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In the ancient times Hippocrates, Aristotle, and Galen appreciated the nature of tapeworms. The Arabs susgested that segments passed with the faeces were a separate species of parasite from tapeworms: they called these segments the cucuribitini, after their similarity to cucumber seeds. Andry, in 1718, was first to illustrate the scolex of a tapeworm from a human. Sexually mature tapeworms live in the intestine or its diverticula ( rarely in the coelum) of all classes of vertebrates. These are a group of parasites which are fairly common in both domestic and wild animals, and humans.

CLASS

This class differs from the in having a tape-like body with no body cavity and alimentarty canal. There is a wide variation in length, ranging from a few milimeters to several meters. The body is segmented, each segment containing one and sometimes two sets of male and female reproductive organs. Almost all the tapeworms of veterinary importance are in the order Cyclophylidea, two exceptions being in the order Pseudophyllidea. During their life cycle, one or two ( or more ) intermediated host are required in each of which the tapeworm undergo a phase of their development.

Order : Family : Taenidae

Genus : , Echinococcus

Family : Anoplocephalidae

Genus : Anoplocephala, Paranoplocephala, Monezia, Thysanosoma,Thysaniezia, Stilesia, Avitellina Family :

Genus : Dipylidium , Amoebotaenia, Choanotaenia, , Diplopylidium

Family : Paruterinidae

Genus : Metroliasthes Family : Davaineidae

Genus : Davainea, , Houttuynia

Family : Hymenolepididae

Genus : Hymenolepis, Fimbriaria, Rodentolepis Family : Mesocestoididae

Genus : Mesocestoides

Order : Pseudophyllidea Family : Diphyllobothridae ; Genus : Diphyllobothrium, Spirometra 2

The body of the typical cestoda can be divided into three regions; 1 ) scolex – the holdfast organ – is the anterior end and its morphology and dimensions are important in the identification of these worms; 2 ) the neck region, situated immediately posterior of the scolex, is an unsegmented, poorly differantiated area that is generally narrower than the scolex and the strobila proper, and is the continuously differentiating zone that gives rise to immature proglottids, or body segments, of these worms and 3 ) the strobila, which constitutes the main bulk of the body, is made up of the chain of proglottids.

A syncytial cytoplasmic covers the surface of cestodes. Tegumental structure is generally similar in all cestodes. The body of tapeworm, including its scolex, suckers nad bothria is completey covered by tegument, which is a living tissue with high metabolic activity. The regulary arranged microvilli of the tegument of cestodes as called microtriches ( singular: microthrix). The tegument is a metabolically active layer which is involved at least in the absorption of nutrients , in osmoregulation and excretion , and in protection against the effects of host enzymes and immun systems; secretion of the tegument proved to have a digestive function, or might be involved in the defence against immun reactions. The microtriches are concerned with three functions: 1 ) as mean of movement and to keep distance, 2 ) as mean of anchoring, 3 ) the microtriches are obviously involved in increasing the surface area and are thus essential for the uptake of nutrients, which also occurs by endocytosis between the base of the microtrichs.

Tissues of most cestodes contain curious structures termed calcareous corpuscles. Possible functions of calcareous corpucles have been subject of much speculation. For example, motilization of the inorganic compounds might buffer the tissue of the worm against the large amounts of organic acids produced in its energy . Another suggestion has been that they provide depots of ions or carbon dioxide for use when such substances are present in insufficent quantity in the environment. Another idea is that they are an excretory products.

The scolex is very small (mostly less than 1mm ) and is provided with specific holdfast systems such as suckers, rostellum, grooves, hooks and bothria. The whole chain is attached to the tissues of the host by the scolex only. It is attached to the host by adhesive organs which may be given the general term holdfast ; these may or may not be supplemented by hooks. Holdfasts are on the scolex only and are never on the proglottids. On the sides of the scolex are four suckers , or acetabula , which sometimes also carry hooks. Some species possess an anteriorly projecting rostellum, which may or may not be armed with one or more rows of hooks. The rostellum can be retracted into the rostellar sac within the scolex. Scolex bears two slit like grooves called bothria ( one on the dorsal surface and one on the ventral surface), which are muscular grooves that provide attachment by pinching host tissue beetwen them. Hooks may be present on the suckers.

