Lecture 4 Parasitology Class Cestoda-1 PDF

Welcome In Parasitology Department School of Veterinary Medicine Badr University  PARASITOLOGY Refaat Atef Ras Assistant Professor of Parasitology, Badr University Phylum: Platyhelminthes (Flatworms) Class: Cestoda (tapeworms). Tapeworms...

Welcome In Parasitology Department School of Veterinary Medicine Badr University  PARASITOLOGY Refaat Atef Ras Assistant Professor of Parasitology, Badr University Phylum: Platyhelminthes (Flatworms) Class: Cestoda (tapeworms). Tapeworms (Cestodes)  Class Cestoda (Tapeworms) - Having a tape like body with no alimentary canal. - Body segmented, each segment containing one and sometimes two set of male and female reproductive organs  Class: Cestoda Order Cyclophyllidea (True tapeworms) General Morphology - The body of the typical adult cestode consists of 3 distinct regions: A) Scolex B) Neck C) Strobila  A) Scolex - Is located at the anterior end and functions as an attachment structure - Has 4 suckers - Bears retractible or non-retractible rostellum in some species armed with one or more rows of hooks.  B) Neck - The neck is an unsegmented, poorly differentiated region immediately posterior to the scolex. - Germinative region produces "segments“ C) Strobila - Chain of segments and each segment as a proglottid (proglottis). - Each proglottid is hermaphrodite with one or two sets of reproductive organs, the genital pores usually openings on the lateral margin or margins of the segments. - The stroblia can be loosely subdivided into 3 regions: - Immature - Mature - Gravid proglottids Immature Proglottids Mature Proglottids  Gravid Proglottid - As the segment matures, internal structure largely disappears and the fully ripe or gravid segment eventually contains only remnants of branched uterus packed with eggs. - Uterus persist as a protective envelope for eggs -------- or eggs passed from it into protective envelop A) Egg capsules------→ Formed by uterus itself. B) Paruterine organ (P. U.) --------→ Families Anoplocephalidea and Davaineidae P. U. Organs may be formed by denser paranchyma near the uterus or rise as dilations of the uterus. Gravid Proglottid The Egg : - Shape: Spherical or globular. - Size: 30-40 um in diameter and brownish color. - A true Outer shell – thin and rarely seen. - A thick dark radially-striated “shell” called Embryophore. - The hexacanth (6-hooked) embryo or onchosphere. Egg Excretory system - flam cells leading to efferent canal segment - Dorsal and ventral excretory canal Nervous system - Nerve ganglia in the scolex - Nerve trunk - Nerve branches  Basic Tapeworm Life Cycle - The typical life cycle of these cestodes is indirect with one intermediate host with few exceptions, the adult tapeworm is found in the small intestine of the final host, the segments and eggs reaching the exterior in the faeces. - When the egg is ingested by the intermediate hosts the gastric and intestinal secretions digest the embryophore and activate the onchosphere. - Using its hooks it tears through the mucosa to reach the blood or lymph stream. - Once in its predilection site the onchosphere loses its hooks and develops, depending on the species, into one of the following larval stages, often known as metacestodes (intermediate stage). Basic Tapeworm Life Cycle Larval (metacestodes or intermediate stages)  Larval (metacestodes or intermediate stages) 1- Cysticercus: Fluid-filled cyst containing an attached single invaginated scolex, sometimes called a protoscolex.  Larval (metacestodes or intermediate stages) 2- Coenurus: Fluid-filled cyst containing attached numerous invaginated scolices and covered with a cuticle  Larval (metacestodes or intermediate stages) 3- Strobilocercus: The scolex is evaginated and is connected to the cyst by a chain of asexual proglottids.  Larval (metacestodes or intermediate stages) 4- Hydatid: This is a large fluid-filled cyst covers by two layers: A) An outer laminated (cuticle) B) An inner lined with germinal epithelium from which produced attach invaginated scolices which lie free (protoscolices) or in bunches surrounded by germinal epithelium (brood capsules). - The contents of the cysts, other than fluid, i.e. Scolices and brood capsules become detached and float freely in the cystic fluid are frequently described as hydatid sand. - The cyst is covered by a thick fibrous capsule formed by the host itself.  