Lecture #8: THE LIVER FLUKES

******  FASCIOLA HEPATICA  ******

Common name:       Sheep liver fluke

Disease:                     Fascioliasis, liver rot

Halzoun or pharyngeal fascioliasis – laryngopharyngitis due to eating raw infected sheep or goat liver; the young adult flukes attached to the pharynx, larynx, Eustachian tube or palates. Signs and symptoms include: dysphagia, dyspnea, deafness and asphyxia

Cutaneous fascioliasis – an ectopic foci wherein the flukes lodged themselves in the subcutaneous tissue causing an oval or round reddish–brown discoloration with associated pain and itchy sensation.

Morphology:

1.      Adult has smaller oral sucker and a slightly bigger ventral sucker. The pharynx is well–developed and following the short esophagus. The intestinal ceca bifurcates which is characteristically dendritic and this extends down to the posterior end. It also has a highly branched paired testis which lies one behind the other. Vitellaria is also highly branched; the branched ovary is situated at the right side of the ventral sucker and opposite it, it is the coiled uterus.

2.      Ova measure about 150u, immature when laid

1^st Intermediate Host:          Lymnea philippinensis

2^nd Intermediate Host:        Aquatic vegetation like water cress

Life cycle

******  CLONORCHIS SINENSIS  ******

Common name:                   Chinese liver fluke

                                                Oriental liver fluke

Disease:                                 Clonorchiasis

Morphology

1.      Adult measure 10–25 mm, spatulate organism attenuated anteriorly and rounded posteriorly. The integument is aspinose. The oral sucker is slightly larger than the ventral sucker. The most characteristic feature of the worm are the large deeply lobed or branched testes which are situated one behind the other in the posterior 3^rd of the body, with branches extending into the lateral fields. The vitellaria are delicate granular aggregates in the lateral field.

2.      Egg measure about 29–35u, broadly ovoidal with moderately thick light yellow brown shell provided with a distinct convex operculum which fits into a rimmed extension of the shell. They have thick posterior and with comma– shaped operculum (old fashioned electric bulb). They are embryonated when laid and contain mature miracedium.

1^st Intermediate Host:          Melanoides tuberculatus; Crithidia, Thiara, Bulimus

2^nd Intermediate Host:        Fresh water fishes

Life cycle

  

******  OPISTORCHIS FELINEUS  *******

Common name:       Cat liver fluke

Disease:                     Opistorchiasis

Morphology:

1.      Adult measures from 7–12 mm, lanceolated in shape with a subterminal oral sucker, the ventral sucker is almost of equal size as the oral sucker, the diagnostic feature is the lobed pair of testes arranged obliquely to each other, on the lateral field of the worm or transversely compressed vitelline follicles; simple intestinal ceca.

2.      Ova measures 30 x 10u, it is elongatedly oval in shape & resembles the Clonorchis ova except for the shape & absence of the prominent shoulder rim.

1^st Intermediate Host:          Melanoides tuberculatus

2^nd Intermediate Host:        fresh fish (Cyprinoid)

Life cycle

*******  OPISTORCHIS VIVERRINI  *******

1.      An important human infection in Thailand.

2.      Similar to O. felineus except for its greater proximity on the ovary and testes, fewer clusters of aggregated vitellaria.

3.      Does not cause any specific symptoms