Animal models in ocular toxocariasis

Ocular toxocariasis is a clearly defined disease. However, much remains to be learned concerning the migratory route, ocular changes, diagnosis and treatment. Studies in paratenic hosts have contributed to our understanding and will yield more information. Various experimental animals have been used, such as mice, rabbits, guinea pigs, primates, hamsters and gerbils. Of these, the last appear to be the most appropriate model due to their high susceptibility to ocular infection. Results obtained from different animal models are often not comparable due to the fact that dose and routes of inoculation are diverse. Early stages in the pathogenesis of ocular toxocariasis are manifested by haemorrhages in the anterior chamber and iris, replaced in time by accumulations of white cells. Ocular migration produces an early cell reaction, formed by an infiltration of neutrophils accompanied by vasculitis and retinal microinfarcts. Over a period of time, an increase of macrophages and the distribution of the infiltrates is observed. Later, granulomatous lesions are formed. These do not necessarily contain a larva and their appearance varies in different animal models. Local production of IgE and the presence of specific IgG have been described.