The unisex contraceptive is a slippery fish for Big Pharma. Chris Arme of Keele University, UK, reckons the parasite Ligula intestinalis could provide some clues, however. Apparently, tapeworm secretions switch off egg and sperm production in freshwater carp. As reproduction can kill female carp, some suggest that host sterilization increases the worm's chances of being passed on to fish-eating birds. Yet, Arme says, "It's 100% effective in either sex." Arme's team found that the worm secretions affect other animals, such as toads (C. Arme, "Ligula intestinalis a tapeworm contraceptive," Biologist, 49:265-9, 2002). So, it might work in humans, too. "Nobody should rush out and get infected with fish parasites," warns Arme, "but one day we may have a 'his-and-hers' contraceptive in our medicine cabinets."
Joe Camp of Purdue University North Central worries about the permanence of the effect, "If it's permanent, that's sterilization rather than contraception." Alas, Arme says it's ...