Larval (metacestodes or intermediate stages) 5- Cysticercoid: A single evaginated scolex embedded in a small solid cyst. It has two types :- A) Cercocystis: A cysticercoid with tail like appendage to the vesicle. B) Cryptocystis: A cysticercoid that has lost its tail like appendage (tailless). Ex. In arthropodes in case of Dipylidium caninum.  Class : Cestoda (tapeworms) Order: Pseudophyllidea Order: Cyclophyllidea Family: Taneniidae Genus: Taenia Family: Diphyllobothridae Genus: Echinococcus Genus: Diphyllobothrium Genus: Spirometra Family: Anoplocephalidae Genus: Anoplocephala Genus: Moniezia Family: Dilepididae Genus: Dipylidium Family: Thysanosomidae Genus: Stilesia Genus: Avitellina Genus:Thysanosoma Genus: Thysaniezia fFamily: Davaineidae Genus: Davainea Genus:Raillietina Genus: Cotugnia Hymenlepididae Genus: Hymenolepis Family Taeniidae  Family Taeniidae - Adults are found in small intestine of the domestic carnivores and man. - The scolex ------→ Four sucker and rostellum except Taenia saginata (scolex unarmed). - Genitalia: single set in each segment. - Mature segment : Squarish in shape. - Gravid segment: Longer than wide. Taenia saginata (Beef tapeworm)  T. Saginata - Common name: The Beef Tapeworm. - Site: Small intestine of man. - Mode of infection: Eating of undercooked cow meat. - Intermediate host: Cattle - Infective stage: Cysticercus bovis in cattle (muscles and other organs such as heart, tongue and in masseter and intercostal muscle). - Diagnostic stage: Eggs and gravid in Feces. Morphology - Length: adult ranges from 4-15 m in length. - Scolex: Four suckers and has neither rostellum nor hooks (Bold tapeworm). - Gravid segment: contain each about 100, 000 eggs and usually shed singly. - Uterus of the gravid segments: 14-32 lateral branches on each side of central stem. - Egg: roughly spherical and 30 -40 micron. Taenia saginata scolex, mature and gravid segments Life cycle An infected human may pass ------→ millions of egg daily either free or intact segments. - After ingestion by Intermediate host (cattle) Oncosphere -----→ via blood -----→ to striated muscle - Man become infected by ingesting of raw or inadequately cooked meat containing cysts. - Prepatent period: 2 – 3 months. - Prenatal infection of calves occurred but rare. Life cycle of Taenia saginata Life cycle of Taenia saginata Life cycle  Cysticercus bovis in heart muscles - In the bovine animal the mature Cysticercus bovis is greish white, about 1.0 cm in diameter and filled with fluid in which the scolex is usually clearly visible. - As in the adult tapeworm it has neither rostellum nor hooks. - It may occur anywhere in the striated muscle and in the other organs such as heart, tongue and in masseter and intercostal muscle.  PATHOLOGY -Definitive Host (Human) - - Nutrient competition in malnourished hosts and may be diarrhea. - Intermediate Host (Cattle) - Cysticercus bovis: The longevity of the cysts ranged from weeks to years, when they die they are usually replaced by a caseous, crumbly mass which become calcified. - Calves given massive infection =➔ severe myocarditis and heart failure. Phylum: Platyhelminthes (Flatworms) Class: Cestoda (tapeworms). Tapeworms (Cestodes)  Class : Cestoda (tapeworms) Order: Pseudophyllidea Order: Cyclophyllidea Family: Taneniidae Genus: Taenia Family: Diphyllobothridae Genus: Echinococcus Genus: Diphyllobothrium Genus: Spirometra Family: Anoplocephalidae Genus: Anoplocephala Genus: Moniezia Family: Dilepididae Genus: Dipylidium Family: Thysanosomidae Genus: Stilesia Genus: Avitellina Genus:Thysanosoma Genus: Thysaniezia fFamily: Davaineidae Genus: Davainea Genus:Raillietina Genus: Cotugnia Hymenlepididae Genus: Hymenolepis  Taenia solium (Pork tapeworm)  Taenia solium Common name: The Pork Tapeworm. Habitat or Site: Small intestine of man Route of infection: Eating of undercooked Pork meat. Definitive host : Human. Intermediate host: Pigs, Human. Infective stage: Cysticercus cellulosae in striated muscles and organs of man and pig. Diagnostic stage: Eggs or gravid in Feces. Disease: Adults causesTaeniasis. Larvae cause cysticercosis ( presences of cysticercus larvae in brain and muscles). Morphology - Length: 3 -5 m long, rarely up to 8 m. - Scolex is typically Taeniid, having a rostellum armed with two concentric rows of hooks - The ovary in the posterior third of the proglottid and has two lobes and accessory third lobe. - The uterus has 7 