FIELD TRIAL FOR REDUCING PORCINE TAENIA-SOLIUM CYSTICERCOSIS IN MEXICO BY SYSTEMATIC VACCINATION OF PIGS

It has previously been demonstrated that immunization of pigs with a c rude extract of Taenia solium metacestodes can confer a high level of protection against an egg challenge. Furthermore, vaccination of infec ted animals also induces an immune response against the larvae, which are either destroyed or rendered non-infectious. To assess the efficac y of immunization as a strategy for reducing the prevalence of porcine cysticercosis, a field trial of this vaccine was performed in an ende mic area in the northern region of the Guerrero State, Mexico. Random samples of pigs belonging to 17 villages were examined for metacestode s by inspection of their tongues. Each animal was immunized with a dos e of 150 mu g of protein (antigenic extract from Taenia solium metaces todes) by the intramuscular route. A prevalence of 2.4% of porcine cys ticercosis on average was found in these villages at the beginning of the trial (62 cysticercotic pigs out of 2650 inspected). Six of these villages were selected for the periodic vaccination of new random samp les of pigs. A statistically significant decline in the prevalence of porcine cysticercosis was observed at the end of the trial, decreasing from 2.4% at the beginning of vaccination to 0.45% at the end of the trial, A reduction of 82% was observed in spite of the poor living con ditions in these villages, These results are consistent with previous data and suggest that it may be possible to turn a susceptible pig pop ulation into a protected one by systematic vaccination.