• *Heterakis*

The genus *Heterakis* was first described and named by Dujardin in 1845. The parasites belonging to this genus are characterized by the following features: they are small worms with the anterior end bent dorsally, and mouth surrounded by three small equal size lips. Small white worms are found in the tip or blind ends of the caeca. The female measures 10–15 mm long and the male 7–13 mm long. Esophagus end in a well-developed bulb, containing a valvular apparatus. Pre-anal sucker well developed in males, papillae present, spicules unequal, uterine branches in the female opposite, vulva near the middle of the body, and eggs with thick and smooth shells [27], while studying six species of *Heterakis*, emphasized that they do not have certain points of interest, especially those related to the sense organs which reveal the possibility of identifying their larval forms since these organs are well developed in larvae The most important gastrointestinal nematode responsible for considerable production losses in poultry is *Heterakis gallinarum* [28].
