Observations on Toxocara pteropodis infections in mice.

Infection in mice with Toxocara pteropodis was investigated. In mice fed infective eggs, third-stage larvae hatched out and penetrated the mucosa, predominantly that of the lower intestine. They travelled via the portal vein to the liver, where they remained at least 14 months. They grew in length from 430 +/- 15 micron, at three days post infection (p.i.), to 600 +/- 50 micron, at six to nine weeks p.i., after which time growth ceased. Blood eosinophilia appeared at 28 days p.i., and eosinophil levels continued to rise gradually beyond this time. In female mice the larvae did not migrate from the liver in response to pregnancy or lactation. When infective eggs were inoculated subcutaneously or intra-peritoneally, larvae hatched out and ultimately appeared in the liver in larger numbers than seen with oral infections.