Antigen-induced protection against infection with Toxocara vitulorum larvae in mice.

Larvae of Toxocara vitulorum hatched and migrated in the tissues of normal mice. Larvae survived in reasonable numbers, particularly in the liver and, to a lesser extent, in the lungs and kidneys, for at least 4-7 days and in muscles, albeit only in low numbers, for at least 3 weeks. Oral infection of mice on three or more occasions with T. vitulorum eggs induced protection against a challenge infection with eggs of T. vitulorum. Prior parenteral immunization of mice with a variety of T. vitulorum soluble antigens (extracts, excretions/secretions, or perienteric fluid and their fractions) from adult parasites and/or infective larvae induced statistically significant protection against infection. The most effective protective immunogens were three or more injections with perienteric fluid from adults (100% protection) and excretions/secretions from infective larvae of T. vitulorum (> 92% protection).