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Class: Trematodes (flukes). Phylum Platyhelminthes – Class Trematoda General characters: Dorsoventrally flattened typically leaf shaped have an oral and.

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Presentation on theme: "Class: Trematodes (flukes). Phylum Platyhelminthes – Class Trematoda General characters: Dorsoventrally flattened typically leaf shaped have an oral and."— Presentation transcript:

1 Class: Trematodes (flukes)

2 Phylum Platyhelminthes – Class Trematoda General characters: Dorsoventrally flattened typically leaf shaped have an oral and a ventral sucker used for attachment and movement. Bifurcate intestine complex life cycle with multiple hosts. mollusc is usually 1 st intermediate host definitive host is a vertebrate most are hermaphroditic except blood flukes.

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5 According to their habitat 1.Blood flukes, Schistosoma species 2.Liver flukes, Fasciola species 3.Intestinal flukes, Fasciolopsis buski 4.Lung flukes, Paragonimus species

6 Blood flukes Schistosoma species

7 Blood flukes Schistosoma species: They differ from other trematodes in that they have separate sexes. Only trematodes that live in the blood stream of warm-blooded hosts Definitive host: Human Intermediate host: Snail Reservoirs: monkeys, rodents, cats, dogs, cattle, horses, swine, wild mammals The human disease known as shistosomiasis, Bilharzia, Bilhariaziasis In 1852 the German parasitologist, Theodor Bilharz, made the first discovery of schistosomes (S. haematobium) while working in Egypt Eggs are responsible for the pathology associated with infections

8 Human Blood flukes: Three major species Schistosoma haematobium Schistosoma japonicum Schistosoma mansoni

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10 Blood flukes Transmission

11 Morphology: 1- All species roughly similar. 2- Sexes are separate (dioecious). 3- size 0.5-2.5 cm in length. 3- Males short and wide, females long, thin. 4- Female adults reside in gynecophoral canal formed by male body.

12 Morphology

13 Eggs are responsible for the pathology associated with infections 100 250 3500 eggs/day Diagnostic stage

14 S. mansoni S. haematobium S.japonicum

15 Schistosoma haematobium Habitat: venules of the urinary bladder Disease: Urinary schistosomiasis Egg: Ellipsoidal with terminal spine. Diagnostic stage Intermediate hosts: are fresh water snails Bulinus

16 Schistosoma mansoni Habitat: in venules of the large intestine Disease: intestinal schistosomiasis Egg: Ellipsoidal with lateral spine Diagnostic stage Intermediate hosts: are fresh water snail Biomphalaria

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18 Schistosoma japonicum Habitat: venules of the small intestine Disease: oriental schistosomiasis Egg:round with rudimentary spine laterally Diagnostic stage Intermediate host: are fresh water snail Oncomelania

19 Life stages

20 Cercaria in the water Infective stage

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23 Symptoms: The first symptom is a localized dermatitis, often observed following cercarial penetration of the skin It is characterized by itching and local edema, which usually disappear after 4 days Following skin penetration. The symptoms of human schistosomiasis appear in 3 phases: Migration phase, Acute phase Chronic phase

24 1- The migration phase (from penetration to egg production) There are often no symptoms It can be characterized by toxic reactions and pulmonary congestion accompanied by fever. This phase may last 4-10 weeks, during which the worms migrate from the lungs to the liver where they reach sexual maturity and mate. 2. The acute phase (begins at egg production) Symptoms such as blood stools (S. mansoni and S. japonicum) and hematuria (S. hematobium) are caused by passage of eggs through the intestinal and urinary bladder walls.

25 Hepatosplenic Schistosomiasis : S. mansoni and S. japonicum Several years after initial infection Granulomas form within the liver and biliary tree Hepatosplenomegaly portal hypertension – liver failure Intestinal Schistosomiasis Adults migrate to intestinal wall Lay eggs which migrate into intestinal lumen and out into stool Severe anemia from chronic GI blood loss Chronic Disease

26 S. haematobium Several years after infection Adults migrate to small venules around the bladder and ureter Eggs are deposited into surrounding tissue and penetrate out into bladder Causes calcifications where eggs are trapped Characterized by hematuria Leads to cancer of bladder Chronic Disease

27 Granuloma or pseudotubercle: forms around each egg or cluster of eggs; the result of leukocyte infiltration and secretion of fibroblast growth factors Small abscesses, accompanied by occlusion of small blood vessels, lead to necrosis and ulceration. Intestinal schistosomiasis: eggs in the wall of the gut Schistosoma egg in the liver : granuloma formation

28 Haematuria

29 Laboratory Diagnosis: 1- Microscopic identification of eggs in stool or urine is the most practical for the diagnosis: S. haematobium eggs in urine are ellipsoidal with a terminal spine. S. mansoni eggs in feces are also ellipsoidal but with a lateral spine. S. japonicum eggs are more round with rudimentary spine laterally. 2- Tissue biopsy (rectal biopsy for all species and biopsy of the bladder for S. haematobium) may demonstrate eggs when stool or urine examinations are negative.biopsy 3- Serological tests are of value in the diagnosis of schistosomiasis when eggs cannot be found.

30 Swimmers Itch: An interesting aspect of schistosome biology concerns cercarial dermatitis or swimmers itch The condition is caused when cercariae of blood flukes that normally parasitize aquatic birds and mammals penetrate the human skin, sensitizing the areas of attack and causing pustules and an itchy rash Since humans are not suitable definitive hosts for these flukes, the cercariae do not normally enter the blood stream and mature Instead, after penetrating the skin, they are destroyed by the victims immune response Allergenic material released from dead and dying cercariae produce a localized inflammatory reaction

31 Cercarial Dermatitis (Swimmers Itch) Due to cercaria of avian schistosomes Avian (bird) schistosomiasis

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