Unit 3: Helminthes (Cestodes)

Transcription

1 Lecture Order Cyclophyllidea In the gravid segment the uterus consist of central longitudinal stem with lateral branches on each side which intern sub branch. Taenia saginata Synonyms: Beef tapeworm, Taeniarhynchus saginata. Disease: Taeniasis saginata. Habitat: Adult tapeworm is attached to the wall of small intestine of man. It is white tape like warm adult worm 5 meters long with OOO- proglottids. Scolex: pyriform with 4 muscular suckers, no rostellum, no hooks, there is a slight apical depression (unarmed tape worms). The terminal proglottid become separated singly or in small groups and pass out with the stool. Egg are liberated by rupture of the ripe proglottid 80,000 eggs in single proglottid, infected person can discharge about 500,000 egg /day. Egg: spherical 31 to 43 µm in diameter have thin transparent outer, embryonal envelope.and thick brown shell, composed of many slender rodes cemented together, within the shell is a hexacanth embryo, which has 3 pairs of lancet shaped hooklets. Life Cycle Strobila: neck, lmmature proglottids, mature prohglottidds, about 12 mm in width with a full set of male and female reproductive organs. Male & Female Reproductive organs: Ovary, bilobed, vagina, ootype, vitellaria, behind the ovaries, blind uterus. Testes, follicle, vasa efferentia coiled vas deferense, cirrus, genital pore on the lateral margin of the segment. The genital pore on the lateral margin of the segment alternate irregularly between the right & left margins. As the segments move towards the posterior end of the worm, they become more elongated & narrower (gravid.seg.) Cysticercus bovis: Oval, elliptical in shape which measures 5 by 10 mm and head likes the adult worm, invaginated into fluid filled bladder., Measly beef: meat that contain cysticercus bovis 57

2 Pathogenesis and symptomatology: Infection with adult T.saginata is without symptoms Abdominal discomfort Diarrhea alternate with constipation. Anorexia, hunger pain. Intestinal obstruction (rarely) Demonstration of proglottid or egg in faeces. Serodiagnosis: IHA, IFA, ElISA. Adhesive cellophane tape technique. Taenia Solium Pork tape worm, armed tape worm, Disease: Taeniasis solium, pork, tapewarm infection. Habitat: small intestine of man. 2-3 meters in length, fewer than 1000 proglottid. Scolex: Globular in shape, 4 suckers, of alternating large and small hooks 22 to36 in number and measuring 140 to 200 µm and 100 to 150-µm long. Niclosamide- praziquantel quinacrine hydrochloride Cattle acquire the larval stage of T.saginata by grazing on moist pasture contaminated with faeces or sewage containing egg EGG remains viable for 2 months in natural condition and for 6 months under optimal condition of moisture & temp. Man is the only natural definitive host of saginata. Man acquires the infection by eating uncooked or under cooked beef containing cysticerci. 1) Proper disposal of human faeces 2) Workers at cattle feed lots examined periodically for sign of infection. 3) Thorough cooking of beef before consumption, heating the meat to 65 degree centigrates is a safe guard. 4) Freezing the beef at -20 degree centigrates for 24 hours or longer kill the cysticerci. Mature proglottids: are wider than long and nearly identical to those of T.saginata, Testes follicles. Gravid Segments: longer than wide, have a uterus, the medial stem with 9 to 10 lateral branches. Eggs: are morphologically similar to that of T.saginata Life cycle 58

3 Cysticercus cellulosae: Pearly white, measuring 5 mm by 8 to 10 mm, the scolex deeply invaginated into fluid filled bladder is provided with 4 suckers and a rostellr as in adult is provided with 4 suckers and a rostellum as in adult worm. Measley pork: pork containing cysticercus cellulosae. Pathogenesis and symptomatology: Infectin with the adult T.solium produce the same clinical manifestations as infection with T.saginata. However, no intestinual obstruction. Similar to that of T.saginata Niclosamide, Praziquantel are the drug of choice However Niclosamide is not recommended causes the proglottids to disintegrate releasing the eggs to the bowel lumen. Human infection with adult T. solium results from eating raw pork containing Cysticercus cellulosae. Man is the only natural host of the adult worm. Man is also a suitable host for the cysticercus. Sanitary disposal of human faeces, Treatment of infected person, Thorough cooking of pork or held in a deep freeze for at least 24 hrs. Hymenolepis nana Common name: Dwarf tape worm Synonyms: Vampirolepis nana Disease: Hymenolepiasis nana, Dwarf tape worm infection. Hymenolepiasis nana is an infection by adult and larval stage of H. nana. It is found warld wide, primarily limited to children in warm climate. Small 25 to 4o mm in length, 1 mm in breadth Scolex: Small, globular with short rectactile rostellum, 4 sucker s and a single ring of 2o to 3o minute hooklets Strobila: 2oo segments, broader than long Mature proglottids: single genital pore on one side of segment There are 3 round testes lie in the posterior part of each segment, Bilobed ovary lie posteriorly between the testes with compact vitelline gland behind. Gravid uterus forms a sac filled with eggs. Gravid segment destroyed in the intestine releasing the eggs which are found in faeces. Egg: nearly spherical 3o _ 47 µ m in diameter. with two thin membranous shell s. The inner one with 2 polar thickenings, each provided with 4 to 8 long thread like filaments extending into the space between the inner and outer shells. The centrally located hexacanth embryo is equipped with 3 pairs of hooklets 59

