The aphasmid nematodes of the cat are represented by the various capillarids, Eucoleus, Aonchotheca, and Pearsonema species, Trichuris, Anatrichosoma, and Trichinella. Other than some of the capillarids, most of these infections are rather rare in cats. The Aphasmida differ from the Secernentea in that the stage typically infective to the final host is the first-stage larva.
Structurally, the aphasmids are also much different from the Secernentean nematodes. The esophagus has a peculiar structure that appears as a chain of glandular cells with a small esophageal lumen. This type of esophagus is called a stichosome esophagus with the individual cells being stichocytes. Another difference with the aphasmidia is that the anal on both the maile and female tends to be terminal. Thus, there is no tail that protrudes beyond the anal opening.