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 tr eatment. Studies in paratenic hosts have contributed to our understanding a nd will yield more information. Various experimental animals have been used , such as mice, rabbits, guinea pigs, primates, hamsters and gerbils. Of th ese, the last appear to be the most appropriate model due to their high sus ceptibility to ocular infection. Results obtained from different animal mod els are often not comparable due to the fact that dose and routes of inocul ation are diverse. Early stages in the pathogenesis of ocular toxocariasis are manifested by haemorrhages in the anterior chamber and iris, replaced i n time by accumulations of white cells. Ocular migration produces an early cell reaction, formed by an infiltration of neutrophils accompanied by vasc ulitis and retinal microinfarcts. Over a period of time, an increase of mac rophages and the distribution of the infiltrates is observed. Later, granul omatous lesions are formed. These do not necessarily contain a larva and th eir appearance varies in different animal models. Local production of IgE a nd the presence of specific IgG have been described.