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The aim of the study carried out on ten young (10-week old) pigs of the native Polish Large White breed experimentally infected with a low dose of 300 invasive muscle larvae (ML) of Trichinella spiralis was intravital detection of trichinellosis using the E-S ELISA test, determination of a variation level of IgG antibodies against excretory-secretory (E-S) antigens of T. spiralis muscle larvae and finally, describing the intensity of T. spiralis larvae infection in selected muscles. The pig sera were collected at 7 and 9 days prior to the experimental infection with T. spiralis and at 9, 14, 20, 23, 25, 27, 30, 33, 37, 41, 46 days post-infection (d.p.i.). The anti-T. spiralis IgG antibodies were detected by a commercial E-S ELISA test (PrioCHECK Trichinella Ab). Average intensity of the T. spiralis infection in the examined muscles of pigs ranged from 1.52 up to 43.09 larvae/g. The studies revealed that the E-S antigen in the ELISA test did not show cross-reaction with the sera of pigs infected with Oesophagostomum spp. The ELISA assay did not recognize trichinellosis in pigs until 27 days after the T. spiralis infection. The anti-T. spiralis IgG antibodies were first detected on day 30 post-infection. A statistically significant increase of IgG antibodies against T. spiralis ML E-S antigens was first observed between days 27-30 (p<0.01) post-infection, and a further significant rise in the antibody level occurred between days 27 and 33 (p<0.01); 30 and 33 (p<0.01); 33 and 37 (p<0.05) following infection.

ABSTRACT:In the early intestinal stage of infection with the nematode Trichinella spiralis alterations in gut motility and chemical code of enteric neurons are observed. The present study was designed to characterize the changes in expression pattern of vasoactive intestinal polypeptide (VIP), substance P (SP) and neuropeptide Y (NPY) in enteric nerves of the rabbit jejunum occurring during long-lasting trichinellosis (35 and 42 days). Sections of the jejunum from healthy and T. spiralis-infected rabbits were processed for double immunocytochemistry in which antibodies against protein gene product 9.5 were used as a pan-neuronal marker and mixed with antisera raised against VIP, SP or NPY. At 35 and 42 days post infection a marked decrease of VIP-, SP-and NPY-immunoreactive (IR) jejunal myenteric neurons was found, whereas the expression of these neuropeptides in submucous neurons was unchanged. In the myenteric plexus and the jejunal circular muscle of T. spiralis-infected rabbits a significant reduction of VIP-IR (but not SP-IR) nerve fibres was noted. In the longitudinal muscle of the jejunum from animals with long-lasting trichinellosis the density of SP-IR nerve terminals was decreased, whereas the number of VIP-containing nerve fibres was unchanged. Long-lasting trichinellosis had no influence on NPY-IR nerve fibres in both circular and longitudinal smooth muscles. The number of NPY-positive (but not VIP-and SP-IR) nerve fibres supplying mucosa and blood vessels was decreased in T. spiralis-infected animals. These data indicate that during long-lasting trichinellosis expression of neuropeptides in jejunal enteric neurons is changed. A possible involvement of VIP and SP in persistent intestinal dysmotility and NPY in altered fluid secretion is discussed.

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