Ocular lesions in gerbils (Meriones unguiculatus) infected with low larval burden of Toxocara canis: observations using indirect binocular ophthalmoscopy

Abstract

To study the frequency of ocular lesions in 30 gerbils infected with 100 embryonated eggs of Toxocara canis, indirect binocular ophthalmoscopy was performed 3, 10, 17, 24, 31 and 38 days after infection. All the animals presented larvae in the tissues and 80% presented ocular lesions. Hemorrhagic foci in the choroid and retina were present in 92% of the animals with ocular lesions. Retinal exudative lesions, vitreous lesions, vasculitis and retinal detachment were less frequent. Mobile larvae or larval tracks were observed in four (13.3%) animals. Histological examination confirmed the ophthalmoscopic observations, showing that the lesions were focal and sparse. In one animal, there was a larva in the retina, without inflammatory reaction around it. The results demonstrated that gerbils presented frequent ocular lesions after infection with Toxocara canis, even when infected with a small number of embryonated eggs. The lesions observed were focal, consisting mainly of hemorrhages with signs of reabsorption or inflammation in different segments of eye, and differing from the granulomatous lesions described in ocular larva migrans in humans.

Larval migration of the ascarid nematode Toxocara canis following infection and re-infection in the gerbil Meriones unguiculatus

“…We do not have a complete explanation for this observed discrepancy. It is likely due to the age of the gerbils, which were 45 and 60 days old, or the amount of inoculum used; inocula with a low number of larvae would be less effective in inducing immune responses in young animals, favouring the migration of larvae (Glickman & Schantz, 1981; Zanandréa et al , 2008).…”

“…Gerbils have recently been used as experimental animals for toxocariasis, especially in studies of ocular lesions and lesions in the central nervous system (Takayanagi et al , 1999; Alba-Hurtado et al , 2000; Akao et al , 2003; Zanandréa et al , 2008). Little information is available concerning the migration of Toxocara larvae in gerbils (Cho et al , 2007; Alba-Hurtado et al , 2009), especially during the first hours after infection.…”

A Comparative Histopathology, Serology and Molecular Study, on Experimental Ocular Toxocariasis byToxocara catiin Mongolian Gerbils and Wistar Rats

“…Ocular larva migrans occurs when Toxocara larvae reach eye tissue, where they induce inflammatory reaction, frequently without the sign or symptoms that accompany the visceral toxocariasis [19–22]. The diagnosis of ocular larva migrans is based on retinoscopic and retinographic studies, and is confirmed by the finding of larvae in lesions [23]. The presence of anti- Toxocara antibodies or antigens in vitreous humor has been reported to be a sensitive method for detecting toxocariasis in infections or human ocular toxocariasis [25].…”

Ocular Larva Migrans: A Severe Manifestation of an Unseen Epidemic

“…Models inoculating the carotid artery, the stomach, periocular tissue, and systemic inoculation have all shown rare ocular infection [22]. Mongolian gerbil models seem to demonstrate some predilection for the eye, given the high prevalence of ocular lesions after infection with low larva burden [25], but this mechanism is yet unknown and has not been demonstrated in either humans or other animal models.…”