The proglottids are continuously budded from the neck region and become sexually mature as they pass down the strobila to the distal end of the tapeworm. The portion of the chain of proglottids immediately behind the scolex is the portion that aries first and it may show no external sign of segmentation into proglottids. It may be narrower than the segmented part of chain that succeeds it and this narrower portion just behind the head is then called the neck. Some species , of which the species of the genus Moniezia are example, have no neck. 3

The most anteriorly situated proglottids are generally immature- that is, the reproductive organs, although visible, are nonfunctional. Proglottids posterior to immature proglottids are sexually mature, while those toward the posterior end of the body are usually gravid, filled with eggs. In the sexually mature proglottids, one or two sets of sexual organs, however, do not mature at the same time. Just behind the neck proglottids are immature , then further posterior are proglottids with mature male organs, then those with mature female organs, and finally those the uterus of which contains fertilized eggs; the latter proglottids are thus described as gravid proglottids. Self fertilization within a single proglottid and between proglottids, and copulation between two worms take place among the species, although the latter is exteremerly rare. The genital pores are usually settled on one lateral margin or two margins of the segment ( in Cyclophylidean tapeworms ), and the genital pore is centrally placed in Pseudophyllidean tapeworms. When a gravid proglottid reaches the end of the strobila, it detaches and passed out intact with the feces or partly disintegrates before reaching the anus, and then the eggs pass with feces in the environment. In cases where the uterus as an opening, the proglottids release the eggs and become detached when exhausted.

The reproductive system is the most important organ system of the adult cestode, for with their complex life cycle millions eggs must be produced to insure that one may some time produce another adult worm.

All known tapeworms are hermaphroditic parasites. Most commonly , each proglottid contains one complete set each of male and female reproductive organs. As the segment moves toward the rear of the strobila, the reproductive organs mature and embryonated eggs are formed. Most commonly, male organs mature first and produce sperms, which are stored until maturation of the ovary. Early maturation of the testes is called protandry.

The male reproductive system contains of many testes, each of which has a fine vas efferens. The vasa efferentia unite into a common vas deferens which drains the sperm toward the genital canal. The vas deferens may dilate into a spheroid external and internal seminal vesicle. The sperm is stored in the seminal vesicle. Eventually, the vas deferens leads into a cirrus pouch, which is a muscular sheath containing the terminal portion of the male system. Inside the cirrus pouch, the duct is modified into a muscular cirrus, the male copulatory organ. The cirrus can invaginate into cirrus pouch and evaginate through the cirrus pore. Often, the male and female genital pores open into a common sunken chamber, the genital atrium. This atrium may be simple. The genital atrium may open on the margin or central on the mature or gravid segments.

The female reproductive system consists of a single ovary, which may be large or small , compact or diffuse, and may be located anywhere within the proglottid, depending of the genus. Asscociated with ovary are vitelline cells ( or vitellaria, vitelline gland ), which contribute to egg shell formation and nutrition for the developing embryo. These may be in a single compact vitellarium or scattered as follicles in various patterns. As ova mature they leave the ovary through a single oviduct that may have a controlling sphincter, the ovicapt. Fertilization usually occurs in the ootype. Around the ootype are unicellular called Mehlis glands , similar to those of the trematoda. Cells from the vitelline glands pass through a vitelline duct, and join with the zygote. The unicellular secreted substance of Mehlis glands 4 pass into the ootype. The Mehlis glands secrete a very thin membrane around the zygote and associated vitelline cells. Eggshell formation is then complete from within the vitelline cells. Leaving the ootype, the embryonating egg pass into the uterus where embryonation is completed. The form of the uterus varies considerably between groups. It may be a simple or convoluted (or twisted) tube, a reticular, lobated or simple sac, or may be replaced by other structures. In Cyclophyllidea tapeworm, there is not a uterin pore . In many tapeworms of this order ( Cyclophyllidea ) , the fertilised eggs are not liberated from the uterus, and sets within the uterus. In some species, however, the uterus disappears while the proglottids still inside the host, before it disappears, the eggs pass into fibrous protective envelopes formed to receive them. These productive envelopes may be formed either from the uterus or from the parenchyma of the proglottids. There are two types the productive envelope. In some groups, the eggs, either single or in groups , are enclosed within hyaline egg capsules embedded within the parenchyma. In other groups one or more fibro-muscular structures, the paruterine organs, form attached to the uterus. In the case the eggs pass from the uterus into the paruterine organs, which assumed the function of a uterus. The uterus then usually degenerates. The gravid proglottids have been detached from the parent chain ( or strobila ), either singly or in short chains ( many proglottides), and have left the host. Sometimes, the gravid segments, which in the small intestine or large intestine , are splited and liberated eggs pass into the faeces. The female genital pore, the vaginal pore, usually opens near the cirrus pore. In the Pseudohpyllidea, the uterus opens to the outside of the body through the genital pore. In such case, proglottids (mature proglottids) continually forms eggs, which are expelled.

