Presentation on theme: "Introduction to tromatodes"— Presentation transcript:
1 Introduction to tromatodes Phylum Platyhelminthes Class Trematoda Order Digenea
2 Morphology Adult worm Flattened (flatworm) and leaf like Sucker: oral & ventral (fluke)Body wall: musculo-tegumental sacParenchyma (structure between body wall and internal organs): connective tissue fibers, cells and space between them
4 Digestive tract: not intact i.e. no anal opening, caecum Reproductive system: hermaphrodite (monoecious) exception of schistosomeMuscular systemNervous systemExcretory system
5 Egg Size divergent Ovoid Operculum (exception of that of schistosome) Content: ovum , vitelline cells, or miracidium
6 Egg of Clonorchis sinensis Clonorchis sinensis egg. These are small operculated eggs. Size 27 to 35 µm by 11 to 20 µm. The operculum, at the smaller end of the egg, is convex and rests on a visible "shoulder". At the opposite (larger, abopercular) end, a small knob or hooklike protrusion is often visible (as is the case here). The miracidium is visible inside the egg.Egg of Clonorchis sinensis
7 Egg of Paragonimus westermani And a third example of a Paragonimus egg. (Original image from a Japanese language site tentatively titled Internet Atlas of Human Parasitology.)来源Egg of Paragonimus westermani
8 Egg of Fasciolopsis buski F.buski eggs are released in feces unembryonated. The operculated eggs are oval, brown and measure by umEgg of Fasciolopsis buski
9 S. japonicum S. Mansoni S. haematobium Schistosome egg
10 Features Reflecting Adaptation to Parasitism Organs of attachment highly developedRetardation of digestive systemHighly developed reproductive system
11 Life CycleComplexAlteration of generation sexual generation and asexual generation alter in the life cycle of parasiteAsexual multiplication in larval stage in snail hostMultiple hosts transfer and having reservoir hosts in majorityWater environment is essential
12 Important Species Liver fluke: Clonorchis sinensis Intestinal fluke: Fasciolopsis buskiLung fluke: Paragonimous westermani P. skrjabiniBlood fluke: Schistosoma spp.
19 Cross section of Clonorchis sinensis adult in the hepatic bile duct Clonorchis sinensis, liver biopsy: most infections are asymptomatic.Cross section of Clonorchis sinensis adult in the hepatic bile duct
20 Egg Size: smallest Shape: just like sesame Color: yellowish brown Operculum distinct: shoulder, knobContent: miracidium
21 Clonorchis sinensis egg. These are small operculated eggs Clonorchis sinensis egg. These are small operculated eggs. Size 27 to 35 µm by 11 to 20 µm. The operculum, at the smaller end of the egg, is convex and rests on a visible "shoulder". At the opposite (larger, abopercular) end, a small knob or hooklike protrusion is often visible (as is the case here). The miracidium is visible inside the egg.Clonorchis sinensis egg. These are small operculated eggs. Size 27 to 35 µm by 11 to 20 µm. The operculum, at the smaller end of the egg, is convex and rests on a visible "shoulder". At the opposite (larger, abopercular) end, a small knob or hooklike protrusion is often visible (as is the case here). The miracidium is visible inside the egg.
