Taenia

2. Taenia classification Kingdom: Animalia.Phylum: Platyhelminthes.Class: Cestoda.Family: Taeniidae.Genus: Taenia Species: T.saginata, T.solium

3. Distribution worldwide in distribution.  Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork and is very rare in Muslim countries. approximately 50 million cases of infection world-wide annually.

4. Host: Definitive host: Humans. Intermeiate host: pigs, sheep, dogs, cats. PATHOGENICITY: Taeniasis Cysticercosis

5. Adult Adult Teania is dividied into three main regions: - Scolex. - Neck - Strobila Length of adult worms is usually 5-7m for T. saginata (however it may reach up to 25 m) and 3-5 m for T. solium.  The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day).  T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 800 proglottids. 

6. Adult Taenia

7. Adult Taenia

8. Scolex

10. Scolex of T.saginata

12. Systems in mature proglotids

15. Reproductive System Male Most structures in the proglottid belong to the reproductive system. The male and female systems share a common genital pore (= gonopore) and genital atrium but are otherwise independent of each other. The common genital pore is a large aperture on either the right or left side of the proglottid. It opens into a shallow, cuplike genital atrium. The male and female systems both open into the atrium via its own gonoduct. Find the two ducts joining the medial border of the genital atrium. The anterior duct is the thicker and is the male gonoduct. The gonoduct is regionally specialized. The wide portion of the gonoduct attached to the atrium is the muscular cirrus sac. Inside the sac is the convoluted, eversible, tubular cirrus, which is the intromittent organ, or penis. During copulation the cirrus is extended from the genital pore and inserted into the genital atrium and vagina of another proglottid. On your slide it may be everted in some proglottids, in which case it looks like a slender worm extending from the genital pore.

16. The next region of the male gonoduct is the tubular sperm duct , also convoluted, which extends to the testes. Its entire length is not visible. The testes are numerous small spheres scattered throughout the parenchyma. Each is drained by a tiny tributary of the sperm duct, but these cannot be seen. There is no seminal vesicle and autosperm are stored in the coils of the sperm duct.

17. Female The smaller and more posterior of the two ducts entering the genital atrium is the female gonoduct, which is also regionally specialized. The first region is the vagina. It receives the partner's cirrus and sperm during copulation. The vagina extends medially and posteriorly to the small seminal receptacle . This is a clear, unstained, oval chamber where allosperm received by the vagina are stored. It is usually easily visible. A short duct exits the posterior end of the seminal receptacle and joins the oviduct. The germarium (= ovary) is divided into large right and left lobes lying on either side of the seminal receptacle. It is the site of oogenesis and produces large numbers of small, yolkless oocytes. The two lobes of the germarium are connected across the midline by a short, wide, transverse isthmus.

18. The follicles of the germarium open into small ducts which drain into the isthmus. The narrow oviduct arises from the isthmus and extends posteriorly for a short distance before receiving the duct from the seminal receptacle. The isthmus is usually easy to see but the oviduct is often obscured by the seminal receptacle and is harder to find. After receiving the duct from the seminal receptacle the oviduct continues posteriorly to the ootype. Fertilization occurs in the oviduct.

19. Yolk cells are produced by the single vitellarium at the posterior end of the proglottid. A short vitelline duct exits the vitellarium and extends anteriorly to join the oviduct at the ootype. Mehlis’s gland surrounds the ootype. The ootype, Mehlis's gland, and associated ducts cannot be seen in most slides. A small uterine duct, usually not discernible, extends from the ootype to the uterus . Shelled eggs move from the ootype through the uterine duct into the uterus. Within the shell meiosis is completed, a zygote forms, and development proceeds to the oncosphere larval stage. The uterus is a blind sac with lateral branches in which embryonated “eggs” are stored. The size and visibility of the uterus vary with the maturity of the proglottid. As the proglottid ages the accumulating “eggs” cause the uterus to become larger, darker, and more visible. They will eventually fill it, distending it so it occupies the entire proglottid. There is no opening of the uterus to the exterior and eggs are released by rupture of the proglottid.

20. Immature proglotids

21. Mature proglotid

23. Gravid proglotid

24. Teania egg The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces.  T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively. eggs of the two species are identical, spherical (31-43 µm), brown to dark-yellow with a thick shell wall and contain an onchosphere.

26. Cysticerci The larval form of Taenia solium, T. saginata, T. crassiceps, T. ovis, T. taeniaeformis or T. hydatigena is called acysticercus Cysticerci are fluid-filled vesicles that contain asingle inverted protoscolex

27. Cysticerci may be found almost anywhere, but each species has a predilection for certain tissues. In pigs, T. solium cysticerci are found mainly in the skeletal or cardiac muscles,liver, heart and brain. In humans, this species is most often found in the subcutaneous tissues, skeletal muscles,eyes and brain

28. cysticercus

30.  Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata or Taenia solium.  Humans are the only definitive hosts for T. saginata and T. solium.  Eggs or gravid proglottids are passed with feces ; the eggs can survive for days to months in the environment.  Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids .  In the animal's intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci.  A cysticercus can survive for several years in the animal. 

31. Humans become infected by ingesting raw or undercooked infected meat .  In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years.  The adult tapeworms attach to the small intestine by their scolex and reside in the small intestine . 

33. Taenia saginata (The Beef Tapeworm)

34. The adult tapeworms have an average length of ~ 5 meters , consisting of approximately 1000 proglottids, but may grow up to 17 metres in length occasionally, and are therefore longer than the adult forms of Taenia solium The scolex in this tapeworm may also be differentiated from T. solium as it is slightly larger, at approximately 2mm in diameter and is unarmed, without any hooks, although the 4 suckers are still present. The mature proglottids have approximately double the number of testes that T. saginata has and are larger have a uterus with more lateral branches, less than T. solium. Larvae (Onchosphere) - These cysticerci are approximately 7.5 - 10mm wide by 4 - 6mm in length. 

35. Taenia solium - The Pork Tapeworm

36. Adults - The adult tapeworms have an average length of ~ 3 meters, but may grow up to 8 metres in length occasionally The scolex in this tapeworm may also be differentiated from T. saginata as it is equipped with a low rostellum with a double crown of approximately 30 hooks. The mature proglottids having trilobed ovaries with a small central lobe in addition to the two lateral lobes and only approximately half the number of testes that T. saginata has The gravid proglottids, measuring approximately 12mm long by 6mm wide, have a uterus with between 8 to 12 lateral branches, less than T. saginata. Larva: approximately 6- 18mm wide by 4 - 6mm in length when found in the muscles or subcutaneous tissues. may however be found in other tissues such as those of the central nervous system where they may grow much larger, up to several cm in diameter.  

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