2.2.1.2. Toxocariasis

a roundworm of dog and cat can infect human, who is an intermediate host, and determine a Loeffler's like syndrome caused by larva migrans as with Ascaris.

Severe respiratory syndromes (ARDS) have rarely been observed (Bartelink AK et *al*., 1983), while asthma-like symptoms are currently reported among pulmonary manifestations.

Defects in neutrophil function have been reported in children with visceral larva migrans. This defect should be explained by the neutrophilic adherence to larvae illustrated else‐ where in animal models (Martin Huwer, 1989).

Exacerbations of inflammatory reactions during antihelminthic treatment emphasize the need of combination with corticosteroids.

#### 2.2.1.3. Pulmonary strongyloidiasis

The causative agent is Strongyloides stercoralis, endemic in the tropics and subtropics. Eggs containing larvae ready to hatch, are the contaminating form after penetrating the skin; they then disseminate in all tissues via venous or lymphatic route in immunodeficient host (Cook, 1987; Longworth and Weller, 1986).

Autoinfestation is a common feature of this parasite, meaning the penetration of filariform larvae in the perianal skin of the infected subject without leaving the host. This phenomenon can determine the persistence of infection even many years after (Scowden EB, 1978).

Lung invasion result from larvae carried by the blood stream to the right heart and then to the lung. Larvae can pierce the pulmonary capillaries and reach the alveoli through the al‐ veolo-capillary membrane, inducing non cardiogenic edema and hemoptyses. After their migration through the bronchi and superior respiratory tree, some larvae can be swallowed in the intestine. Hyperinfection syndrome is related to severity of symptoms in the lung and the intestine, which are common sites of the parasitic life cycle, while disseminated disease represent the invasion of other organs not generally involved in the growth of the parasite (Longoworth DL, and Weller PF, 1986).

## Pathophysiology

The skin penetration by the larva determines an hypersensitivity reaction as the result of a strong cell mediated immunity reaction in immunocompetent host preventing the tissue in‐ vasion (Neva FA, 1986). Marked autoinfection and subsequent hyperinfection are the main determinants of tissue dissemination in immunosuppressed subjects such as AIDS patients (Lessman KD, 1993), individuals on long term corticosteroid therapy, or with malnutrition, lymphomas etc..(Casati A, 1996; Genta RM, 1989).

Mechanical action by the adult worms and host reaction are responsible for digestive mani‐ festations.

Secondary gram negative bacterial infection by gram- pathogen is frequent, bacteria being carried by larvae during the crossing of the intestinal wall. The migration through the lung can determine bronchopneumonia,alveolar hemorrhages, and pulmonary abscess and hae‐ moptyses.
