*3.2.1 Nematodes*

They constitute the most important group of helminth parasites of poultry both in a number of species and external damage they cause. The main genera include *Capillaria, Heterakis* and *Ascaridia* (**Figure 1**) [23].

*A. galli* is a parasitic roundworm belonging to the phylum Nematoda. Nematodes of the genus Ascaridia are essentially intestinal parasites of birds. Nematodes and cestodes) are common GI parasites of commercial poultry. The parasites typically cause acute irritation and might occasionally result in bleeding. The gut lining may erode severely and cause death. Deep litter households may experience a serious problem with these parasites. Heavy infections may lead to decreased fertility, egg production,

**Figure 1.** *Small intestines of a broiler chicken impacted with Ascaridia galli [22].*

and growth. Nematodes of poultry infection are widely distributed in different parts of the world, and numerous types of research have existed to prevent the mortality of poultry from parasitic diseases [22].

### • **Ascaridia**

The genus Ascaridia was first established by Dujardin in 1845. Nematodes of this genus are hosts specific to the class Aves. A large number of species have been reported from fowl; the common ones are as follows: *A. galli* is a parasitic roundworm belonging to the phylum Nematoda. *A. galli* is the most prevalent and pathogenic species, especially in domestic fowl. It inhabits the small intestine and causes ascaridiasis, a condition that affects poultry, especially hens and turkeys, and is caused by severe worm infestation. In birds, *A. galli* is the biggest nematode. The body is cylindrical, creamy white, and semitransparent. The mouth is prominent and is bordered by three broad trilobed lips on the anterior end. There are teeth-like structures on the borders of the lips [24]. detailed in fully the anatomy of *A. galli*, a creature whose body is totally wrapped in a thick protein structure known as a "cuticle." The cuticular alae are underdeveloped, and the cuticle is striated transversely over the length of the body. The dorsal lip has two noticeable papillae, and the sub-ventral lips have one each. The nematode's sensory organs are these papillae. *A. galli* exhibits clear sexual dimorphism and is diecious. With a vulva opening roughly in the middle of the body, halfway between the anterior and posterior ends, and an anus at the back end, females are noticeably longer and more robust [25]. It is typical for females to have a blunt, straight tail end. Males tend to be smaller and shorter than females, and they have distinctively pointed, curved tails. To the rear of the body, there are 10 pairs of caudal papillae that are grouped linearly into distinct groups such as precloacal (3 pairs), cloacal (1 pair), post-cloacal (1 pair), and sub-terminal (3 pairs). All types of poultry are affected by the nematode, however, young birds under the age of 12 weeks frequently exhibit the most severe damage. Reduced egg production and weight depression in poultry husbandry are primarily caused by heavy infection. Intestinal obstruction can happen in cases of severe infections. In heavy infections, adult worms may move up the oviduct and be found in hens' eggs, and sometimes they are also found in the feces of the infected birds [26].
