Ocular larva migrans caused by Toxocara cati in Mongolian gerbils and a comparison of ophthalmologic findings with those produced by T. canis.

To elucidate the pathogenic potential of Toxocara cari, we observed the ophthalmologic changes of the fundi in Mongolian gerbils, Meriones unguiculatus, after oral inoculation of 17 embryonated eggs/g body weight. Ophthalmic conditions in 8 T. cati-infected gerbils were monitored using an ophthalmoscope from day 0 to day 156 and were compared with those of 57 T. canis-infected gerbils. The results showed that T. cati larvae migrated into the eye of the gerbil and then elicited ophthalmic changes, including retinal (25%) and vitreous (50%) hemorrhaging, vasculitis (37.5%), and exudative lesions (25%). Lesions were less prevalent, however, in T. cati-infected than in T. canis-infected gerbils. Unlike in T. canis-infected gerbils, the hemorrhagic lesions did not reappear in T. cati-infected gerbils after they were absorbed. These findings suggested that T. cati larvae are a potentially hazardous pathogen for ocular toxocariasis and that Mongolian gerbils infected with T. cati may be a useful model for the study of human ocular toxocariasis caused by T. cati. This is the first study to report that T. cati larvae can induce ophthalmic lesions in the retina of gerbils.

New animal model for human ocular toxocariasis: ophthalmoscopic observation.

BACKGROUND/AIMS: Although human ocular toxocariasis causes severe vision defect, little is known about its aetiology, diagnosis, and treatment. To develop a new animal model for human ocular toxocariasis, ophthalmological findings of fundi in Mongolian gerbils, Meriones unguiculatus, and BALB/c mice were investigated following infection with Toxocara canis. METHODS: Using an ophthalmoscope, which was specifically developed to observe the fundi of small animals, ocular changes of fundi of 20 gerbils and 11 mice were monitored after oral infection with embryonated eggs of T canis. RESULTS: Vitreous, choroidal, and retinal haemorrhages were consistently observed in Mongolian gerbils, but rarely in mice. Severe exudative lesions and vasculitis were often present in gerbils but not in mice. Migrating larvae were also frequently observed in gerbils. CONCLUSION: Mongolian gerbils are more appropriate animal model for human ocular toxocariasis than previously used experimental animal such as mice, guinea pigs, rabbits, and monkeys because of its high susceptibility of ocular infection.

A retrospective study of ocular toxocariasis in Japan: correlation with antibody prevalence and ophthalmological findings of patients with uveitis.

To classify the clinical characteristic of ocular toxocariasis in Japan, the prevalence of antibodies to Toxocara antigens was examined in patients with uveitis of unknown aetiology. From 1982 to 1993, serum specimens of 383 cases and intraocular fluid samples of 22 cases were serologically screened for Toxocara infection with five immunodiagnostic tests. Fifty-five sera and 11 intravitreous fluid samples were estimated to have significantly high antibody levels against larval excretory-secretory (ES) antigens of T. canis. Eight cases were positive in both serum and vitreous fluid, and three were positive only in the vitreous fluid. Among the 58 antibody positive samples, 20 cases were omitted due to a lack of detailed description of ocular findings. The remaining 38 cases are described in this study. Of these 38 cases, 34 (89%) were older than 20 years of age. Ocular lesions were located in the posterior fundus in 11 cases, in the peripheral fundus in 18 cases, and in both areas in seven cases. Of the eight cases in which papillary oedema or redness was observed, chorioretinal lesions were also present in seven of them. Tractional retinal detachment was present in five cases. These observations suggest that ocular toxocariasis in Japan has a different clinical profile compared with those in the other countries, and indicate a need for revised classification of ocular toxocariasis.