The whole chain of proglottids, thus made up of a series of hermaphrodite units, has a common excretory and a common nervous system. The excretory system, which is also called the osmo-regulatory system, ususally consists of two longitudinal collecting canals running down each side of each proglottids. The canals end blindly and at their blind ends there are the flame cells the parenchyma . The nervous system apperars to be a modified ladder – type, with a longitudinal cord near each lateral margin and transverse commissures in each segment . The two lateral cords are united in a arrangement of ganglia in the scolex .

Most tapeworms possess well – defined, longitudinal bundles of muscule fibers and scattered dorsavenral fibers. The scolex is well supplied with muscle fibers, making it extraordinarily motile.

The alimentary canal is absent from all tapeworms. Most adult tapeworms live in the intestine of their host and are therefore surrounded by the products of the host’s digestive processes. All nutrients molecules must be absorbed across the tegument. The mechanisms of absorption include active transport, mediated diffusion, simple diffusion. Glucose is the most important nutrient molecule to fuel energy processes in tapeworm. Amino acids are also actively transported and accumulated. Fatty acids, monoglycerids, and sterols absorbed at a considerably greater rate.

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The tapeworms eggs: The eggs of tapeworms are vary size and shape.

Types of Cyclophyllidea egg : The fully embryonated egg of Cyclophyllidea consists of :

1 ) the hexacanth ( six hooks) embryo or oncosphere

2 ) a thick , dark, radially striated or not radially striated “shell” called the embryophore (in Mesocestoidiae it is apparent as a thin cellular membran )

3 ) a true shell, which is a delicate membrane and is often lost while still in the uterus

Taenia spp. egg : Taenia eggs are subspherical or slightly elliptical and measure 24-35 X34-39 µm. They have a smooth thick shell with radially striated embryophore and contain a hexacanth embryophore oncosphere.

Dipylidium egg : The eggs are yellowish – brown in colour and almost spheric, and the indivual eggs are measure 35-50µm., and contain a hexacanth embryo, and have no contain thick shell with a radially striated embryophore. The eggs are contained in an eggs capsule ( about 120- 200µm. ), which may hold up to 30 eggs.

Moniezia spp. egg: The irregularly triangular – shaped eggs have a well – defined pyriform apparatus and vary about 50 to 67µm. diameter.

Joyeuxiella egg : The eggs of Joyeuxella spp. eggs resemble of Dipylidium eggs, but the egg capsule contains only a single egg.

Rodentolepis nana egg : The eggs are small, round or oval in shape and measures 30-55µm. by 44-62µm. They are colourles with a smooth shell and contain a lemon-shape embryophore with protuding polar plugs that bear long fine undulated filaments. The embryo has three pairs of small hooks.

Rodentolepis diminuta egg : The egg of R. diminuta is more spherical and measures 30-55µm. by 62-88µm. Embryophore has protruding polar plugs, but have no undulated filaments. . The embryo has three pairs of small hooks.

Types of Pseudophyllidea egg : Diphyllobothrium egg : The eggs of Diphyllobothrium spp. are oval and possesses a distinct operculum at one pole of the shell. The eggs are light brown and have dimensions that average 40-50 X 67-70µm. The eggs tend to be rounded at one end. The operculum is present on the the end opposite the rounded pole.

Life cycle of the tapeworms : The typical life cycle of the tapeworm is indirect with one or more intermediate hosts. With few exceptions, the adult tapeworm is found in the small intestine of the final hosts, the segment or eggs reaching the exterior in the feces.

When the eggs is ingested by the intermediate host, the gastric and intestinal secretions digest the embryophore and activate the oncosphore. Using its hooks, it tears through the mucosa to reach the blood or lymph stream or, in the case of vertebrates, the body cavity. Once in its predilection site the oncosphere loses its hooks and develops, depending on the species, into one of the following larval stages, often known as metacestode. 6

Larvae types of Cyclophyllidea:

Cysticercus : single fluid – filled cyst or bladder containing an attached single invaginated scolex, sometimes called a protoscolex. When it is ingested by the final host the scolex evaginates and whole structer, excepting the scolex, is digested off.

