cestodes 60 (1).pptx

cestodes Lecturer Liliana Tskitishvili  Introduction. General Character istics (Greek kestos-girdle or ribbon) are multisegmented Cestodes , dorsoventrally flattened tape -like worms whose sizes vary from a few milli-meters to several meters. The adult worms are found in the small i...

cestodes Lecturer Liliana Tskitishvili  Introduction. General Character istics (Greek kestos-girdle or ribbon) are multisegmented Cestodes , dorsoventrally flattened tape -like worms whose sizes vary from a few milli-meters to several meters. The adult worms are found in the small intestine of humans. Classification of Cestodes Cestodes belong to Phylum Platyhelminthes and class Cestoidea. The class Cestoidea includes 2 orders: Pseudophyllidea Cyclophyllidea Introduction. General Character istics Adult Worms consists of 3 parts: Head (scolex) Neck Trunk (strobila) Tapeworm. A. Scolex or head; B. Neck, leading to the region of growth below, showing immature segments; C. Mature segments; D. Gravid segments filled with eggs Head (Scolex) It is the organ of attachment to the intestinal mucosa of the definitive host, human or animal. In parasites of the order Cyclophyllidea, the scolex possesses four suckers (or a cetabula). In some Cyclophyllidea like Taenia solium, scolex has an apical protrusion called as the rostellum. The rostellum may or may not be armed with hooks. Neck It is the part, immediately behind the head and is the region of growth from where the segments of the body (proglottids) are being generated continuously. Trunk (Strobila) The trunk also called as strobila is composed of a chain of proglottids or segments. The proglottids near the neck, are the young immature segments, behind them are the mature segments, and at the hind end, are the gravid segments. Tapeworms are hermaphrodites (monoecious) and every mature segment contains both male and female sex organs. In the immature segments, the reproductive organs are not well-developed. They are well-developed in the mature segments.The gravid segments are completely occupied by the uterus filled with eggs. Tapeworms do not have a body cavity or alimentary canal. Rudimentary excretory and nervous systems are present. The embryo inside the egg is called the oncosphere (meaning hooked ball) because it is spherical and has hooklets. Oncospheres of human tapeworms typically have three pairs of hooklets and so, are called hexacanth (meaning six- hooked) embryos Life Cycle Cestodes complete their life cycle in 2 hosts: definitive host intermediate host. Humans are the definitive host for most tapeworms, which cause human infection. An important exception is the dog tapeworm, Echinococcus granulosus, for which dog is the definitive host and man is the intermediate host. In Taenia solium, man is ordinarily the definitive host, but its larval stages also can develop in the human body. CYCLOPHYLLIDEAN TAPEWORMS Taenia saginata ­Beef tapeworm Taenia solium ­Pork tapeworm History and Distribution Tania (Greek word meaning tape or band). In 1782 Goeze differentiated T. solium and T. saginata. Life cycle of T. saginata →Leuckart (1861).  T. saginata is worldwide in distribution, but the infection is not found in vegetarians and those who do not eat beef.  T. solium is also worldwide in distribution except in the countries and communities, which proscribe pork as taboo.  Higher rates of illness have been seen in people in Latin America, Eastern Europe, sub-Saharan Africa, India, and Asia. Infections with T. saginata occur wherever contaminated raw beef is eaten, particularly in Eastern Europe, Russia, eastern Africa and Latin  Taenia Saginata and Taenia Eggs: Solium Eggs of both species are indistinguishable. The egg is spherical, measuring 30-40 um in diameter. It has a thin hyaline embryonic membrane around it, which soon disappears after release. The inner embryophore is radially striated and is yellow brown due to bile staining. In the center is a fully-developed embryo (oncosphere) with three pairs of hooklets (hexacanth embryo). The eggs do not float in saturated salt solution. Larva: The larval stage of Tania is called as cysticercus. Cysticercus bovis is the larva of T. saginata. Cysticercus cellulosae is the larva of T. solium.  