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Cestodes

This article explores the classification of cestodes, specifically Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm), within the phylum Platyhelminthes. It details their unique morphology, life cycles, and the impact of their larval forms on humans, including neurocysticercosis. The guide discusses their habitat classification, diagnostic methods, and treatment options for both taeniasis and cysticercosis. Understanding these parasites is crucial, especially in regions with poor sanitation, where infection rates can be significant.

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Cestodes

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  1. Cestodes Taeniasaginata Taeniasolium

  2. Classification • Cestodes belong to Phylum –Platyhelminthis Class—Cestoidea Subclass—Eucestoda Order—Pseudophyllidea Cyclophyllidea

  3. Classification based on Habitat • Intestinal Cestodes—Diphyllobotrium , Taenia,Hymenolepis,Dipylidiumspicies • Somatic or Tissue Cestodes(Larvae in Human Muscle or Organ)—T.solium,T.multiceps,Echinococcus,Spirometra species

  4. Order Family Genus PseudophyllideaDiphyllobothriidaeDiphyllobdthrium Spirometra CyclophyllideaTaeniidaeTaenia Echinococcus HymenolepididaeHymenolepis DipylidiidaeDipyllidium

  5. They exist in three morphology—Adult worm , Egg and, Larva . • Adult worm---intestine of human and animals . They are usually long, segmented, Flattened and tape like. • Few mm to meters—1 to 4cm to 10 mts.

  6. Morphology of Cestodes

  7. HOSTS • INTERMEDIATE: harbors the immature forms of the parasite. Insect of herbivorous vertebrate that ingest parasite eggs • DEFINITIVE: Harbors the mature forms of the parasite. Carnivorous or omnivorous mammal that acquires infection by consuming larval cysts in the uncooked tissues of an IH

  8. scolex neck strobila Tapeworms • The body plan of adult cestodes includes a scolex (looks like the “head”), a neck and strobila that can extend for only a few proglottids or thousands • The strobila is not truly metameric though as several organs like the excretory system extend through the entire worm • Proglottid: each individual segment • Most worms are very long: occupying the entire length of small intestine

  9. Taeniasaginata (Beef tapeworm) • Ranges in length from 6-30 ft • Geographic distribution: cosmopolitan. • Most common where poor sanitation and no inspection of meat combine • Africa and South America • Transmission: Ingestion of larval form in undercooked beef • In N. America 1 in 100 is infected. In third-world nations could be up to 10% • No symptoms or some abdominal discomfort • Diagnosis: finding eggs or proglottids in feces

  10. Life cycle

  11. Taeniasolium • T. solium has a scolex (A) with four suckers and a double crown of hooks, a narrow neck, and a large strobila (2-4 m) (B) consisting of several hundred proglottids. • About 2 months after ingestion, proglottids begin to detach from the distal end and are excreted in the feces. • Each segment contains 50-60,000 fertile eggs.

  12. TAENIA SOLIUM • The larval stage of the pork tapeworm infects the human nervous system causing neurocysticercosis. • One of the main causes of epileptic seizures. • Endemic in less developed countries where pigs are raised as food source. Latin America, most of Asia, sub-saharan Africa, and parts of Oceania. The Lancet (2003) 361: 547

  13. Cysticeruscellulosae • Larval stage of T.soliumin tissues • Humans acquire cysticercosis through faecal-oral contamination with T. solium eggs • The oncosphere in the eggs is released by the action of gastric acid and intestinal fluids • Cross the gut wall and enter the bloodstream • They are carried to the muscles and other tissues • They encyst as cysticerciat small terminal vessels (1 cm) (A) and (B) • Neurocysticercosis and ophtalmiccysticercosis serious

  14. Neurocysticercosis • The parasite infects the CNS • Epileptic seizures (58-80% when parenchymal brain cysts). • Intracranial hypertension, hydrocephalus, or both. This syndrome is related to the location of parasites in the cerebral ventricles or vasal cisterns. • Occasionally a cyst may grow larger (giant cyst) • Geographical variation in clinical manifestations

  15. Cysticercusbovis • Larval forms of T.saginata in tissues • Occurs in cattle but not in humans

  16. Lab diagnosis - Intestinal taeniasis • Stool examination • Segments of adult worm • eggs

  17. Lab diagnosis of cysticercosis • Serologic diagnosis: • Antibody assays for cysticercosis: 8 kDa antigens, GP50, FAST-ELISA with the 8 kDA antigen • Antigen-detection assays: circulating antigens means live parasites. Ongoing viable infection. Monoclonal antibodies seem to detect AGs in CSF. • Antibody assays for taeniasis: TSE33 and TSE38 were recognized by a panel of taeniasis but not cysticercocis, patient serum samples.

  18. Neuroimaging diagnosis: CT and MRI provide objective evidence on number and location of cysticerci. Also their viability and the severity of the host inflammatory reaction.

  19. Treatment • Treatment should be individualized based on cyst location, level of immflamation and clinical presentation • Parenchymalcysticercosis with viable cysts: Albendazole 15 (mg/kg/day) with dexamethasone (0.1 mg/kg/day). Praziquantel. • Subarachnoid ccs: antiparasitic therapy • No reason to use antiparasitic drugs to treat dead calcified cysts. Symptomatic therapy. • Surgical therapy: ventricular shunting to resolve hydrocephalus. Also excision of giant cysts or intraventricular cysts • Taeniasis treatment: niclosamide and praziquantel

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