Indeed, morphological examination of the mucosa shows epithelial cells in various states of degradation in the vicinity of the schistosome egg (56). Alternatively, the diminished secretion could result from adaptation of the ileal mucosa to the infection. Such an adaptive response has been described for N. brasiliensis-infected rats RGFP966 and is directed by a neurally mediated mechanism possibly aimed at preventing excessive fluid loss (57). Likewise, in T. spiralis infected ferrets,
basal and stimulated jejunal secretions were attenuated during the enteric stage of infection (58). In these models, the reduced secretion was accompanied by a shift from cholinergic to noncholinergic regulation of secretion, which was associated with an increase in substance P immunoreactivity within
the mucosa. Interestingly, in this context, S. mansoni infection in the mouse results in increased immunoreactivity for the neuropeptide CGRP in close apposition to MMC within the ileum (6,7). Although the role of CGRP in S. mansoni infection remains to be elucidated it is likely that CGRP is involved in neuro-immune interactions between local primary afferent nerve fibres and mast cells (7). Extrapolation of these murine data to man involves a large number of uncertain assumptions, partly arising out of the lack of adequate human data [for reviews see (59,60)] but also since schistosome infection in mice differs in many respects
from that in humans (60). In both human and murine, however, the majority of pathology develops FK506 in vitro at the sites of maximal accumulation of eggs: the intestine and the liver (59,60). Gastrointestinal schistosomiasis is characterized by chronic abdominal pain and discomfort, loss of appetite and diarrhoea that commonly contains occult blood (60). The present results show that in mice, in addition to the previously described impairment of sugar and fluid transport (61), the basal secretion and the maximal secretory capacity of the ileal epithelium are severely reduced 8 weeks after schistosome infection. next If and how this finding relates to the patient symptoms cannot be inferred at present, but a derangement of fluid transport may explain some of these. The reported impairment of the mucosal barrier in the murine ileum suggests that translocation of bacteria from the gut lumen to extra-intestinal sites (62) might be increased during schistosomiasis. At present, only limited information is available on the effects of schistosomiasis on murine intestinal function (63). The present results suggest, however, that use of murine models may be of importance for the dissection of the intestinal pathologies. In summary, in S. mansoni-infected mice, the intestinal barrier is severely impaired both in WT and in Mcpt-1−/− mice and egg excretion takes place independently of mMCP-1.