HABITAT: Adult worms lives in the small intestine , Taenia saginata Taenia solium commonly in Jejunum Moves Eggs– Infective to both pig and against Eggs –– Infective only to cattle man. the peristaltic  Larva Taenia Saginata Cysticercus bovis-It is the larval form of T. saginata. The name cysticercus in derived from the Greek, kystis bladder and kerkos-tail. The larva (cysticercus bovis) is infective stage for humans. The cysticercus is an ovoid, milky-white opalescent fluid filled vesicle measuring about 5 mm x 10 mm in diameter, and contains a single invaginated scolex (bladder worm). The cysticerci are found in the muscles of mastication, cardiac muscles, diaphragm and tongue of infected cattle. Cysticercus bovis is unknown in humans. They can be seen on visual inspection as shiny white dots in the infected beef (measly beef).  Larva Taenia Solium Cysticercus cellulosae-It is the larval form of T. solium and also the infective form in of the parasite. It can develop in various organs of pig as well as in man. The cysticercus cellulose or "bladder worm" is→ Ovoid opalescent milky-white, Measuring 8-10 mm in breadth and 5 mm in length. The scolex of the larva, with its suckers, lies invaginated within the bladder and can be seen as a thick white spot. It remains viable for several months. Taenia Saginata and Taenia Solium Intestinal taeniasis: It can be caused by both T. saginata and T. solium. The adult worm, in spite of its large size, causes surprisingly little inconvenience to the patient. When the infection is symptomatic Vague abdominal discomfort, Indigestion, Nausea, diarrhea and Weight loss may be present. Occasional cases of Acute intestinal obstruction, Acute appendicitis and Pancreatitis have also been reported.  Cysticercosis: It is caused by larval stage (cysticercus cellulosae) of T. solium. Cysticercus cellulosae may be solitary or more often multiple. Any organ or tissue may be involved, the most common being subcutaneous tissues and muscles. It may also affect the eyes, brain, and less often the heart, liver, lungs, abdominal cavity and spinal cord. The larvae evoke a cellular reaction starting with infiltration of neutrophils, eosinophils, lymphocytes, plasma cells, and at times, giant cells. This is followed by fibrosis and death of the larva with eventual calcification. The clinical features depend on the site affected: Subcutaneous nodules are mostly asymptomatic. Muscular cysticercosis may cause acute myositis. Cysticercosis: Taenia Solium Ocular cysticercosis, cysts are found in vitreous humor, subretinal space and conjunctiva. The condition may present as Blurred vision or loss of vision, Iritis, Uveitis, Palpebral conjunctivitis  Neurocysticercosis Neurocysticercosis (cysticercosis of brain) is the most common and most serious form of cysticercosis. About 70% of adult-onset epilepsy is due to neurocysticercosis It is considered as the second most common cause of intracranial space occupying lesion (ICSOL) after tuberculosis in India Other clinical features of Neurocysticercosis are Increased intracranial tension, Hydrocephalus, Psychiatric disturbances, Meningoencephalitis, Transient paresis, Behavioral disorders, Aphasia and Visual disturbances. Taenia Saginata and Taenia Solium Laboratory Diagnosis Stool examination: Eggs:→ Microscopic examination of feces shows characteristic eggs of Tania in 20- 80% of patients. Formol-ether sedimentation method of stool concentration is useful. Eggs can also be detected by cellophane swab method (NIH swab) in 85-95% patients. Species identification cannot be made from the eggs, since the eggs of T. saginata and T. solium are similar. Proglottids: → Species identification can be done by examining with hand lens. Gravid proglottid pressed between two slides, when branching can be made out (15-20 lateral branches in T. saginata; under 13 in T. solium). Taenia Saginata and Taenia Solium Scolex: Definitive diagnosis can also be established by demonstration of unarmed scolex in case of T. saginata after anthelmintic