4 Life Cycle Hymenolepis dimenuta Common name: Rat tape worm infection Habitat: in the small intestine of Rat and mice and rarely in Human. 2o-6O Cm in length by 3.5 to 4.o mm in width, with 1,ooo proglottids Scolex: o.4 mm wide with 4 suckers and retractable and un armed rostellum. Proglottids as in H.Nana. Egg: Ovoid to sub spherical 72 to 86 µm by 6o to 79 µm with a space between the outer tanned egg membrane and the hyaline inner membrane which provided with a pair of pollar thickenings but lack the polar filaments. Pathogenesis and symptomatology: Infection with H. nana produces No symptoms in light infection or may be diarrhea, anorexia, vomiting, loss of weight, pruritus of the nose and anus, urticaria. Heavy infection causes diarrhea, abdominal pain, anorexia and nervous disorders. Life cycle By demonstration of the egg in the stool. Niclosamide is the drug of choice in a course of 5-7 days Infection iscommonly acquired by anus to mouth transmission of eggs. (Hand, food) is more common in children. Occasional infection may occur from rodent source. a) Good personal hygiene and sanitation b) Treatment of infected person. Pathogenesis: Nonpathogenic but may produce mild diarrhea and abdominal pain. By demonstration of eggs in stool. Similar to that for H. nana 60

5 H. diminuta is worldwide in distribution. Human infection is associated with the contamination of cereals, grains by infected grain beetles. Infected fleas may transferred to the mouth by dirty hands. Life cycle 1) Eradication of rat around the home. 2) Protection of food such as grain and cereals from rat dropping and from insect. Dipylidium caninum Common name: Dog / cat tape worm Disease: Dipylidiasis, dog tape worm infection Habitat: Adult in the small intestine of dogs and cats. Occasionally in human mostly in children, infants. Adult median size 1o _ 7o cm in length, 6o_17o proglottids. Scolex: rhomboidal in shape, o.3_ o.5 mm in diameter, 4 suckers, introversible apical club _shape proboscis with 6 rows of minute hooklets. Mature proglottids: Contain paired reproductive organs with a genital pore at each lateral margin. Gravid proglottids: Resemble cucumber seeds in shape, size. Uterus disappear early in development and replaced by hyaline, non-cellular masses of egg capsules, each egg capsule filled with 1 to 2 o fully embryonated eggs. Egg: 3o_ 6o µm in diameter consist of typical 6 hooked oncosphere. Pathogenesis: In a child may produce diarrhea, unrest, sometimes urticaria, fever, eosinophilia and rarely convulsion. Based on recovery of egg packets or gravid segment in stool. Niclosamide, praziquantel, quanacrine hydrochloride. Human infection especially children occur upon ingestion of the fleas intermediate host, by licking of an infected dog or cat or by hand to mouth contamination 1) Infected dogs and cats should be treated. 2) Children should be taught not to let dogs or cats lick them in their mouth. 61

