An attempt to artificially select Strongyloides ratti for resistance to the host immune response.

Previous work has selected Heligmosomoides polygyrus for increased survival and reproduction in hosts with prior exposure to H. polygyrus, and therefore 'immune' to this parasite. We investigated whether Strongyloides ratti would respond similarly to selection for survival and reproduction in S. ratti-immune hosts. During 32 generations of selection, there appeared to be an initial, brief response to this selection, but this was not sustained and, eventually, the immune-selected line died out. Specific measures of the response to selection at generations 6, 12 and 25 did not detect any significant response to selection. Therefore, we have failed to select a line of S. ratti for increased resistance to its host immune response.