Main » Infectious diseases » Soil-mediated Helminthiases » Toxocariasis
Photo 1. Adult Toxocara canis.
Visceral larva migrans results from accidental infection of man with eggs of the ascarid roundworm of the dog Toxocara canis, and cat T. cati. The adults are about 10 cm long and similar in general appearance to A. lumbricoides. (x1/3). Uncontrolled contamination of soil by dogs and cats is common everywhere. Like those of Ascaris the eggs of Toxocara canis and T. cati can survive even in a cold climate.
Photo 2. Longitudinal section of human eye. The life cycle in the animal host is the same as that of Ascaris but the invasive larvae in man become arrested in various tissues where they are gradually phagocytosed. In the process they induce marked eosinophilia and local tissue reaction. Invasion of the eye produces a retinoblastoma-like appearance, and may lead to blindness. Sometimes the eye is mistakenly enucleated.
Photo 3. Section of Toxocara canis larvae in human eye. The larva is seen in the centre of the tumour-like mass at the posterior part of the eye (see 2). (x20)
Photo 4. Migrating larvae in liver. Indefinite symptoms of hepatic involvement associated with marked eosinophilia should lead to a suspicion of visceral larva migrans as the causative agent. (x 150)
Photo 5. Serological diagnosis.
The diagnosis is supported by a positive serological response to Toxocara antigen such as the CFT. (Top row is a negative control serum; second row - positive response at 1/64 from a patient with visceral larva migrans; third row - negative serum from another patient with suggestive symptoms, fourth row - complement control.)
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