Which species of strongyle is the smallest?

The cyathostomum is the smallest of the strongyle. It is a genus of small strongyle nematodes that have been variously divided into a number of genera and subgenera. Approximately 40 species affect horses and elephants, colonizing the cecum and colon; results in weight loss, hypoalbuminemia and diarrhea. The small strongyles include 40 or so species that commonly infect the cecum and colon of horses and donkeys.

Approximately 30 of these have been assigned to the subfamily cyathostominae. Thus they are commonly called the Cyathostomes. They vary in size from 6 to 22mm in length with a reasonably well developed buccal capsule that is also much smaller than those seen in the large strongyles.