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A total of 72 specific pathogen-free (SPF) and Iberian pigs (three animals per group) were inoculated with 200, 1000 or 20,000 muscle larvae of T. spiralis, T. nativa, T. britovi and T. pseudospiralis. For each animal, the muscle larva burden was evaluated in nine muscle samples by digestion. The anti-Trichinella IgG kinetics in blood samples, taken twice prior and at days 5, 10, 15, 20, 25, 30, 40, 50 and 60 post-inoculation, and in muscle juice, obtained at necropsy, was evaluated by an ELISA using an excretory/secretory antigen. The mean larval recovery rate in SPF/Iberian pigs corresponded with the level of inoculum dose, and tongue, diaphragm and masseter were identified as predilection muscles. In SPF and Iberian pigs receiving 20,000 larvae of T. spiralis, an earlier seroconversion was detected from day 25 post-inoculation. At a 10-fold dilution, the muscle juice showed a good test agreement with blood serum.

The immunodetection of local Ascaris suum antigens and local and systemic antibodies were analysed in pigs reinfected with eggs or immunized with the 14, 42 and 97 kilodalton (kDa) fractions from A. suum. Twenty-one Iberian pigs were divided in 7 groups of 3 pigs. Groups 1 and 2 were uninfected and challenge control groups, respectively. Groups 3 and 4 were infected weekly with increasing doses of A. suum eggs and Group 4 was additionally treated with pyrantel pamoate. Groups 5, 6 and 7 were immunised with the 14, 42 or 97 kDa fractions from adult worms, respectively. Groups 2-7 were challenged with 10,000 infective eggs. Animals of Groups 3 and 4 showed a pulmonary granulomatous reaction with moderate number of eosinophils and leukocytes, while Groups 5-7 presented higher number of cells, especially in animals immunized with the 42 kDa fraction. These immunized groups presented abundant deposition of Ascaris body fluid (BF) and body wall (BW) antigens as well as the 14 and 42 kDa fractions in the pulmonary and intestinal tissues, while lower deposition of antigens was observed in animals of Groups 3 and 4. The immunized pigs of Groups 5 and 6 showed the highest systemic IgG titres in serum and these antibodies were negatively correlated with the number of larvae recovered in the lungs, suggesting that the IgG response may have a protective function against the ascariosis. The highest concentrations of IgA-bearing cells were observed in animals of Groups 3 and 4 compared to the immunised pigs (Groups 5-7), suggesting that local IgA production may be involved in the protection against migrating larvae. The main localisations of IgA-bearing cells were the bronchial and peribronchial areas of lungs and the lamina propia of duodenum. Low numbers of local IgG-bearing cells were observed in all animals and no IgM-bearing cells were detected in the local tissues.

In the present work, we carry out an immunopathological study of the swine ascariosis, under different conditions (control, infection and immunization). Twenty-one Iberian pigs were used and divided in seven groups. Groups 1 and 2 were the uninfected and challenged controls, respectively. Groups 3 and 4 were weakly infected with increasing doses of Ascaris suum eggs and treated with pyrantel (Group 4). Groups 5-7 were immunized with 14, 42 and 97 kDa proteins from the parasite, respectively. Groups 2-7 were challenged with 10,000 infective eggs 7 days before the sacrifice. The focal parasitic granulomata with eosinophils and lymphocytes were the main histopathological lesions in the liver of reinfected pigs, while more marked cellular infiltrate and abundant connective tissue were seen in the livers of immunized animals. There were important deposits of antigens in the livers of immunized and infected pigs. Antigens were mainly located in the connective tissue, with positive staining detection of the somatic larvae antigen, the body wall from the adult worms and the 14-, 42- and 97-kDa proteins. However, cholangiols, biliary ducts and macrophages presented an immunohistochemical positive stain against excretory-secretory and somatic antigens from the larvae and the body fluid antigen from the adult parasite. The detection of A. suum antigens in the liver of infected pigs improves the diagnosis of swine ascariosis. It may be possible to apply these procedures for diagnosis of human ascariosis in liver biopsies since A. suum from swine have been previously used as a substitute for the study of the human parasite Ascaris lumbricoides.