Coenurus : This large cyst is similar to a cysticercus, but with numerous invaginated scolices attached to the cyst wall.

Hydatid :This is the most complex the larval forms. This is a large, fluid-filled, complex cyst lined with germinal epithelium from which are produced invaginated scolices which free or in bunches, surrounded by germinal epithelium ( brood capsules ). The contents of the cysts other than the fluid (i.e. scolices and brood capsules ) are frequently described as ‘ hydatid sand ‘. Occasionally also, daughter cysts complete with cuticle and germinal layer are formed endogenously or, if the cyst wall ruptures, exogenously.

Cysticercoid : A single evaginated scolex embeded in a small solid cyst. Typically found in very small intermediated hosts such as arthropods.

Strobilocercus : The scolex is evaginated and is connected to the cyst by a chain of segmented asexual proglottids. The later are digested away after ingestion by the final host, leaving only the scolex.

Tetrathyridium : Worm-like, flattened and elongate larva with an invaginated acetabular scolex; found only in Mesocestoididae.

When the metacestode ( larvae ) is ingested by the final host the scolex attaches to the small intestinal mucosa, the remainder of the structure is digested off, and a chain of proglottids begins to grow from the base of the scolex.

Larvae types of Pseudophyllidea :

Coracidium : The coracidium is a ciliated embryo, which develops into the eggs of tapeworms. The coracidium, which emerges after hatching, is an oncosphere with an embryohore which is ciliated for mobility in water.

Procercoid : The coracidium enters a copepod crustacean, losing its ciliated tegument, develops into a solid , elongate larva, which procercoid . The procercoid is a solid elongated larval stage, with a cephalic invagination and six embryonic hooks are still present in a small, globular cystic or solid caudal appendage, called cercomer,which is eventually lost.

Plerocercoid : The plerocercoid larva has a solid body and has lost the embryonic hooks. It has developed in their place the bothria characteristic of the adult tapeworm. It is, in fact, an immature tapeworm and differs anatomically from the adult only in its lack of segmentation and reproductive organs. 7

ORDER PSEUDOPHYLLİDEA

The morphology of the Pseudophyllidea is generally similar to that of the Cyclophyllidea, but there are three distinct features. First, the unarmed scolex has no suckers and instead has two weakly muscular, shallow longitudinal grooves or bothria, which become flattened to form organs of attachement. Secondly, proglottids possess uterine pore that enables eggs to be discharged from a large lengh of the strobila. The terminal proglottids are not gravid and usually are exhausted and may become detatched in short chains. Thirdly, the eggshell is thick, brownish-yellow and operculate, and the coracidium, which emerges after hatching, is oncosphere with an embryophore which is ciliated for mobility in water.

The order contains only two genera of veterinary importance, Diphyllobothrium and Spirometra.

Family Diphyllobothriidae : Parasites of fish-eating mammals and other vertebrates with well- developed bothria.

Genus Diphyllobothrium : This genus is an important cestode of humans and fish-eating mammals, and they are long tapeworms with an unarmed scolex, with two muscular bothria. Diphyllobotrium latum :

Predilection site : Small intestine

Description : A very long ivory-coloured tapeworm, up to around 10-15 m in legth, with several hundred proglottids. The scolex is unarmed with two weak muscular longitudinal grooves or bothria as organs of attachement. Anterior proglottids are broader than long while the mature and gravid segments are rectangular-shape with a central genital pore. The reproproductive organs are located at the centres of the segments. The uterus is situated centrally and is rosette-shape. The eggs are yellowish-brown , ovoid with rounded poles, operculate, and measure around 66-70 by 45-50µm.

Final hosts : Humans and fish-eating mammals, such as dog, cat, fox, pig, mink, seal and bear.

Intermediate hosts: Host 1 :copepods of the genus Diaptomus, Host 2 : freshwater fish (pike, trout, perch, minnow)

Life cycle : Eggs are continuosly discharged from the genital pores of the attached gravid segments of the strobila and pass to the exterior in the feces. The eggs must develop in water and within a few weeks each hatches to liberate a motile ciliated cocacidium which, if ingested by copepod, develops into the first parasitic larval stage, a worm-like procercoid. When the copepod is ingested by a freshwater fish, the procercoid migrates to the muscles or viscera to form the second larval stage, the plerocercoid. The life cycle is completed when infected fish is eaten raw, or unsufficiently cooked, by the final host.

