Armitstead had been poised to lead the six-person squad, but her illness means Nicole Cooke is expected to be the focal point of a team with one competitor fewer than their rivals.
The 23-year-old’s absence is another blow in a week that has brought British cycling down to earth slightly following the euphoria of this year’s Olympic, Tour de France and Tour of Britain successes.
Emma Pooley missed out on a medal by nine seconds in the women’s individual time trial on Tuesday, in which compatriot Wendy Houvenaghel finished 14th.
Alex Dowsett was eighth in the men’s equivalent yesterday, with London 2012 champion Bradley Wiggins absent and his Team Sky colleague Chris Froome a late withdrawal this week. Germany’s Tony Martin retained his title, completing the 45.7km route in 58 minutes 38.76 seconds, with American Taylor Phinney second and Vasil Kiryienka of Belarus third.