to 12 side branches on either side. - Cysticercus cellulosae contains an invaginated scolex with rostellum armed with two concentric rows of hooks. -The larval stage cysticercus cellulosae occurs naturally in pigs and wild boars but man can also be infected, with serious and often fatal results. Thus man can act both as a definitive and an intermediate host - The gravid segments are 10-12 mm long by 5-6 mm wide. - The uterus has seven to twelve side-branches on either side. - The gravid segments, which each contain about 40.000 eggs are frequently detached in short chains and passed in the faeces of the host. Taenia solium (Scolex, mature segment and gravid segment) Life cycle - Mode of infection: the final host become infected by A) Ingestion of poorly cooked pork containing cysticercus cellulosae B) Accidental ingestion of T. solium eggs C) In the person with adult tapeworms from liberation of onchospheres, after digestion of a gravid segment ----→ onchospheres reach stomach from duodenum by reverse peristalsis-----→Auto-infection. Cysticerci: found in any organs but most common in subcutaneous tissue, then the eye and then the brain. - In brain--→ ventricles ---→ racemose in character Cysticercus racemosus Life cycle of Taenia solium P.P.P. Between 2 -3 months Life cycle of Taenia solium Pathogenesis - As in T. saginata infection, clinical signs are in apparent in pigs and insignificant in humans with adult tapeworms. - Man is infected with cysticerci, various clinical signs based on location of the cysts in the organs: A) Either muscles or Subcutaneous tissues. B) More serious in CNS ======➔ mental disturbance or clinical signs of epilepsy or intercranial hypertension Or develop in eyes --------→ loss of vision. Cysticercus cellulosae Neural cysticercosis Some characteristics for differentiating between Taenia saginata and Taenia solium Characteristic Taenia saginata Taenia solium 1- Final host Man Man 2- Intermediate hosts Cattle Pig and man 3-Site of development Muscles and viscera Muscles, brain, skin 4-Scolex; adult worm It has rostellum carring two rows of It has neither rostellum nor hooks hooks 5- Scolex; cysticercus It has rostellum carring two rows of It has neither rostellum nor hooks hooks 6- Uterine branches 23 (14-32) 8 (7-12) 7- Passing of proglottids Singly, spontaneously In groups (chain) passively 8- Ovary 2 lobes 3 lobes (third accessory) 9- vagina; sphincter muscle Present Absent 10- eggs a) Not affected by Hcl a) digested by Hcl b) Roughly spherical or globular. Not b) roughly spherical and contain a hooked contain a hooked onchosphere onchosphere c)The embryophorous membrane c)not acid fast inside the shell is acid fast d) It measures 40-50  in diameter d) It measures 30-40 in diameter 11- larva or metacestode Cysticercus bovis Cysticercus cellulosae 12- Pathogenesis to man Not dangerous since cysticercosis does More dangerous for the present of two not occur in man rows of hooks and occurrence of  Cysticercosis - In man, this means the occurrence of Cysticercus cellulosae inside the body of man====➔Man is final and intermediate hosts. 1- Food contaminated with Taenia solium eggs or gravid segments --→small intestine -----→ circulation to various tissues. 2- Autoinfection: - Internal autoinfection - External autoinfection  Internal auto –infection If man is infected with the adult parasite (acting as a definitive host), sometimes due to various reasons, it may happen that some detached segments, instead of going out with faeces, get carried upwards by some antiperistaltic movements, to the stomach and become broken up liberating the eggs back to the intestines and they hatch and liberate the onchospheres which penetrate to the tissues.  External auto-infection - If the patient harbouring the adult and contaminates his fingers from his own stool with eggs. - Swallowing these eggs also results in cysticercosis.  Taenia hydatigena Hosts: dog and wild canids. Intermediate hosts: sheep, goat, cattle, pig and wild ruminants. Metacestode or Larva: Cysticercus tenuicollis Site: adult in small intestine of dog and wild canids Cysticercus tenuicollis occurs normally in the peritoneal cavity of sheep, goat, cattle, pig and wild ruminants.  