Evidence for the involvement of the optic nerve as a migration route for larvae in ocular toxocariasis of Mongolian gerbils

Abstract

Although Toxocara canis, an important pathogen of ocular disease, tends to migrate to the eye, the precise migratory route has yet to be determined experimentally. Mongolian gerbils, Meriones unguiculatus, known as a useful animal model for human toxocariasis, were used to investigate the migration route toward the eyes. Infective larvae of T. canis were directly inoculated into the intracranial region. Haemorrhagic lesions or larvae were observed in 56.3% of cases. Histopathologically, a larva was observed in the optic nerve of gerbils 6 days after inoculation, and two larvae were found in the optic chiasma in the gerbils having a haemorrhage in the retina 9 days after inoculation. These results indicate that T. canis migrates from the brain to the eye through the optic nerve. Considering these data and previous studies showing that the ocular changes appear as early as 3 days of infection in the oral-administrated gerbils, there are two phases in the migration to the retina: a haematogenous early phase and an optic nerve route late phase.

Cerebral Toxocariasis: Silent Progression to Neurodegenerative Disorders?

“…Hayashi et al (115) observed that the migratory route of T. canis larvae to the eye may be from the brain through the optic nerve, as assessed in one experimental study using a gerbil animal model (although the gerbil is not a natural paratenic host of T. canis). Other researchers postulated that it is more likely that larvae travel in blood vessels rather than by burrowing and that the route by which larvae reach the eye remains to be determined (103).…”

“…While our understanding of the mechanisms underlying human NT is incomplete, seroepidemiological surveys demonstrate high levels of exposure to Toxocara in the population, suggesting that NT may be an underestimated public health implication of infection (36). Recently, Toxocara was described as "America's most common neglected infection of poverty and a helminthiasis of global importance" (115,122); however, the number of cases of NT will tend to be underestimated due to nonspecific clinical signs compared with VLM, as well as due to a lack of availability of appropriate testing, thus leading to possible underdiagnosis (18,122).…”

ExperimentalToxocara catiInfection in Gerbils and Rats

“…Dubey [17] showed larval migration patterns of T. cati in mice. In other previous studies, it was proved that Mongolian gerbils could be a paratenic host for T. cati , which may result in ocular larva migrans and neurotoxocariasis [18,21]. The present study presents further information on the experimental infection of Mongolian gerbils and Wistar rats with T. cati and larval recovery at different times of infection.…”

“…The animals were maintained under standard conditions, in an environment with controlled temperature and humidity. Each animal in the experimental groups was intubated with approximately 240 and 2,500 embryonated T. cati eggs, respectively [18,21,22]. The eggs were derived from adult female worms and were embryonated according to our previous paper [23].…”

Parálisis de Bell y dolor facial asociados con infección por Toxocara sp

“…Introducción E l compromiso de nervios craneales por larva migrans de Toxocara canis es sumamante inusual y casi exclusivamente afecta al nervio óptico 1 . No ha sido descrita la afectación del séptimo nervio craneal asociada a larva migrans de T. canis.…”