treatment. Detection of Taenia antigen in feces: Antigen capture enzyme-linked immunosorbent assay (ELISA) using polyclonal antisera against Tania are employed to detect coproantigen in feces since 1990 and is more sensitive than microscopy (specificity 100% and sensitivity 98%). The drawback of the test is that it cannot differentiate between T. saginata and T. solium. Taenia Saginata and Taenia Solium Serodiagnosis: Specific antibodies to adult stage antigen in serum can be demonstrated by ELISA, indirect immunofluorescence test and indirect hemagglutination (IHA) test. Molecular diagnosis: Both deoxytibonucleic acid (DNA) probes and polymerase chain reaction (PCR) technique are used to detect and differentiate between eggs and proglottids of T. saginata and T. solium. It can also differentiate between the two subspecies of T. saginata, viz. T. saginata saginata and T. saginata asiatica.  Taenia Saginata and Taenia Solium Diagnosis of cysticercosis is based on the following: Biopsy: Definitive diagnosis of cysticercosis is by biopsy of the lesion and its microscopic examination to show the invaginated scolex with suckers and hooks. Imaging methods: X-ray: Calcified cysticerci can be detected by radiography of subcutaneous tissue and muscles particularly in the buttocks and thigh. X-ray of the skull may demonstrate cerebral calcified cyst. Computed tomography (CT) scan of brain is the best method for detecting dead calcified cysts. Taenia Saginata and Taenia Solium The cysticercal lesions appear as small hypodensities (ring or disk-like) with a bright central spot. Magnetic resonance imaging (MRI) scan of the brain is more helpful in detection of noncalcified cysts and ventricular cysts. It also demonstrates spinal cysticerci. Taenia Saginata and Taenia Solium Intestinal taeniasis: Single dose of praziquantel (10-20 mg/ kg) is the drug of choice. Niclosamide (2 g), single dose, is another effective drug. Purgation is not considered necessary. Cysticercosis: Excision is the best method, wherever possible. For symptomatic cerebral cysticercosis, praziquantel in a dose of 50 mg/kg in three divided doses for 20-30 days and albendazole in a dose of 400 mg twice daily for 30 days may be administered. Corticosteroids may be given along with praziquantel or albendazole to reduce the inflammatory reactions caused by the dead cysticerc Echinococcus spp Echinococcus causes hydatid disease. There are four species of Echinococcus known to infect humans. 1. E. granulosus: Causes cystic hydatid disease 2. E. multilocularis: Causes alveolar hydatid disease 3. E. vogeli and E. oligarthrus : Cause polycystic hydatid disease. Echinococcus Granulosus. Dog Tape Worm History and Distribution Hydatid cysts had been described by Hippocrates and other ancient physicians. Adult E. granulosus→Hartmann (1695). Larval form (Hydatid cysts) → Goeze (1782). The disease is prevalent in most parts of the world, though it is most extensive in the sheep and cattle- raising areas of Australia, Africa and South America. It is also common in Europe, China and the Middle East. It is a significant health problem in India. It is seen more often in temperate than in tropical regions. Echinococcus Granulosus. Dog Tape Worm Habitat. The adult worm lives in the jejunum and duodenum of dogs and other canine carnivora (wolf and fox). The larval stage (hydatid cyst) is found in humans and herbivorous animals (sheep, goat, cattle and horse). Morphology Adult worm: It is a small tapeworm, measuring only 3-6 mm in length. It consists of a scolex, a short neck and strobila. Scolex Pyriform, with four suckers and a prominent rostellum bearing two circular rows of hooklets Echinococcus Granulosus. Dog Tape Worm The neck is short than the rest of the worm (3 mm x 6 mm). The strobila is composed of only three proglottids: (1) the anterior immature, (2) the middle mature and (3) the posterior gravid segment. The terminal proglottid is longer and wider than the rest of the worm and contains a branched uterus filled with eggs. The adult worm lives for 6-30 months. Egg: The eggs of Echinococcus are indistinguishable from those of Tania species. It