Morphology - This large tapewom, up to 500 cm long, is found in the small intestine of dog and wild canids. - The rostellum bears two rows of hooks, the gravid segments, measure 10-19 by 4-7 mm and the uterus have five to ten branches on either side. - The egg is elliptical and measures 39 x 35 . Life cycle: - Ingestion of contaminated food with eggs with T. hydatigena - Hexacanths embroyo-----→intestine---→liver -----burrow small channels in the liver paranchyma--→ surface of liver → peritoneal cavity after about 3 -4 weeks. - Cysticercus tenuicollis (bladder worm) ----→bladder like cyst contains a watery fluid and a single invaginated scolex. - Large number of developing cysticerci that migrate in the liver paranchyma of sheep and pig producing hepatitis cysticercosa a condition which its pathology resemble acute fascioliasis Cysticercus tenuicollis Life cycle of T. hydatigena Taenia ovis Hosts: dog and wild carnivores Intermediate hosts: sheep and goats. Metacestode or Larva: Cysticercus ovis Site: adult in small intestine of dog and wild canids Cysticercus ovis, being found in the muscle, and under the epicardium and the pleura of the diaphragm of sheep and goats. - Morphology and life cycle - length: 200 cm - The scolex has four sucker with a rostellum bears 24 to 36 hooks arranged in two rows..- Cysticercus ovis, being found in the muscle, and under the epicardium and the pleura of the diaphragm. - It grows mature in about 3 months in sheep and goats. - Adult takes 7 weeks to grow in dog.  Taenia pisiformis Hosts: dog and wild canids. Intermediate hosts: rodents, chiefly rabbit Metacestode or Larva: Cysticercus pisiformis Site: adult in small intestine of dog and wild canids Cysticercus pisiformis found in the peritonium of rabbit and hare. Morphology: - The adult worm in small intestine of dog and wild canids, it may reach, up to 200 cm long. - The rostellum bears thirty four to forty-eight hooks in two rows. - The uterus of the gravid segment has eight to fourteen lateral branches on either side. Life cycle - The life cycle of this worm is similar to that of T. hydatigena but the intermediate hosts are rodents, chiefly rabbit. - The intermediate stage Cysticercus pisiformis; the pea-like, is found on the peritoneum of rabbit and hare. - The young stages, after having developed in the liver for about 15-30 days, penetrate through the parenchyma of the liver and the adult bladder worm in found in the peritoneal cavity attached to the viscera and the great curvature of the stomach. - The effect of the adult worm resembles those of other adult taeniasis, but heavy infection with the cysticerci that wandering through liver parenchyma may causes “hepatitis cysticercosa”, as in the case of Cysticercus tenuicollis. - The affected rabbit may die suddenly or in more chronic cases, emaciation develops as the result of digestive disturbance.  Taenia multiceps (Syn: Multiceps multiceps) Hosts: dog and wild canids. Intermediate hosts: sheep, goat, cattle, horse and man. Metacestode or Larva: Coenurus cerebralis Site: adult in small intestine of dog and wild canids. Coenurus cerebralis found in the brain and spinal cord of the sheep, goat, cattle, horse and man Morphology: - The adult tapeworm is up to 100 cm long and is found in the dog and wild canids. - The scolex is small, 0.8 mm in diameter and has rostellum bearing twenty-two to thirty –two hooks in two rows. - The uterus of the gravid segment has nine to twenty six lateral branches on either side. - The intermediate stage, Coenurus cerebralis, develops in the brain and spinal cord of the sheep, goat, cattle, horse and man. - Coenurus cerebralis develops in the brain and spinal cord of sheep, goat, cattle, horse and man. - The onchosphere after hatching in the intestine, pass via blood stream to various parts of the body. Only those reach the central nervous system will develop. - The young cysts fully developed in 6 -8 months. The fully cysts measure 5 cm (delicate, translucent with several invaginated scolices). Coenurus cerebralis in brain Life cycle of Taenia multiceps Gid or sturdy or staggers - Infection of sheep and calves by larval stages of T. multiceps (Coenurus cerebralis) and clinical syndrome characterized by: - At 1 -3 weeks post-infection, migration of immature cyst in the brain=====➔Cortical encephalitis. - At 2- 7 months post-infection (the mature cyst become establish), the animal performs forced movement varying in nature and position of mature cyst in C.N.S. - When the infection occurs in the parietal region of cerebral hemisphere, forced movement of head from the opposite site of infection had occurred which move the head in circle from the opposite site. - When infection occurs in the anterior part of the brain, the animal steps high (trotters). - When infection occurs in the cerebellum, the clinical signs appear as staggering gait (jerky movement) in hind legs where complete loss of balance had occurred, griding of teeth, salivation and convulsion may be seen.  