Lesions of the enteric nervous system and the possible role of mast cells in the pathogenic mechanisms of migration of schistosome eggs in the small intestine of cattle during Schistosoma bovis infection

The enteric nervous system in the small intestine of cattle during Schistos oma bovis infection was studied by histological stains and immunohistochemi cal methods. Lesions due to migration of schistosoma eggs were located main ly in the mucous and the submucous layer overlaying the submucous vascular arcades. Granulomas destroyed ganglia, neurons, nerves fibre strands and ne rve fibres. Ganglia situated within or near granulomas were infiltrated by mast cells, eosinophils, lymphocytes, globule leukocytes, neutrophils and m acrophages. Mast cells were in close contact with degenerating neuronal per ikarya. Whereas vasoactive intestinal peptide-like immunoreactivity in the nerves and neurons in the ganglia within and around granulomas was increase d, the neurofilament-like immunoreactivity was reduced. Compared to the mye nteric and external submucous plexuses, the internal submucous and mucous p lexuses were the most damaged. These changes imply reduced functional capac ity in the nervous tissue which might cause reduced motility, malabsorption and partly account for the loss of body weight and condition and failure t o thrive which occur in schistosomosis. Biotinylated affinity purified swine anti-rabbit and mouse anti-rabbit immu noglobulins reacted nonspecifically with a subset of mast cells. The reacti on revealed many mast cells in early forming granulomas and around schistos ome egg tracts and infiltration of mast cells into the ganglia of intestina l nerve plexuses. The observation shows a localized, Type I hypersensitivit y reaction suggesting for the release of mast cell-derived chemical mediato rs in the intestinal reaction to trap or evict S. bovis eggs and to cause d iarrhoea. (C) 2000 Elsevier Science B.V. All rights reserved.