6 Larval tape worm infection The majority of adult tape worm parasitize the small intestine of human.the larval stage (meta cestode) and several spp.of tape worm develop in the extra intestinal tissue of human (somatic tape worm) namely cysticercus of T.solium,coenurus of T.multiceps,hydatid cyst of Echinococcus granulosus and sparganum (plerocercoid) of spirometra spp. Sparganosis: The plerocercoid larvae or spargana of spieces of pseudophyllidea.tape worm may infect human & cause sparganosis. Most of spargana reported in human are believed to be " spirometra mansoni " and other spieces. Cats,dogs and related wild animals are definitive host Copepods Cyclops being the 1 st intermediate host Several spp.of vertebrates, fish, frog &snakes as 2 nd intermediate host. Human infection occurs by swallowing a procercoid in a copepod or a plerocercoid in 2 nd int.host. Life cycle: the life cycle of Spirometra species follows the same pattern as that of Diphyllobothrium sp. Pathogenesis & Symptomatology: Little host tissue reaction occurs in the early stages later in the infection, the area around the worm become edematous & painful to the touch. Death of the parasite result in marked inflammation with local eosinophilia and charcot leyden crystal. Ocular sparganosis: intense pain, irritation, excessive lacrymation & edema. 1) Biopsy: typical worm structure can be seen by biopsy (subcutaneous cyst). 2) Speices.diagnosis: can be made by feading a living sparganum to cat or dog and subsequentelly examinating the adult worm. 3) Serodiagnosis: a. Indirect IF Ab test. b. agar gel diffusion c. Indirect haemagglutination test Consist of surgical removal of the sparganum from the tissue. Infection about the eye treated with injection of 2-4 ml of 4% ethyl alcohol with procaine (epinephrine free). Man becomes infected by: 1) Swallowing infected Cyclops in drinking water from pond, stream, lake). 2) Eating raw infected frog, snakes, small mammals. 3) Applying plerocercoid infected flesh of frog or snakes for treatment of inflamed eye or finger In such case, larvae migrate into human tissue and encysted in various parts of the body. 4) human infection is also acquired from eating raw pork as sparganum develop also in pigs 1) drinking only safe waer 2) Eating only well-cooked flesh of animals. 62

7 Cysticercosis: Is an infection by the larval stage of T.solium, the pork tape worm refered to as cysticercous cellulosae Man is the definitive host. Pig is the intermediate host in which the hexacanth embryo hatch from egg and develop into cysticercus cellulosae or bladder worm. Man is also satisfactory host for development of this larvae.so man may serve as intermediate host when egg is ingested by mouth, hatch in the small intestine, liberated oncosphere burrow into the mucosal circulation & carried to different organs & tissues producing (human cysticercosis) The fully developed cysticercus is a small ovoid,smooth bladder or cyst filled with fluid & measure 5 mm x 10 mm in size,developed from the inner wall is single invaginated scolex with 4 sucker & a double circular crown of hooks (9-10weeks to develops) Dead cysicercus possess a cloudy fluid and yellowish color scolex. Racemose Cysticercus: This type is unencapsulated larva with numerous branches reaching length of 15cm.It is only seen in CNS mainly in the ventricular and subarachnoid spaces at the base of the brain. Pathogenesis: The most common location of cysticerci inhuman body is the CNS followed by muscle, subcutaneous tissues, eye, lung, heart, liver and other visceral location. Cysticerci survive in man for 4 to 5 years The clinical feature depends on their location and the number. Except in the brain and eye, live cysticerci are surrounded by a tough adventitious. Cysticerci in human are surrounded by a tough adventitious capsule which allow them to be detached easily from the surrounding tissue. Cysticerci that develop in the subcutaneous and muscle tissue cause no pain. Symptom result from the death of larvae in the visceral organs.with the death of the parasite cyst capsule distended with fluid,increase in size replaced by fibrous tissue or undergo calcification and surrounded by capsule of Connective tissues. Cysticerci in brain cause: Epileptic, seizures, hydrocephalus, stroke also severe headaches, nausea, vomiting, dizziness, diplopia and psychic changes. Living cysticerci (race mose type) in the eye cause damage to any tissue of the eye ball resulting in uveitis, iritis, detachment of the retina, atrophy of the choroid. 1) Biopsy: surgical removal of the nodule and doing histopathological examination. 2) Radiology: calcified larvae on x-ray film of muscle. ocular cyst can be detached by ophthalmoscopy. computed tomography of the brain for neurocysticercus. 3) Serological test: CFT (Complement Fixation Test), IHA haemaglutination test, ELISA, immune electrophoresis are used. using purified Ag and crude Ag ( extract of pig cysticerci) Syrgical removal of the cyst is useful in treating some ocular or cerebral cases. Chemotherapy: praziquantel following or accompanying administration of corticosteroid is effective. Human acquired infection of cysticercus by: 1) Accidental ingestion of eggs of T.solium in contaminated food or drink (heteroinfection).it is the usual mode of transfer. 2) Anus to finger to mouth contact & that called external autoinfection. 3) Internal autoinfection: gravid proglottids. in infected person with T.solium detached from strobila and regurgitated into stomach as a result of reverse peristalsis then return to the duodenum. 1) Early detection & treatment of case of T.solium. 2) Improvement in sanitation. 3) Good personal hygiene. 4) Adequate cooking as prior freezing of pork to prevent infection with the adult worm. 63