Taenia serialis -Hosts: dogs and wild canids. Intermediate hosts: rabbit and man. Metacestode or larva: Coenurus serialis Site: adult in small intestine of dog and wild canids Coenurus serialis found in intermuscular connective tissue or subcutaneously in rabbit and has also been found in man. Morphology & Life cycle: - It measures up to 70 cm and the scolex bears two rows of twently six to thirty-two hooks. - The gravid uterus has twenty to twenty five lateral branches on either side. - The egg is elliptical in shape. - The intermediate stage, Coenurus serialis, develops in the intermuscular connective tissue or subcutaneously in rabbit and has also been found in man. Morphology of Coenurus serialis: - Cyst characterized by a number of scolices which are arranged in lines radiating from a center and are invaginated into their neck. This characters in contrast with Coenurus cerebralis which unable to produce these structures. -Mode of transmission: Dog become infected by eating the raw flesh of infected rabbit with mature cysts of coenurus serialis. - Pathology The adult worm is not pathogenic as seen in other taeniasis but the larval stages in rabbits may be important according to the site of larvae specially in heavy infection. Taenia taeniaeformis (syn Hydatigera taeniaeformis) Hosts: Cat. (Cat tapeworm) Intermediate hosts: mice and other rodents. Metacestode or Larva: Cysticercus fasciolaris or Strobilocercus fasciolaris Site: adult in small intestine of cat. Cysticercus fasciolaris is found in the liver of mice and other rodents Morphology - Tapeworm is 60 cm long, it has characteristic is absent of neck and bell shaped posterior proglottids. Life cycle - The strobilocerci are found within pea-size nodules partially embedded in the liver parenchyma of rodents. - The cat infected by eating Cysticercus or strobilocercus fasciolaris in the intermediate hosts. - Cysticercus fasciolaris is found in the liver of mice and other rodents - Cysticercus or strobilocercus fasciolaris composed of small vesicle attached to scolex with long false segmented strobila or asexual proglotiide. The scolex not invaginated (evaginated) and has four suckers and rostellum armed with double row of hooks. Life cycle of Taenia taeniaeformis Cysticercosis in animals: - Cysticercus of canine Taeniid tapeworm -----→migrate through liver tissue (C. tenuicollis and C. pisiformis). - Massive infections ---------→Trumatic hepatitis. - Cysticercus ovis of the second canine Taniid tapeworm Taenia ovis infects cardiac and skeletal muscle of sheep -- --→ pathological lesions. - Coenurosis: Coenurus of canine Taeniid tapeworm Taenia multiceps====➔ invade cranial cavity of sheep and goat and sometimes cattle, equine and man. - Neurological signs---→ blindness and walking in circles.  Final Adult tapeworms Site of adult Metacestodes Site of larvae Intermediate hosts host Cysticercus Taenia saginata man small intestine muscles cattle bovis Muscles , brain and Taenia solium man small intestine Cysticercus cellulosae Pig and man s/c Taenia ovis dog small intestine Cysticercus ovis muscles Sheep and goat central nervous Sheep ,goot ,cattle Taenia multiceps dog small intestine Coenurus cerebralis system and equine Taenia pisiformis dog small intestine Cysticercus pisiformis peritoneum rabbit Intermuscular Taenia serialis dog small intestine Coenurus serialis connective tissues and rabbit s/c Sheep, goot, cattle Taenia hydatigena dog small intestine Cysticercus tenuicollis peritoneum and pig Cysticercus or Taenia Rodents; rat; cat small intestine Strobilocercus Liver taeniaeformis mouse and rabbit fasciolaris Echinococcus All mammals Unilocular granulosus dog small intestine Mainly liver and lungs except horse and hydatid cyst granulosus donkey Dog and Echinococcus Unilocular red small intestine Mainly liver and lungs Horse and donkey granulosus equinus hydatid cyst fox Echinococcus Dog, cat Multilocular hydatid Rodents and small intestine Mainly liver multilocularis and fox cyst man