Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5% potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11.1%) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

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SUMMARY Male mice, strain C57 black, were infected with Toxocara canis by a single intragastric dose of 1500 infective eggs. The eyes were studied at sequential time periods after infection (6 to 63 days) by conventional microscopic techniques, and the histological characteristics of the inflammatory response were recorded. In the majority of animals the disease was unilateral. Twenty-six larvae were found in the retina, in the retinal vessels, and in the subretinal space in 20 eyes, while in 29 eyes there were inflammatory changes which were not related to the presence of intact or fragmented larval forms. The inflammatory reaction began as a polymorphonuclear response but after day 13 became a granulomatous reaction. This suggests that the inflammatory phenomenon may be propagated by the secreted surface antigens in the absence of the living or dead larvae.Children and adults'2 become infected by the accidental ingestion of dog faecal material containing Toxocara canis ova. The clinical manifestations of ocular toxocariasis are solitary and usually occur in older children (average 7-5 years) without the generalised eosinophilia, hyperglobulinaemia, and hepatomegaly characteristic of visceral larva migrans (VLM).3 Lesions occur unilaterally as a solitary retinal granuloma in the posterior pole in proximity to the disc and macula and/or as chronic endophthalmitis with retinal detachment.4 Wilder-found nematode larvae in 24 cases of pseudogliomata, and Nichols6 identified these larvae as Toxocara canis. In such studies eyes were usually enucleated because of the difficulty of excluding retinoblastoma.Although ocular toxocariasis is an uncommon form of uveitis and retinitis in the routine uveitis clinic,7 treatment of the majority of cases in which there is an exudative retinal detachment is unrewarding. Subtotal pars plana vitrectomy8 has been added recently to the current therapeutic measures, which included topical and systemic corticosteroids, anthelminthic therapy, and laser photocoagulation. The pathogenic mechanisms which lead to retinal damage are poorly understood, notably the immunopathological interreactions between the host and the parasite, so that there is a dearth of information on which to base therapy. It is therefore of value to develop cheap and reliable animal models with a low degree of mortality and a high degree of morbidity in order to apply the rapidly developing techniques of immunohistochemistry to the study of nematode-induced inflammatory disease. To this end we present our findings in a preliminary study of ocular toxocariasis in the mouse. To our knowledge there has not been a detailed histological study over an extended period of the effects of toxocariasis on the pigmented eye of a laboratory animal. Materials and methodsAnimals. Three uninfected 10-week-old mice (C57 black strain) were used as controls to determine the normal ocular histology in this strain. Twenty-seven male C57 black mice, 10 weeks old, were infected with a single dose of 1500 infective eggs by intragastric intu...

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