is ovoid in shape and brown in color. It contains an embryo with three pairs of hooklets. Echinococcus Granulosus.Dog Tape Worm Sheep is the ideal intermediate host. Man acts as an accidental intermediate host (dead end). The larval stage of the parasite is passed in intermediate hosts, including man, giving rise to hydatid cyst. The adult worm lives in the small intestine of dogs and other canine animals. These animals discharge numerous eggs in the feces. Intermediate hosts (sheep and cattle) ingest them while grazing. Human infection follows ingestion of the eggs due to intimate handling of infected dogs or by eating raw vegetables or other food items contaminated with dog feces. - Life Cycle of Echinococcus granulosus its life cycle in 2 hosts Definitive host: Dog (optimal host), wolf, jackal, and fox Intermediate host: Sheep and Cattle. Sheep is the ideal intermediate host.  Echinococcus Granulosus. Dog Tape Worm The ova ingested by man or by sheep and cattle are liberated from the chitinous wall by gastric juice liberating the hexacanth embryos It penetrate the intestinal wall and enter the portal venules, to be carried to the liver along the portal circulation. These are trapped in hepatic sinusoids, where they eventually develop into hydatid cyst. About 75% of hydatid cyst develops in liver, which acts as the first filter for embryo. Echinococcus Granulosus. Dog Tape Worm However, some embryo which pass through the liver, enter the right side of heart and are caught in pulmonary capillaries (forming pulmonary hydatid cysts), so that the lung acts as the second filter. Echinococcus Granulosus. Dog Tape Worm A few enter the systemic circulation and get lodged in various other organs and tissues such as the spleen, kidneys, eyes, brain, or bones. When sheep or cattle harboring hydatid cysts die or are slaughtered, dogs may feed on the carcass or offal. Inside the intestine of dogs, the scolices develop into the adult worms that mature in about 6-7 weeks and produce eggs to repeat the life cycle. When infection occurs in humans accidentally, the cycle comes to a dead end because the human hydatid cysts are unlikely to be eaten by dogs. Echinococcus Granulosus. Dog Tape Worm Pathogenesis Evolution of hydatid cyst: At the site of deposition, the embryo slowly develops into a hollow bladder or cyst filled with fluid. This becomes the hydatid cyst (Greek hydatis: a drop of water). It enlarges slowly and reaches a diameter of 0.5-1 cm in about 6 months. The growing cyst evokes host tissue reaction leading to the deposition of fibrous capsule around it. The cyst wall secreted by the embryo consists of three indistinguishable layers. Echinococcus Granulosus.1.Dog Tape Worm Pericyst. Outer host inflammatory reaction consisting of fibroblastic proliferation, mononuclear cells, eosinophils and giants cells, eventually developing into dense fibrous capsule which may even calcify 2. Ectocyst→ Intermediate layer composed of characteristic a cellular, chitinous, laminated hyaline material. It has the appearance of the white of a hard boiled egg. 3. Endocyst → Inner germinal layer which is cellular and consists of number of nuclei embedded in a protoplasmic mass and is extremely thin (22-25 um). The germinal layer is the vital layer of the cyst and is the site of asexual reproduction giving rise to brood capsules with scolices. It also secretes hydatid fluid, which fills the cyst. Echinococcus Granulosus. Dog Tape Worm hydatid fluid Composition→ It contains salts (sodium chloride 0.5%, sodium sulfate, sodium phosphate, and salts of succinic acid) and proteins. It is antigenic and highly toxic so that its liberation into circulation gives rise to pronounced eosinophilia or may even cause anaphylaxis The fluid was used as the antigen for Casoni’s intradermal test. A granular deposit or hydatid sand is found at the bottom of the cyst, consisting of free brood capsules and protoscolices and loose hooklets. Echinococcus Granulosus. Dog Tape Worm Brood capsules→ From the germinal layer, small knob-like excrescences or gemmules protrude into the lumen of the cyst. These enlarge, become vacuolated, and