Cestode tapeworm GENERAL INTRODUCTIONS Taxonomic position Phylum platyhelminthes

Cestode (tapeworm)

GENERAL INTRODUCTIONS • Taxonomic position Phylum platyhelminthes Class Cestoda

MORPHOLOGICAL FEATURES • Flat and Segmented • Scolex-equipped with organs of attachment: • suckers, hooks, grooves • Neck - germinal portion • germinal – development • Strobila: – Proglottids – – Immature proglottid – Mature proglottid – gravid proglottid

• Proglottids – each segment in the strobila of a tapeworm, containing a complete sexually mature reproductive system. • Gravid – carrying eggs

MORPHOLOGICAL FEATURES • Body wall: Tegument and subtegument (syncytial layer); no coelomic cavity • Monoecious

• A coelom is a cavity lined by an epithelium derived from mesoderm. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks

• Monoecious - (of a plant or invertebrate animal) having both the male and female reproductive organs in the same individual; hermaphrodite.

• syn·cy·tium - a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.

PHYSIOLOGY AND PATHOGENESIS • Surface absorption capabilities • Highly developed reproductive functions • Anaerobic metabolism • All species are parasitic • Pathogenic stage may be adult or the larva

Metacestode stage • Larval stage of a cestode that develop in the intermediate host. – Cysticercus - Taenia spp. – Hydatid cyst - Echinococcus granulosus – Alveolar hydatid cyst - E. multilocularis – Cysticercoid - Hymenolepis spp.

Important species – Taenia solium – Teania saginata – Echinococcus granulosus – Spirometra mansoni – Hymenolepis nana – Hymenolepis diminuta

Taenia solium Taenia saginata

Taenia solium GENERAL INTRODUCTION • Worldwide distribution • Large tapeworm • Larval infection of Taenia solium may cause serious clinical disease ---CYSTICERCOSIS

Morphology • Can be up to 2 to 4 meters long • It has a globular scolex with four suckers and 2 circular rows of hooks (rostellum) • The gravid proglottids are 5× 10 mm with a 7 -13 branched uterus • The eggs of T. solium and T. saginata are indistinguishable

scolex of T. solium.

eggs of Taenia solium and T. saginata The eggs are rounded or subspherical, diameter 31 - 43 µm, with a thick brown embryophore. Inside each egg is an embryonated oncosphere with 6 hooks. A complete egg always has the primary membrane (shell) that surrounds eggs.

Cysticercus

• Cyticercus - a larval tapeworm that is at a stage in which the scolex is inverted in a sac, and that is typically found encysted in the muscle tissue of the host.

Life cycle of T. solium

Main points of the life cycle • Man is the only definitive host, but he can also be the intermediate host for T. solium • Pig is the important intermediate host for T. solium • Adult worm reside in the lumen of the upper part of small intestine • The infective stage to man are both egg/gravid proglottid and cysticercus for T. solium

• A tapeworm larval cyst (cysticercus) is ingested with poorly cooked rice-like meat • The larva escapes the cyst and passes to the small intestine where it attaches to the mucosa by the scolex suckers • The proglottids develop as the worm matures in 3 to 4 months

Main points of the life cycle • The adult may live in the small intestine as long as 25 years and pass gravid proglottids with the feces • When eggs consumed by pigs in which they hatch and form cysticerci • T. solium eggs can also infect humans and cause cysticercosis (larval cysts in lung, liver, eye, maxillofacial region and brain)

Pathogenesis and clinical features • Adult worm —Taeniasis – Light infections remain asymptomatic – Heavier infections may produce abdominal discomfort, epigastric pain, vomiting and diarrhea

• Metacestode stage –Cysticercosis – The cysticercus stage of T. solium can be found anywhere in the body -- subcutaneous, muscles, eye, brain – Regardless of the tissue affected, pathological consequences are those of a space-occupying lesion – Cysticerci in brain tend to grow a larger size than those in other tissues – The process of calcification may be accompanied by the release of antigens -- inflammatory reaction

Cysticercosis • The incidence of cerebral cysticercosis can be as high 1 per 1000 population and may account for up to 20% of neurological case in some countries (e. g. , Mexico); cysticercosis ocular involvement occurs in about 2. 5% of patients and muscular involvement is as high as 10% (India).

Cysticercus on the eyeground subcutaneous nodules pseudohypertrophy of muscle

Cysticerci in brain

Cysticerci in heart

Cysticerci in tongue

DIAGNOSIS • For adult worm infection (Teaniasis) ＊ History of eating raw pork ＊ Find gravid proglottids in feces ＊ Perianal swab to find eggs

• For cysticercosis ＊ Specific diagnosis is difficult to establish, the history and adult worm infection attribute to strong suspicion ＊ Biopsy to subcutaneous lesions ＊ Computerized axial tomography or magnetic resonance imaging ＊ Serological examination for specific antibody

Epidemiological distribution World-wide distribution. Epidemic in central and south America (Mexico), Africa, South-east Asia, eastern Europe, Micronesia. High prevenlence Medium prevelence Low or no prevelence Epidemic limited area Data unavialable

PRINCIPLES OF CONTROL • Treat all patients to eradicate the source of larvae parasitism Pumpkin seed and areca nut ; Praziquantel • Avoid the fecal contamination of pig feed • Modernization of raising pigs • Pay attention to personal and food hygiene • Intensive examination of the pork • Adequate cooking or freezing of meat are effective precautions – cysticerci do not survive at temperatures below -10℃ and above 50 ℃.

Teania saginata v v Can be up to 4 to 8 meters long The scolex with four suckers The gravid proglottids with a 15 -30 branched uterus The eggs of T. solium and T. saginata are indistinguishable

gravid proglottid of T. solium gravid proglottid of T. saginata

LIFE CYCLE

LIFE CYCLE • Human is the only definitive host, cattle is the intermediate host • Adult worm reside in the lumen of the upper part small intestine • The infective stage to man is larva • No cysticercus in human

PATHOGENESIS • The adult parasite induces some host reaction • The process of calcification may be accompanied by the release of antigens -- inflammatory reaction

DIAGNOSIS • For adult worm infection Find gravid proglottids in feces

DISTRIBUTION • T. saginata is prevalent in regions where cattle are raised: Africa, Middle-East, Central and South America, Europe and Asia.

PRINCIPLES OF CONTROL • Treat the patients --Pumpkin seed and areca nut; Praziquantel • Modernization of raising cattle • Intensive examination of the beef

COMPARISON OF THE TWO TAPEWORMS T. solium T. saginata Size 2 -4 m 4 -8 m Scolex Rostellum & hooks No Mature Proglottid 3 lobes of ovary Gravid proglottid Intermediate Host Uterine Branches<13 2 lobes of ovary >15 Swine & Human Cattle Disease caused Infective stage Diagnosis Clinical significance Taeniasis & cysticercosis Taeniasis only Cysticercus Only Much more important Perianal egg exam Less than T. solium Chemotherapy Should be instant Not so urgent Egg & Cysticercus Egg may be found in stool