structure life cycle pathogenicity and control measurment of fasciole hepatic

Structure:

The structure of a fluke is more or less similar to that of planarian.

1.Shape and size: Fasciola hepatica has a thin, flattened leaf-shaped body,rounded anteriorly and bluntly pointed behind.It has a triangular cone or head at the anterior end giving it a shouldered appearance. It is about 1.8 to3 cm long.Maximum width is about 0.4 to 1.5 cm which is a little in front of the body . There are two muscular suckers, an oral sucker at the anterior end enclosing a mouth, and a large ventral sucker behind the head lobe on the ventral side.Sucker are muscular cups for attachment to the host by vacuums. Anterior to the ventral sucker is a common genital aperture or gonopore lying vertically.

2.Colouration : Colour is usually pinkish,but the transparency of body wall enable the observer to see the blackish or brownish vitelline glands along the lateral margin,and the alimentary canal, which appears brownish due to ingestible of the host.

3.Oral canal: Anterior end of the body is drawn out into a prominent conical projection termed out of the oral cone or head lobe, bearing at its tip a somewhat triangular aperture the mouth.

4.Sucker: There are two small suckers,anterior and ventral.Both are devoted of hook and spines.

(a) Anterior sucker: Mouth is situated at the centre and bottom of a cup-shaped muscular organ, known as

(b) Ventral sucker: About 3 to 4 mm behind the oral sucker,situated mid-vertically,is another bowl-like adhesive sucker,the

5. Aperture: In addition to mouth, there is two more permanent aperture in the body. A small common genital aperture gynophore situated mid-ventrally a little in front of the acetabulum.A single excretory pore lies dorsal surface, a little anterior to the middle of the body. The alimentary canal being incomplete as there is no anus.

6. Scales: Body of liver fluke is covered with a tegument (cuticle), from which project numerous minute backwardly directed spinules or scales. These anchors the body to the wall of host's bile duct, protect the body and help in locomotion.

Life cycle of Fasciola hepatica

Copulation and fertilisation;Through Fasciola hepatica are hermaphrodite even cross-fertilization is of common occurrence.Hence,before fertilisation copulation occurs;during copulation, which occurs in bile duct of the sheep, the cirrus of one Fasciola is inserted into the Laurer's canal of other Fasciola and the sperm are deposited into the oviduct, so that cross-fertilization takes place. During self-fertilization, which only when cross-fertilization does not take place, the sperm from the same Fasciola enter the same Fasciola enter the female genital aperture and pass down the uterus to fertilise the eggs in the oviduct.

Formation of lays eggs capsules: The eggs are brownish in colour,oval in shape and measure about 130 to 150m in length and 63 to 90m in width.The eggs are fertilised in the oviduct,the fertilised eggs receive yolk cells giving out droplets, the shell and become brownish-yellow the shell has an operculum or lid .Mehli's glands play no role in the formation of the shell. The completed 'eggs' are called capsules which are large in size and they pass into the uterus where development starts.Capsules come fall water

Development : Development starts in the uterus and is continued on the ground.The fertilised egg divides into a small propagation cell and a larger somatic cell. The somatic cell divide and forms the ectoderm of the larva Later the propagator cell divide into two cells, and the other forms a mass of germ cell at the posterior end of the larva.This method of development takes place in the formation of all the larval stages during the life history.In two weeks time, a small ciliated miracidium is formed and it comes out of the shell by forcing the operculum. The miracidium produces a proteolytic enzyme which erodes the lower surface of the operculum.

Infection of the primary host(sheep): Further development of the metacercaria takes place only if it is swallowed by the final host, the sheep.Metacercaria can also infect man if they are swallowed by eating cress on which cercariae encyst, but such case is rare.But metacercaria is not infected until 12 hours after encystment.In the alimentary canal of sheep, the cyst wall is digested and is young fluke emerges and bores through the wall of the intestine to enter the body of the host. After about two to six days they enter the liver and their movements in the liver for seven or eight weeks feeding mainly on blood and they enter the bile duct and the bile passages The young flukes have been growing in the liver and after several weeks in the bile duct, they become a sexually mature adult. The period of incubation in the sheep takes 3 to 4 months.

