most parasitic nematodes need an intermediary host
http://www.jstor.org/stable/3221896
http://news.nationalgeographic.com/news ... t-mutants/
http://www.colorado.edu/eeb/facultysite ... #trematode
http://www.parasitesandvectors.com/content/5/1/208
this one done in nz
http://nzetc.victoria.ac.nz/tm/scholarl ... dy-d3.html