Correlation Between Small Intestine Enterochromaffin Cells and Migrating and Excreted Schistosome Eggs During Experimental Schistosoma bovis Infection in Cattle

Abstract

In schistosomiasis, the mechanisms of extravasation and migration of schistosome eggs into the intestinal lumen, and diarrhoea are not very well understood. In addition, the role of the neuroendocrine system has not been investigated. Therefore, Schimorl's ferricyanide stain and immunohistochemical staining for 5-hydroxytryptamine- like immunoreactivity were used to study enterochromaffin cells in the jejunum and ileum of 12, one year old, Jersey and Friesian Boran crossbred male calves during experimental Schistosoma bovis infections to elucidate their role in the pathophysiology of migration and egress of Schistosoma bovis eggs and diarrhoea. Most of the enterochromaffin cells reached the intestinal cryptal lumina. 5-hydroxytryptamine immunoreactive granules in the enterochromaffin cells varied in size and were in most cells dispersed in the entire cytoplasm and in addition, some reactivity could be traced in the uppermost parts and in the cryptal lumina. Smaller granules appeared in the luminal part of the cytoplasm, while the larger and more intensely stained granules were localized in the basal compartment. Between weeks 9 - 13 post infection, when diarrhoea was recorded in two infected calves, the excretion of eggs was at maximum and the numbers of enterochromaffin cells in infected calves increased to become significantly higher than those in control calves during weeks 11- 13. The numbers of enterochromaffin cells in infected calves were pos itively correlated to the number of schistosome eggs per gram of faeces. The results are discussed with respect to the mechanisms of migration and egress of schistosome eggs from intestinal wall outside the host body and diarrhoea