are filled with fluid. These are called as brood capsules Echinococcus Granulosus.Dog Tape Worm. They are initially attached to the germinal layer by a stalk, but later escape free into the fluld-filled cyst cavity. From the inner wall of the brood capsules, protoscolices (new larvae) develop, which represent the head of the potential worm, complete with invaginated scolex, bearing suckers and hooklets. Several thousands of protoscolices develop into a mature hydatid cyst, so that this represents an asexual reproduction of great magnitude. Inside mature hydatid cysts, further generation of cyst, daughter cysts and granddaughter cysts may develop. The cyst grows slowly often taking 20 years or more to become big enough to cause clinical illness and is therefore, particularly seen in man Echinococcus Granulosus. Acephalocysts→ Dog TapeSome Worm cysts are sterile and may never produce brood capsules, while some brood capsule may not produce scolices. These are called acephalocysts. Fate of hydatid cysts → The cyst may get calcified or spontaneously evacuated following inflammatory reaction. Hydatid cyst of liver may rupture into lung or other body cavity producing disseminated hydatid lesions. Clinical Features → Most of the times infection is symptomatic and accidentally discovered. Clinical disease develops only when the hydatid cyst has grown big enough to cause obstructive symptoms → pressure effects caused by the enlarging cysts. In about half the cases, the primary hydatid cyst occurs in liver (63%), mostly in the right lobe. Echinococcus Granulosus. Dog Tape Worm. Hepatomegaly, pain and obstructive jaundice are the usual manifestations. The next common site is the lung (25%) (most common being the lower lobe of the right lung). Cough, hemoptysis, chest pain, pneumothorax and dyspnea constitute the clinical picture. In the kidney (2%), hydatid cyst causes pain and hematuria. Other sites affected include spleen (1%), brain (1%), pelvic organs, orbit and bones (3%). Cerebral hydatid cysts may present as focal epilepsy. Echinococcus Granulosus. Dog Tape Worm Hydatid cyst inside the bones, the laminated layer is not well- developed because of confinement by dense osseous tissues. The parasite migrates along the bony canals as naked excrescences that erode the bone tissue. This is called osseous hydatid cyst. Erosion of bone may lead to pathological fractures. Echinococcus Granulosus. Dog Tape Worm Apart from pressure effects, another pathogenic mechanism in hydatid disease is hypersensitivity to the echinococcal antigen. The host is sensitized to the antigen by minute amounts of hydatid fluid seeping through the capsule. Hypersensitivity may cause urticaria. But if a hydatid cyst ruptures spontaneously or during surgical interference, massive release of hydatid fluid may cause severe, even fatal anaphylaxis Echinococcus Granulosus. Laboratory Diagnosis Imaging→ Ultrasonography (USG), CT scan and MRI reveal the diagnosis in most cases of cystic echinococcosis. Ultrasonography is the diagnostic procedure of choice. Cyst wall typically shows double echogenic lines separated by a hypochoic layer (double contour). Pathogenic findings include daughter cysts and the "water-lily" sign due to detached endocyst floating within the cavity. Computed tomography scan is superior for the detection of extrahepatic disease. Magnetic resonance imaging→ especially at difficult sites such as spinal vertebrae and cardiac cyst  Echinococcus Granulosus. Dog Tape Worm. Plain X-rays permit the detection of hydatid cyst in lung and bones. In cases where long bones are involved, a mottled appearance is seen in the skiagram. Intravenous (V) pyelogram is often helpful for detection of renal hydatid cyst. Examination of cyst fluid Examination of aspirated cyst fluid under microscope after trichome staining reveals scolices, brood capsules and hooklets. Exploratory puncture of the cyst to obtain cystic fluid should be avoided as it may cause escape of hydatid fluid and consequent anaphylaxis. Therefore, fluid aspirated from surgically removed cyst should only be examined. Echinococcus Granulosus.Casoni's Dog Tape