Diphyllobotrium latum is a very fast-growing cestode, and can reach a length of a metre in three weeks, the first eggs appering in the feces about four weeks after ingestion of the plerocercoid. It has been estimated that, in a life time of ten years, and this tapeworm produces about seven kilometres of segments. 8

Geographical distribution : Parts of Scandinavia, Russia, Japan and North America

Pathogenesis and clinical signs : In humans , infections are often asymptomatic but there can be fatigue, dyspepsia,vomiting and transient diarrhoea. Infection is usually asymptomatic in animals, although occasionally vitamine B₁₂ deficiency can occur. The clinical effect is the production of pernicious anaemia.

Diagnosis : This depends on the detection on the characteristic eggs in the feces.

Epidemiology : Diphyllobotrium latum is essentially a parasite of humans since in other hosts the cestode produces few fertil eggs.

Treatment : Praziquantel is effective against the adult tapeworm.

Genus Spirometra : Spirometra are small to medium-size tapeworm of dogs, cats, and wild carnivores and an occasional human zoonosis ( sparganosis ). A couple of features enable differentiation from the very similar genus Diphyllobothrium : the vagina and uterus exit separately onto the ventral surface of the proglottid; and uterus has a spiral form whereas in Diphyllobothrium it has a rosette shape. Spirometra species in animals and human

Species Hosts Site Intermediate host

Spirometra mansoni dog,cat, wild small intestine Copepode(procercoid) carnivores, amphibia,reptiles,birds human (plerocercoid ) S. mansonoides cat,bobcat, small intestine crustacea(procercoid) raccoon,dog rats,snakes,mice

(plerocrecoid)

S. erinacei dog,cat,fox small intestine crustacea(procercoid) frog(plerocercoid)

Description : The adult tapeworms are very similar to Diphyllobotrium, measuring around 6 cm. by 1.5 m in length. The plerocercoids, also called spargana, are white, ribbon-like, crinkled and can measue around 30-40 mm. The operculate eggs have pointed ends and measure on average 65 by 45µm.

Life cycle : The life cycle is, similar to that D. latum, the procercoids being found in crustaceans, such as cyclops, the plerocercoids in a wide variety of hosts. These can also act as paratenic hosts. The prepatent period is around 2-30 days. Geographical distribution : South America and Asia 9

Pathogenesis and clinical signs : The tapeworm usually causes little effect in the intestine of dogs and cats.

Occasionally, humans may become infected with plerocercoids, either through drinking water containing procercoid-infected crustacea or from eating a plerocercoid-infected host. This zoonosis, known as sparganosis (sparganum was the old name for these plerocercoids), is charaterised by the presence of larvae up to 35 mm long in the muscles and subcutaneous tissues, particularly the periorbital area, causing oodema and inflammation. Occasionally,the spargana disintegrate the into several pieces (proliferating disease ), which develop separately, and this can be fatal. Genus Ligula :

Ligula intestinalis : This helminth species is important interms of fish health and causes ligulosis. Ligula intestinalis is widely encountered in freshwater in the Northern Hemisphere, which includes Turkey, and is a cestode that reaches 28 cm in adults and 40 cm in plerocercoids.

The final hosts are piscivorous birds such as gulls and grey herons. The parasites persist in the small intestine of birds for only a few days to reach sexual maturity and to reproduce. Its eggs are shed in the birds’ faeces and hacth in water to form infective coracidium, which are ingested by copepod. Coracidium transforms into procercoids by penetrating the internal wall of these copepods and by locating into the body tissue. Freshwater fish, which are the second intermediate host of L. intestinalis, ingest procercoids by eating the first intermediate hosts. The procercoids, locating in the body cavity by piercing through the intestinal wall of the fish, transform into plerocercoids. The plerocercoids transform into adult form in birds that eat the second intermediate host fish of the main host waterfowl.

The plerocercoids, filling the body cavity of the fish , cause pressure on the organs in the abdominal cavity. As a result of this, the heart is pushed toward the front, the liver becomes deformed, and abdominal wall thinning, loss weight, and parasitic sterility (unproductiveness) caused by suppressing the development of the gonads are seen. Death occurs in severe infections. Fishes infected by L. intestinalis plerocercoids are not able to swim properly, and their abdominal cavity are swollen; furthermore, it can be seen that abdominal cavity burst and the parasites get out.