8 Hydrated disease (hydatidosis), Echinococcosis The larval stage of species of the tape worm Echinococcus is known as the hydatid cyst, several species occur in human Echinococcus granulosus Common name: dog tape worm, hydatid tape worm. Disease: unilocular hydatid disease. Geographic distribution: Echinococcus granulosus widely distributed throughout temperate and subtropical regions,commonly in sheep and cattle raising countries. Human infection is common in south America,parts of Africa and Europe,the middle east,southern Australia, New Zealand,extensive area of Asia, south western united states, Canada. Habitat : Man harbours the larval form (hydatid cyst ) specially in liver and lungs Adult worm is found in the small intestine of dog and other canines. Adult worms are small in size up to 6 mm long, Scolex: pyriform in shape, has a rostellum with 28 to 50 hooks in 2 rows and 4 suckers. Strobila: with neck,one immature,one mature and one or two gravid proglottids Mature segment: with male and female genital organ, male with testes. Gravid segment: measures more than half the total length of the whole tape worm with sac like uterus. Eggs: spherical, m in diameter,morphologically similar to those of either taeniid species of dog Outer shell surround ---- with radially striated embryophore (inner shell) Hexacanth embryo Morphology of larval stage (Hydatid cyst): Larval stage found in organs and tissues of herbivorous host such as sheep, cattle, hogs. These animals act as Intermediate host Man also becomes accidentally infected and act as intermediate host. The most common site for development of the cyst in man is liver followed by lungs (about 70% in liver and 25%in lungs) Less frequently the spleen, kidneys, heart, bones, peritoneum and CNS These are 2 morphologic types in human tissue 1-Unilocular cyst 2-Osseous 1- Unilocular hydatid cyst: Is a fluid filled cyst that is spherical in shape Cross-section of the cyst wall reveals.an external,milky white laminated membrane about 1 mm thick without nuclei and an inner germinal layer About m in thickness with nuclei. An outer layer of fibrous connective tissue is formed as a result of host reaction to the presence and growing of the cyst. From the inner germinative layer small secondary cysts develop,they are known as broad capsules and as they grow protoscolices develop from their inner wall (A protoscolex is ovoid scolex with typical 4 sucker, rostellum, a double crown of hooklets deeply with drawn into the post sucker region ) The brood capsules may detach to form daughter cysts, which with free scoleces, form hydatid sand within the cyst cavity. The majority of human hydatids are unilocular,with a size depends on the site and on its age After years it may be 15 cm in diameter or more. (Slowly growing) containing a liter or more of clear sterile hydatid fluid. Some cyst fail to develop broad capsules they become sterile cyst Multiple cysts in the liver may be the result of multiple egg infections or the formation of exogenous daughter cysts as a result of herniation of the germinative layer before the host response has resulted in a fibrous connective tissue wall. 2- Osseous hydatid: This type of hydatid cyst form in bone of man particularly the long bone and pelvic arch. Larval growth in bones is atypical the outer membranes are not produced and the organism proceeds to grow as a protoplasmic stream that erodies the cancellous tissues. 64