Pathogenesis/ symptoms : During the movement of the immature stage of Fasciola hepatica, which may continue for months. Infection of Invertebrates host (snail) result case Of significance economic importance of the effect of F.hepatica on its invertebrate host, whose bile duct as well as liver may follow by calcification and formation of gallstones . Heavy infections upset the normal metabolism of liver.This is due to haemorrhage caused and irritation infected by cortical spines. This disease thus caused called liver-rod or fascioliasis.Symptoms may include abdominal pain, an enlarged liver, fever vomiting, and diarrhea. In the chronic phase of the infection (from that parasite), symptoms result from the intermittent blockage of the bile and inflammation.Occasionally ectopic infection can occur in the intestine wall, lungs, or subcutaneous tissue.Symptoms of liver-rot, are more acute limbs than in a sheep, appear about a month after infection.Frequently, death may soon result due to cerebral apoplexy .However, if the host survives few weeks of infection, it falls a victim to acute anaemia and falls even at mild contact.Its appetite declines, rumination (chewing the cud) become irregular and at times there are fever and increase in respiratory activity. Conjunctive become whitish-yellow,dry and brittle wool falls off. After three months of infection comes the fatal period. Large oedemas or swellings ("watery poke") appear on jaws. Lactation and breeding are greatly reduced. Rarely does the host survive this

In case it does, the fluke may migrate to the duodenum and finally escape to the outside world with faeces.When this happen, or when fluke somehow dies in situ, the host recovers considerably.Infection by F. hepatica takes a huge toll of sheep annually.InEnglandit caused the death of about one and a half million sheep in 1830 and about double in number in 1879-1880.Ireland lost 60% of its flocks in 1882.

Control/Treatment and prevention of Fasciola hepatica:

Treatment of infection is not easy because it is difficult to introduce drugs in bile passage of infected sheep.Anti helminths drug such as Hexachloroethane,Carbon tetrachloride ,filling emetine hydrochloride, phenothiazine, and tetrachloroethane are being employed for treating of liver rot.These drugs are fairly effective in killing stage of the parasite in liver.Infection of Fasciola hepatica can be prevented or control by not consuming raw plants containing metacercariae. This can be accompanied by inspecting the plants, especially watercress, very carefully for the metacercaria or more effectively by not eating plants grown in areas where herbivorous mammals (especially ships) are found.

The contamination of water with feces from infected animals or people in areas where the aquatic plants are used for food should be prevented.It is better to prevent infection by control of the vector or intermediate host. Preventive measure include

1) killing heavily infect sheep,

2) destroying eggs and mature of infected sheep,

3) feeding infected sheep with salt and little dry food,

4) killing or checking snail population.

Snailskilledlledby adding copper sulphate solution in ponds and ditches or by draining their pastures as they are unable to survive long dry periods. Ducks feed on snails and can be usually employed in removing their population.Breeding of snail can be checked by removing vegetation from ponds and stream they inhibit Man can avoid infection by consuming thoroughly washed and frequently cooked vegetables.

Reference:

Aggarwal Sarita. A Text Book of Biology. New Delhi.: Madhuban Educational Books, 2011.

Bhamrah, H.S., and Kavita, Juneja. A Text Book of Invertebrates, New Delhi: Anmol Publications Pvt Ltd, 2011.

Jordan E.L. and P. S., Verma. Invertebrate Zoology, New Delhi,: S. Chand and Company Pvt. Ltd., 2011.

Kotpal, R. L., Modern Text Book of Zoology: Invertebrates, New Delhi, India: Rastogi Publications,2011.

http://www.biologydiscussion.com/

https://en.m.wikipedia.org/wiki/Fasciola_hepatica

http://www.parasitesinhumans.org/fasciola-hepatica-liver-fluke.html

http://patient.info/doctor/fasciola-hepatica