Answer: Trichuris trichiura (whipworm)
This was a tough case, as evidenced by the responses I received. Most of us are not taught the features of worms in histologic sections, but they not uncommonly pop up and pathologists and microbiologists alike are called upon to identify them.
In this case, the characteristic features of this nematode include variable diameter along the length of the organism, stichosome, bacillary band, annulated cuticle and nucleated hypodermis. A few of these features are highlighted in the images below. Thank you all for taking a chance on this one and writing in with your thoughts!