratory system such as bronchitis and pneumonia may also occur. Almost all cases of toxocariasis are characterized by eosinophilia.
The intravitam parasitological diagnosis of toxocariasis is almost impossible to discover due to the difficulty of detection of the migrating larvae. Histological studies (biopsies) are only useful in some cases. At the same time, numerous studies have shown that serological testing, including ELISA, using purified antigens of larvae, is a sensitive and specific diagnostic method. To date it is possible to detect specific antibodies for excretory-secretory and somatic antigens of T. сanis larvae.