Introduction to Trematode PDF

Helminthes (worms) Helminthes Trematode Cestode Nematode  Nematode Cestode Trematode shape Elongated , Tape like Leaf like Cylindrical segmented None segmented...

Helminthes (worms) Helminthes Trematode Cestode Nematode  Nematode Cestode Trematode shape Elongated , Tape like Leaf like Cylindrical segmented None segmented None segmented Digestive system Complete Absent Incomplete (end with anus) ( no anus) Body cavity Present Absent Absent Sex Separate Not separate Not Separate ( except Schistosoma) Trematoda general character of trematode Trematodes are parasites of vertebrates. They have complex life cycles requiring one or more intermediate hosts. Most of them sex ( not separate ) Inhabitants of the alimentary canal or its associated organs, especially the liver, Organ of fixation is sucker The first intermediate host is usually snail Form and Function Most species are elongate and dorso-ventrally flattened There are typically 2 suckers, an anterior oral sucker surrounding the mouth, and a ventral sucker on the ventral surface Tegument*(cuticle)  In addition to its obvious protective role, absorption of nutrients synthesis and secretion excretion and osmoregulation sensory role (due to the presence of various sensory organs) Muscular System The bodies and parts of bodies of flatworms are often seen to expand, contract, and twist, and this movement indicates the presence of muscles Nervous System Paired ganglia at the anterior end of the body serve as the brain; from here, nerves extend anteriorly and posteriorly Most sensory receptors are lacking among the adults Larval stages have many kinds of sensory receptors, important for locating hosts in the environment Excretion and Osmoregulation The flame cells are connected by tubules uniting to form larger ducts that open either independently to the outside or join to form a urinary bladder Male Reproductive System Protandry is the general rule among the Digenea Usually 2 testes are Female Reproductive System cont. Single ovary with an oviduct Fasciola  Fasciola spp. Site bile ducts (liver) F.H. humans I.H lymnea spp. (snail) Fasciola life cycle Fasciola life cycle Infection and Pathogenicity Mode of infection Infection with Fasciola spp. occurs when metacercariae are accidentally ingested on raw vegetation. The metacercariae exist in the small intestine, and move through the intestinal wall and peritoneal cavity to the liver where adults mature in the biliary ducts of the liver. Eggs are passed through the bile ducts into the intestine where they are then passed in the feces. Symptoms fever, abdominal pain, gastrointestinal symptoms, anemia jaundice, and respiratory symptoms.  Halzoun that ingestion of infected raw sheep and goat livers may result in attachment of adult living worms by their suckers to the pharyngeal mucosa causing edema of the soft palate, pharynx and larynx. This edema is accompanied by dyspnea and occasionally asphyxia. Diagnosis Fecal examination generally not helpful because the worm eggs can seldom be detected in the chronic phase of the infection Histiopathology PCR Mode of infection (ingestion of metacercaria) Infective stage (metacercaria) Dignostic stage (egg)