*3.2.2 Cestodes*

There are two important genera infecting chickens, *Railleitina* and *Hymenolepsis*. *Raillietina* is the name of a genus of tapeworms that includes helminth parasites of vertebrates, and mostly of birds. The genus was named in 1920 by Louis-Joseph Alcide Railliet. of the 37 species recorded under this genus, *Raillietina demerariensis, R. asiatica*, and *R. formsana* are the only species reported from humans, while the rest is found in birds*. R. echinobothrida, R. tetragona,* and *R. cesticillus* are the most important species in terms of prevalence and pathogenicity among wild and domestic birds (**Figure 4**) [31]. There are many different species of tapeworms that can infect backyard poultry. The majority of these species are totally harmless, however, large numbers of tapeworms may cause weight loss and loss of egg production.

*Raillietina tetragona* occurs in the posterior half of the small intestine (ileum) of the chicken, guinea fowl, pigeon and other birds. It is cosmopolitan in distribution. It is one of the largest of the fowl tapeworms and the adults reach up to 25 cm in length. The scolex is smaller than that of *R. echinobothridia* and the rostellum is armed with one or two rows of hooks and the suckers are oval and armed. The genital pores are

**Figure 4.** *Cestode in the small intestine of chicken [32].*

**Figure 5.** *Scolex of Raillietina tetragona 336×448 pixels [32].*

*Poultry Farming: New Perspectives and Applications Chapter – Parasitic Diseases of Chickens DOI: http://dx.doi.org/10.5772/intechopen.109962*

usually unilateral and the eggs are found in egg capsules each containing 6 to 12 eggs. The eggs are 25–50 um in diameter (**Figure 5**) [33].

*Raillietina echinobothrida* is the most prevalent and pathogenic helminthic parasite in birds, particularly in domestic fowl (*Gallus gallus domesticus* Linnaeus), It requires two hosts, birds and ants, for completion of its life cycle [34]. The parasite is to blame for the chicken version of "nodular tapeworm sickness." A typical tapeworm structure, the body of an adult *R. echinobothrida* is made up of a number of ribbon-like body segments that enlarge gradually from the anterior end towards the posterior. It is dorso-ventrally flattened, pale in color, extremely elongated, and fully covered in a tegument. The body can be up to 25 cm long and typically measures 1–1.5 cm in width. *Raillietina cesticillus* is very common throughout the world in domestic poultry, macroscopically is about 15 cm long and the anterior border of the segment is shorter than the posterior one. The scolex is cylindrical or nearly globular in shape and smaller in size [32] in **Figure 6**. Hosts. *R. echinobothrida* infections are observed in chickens and turkeys, tetragonal infections are most common in chickens, guineafowl, and pigeons, and domestic chickens are infected with *S. cesticillus*. The range of all three species is international. The worms are found in the small intestine, where the scolex is embedded in the mucosa, as their preferred habitat. 36 Morphology: *S. cesticillus* measures 9–13 cm, whereas *R. echinobothrida* and *R. tetragona* can grow to a length of 10–25 cm. All three species' eggs are the same size, measuring 74×93, however, the quantity of eggs in each gravid segment differs. The *R. tetragona* gravid proglottid has the most

**Figure 6.** *Scolex of Raillitinia cesticulls 150×141pixels [32].*

egg capsules overall. *R. echinobothrida* and *R. tetragona* have different gravid segment morphologies than *S. cesticillus* because the segments of the first two are replaced by numerous fibrous walled egg capsules, each containing several eggs, as opposed to the numerous thin-walled egg capsules, each containing a single egg, in *S. cesticillus*.

The family of tapeworms known as *Davaineidae* contains helminth parasites of vertebrates. This family has 14 genera, of which *Davainea* is the best known and has been the subject of the most in-depth research. Members of the family can be identified by the rostellum, which is a crown of mattock- or hammer-shaped hooks, present at the tip of the scolex. Suckers with spines encircle the rostellum on both sides. The most frequent hosts of these tapeworms are birds, though they can also be discovered in some cases in mammals. Small insects like ants serve as intermediate hosts. The intermediate hosts for *Davainea proglottina* are slugs and chickens (**Figure 7**) [35]. Clinical symptoms and pathogenicity: Despite its small size, *D. proglottina* is one of the more dangerous species, especially in young birds and especially if it happens frequently. Clinical symptoms include a lifeless appearance, sluggish movements, decreased weight gain, emaciation, dyspnea (breathing problems), leg paralysis, and death. It is possible to notice microscopic necrosis, hemorrhages, and thicker mucosal membranes.

*Amoebotaenia sphenoids* occur in domestic poultry and have a global distribution. It is a little tapeworm with dimensions of 2 to 3.5 mm in length and 1 mm in breadth. It is generally triangular in shape and has 20 segments. Earthworms serve as the cestode's intermediary hosts during its development. About 4 weeks after consuming infected earthworms, mature tapeworms are discovered in chickens. Even though this parasite does not cause any clinical symptoms, enteritis and wasting have been linked to it when there are significant infections present (**Figure 8**) [37–40]. It is small, up to 4 mm long, and roughly triangular in shape • The rostellum is armed • The genital pores usually alternate irregularly at the extreme anterior end of the proglottid margin • The uterus is sac-like and slightly lobed.

**Figure 7.** *Adult stage of Davainea proglottina, 186×480pixels [32].*

*Poultry Farming: New Perspectives and Applications Chapter – Parasitic Diseases of Chickens DOI: http://dx.doi.org/10.5772/intechopen.109962*

**Figure 8.** *Adult stage of Amoebotaenia cuneata = sphenoides 400×542pixels [36].*
