Toxocarose

Definition

The toxocarose is a Zoonose verminous cosmopolitan related to the intra-tissue presence of larvae of ascaridés " in attente" , whose evolution towards the adult stage can be done only at the dog or the cat. This phenomenon is known under the name of larva migrans visceral (VLM).

Epidemiology

Two round worms (nematodes) are responsible for the human toxocarose: Toxocara canis , parasite of the dog, and Toxocara gloss , parasite of the cat. These worms blanchâtres and cylindrical of the family of the Toxocaridae live in the Small intestine their final hosts. The male measures ten centimetres length and the female a fortnight.

The reproductive cycle of T. canis is complex because depend on the age and the sex of the final host, the dog. The adult worms lay each day of the thousands of eggs which, rejected with the canine excrements, go embryonner in the ground in 3 weeks if the environmental conditions are favorable (shade, moisture and temperature around 25°C). Introduced by a dog, these eggs hatch in the Duodénum and release from the larvae which pass through the intestinal wall . Circulating by blood way, they reach the Foie which they cross, join the Poumon S where they leave the pulmonary small arteries to borrow the venous bed which will bring them in the middle left. Launched in great circulation, they go finally emboliser in the irrigated bodies where they fall into a state from slowed down life If the dog is a male, these larvae generally do not have any future and will end up dying in fabrics. It is rare that they continue their evolution to give adult worms in the digestive tract. If the dog is a female, and that this one becomes gestante, the hormonal impregnation will reactivate the larvae which will parasitize the embryos (stage 4 of the parasitic cycle). During gestation, the larvae evolve/move at those to give adult worms: the pups are thus parasitized as of the birth and are the independent factor of contamination of the environment. The parasitism of the pups is maintained by breast feeding, during which larvae pass from maternal fabrics in milk.

When a Mammalian - Man included - other that the dog introduces embryonnés eggs of T. canis , the larvae achieves in its organization a migration comparable with that described above. With final, this Mammal will lodge in its fabrics of the Larve S in a state of increasingly slowed down life, and will be called host of waiting. When this host of waiting, often a rodent , is devoured by a dog, the larvae released during digestion will give adult worms in the intestine of the predator: this mode of contamination is most frequent in the adult dog.

The Man infects himself by introducing eggs embryonnés present on vegetables, especially salads, having pushed in a ground contaminated by the dejections of pets. A lack of personal hygiene (dirty hands) is also a risk factor. In the child, géophagie and plays in soiled sand vats are the most frequent causes of contamination.

Geographical distribution

The toxocarose is present in the whole world. The epidemiologic bulletins show a rate of prevalence from 2 to 5% in the adults in good health of the urban areas of the Western countries and of 14,2 to 37% in the rural areas.

In the tropical countries, the evaluations show a rate prevalence of 63,2% with Bali, 86% with St Lucia, and of 92,8% with the Réunion.

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