IMMUNIZATION AGAINST PORCINE CYSTICERCOSIS IN AN ENDEMIC AREA IN MEXICO - A FIELD AND LABORATORY STUDY

An antigenic extract from Taenia solium metacestodes was evaluated for immunogenicity in pig populations from a large area of endemic porcin e cysticercosis in the State of Guerrero, Mexico. A total of 3,295 pig s from 18 villages were immunized with a single dose of 250 mug of pro tein administered intramuscularly. Systematic immunization was also pe rformed on pigs (1,076 immunizations) from two of the villages with th e highest percentages of cysticercosis. A year after immunization, por cine cysticercosis decreased from 4.8% and 5.4% to 0%. Immunity agains t the T. solium metacestode was estimated in vitro by measurements of H-3-thymidine uptake and inhibition of leukocyte migration. Peripheral blood lymphocytes from immunized cysticercotic (pigs that had cystice rcosis prior to immunization), cysticercotic immunized (pigs that acqu ired cysticercosis after immunization), and normal control pigs incorp orated H-3-thymidine better than lymphocytes from cysticercotic pigs w hen stimulated with concanavalin A. A significant inhibition in the le ukocyte migration inhibition test was also found in leukocytes from im munized cysticercotic pigs (P < 0.01). Histopathologic studies reveale d granuloma formation surrounding the metacestodes of the immunized cy sticercotic and cysticercotic immunized pigs. These metacestodes exhib ited several stages of destruction. Large numbers of eosinophils were frequently observed in a close association with the degeneration and d estruction of parasites. Metacestodes in control cysticercotic pigs we re intact and surrounded by a minor inflammatory reaction. Finally, th e rate of in vitro evagination of scolices was high in metacestodes ob tained from cysticercotic pigs and low or absent in those from immuniz ed pigs (P < 0.01).