22 Egg of Clonorchis sinensis Clonorchis sinensis/ O.viverrini egg: eggs of the two species are similar. They measure by um are operculated at one end and have a small knob on the other end. The colour is yellowEgg of Clonorchis sinensis
23 Life cycle of Clonorchis sinensis Embryonated eggs are discharged in the biliary ducts and in the stool . Eggs are ingested by a suitable snail intermediate host ; there are more than 100 species of snails that can serve as intermediate hosts. Each egg releases a miracidia , which go through several developmental stages (sporocysts , rediae , and cercariae ). The cercariae are released from the snail and after a short period of free-swimming time in water, they come in contact and penetrate the flesh of freshwater fish, where they encyst as metacercariae . Infection of humans occurs by ingestion of undercooked, salted, pickled, or smoked freshwater fish . After ingestion, the metacercariae excyst in the duodenum and ascend the biliary tract through the ampulla of Vater . Maturation takes approximately 1 month. The adult flukes (measuring 10 to 25 mm by 3 to 5 mm) reside in small and medium sized biliary ducts. In addition to humans, carnivorous animals can serve as reservoir hosts.Life cycle of Clonorchis sinensis
24 Life Cycle A model pattern of trematode Main points Definitive host: human beingReservoir host: dog, cat, etc.Residing: hepatic bile ductDischarge of eggs with feces
25 Hatching in the host small intestine 2 intermediate host I: snails, such as Bithynia,Parafossarulus II: freshwater fishes, such as Cyprinus2 generation of asexual proliferationInfective stage: metacercaria in fishInfective route: oral consumption
26 Pathogenesis Due to adult worm Mechanism Mechanical: sucker Chemical: excretions, secretions, metaboliteBiological: nutrition deprivation
27 Pathological process Inflammation Proliferation ThickeningOcclusion Extensive involvementFibrosis of the liver
35 The Lung Fluke Genus paragonimus Zoonotic parasite (cause zoonosis) Animal infection> human infection2 major species in China
36 Introduction Pathogen of lung disease Endemic hemoptysis Favorite lodging site: lungEctopic site: brain, abdomen, muscle, etc.
37 Morphology Adult worm Body thick (a half piece of a bean grain) Tegument: spinousSucker: oral = ventralParallel arrangement of reproductive organ lobular testes (posterior) lobular ovary & uterus (anterior)
38 Paragonimus westermani, adult, stained whole mount; approximate size = 9 mm in length. Click here to view an image in which some of the internal organs are labeled, or click here to view a labeled line drawing来源
39 Cross section of lung containing adult Paragonimus westermani.
40 Egg Median size, ovoid (water pot) Golden yellow Distinctive & wide operculumContain 1 germ cell & several yolk cells
41 Egg of Paragonimus westermani. And a third example of a Paragonimus egg. (Original image from a Japanese language site tentatively titled Internet Atlas of Human Parasitology.)来源Egg of Paragonimus westermani.
42 Life cycle of Paragonimus westermani. Crab or crayfishThe eggs are excreted unembryonated in the sputum, or alternately they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P. westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5 to 12 mm by 4 to 6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycles is not achieved, because the eggs laid cannot exit these sites. Time from infection to oviposition is 65 to 90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P. westermani.Life cycle of Paragonimus westermani.
43 Life cycle Definitive host: human being Reservoir host: carnivorous animalsHabitation: lung & ectopic siteIntermediate host: I: Melania snails II: stream crabs, crayfish
44 Infective stage: metacercaria Infective mode: oral route, may via paratenic host (swine)Migration & Preadult wonderingEctopic parasitism: cerebral, abdominal,etc.Eggs discharged with sputum & feces3 generation of asexual multiplication
48 Laboratory diagnosis Disease history + physical examination Etiological diagnosis eggs in sputum or feces by sedimentationImmunological diagnosis for ectopic infections
49 EpidemiologyGlobal main continent except EuropeChina 23 provinces
50 Paragonimus westermani infection occurs in Asia (especially in China, Corea, India, Japan, Laos, Philippines, Sri Lanka, Taiwan, Thailand, Viet-Nam), Central-West Africa, South America (Ecuador, Per? Venezuela).Paragonimus westermani infection occurs in Asia (especially in China (Taiwan), Corea, India, Japan, Laos, Philippines, Sri Lanka, Thailand, Viet-Nam), Central-West Africa, South America (Ecuador, Peru Venezuela).
