Sometimes all it takes is one genetically engineered parasite to break all sexual taboos on a resort island. David Cronenberg's 1975 film Shivers draws a connexion between unrestrained sexuality and experimental surgery as only David Cronenberg can. An early film for him, it isn't as thematically complex as his follow up Rabid but still quite fun.
The casually bizarre, deep-voiced actor Joe Silver as Doctor Linksy explains how another doctor, Doctor Hobbes, decided to try creating parasites to replace irreparably damaged or diseased internal organs like livers and kidneys. The parasites perform the same filtering functions and just take a bit of blood in return.
Things don't work out very well. The film opens with Hobbes murdering his teenage mistress in whom he'd implanted the first parasite. It turns out the parasites cause the host to experience a raging nymphomania so the girl had slept with people all over the island apartment building and in so doing spawned more parasites.
The film's protagonist is the dull resident doctor Roger St. Luc, who's too busy on the phone to notice is knock-out nurse performing a strip tease for him.
This is no non-sequitur. Aside from scenes of rape and a father making out with his daughter, the film seems to portray the sterile, parasite-free humans as being rather repressed compared to everyone who has a parasite. It's certainly hard to see anything wrong with Barbara Steele making out with Susan Petrie.
The film actually doesn't take sides, perhaps portraying the parasites more as a conquering civilisation with all the beauty and horror a conquering civilisation brings.