Resistance against migrating Ascaris suum larvae in pigs immunized with infective eggs or adult worm antigens

Resistance to Ascal is suum infections was investigated in 8- and 15-week-old Iberian pigs. Groups of 3 or 5 pigs were immunized weekly for 6 weeks with antigens of adult A. suum: a 97 kDa body wall (BW) fraction, a 42 kDa fraction of pseudocoelomic fluid (PF) or a 14 kDa PF-fraction; or were inoculated with increasing doses of infective eggs (500-20 000), with or without abbreviation by pyrantel pamoate. All immunized pigs and unimmunized control pigs, were challenged with 10 000 infective eggs 7 days after the last immunization. The number of liver lesions and lung larvae was substantially lower in the older pigs than in the younger ones 7 days after challenge, but the resistance in immunized pigs of both age groups was similar in comparison to the challenge controls of the same age. The highest degree of resistance against lung larvae was observed in pigs immunized with A. suum eggs (97-99%). The pigs immunized with the 11 kDa and 42 kDa PF-fractions were also well protected (67-93%), while no protection was produced by the 97 kDa BW fraction (0-49 %,). The reduction of white spots following immunization was less evident, with a maximum of 82%, reduction in egg-inoculated young pigs.