51 Principle of control Treat patient: praziquantel Hygienic education Social construction, economic refinement
53 Morphology Adult worm Like a ginger piece Big muscular trematode Have strong suckers，ventral >> oral
54 Adult fluke of Fasciolopsis buski Adult fluke of Fasciolopsis buski. The adult flukes range in size: 20 to 75 mm by 8 to 20 mm. Image contributed by Georgia Division of Public Health.Adult fluke of Fasciolopsis buski The adult flukes range in size: 20 to 75 mm by 8 to 20 mm
57 F. buski eggs are released in feces unembryonated F.buski eggs are released in feces unembryonated. The operculated eggs are oval, brown and measure by umF.buski eggs are released in feces unembryonated. The operculated eggs are oval, brown and measure by um
58 Life cycle of Fascilopsis buski Immature eggs are discharged into the intestine and stool . Eggs become embryonated in water , eggs release miracidia , which invade a suitable snail intermediate host . In the snail the parasites undergo several developmental stages (sporocysts , rediae , and cercariae ). The cercariae are released from the snail and encyst as metacercariae on aquatic plants . The mammalian hosts become infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum and attach to the intestinal wall. There they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs) . The adults have a life span of about one year.Life cycle of Fascilopsis buski
59 The adult flukes (20 to 75 mm by 8 to 20 mm) reside in the duodenum and jejunum of mammalian hosts (humans and pigs), where they are attached to the intestinal wall. Immature eggs are discharged into the intestine and stool. After development in water, each egg releases a miracidium which invades a suitable snail intermediate host. In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic plants. The mammalian hosts become infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum and attach to the intestinal wall. They develop in approximately 3 months into adults, which have a life span of one year. Fasciolopsis buski infects humans and pigs.
60 Life Cycle Definitive host: human being Reservoir host: swine, etc. Intermediate host: Planorbis snailsAquatic plant vectors: caltrops, water chestnut, etc.Habitation: small intestine
61 Infective stage: metacercaria Infective route: oralDevelopmental stages: as Paragonimus3 generation of asexual proliferation
70 Distribution and Epidemic Situation Worldwide200 million of population infected in 74 countries (S.m. 55; S.h. 55; S.j. 4; S.i. 10; S.me. 2; S.ma. 1)China11 million in 12 provinces 0.7 million in 8 provinces50 years
71 Regional distribution of S. japonicum infection in China Before control After control (1996)Regional distribution of S. japonicum infection in China
72 Morphology Difference from other trematodes Dioecious adults Non-opeculate eggBifurcated (forked) cercaria invades the final host by skinAdults parasitize blood vessels
73 Adult Male (15 mm length) < female (22 mm) Oral sucker < ventral sucker2 paralleled guts form a blind caecum in the posterior ends7 testes in male and single ovary with a tubule uterus in femaleGynecophoric canal (male) in which female repose
75 adult schistosomes live in pairs in the portal system and in mesenteric venules; adults of S.japonicum are bigger than adults of S.mansoni. males are mm in lenght and 0,5 wide, and have a ventral infolding from the ventral sucker to the posterior end forming the gynecophoric canal. Adult male with female in the copulatory groove
76 A scanning electron micrograph of schistosomes in copula
77 Egg Miracidium Cercaria Ovoid and non-opeculate 74~106 m × 55~80 m Contains one miracidiumBear a minute lateral knob.MiracidiumCercaria
78 S. japonicum S. Mansoni S. haematobium Schistosome egg
80 cercarae are the infective forms. They measure about 500 micron cercarae are the infective forms. They measure about 500 micron. After encountering the skin, the cercariae penetrate and lose the tail transforming into schistosomulaeSchistosome cercaria
81 Life CycleEggs discharged fresh water (hatch) miracidia penetrate oncomelania(I.H.)mother sporocysts (multiplication) daughter sporocysts (multiplication) cercariae (infective form) skin penetration of D.H. schistosomulum right heart lungs left heart systemic circulation portal system pairing and sexual maturation mesenteric veins lay eggs eggs develop and live in tissue for 21 days( 23% in liver tissue, 60% in intestinal tissue, 17% discharged)
