Class Trematoda

Phylum Plathelminthes. General characteristics. Bilaterally symmetrical. No endoskeleton. No coelom. Body cavity filled by parenchyma (a connective tissue). Flame cells and excretory ducts are always present. Alimentary canal maybe present or absent. Anus never present. No digestive tract. All are hermaphrodites.  Classes: Trematoda and Cestoda.
Class Trematoda Have 2 muscular suckers, oral sucker (at ant. end) and large ventral sucker. 1) Body wall: Tegument contains endoplasmic reticulum, vacuoles, mitochondria and hard spines and scales. After the tegument is has a layer of voluntary muscles (circular,longitudinal and layer of diagonal muscle fibres). After this there is a branched tegument secreting cells (These cells lie in parenchyma). 2) Digestive system: Oral sucker à funnel shaped mouth cavity à Round muscular pharynx à short narrow oesophagus à intestine à Divides into 2 branches or caeca – goes to posterior and end blindly. No Anus. Fluke feeds on bile, blood, and lymph and cell debris. 3) Excretory system: Protonephridial system. Excretory pore à Flame cells. 4) Nervous system: Nerve collar surrounds the oesophagus. Nerve cords are connected by transverse commissures. This is orthogonal nervous system. Sense organs are lost. 5) Reproductive system: They are Hermaphrodites. But cross fertilization takes place. Male:- 2 highly branched tubular testes à Vas deferens à Seminal vesicle à Ejaculatory duct à Cirrus à Male genital aperture à Genital atrium à Gonopore Female: - Single tubular ovary. Has follicles behind testes and both lateral sides, constituting vitelline glands (yolk glands) which produce albuminous yolk. à Vitelline duct à oviduct (both connects to form ovo-vitelline duct) à Here has a Mehlis gland (lubricates passage) à Ovo-vitelline has ootype à arises a wide convoluted uterus. à Genital atrium à Terminal part of uterus has muscular walls called metraterm (which ejects the eggs). General Life cycle:- Egg à Miracidium à Sporocyst à Redia larva à Cercaria à Gets encysted to form Adolescaria à Metacercaria
11) Fasciola Hepatica	Morphology: It is a parasite in liver and bile duct of sheep, goats, cattle and human in some cases. 25-40mm long. Morphological features are the same of class in general. Have digestive system, protonephridial excretory system, orthogonal nervous system and reproductive system. It is hermaphrodite.	Life cycle: * Requires 2 hosts (Digenetic): - Intermediate host (some species of amphibious snails of genus limnaea) i.e. Only one intermediate host. - Definitive host (sheep, goat and other grass eating animals. Humans are the accidental host) * Life cycle is same as described in the general life cycle of trematoda. Adolescaria (infective stage) lives for 1 year. This is not infective until after 12 hours of encystment. In the stomach of the host a young fluke emerges. * Before enzymes act on upon the young fluke, it bores through the wall of intestine and goes to liver and stay for 7-8 weeks. And they enter the bile duct and bile passages. After several weeks in bile duct they become sexually matured adults. Period of incubation: 3-4 months. Adult flukes remain in the biliary tract for many years.	Diagnosis: Eosinophilia is common in early phase of the illness and is associated with liver biochemical abnormalities. Laboratory diagnosis: Eggs (diagnostic stage) are not found in stool until after the second phase of illness when the mature flukes establish themselves in the biliary tract. * Diagnosis is then confirmed by the identification of eggs in the duodenal aspirate or by serological tests.	Disease: Adult worm is pathogenic stage. Symptoms: Intermittent fever, malaise, weight loss and skin rash relate to migration. Second phase of illness: Presence of flukes in the biliary tract, where they can cause jaundice and cholangitis, although infection may remain asymptomatic. Flukes have been found in many ectopic sites including lung, brain and skin. Prevention: Fasciola is only accidentally transmitted to man via consumption of wild watercress grown on the land of grazing land of infected animals or vegetables which are watered by water taken from river in which infected snails live. Measure of prevention: Individual hygiene.
12) Opisthorchis Felineus	Morphology: Prevalent in cats, dogs, foxes and hogs in eastern and southeastern Europe and Asiatic areas of the former USSR. Found in humans also. It is 7-12mm. Its habitat is the distal bile ducts, occationally the pancreatic duct. Life span probably several years.	Life cycle: Totally 3 hosts involved. Egg à Snail bulimus à Miracidium à Sporocyst à Redia à Cercaria leave the snail à Encysted adolescaria à Goes to Cyprinoid fish à Metacercaria à Vertebrate host à Excyst in duodenum à Pass to distal bile duct. (They mature here in 3-4 weeks). i.e. 2 Intermediate hosts. - Snail bulimus - Cyprinoid fish	Diagnosis: Presence of characteristic eggs (diagnostic stage) in feces or duodenal drainage is diagnostic.	Disease: May be prevented by cooking fish and by sanitary excretory disposal.
13) Dicrocoelium Lanceatum	Morphology: Habitat: Liver bile duct. Found throughout the Europe, Middle east, Asia, Africa, North and South America and Australia. Tend to be found in areas that favor the intermediate hosts such as fields with dry, chalky and alkaline soils. Has flat body. 5-12mm. Has characteristic taper at the anterior and posterior ends. Ant. Has oral sucker at the point, an acetabulum. Has pair of lobed testes in anterior. Posteriorly uterus is found. In midsection, vitelline glands are involved in egg formation. Eggs are brown. Assymetrical with operculum.	Life cycle: Mode of transmission: By ingestion of infected ants. To humans through water where infected ants are found. Reservoirs: Sheep, cows, land snails and ants. Totally 3 hosts involved. Embryonated eggs pass down the bile duct à Deposited in feces à 2 Intermediate hosts involved. à (1) Terrestrial snail (first intermediate) eats it à Miracidium hatches within the snail à Migrates to digestive gland à Several months later, cercariae are released. Redia stage is absent!!! Cercaria stays in the respiratory tract of snail. à Mucus is secreted around them àThe snail expels this mucus as a slime ball. (2) Ant (genus formica) [second intermediate host] uses the trail of slime ball as a source of moisture. à The slime ball encysts as Metacercariae (infective stage) in the ant. But some encyst in the sub esophageal ganglion of snail.	Diagnosis: Incubation period is currently unknown. Adult worm (pathogenic stage) infects the bile ducts of human. Symptoms: Skin rash, Abdominal pain, fever, general gastrointestinal disturbances (nausea, diarrhea). In heavier infection, bile ducts and the biliary epithelium may become enlarged. Causes hepatomegaly (enlargement of liver) or inflammation of liver (cirrhosis). Other symptoms: Recurrent pain in upper quadrant, loss of appetite, irregular defecation. Laboratory diagnosis: Identification of eggs (diagnostic stage) in the feces of human. Examination of bile or duodenal fluid for eggs. Adult worms may be present too. Immunological test – ELISA test.	Disease: Dicrocoeliasis. Treatment: Praziquantel or Triclabendazole, Mirazid. Prevention: Do not ingest invasive ants with fruits and vegetables. Treat the sick persons. Control the vector snails. Vetenary control of animals. Educating the people about transmission of infection. Immunoprophylaxis is not available.