9 Life cycle Pathogenesis and symptomatology: Most of the hydatid cysts of the unilocular type, develop in the liver, infection of the lung is next in prevalence, the other organs also invaded occasionally An inflammatory reaction by the host results in the enveloping of the cyst by a fibrous connective tissue wall. After years.may die, shrink, calcify As the cyst grows, pressure and necrosis may result in the destruction of the normal liver tissue and impaired liver function. Leakage or rupture of the cyst causing the liberation of hydatid sand into the pleural,peritoneal or pericardial cavities and the associated dissemination of scoleces result in multiple secondary hydatid cyst formation. The antigenic stimulus from the leakage may result in anaphylactic shock marked allergic reactions with high eosinophilia. Rupture of pulmonary cyst cause chest pain, dyspnea, cough. Hydatid cyst in the brain produce increasing symptomatic evidence of an intracranial tumor. Osseous hydatid: there is minimal response on the part of the tissue,so fibrous outer layer is not produce.and there is extensive bone erosion to a stage at which fracture or crumbling suddenly occur Most infection in human begins in childhood and discovered in adult life. 1) Casoni s test (Intradermal test) Based on the principle of immediate hypersensitivity. The antigen used is hydatid fluid collected from animal or human cysts and sterilized by (seitz filter). 0.2 ml of the antigen injected intradermally on one arm--- --and 0.2 ml saline as a control on the other hand. In positive cases a large wheal about 5 cm in diameter with multiple pseudopodia appear within 1/2 hr at the test side and fades away in an hour. A delayed reaction appears after 18 to 48 hours Characterized by Oedema and indurations 5-6 cm surrounding the site of injection.anegative reaction does not exclude echinococcal infection. The test usually becomes positive 8-12 weeks after infection and remains positive after surgical removal of cyst from the patients.it is sensitive but not specific as false +ve reaction occur in many other infection like cysticercosis 2) Radiology: X-ray film demonstrate hydatid cyst in lung, bone, detect uncalcified cysts. Ultra sound, CT scan.magnetic Resonance Imaging (MRI) 3) Exploratory cyst puncture: Needle aspiration of cysts is dangerous because of possible spillage of the contents causing secondary spread or anaphylaxis. 4) Serological Tests: Based on detection of antibodies and antigen in the patient serum..useful tests include ELISA, indirect haemagglutination,latex agglutination FIAimmunoelectrophorensis test, the first 3 are highly sensitive for initial screening of serum. Specific confirmation of reactive serum can be obtained with immunoelectrophoresis to detect the diagnostic (arc 5) Cysticercosis gives cross reacting antibodies to Echinococcus antigen 5 5) Histological examination of removed specimen. Surgical removal of the cyst.is the most effective treatment. If surgical removed is not possible. Oral therapy with mebendazole is useful,in a dose of mg 3 times a day for a period of 21 to 30 days. 65

10 Human infection with hydatid cyst occur in sheep or (other herbivores) raising area. Dogs harbor the adult worms, Sheep or hogs serve as common reservoirs of the larval stage Hydatid in cattle is sterile, Exposure commonly occur in childhood among boys playing with infected dogs Hydatid may grow for 5 to 20 years before diagnoses is made. To break the E.granulosus life cycle and subsequently halt the spread of human disease several preventive measure are essential. All infected viscera should be buried or incinerated. Stray dogs should be destroyed. Domestic dogs should be periodically dewarmed Personal hygiene to avoid ingestion of the eggs. Hydatid of Echinococcus multilocularis Disease: Alveolar hydatid diseases as multiloculae hydatid disease. Habitat: Adult worm E.multilocularis occur in small intestine of foxes and other wild canines (definitive host) Natural intermediate host wild mice, in which larval form recoverd. Alveolar hydatid in man occur in USSP, Jappan and Adult: smaller than E.granulosus 1.2 to 3.3 mm long and differ in the position of the genital pore with respect to the genital organs also in the number of tests Egg: are like other taeniid egg but more resistant to cold and other environment condition. Larval form: Alveolar cyst or multiloculares cyst. The cyst grow by exogenous budding into small irregular cavities, each within a hyaline membrane, frequently without fibrous encapsulation, thus there are resultant metastases through the lymphaties and circulation. Brood capsule scattered in the cyst Scolices in the alveolar hydatid in man are few or none. Most alveolar cyst occur in the liver. Life cycle: In general life cycle is similar to that of E.granulosus. Pathogenesis and symptomatology: Liver is the most common site to be affected in the alveolar hydatid cyst.rarely in lung. It is a lethal disease. In human.intra hepatic portal hypertension results in Jaundice, ascites, splenomegaly. Biopsy. Ct scan, ultrasound helpful in ascertain the site & shape. -Immunological test. Alveolar cyst is not amenable to surgical removal. Chemotherapy with mebendazole is useful. Infection acquired from eating raw fruits and vegetable picked off the ground and contaminated with the faeces of infected foxes and other caniidae. Personal hygiene Good sanitation Sacrifice of infected animals Hydatid cyst of Echinococcus vogeli Disease: Polycystic hydatid disease. Habitat: in the small intestine of bush dog (definitive host) in latin America. Rodent, paca (natural intermediate host). Adult differs from E. granulosus in greater length mm and more slender proglottids Polycystic hydatid: is alveolar in characters but less so than that of E. multilocularis, so it is intermediate between cystic and alveolar hydatid disease, present like a mass of tumor in the liver 66