83 Cercarial dermatisis due to avian schistosome Typically, hosts of avian schistosomes are migratory water birds, including shorebirds, ducks, and geese. Adult worms are found in the blood vessels and produce eggs that are swallowed and passed in the feces. On exposure to water, the eggs hatch and liberate a ciliated miracidium that infects a suitable molluscan intermediate host. The parasite develops the in this intermediate host, usually a certain species of snail, to produce free-swimming cercariae that are released under appropriate conditions and penetrate the skin of the birds to complete the cycle. Humans are inadvertent and inappropriate hosts; cercariae may penetrate the skin but do not develop further. A number of species of dermatitis-producing cercariae have been described from both freshwater and saltwater environments, and exposure to either type of cercariae will sensitize persons to both.Cercarial dermatisis due to avian schistosome
84 Main Points of Life Cycle Residing site: mesenteric veinI.H.(Only one): Oncomelania hupensisNo metacercaria and redia stageTwo generation of sporocystInfective stage: cercariaRoute of infection: skin penetration
85 Adult of Schistosome in mesenteric veins of hamster S.mansoni : Females are slender (1 mm in diameter) and longer (9-17 mm in lenght), and are held in the ginecophoric canal during copulation. Each female lays about 300 eggs per day. Adult male with female in the copulatory groove. Adult of S.mansoni in mesenteric veins of hamster.Adult of Schistosome in mesenteric veins of hamster
86 Onchomelania hupensis intermediate host of S.japonicum are snails of the genus Onchomelania, hupensis spp.Onchomelania hupensis
87 Skin penetration of cercaria first appearance of eggs: 30~35 days Life spans in human: 4~5 years, longest: 35 years
88 Significance of tissue egg The egg which can develop and live in tissueSignificance of tissue eggMajor pathogenic stage, inflammation and granuloma around the eggDiagnosis and evaluation of therapeutic efficacy
89 Immunity Concomitant immunity Host carrying an initial infection of adult schistosomes shows the protection to a cercarial challenge infection (攻击性感染）and this protective immunity will disappear with eradication of schistosomes in the host
90 Immuno-evasion: It’s an ability by which the schistosome adult can evade the host immune response. The possible mechanism of evasion.Acquire host antigen on it surfaceHost-like antigen produced by parasiteChanging of tegument very quicklyParasite may inactivate or down-regulate immune effectors
91 PathogenesisSchistosomiasis at each stage of the life cycle in human bodyCercaria (skin-penetration)DermatitisSchistosomula (migration)Larva migransAdult: (immunocomplex)Immuno-nephropathy
92 Tissue egg: principal pathogenic stage Miracidium within eggSEASensitization of T CellTh1IL-2, INF-, TNF activate macrophage, induce cell-mediated immunityTh2IL-4, IL-5 stimulate IgE production or eosinophiliainflammation and granuloma fibrosis portal hypertension intestinal polyp
93 Clinical Form Acute schistosomiasis Chronic schistosomiasis Fever, diarrhea, abdominal pain, enlargement of liver or spleenChronic schistosomiasisasymptomatic or diarrhea, abdominal pain, enlargement of liver or spleenAdvanced schistosomiasisAscites; splenomegaly;collateral circulation; dwarfism;Ectopic lesion: encephalitis; focal epilepsy
94 Advanced schistosomiasis patient with portal hypertension and ascites Brazilian with portal hypertension and ascites due to S.mansoni.Advanced schistosomiasis patientwith portal hypertension and ascites
95 A patient with S. j has marked ascites, splenomegaly, umbilical hernia and distended superficial abdominal veins.
96 DiagnosisParasitological diagnosis (etiological, definitive diagnosis)Demonstrating eggs by stool examinationStool examination after concentration (sedimentation)*Miracidium-hatching from eggsRectal biopsy — eggs-demonstration
97 Miracidium-hatching from eggs Necessity: tissue ova;low egg burden due to mass treatmentPossibility:Hatch quickly (T:25; limpid water; free of Cl2;light; pH= )Three tropism:limpidity, phototrophic, ascendancySwimming in a zigzag way
98 Immunodiagnosis (indirect diagnosis) Detection of antibodies in serum, urine, saliva by ELISA, but is impossible to distinguish current infection from past infection.Detection of antigens (circulation anodic and cathodic antigen)
99 Combined diagnosis: including epidemiological antecedent, symptoms and signs, parasitological and immunological examination.
100 TreatmentPraziquantel 60 mg/kg divided in 3 doses.
101 Factors of Transmission and Prevention Source of infection: patients and reservoir hostIntermediate host: OncomelaniaContact with cercaria-infected water
102 Preventive measuresDetection and treatment of patients and reservoir hostElimination or control of oncomelaniaProtection of susceptible population and avoidance of contact with cercaria-infected waterPrevention of water contamination by human night soil
103 Distinguishing of 3 major schistosomes (see page 54, Table 3-1)