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. 1999 Aug;83(8):967–972. doi: 10.1136/bjo.83.8.967

New animal model for human ocular toxocariasis: ophthalmoscopic observation

T H Takayanagi 1, N Akao 1, R Suzuki 1, M Tomoda 1, S Tsukidate 1, K Fujita 1
PMCID: PMC1723141  PMID: 10413704

Abstract

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.



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Figure 1  .

Figure 1  

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Normal fundus of BALB/c mouse and Mongolian gerbils. (A) Normal fundus of BALB/c mouse. (B) Normal fundus of Mongolian gerbils. Rod-shaped multiple white spots were seen in normal fundus of gerbils.

Figure 2  .

Figure 2  

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Haemorrhagic changes. (A) Vitreous haemorrhage—was seen in two of the 20 gerbils from day 7 after infection of T canis. This was associated with vitreous opacity and was absorbed within 1 month. (B) Choroidal haemorrhage—was found in 95% of gerbils with a single oral inoculation of T canis embryonated eggs. (C) Retinal haemorrhage—was seen in 55% of T canis infected gerbils. Large central retinal haemorrhage was observed. (D) White centred retinal haemorrhage. Multiple small haemorrhage with a white central part were found in the periphery.

Figure 3  .

Figure 3  

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Exudative lesion. Irregular colour changes of retinal pattern and soft or hard patches suggested chorioretinitis in 70% of gerbils with oral inoculation of T canis.

Figure 4  .

Figure 4  

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Vasculitis. (A) Tortuosity, dilatation, and narrowing of vessels. (B) White exudative lesion around the bifurcation of vessels. (C) Eosinophils (arrows) and lymphocyte infiltration were seen on the vessel wall.

Figure 5  .

Figure 5  

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Motile larvae of T canis. Larva (arrow) can migrate vigorously in the retinal layer. Larvae could be found in 80% of gerbils.

Figure 6  .

Figure 6  

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Trace of larvae of T canis. This trace disappeared within 20 days.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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