intradermal test Worm It is an immediate hypersensitivity (Type 1) skin test introduced by Casoni in 1911, using fresh sterile hydatid fluid. The antigen in hydatid fluid is collected from animal or human cysts and is sterilized by Seitz or membrane filtration. The fluid is injected (0.2 mL) intradermally in one arm and an equal volume of saline as control is injected in the other arm. In a positive reaction, a large wheal of about 5 cm in diameter with multiple pseudopodia like projections appears within half an hour at the test side and fades in about an hour. A secondary reaction consisting of edema and induration appears after 8 hours. The test is almost abandoned now due to nonspecificity and has been supplemented by serological tests. Echinococcus Granulosus.Dog Tape Worm Antibody detection Detection of serum antibodies using specific antigens (8 and 16 kDa) from hydatid fluid are frequently used to support the clinical diagnosis of cystic echinococcosis. The tests include indirect hemagglutination (IHA), indirect immunofluorescence and ELISA. In hepatic cysts, the sensitivity of test is relatively superior (85-98%) than pulmonary cyst (50-60%), The slide latex agglutination test and immune electrophoresis using hydatid fluid fraction 5 antigen are also widely used. Precipitin test and complement fixation test (CFT) with hydatid antigen have also been found to be positive  Echinococcus Granulosus. Dog Tape Worm. CFT is not very sensitive and false-positive reaction is seen in those receiving neural antirabic vaccine. CFT is useful after surgical removal of cysts, when a negative test has a better prognostic value. Antigen detection→ Specific echinococcal antigen in sera and in CSF can be detected by double diffusion and counter immunoelectrophoresis (CIEP) technique. Blood examination → It may reveal a generalized eosinophilia of 20-25%. Excretion of the scolices → Excretion of scolices into the sputum or urine may be observed in pulmonary or renal cyst, respectively and can be demonstrated by acid-fast staining or lactophenol cotton blue (LPCB) staining. Specific molecular diagnostic → Specific molecular diagnostic methods have been developed involving DNA probes and PCR, but their application is limited by their technical complexity Echinococcus Granulosus.Dog Tape Worm Traditionally surgical removal was considered as the best mode of treatment of cysts. Currently, ultrasound staging is recommended and management depends on the stage. In early stages, the treatment of choice is puncture, aspiration, injection and respiration (PAIR). The basic steps involved in PAIR include→ Ultrasound or CT-guided puncture of the cyst. Aspiration of cyst fluid. Infusion of scolicidal agent (usually 95% ethanol; alternatively, hypertonic saline). Respiration of the fluid after 5 minutes Echinococcus Granulosus.Dog Tape Worm Great care is taken to avoid spillage and cavities are sterilized with 0.5% silver nitrate or 2.7% sodium chloride for prophylaxis of secondary peritoneal echinococcosis due to inadvertent spillage of fluid during PAIR. Albendazole (15 mg/kg in two divided doses) is initiated 4 days before the procedure and continued for 4 weeks afterwards. Surgery It is the treatment of choice for complicated E. granulosus cysts like those communicating with the biliary tract and in those cysts where PAIR is not possible The preferred surgical approach is pericystectomy. For pulmonary cyst, treatment consists of wedge resection or lobectomy. Recurrence after surgery is common Echinococcus Granulosus. Dog Tape Worm Pre and postoperative chemotherapy with albendazole for 2 years after curative surgery is recommended. Positron emission tomography (PET) scanning can be used to follow disease activity. Other new treatment modalities include laparoscopic hydatid liver surgery and percutaneous thermal ablation (PTA) of the germinal layer of the cyst using radiofrequency ablation device. Prophylaxis Personal hygiene including avoidance of close contact with dogs. - Control in movement of dogs. - General health Education. - Not allowing the dogs to eat carcasses of slaughtered animals in endemic areas.