Fasciola: Liver Rot disease and Parasitic adaptations
Posted on : 30-11-2017 Posted by : Admin



When sheep are infected by the liver fluke or Fasciola hepatica, the liver of the sheep is seriously affected in terms of the structure and function. A single sheep may accommodate around 200 adult flukes in its liver and as a result the liver may stop to function. Consequently liver rot occurs. For this reason, this disease is known as liver rot or Fascioliasis.



The vertebrate host (Sheep, goat etc.) may catch the infection by grazing on the grass and leaves which have metacercaria larva attached to them. On the other hand the invertebrate host (snail) acquires the disease when a miracidium larva established contact with the suitable part of the snail body.



The infection in the invertebrate host results in the partial or complete destruction of the effected site (liver or gonads). Heavy infection may result in the increase in size of the snail.

The infection in the primary host is of major economic importance. In the sheep the bile ducts and the liver are damaged. In bile ducts it causes inflammation resulting in the loss of epithelium and gall stones. Also the normal metabolism of the liver is affected by heavy infection. The infection if the sheep is called as liver rot or Fascioliasis.



The symptoms of liver rot include,

  • Decline in appetite
  • Anemia
  • Irregular rumination
  • Fever
  • Increase in respiratory activity
  • Conjunctiva becomes whitish-yellow
  • Wool becomes dry, brittle and finally falls off
  • Finally it leads to the death of the infected host

Also in some cases the parasite may escape out through the faeces and there are chances that the host recovers and survives.



The treatment of this disease is not easy as it is not possible to introduce drugs into the bile passage of the infected sheep. Anti-helminth drugs namely hexachloroethane, carbontetrachloride, filcin, emetine hydrochloride, phenothiazine and tetrachloroethane are used for the treatment of the liver rot cases. These drugs are effective in killing the stages of parasite in liver.



The control of the vector is the best method to prevent the disease. Also other preventive measures include the following:

  • Separation and Killing of heavily infected sheep
  • Destroying manure and eggs of infected sheep
  • Feeding infected sheep with salt and little dry food.
  • Also killing of the snail population would be effective. Snails are killed by adding copper sulphate solution in the ponds and ditches. Also ducks can be employed to eat on the snails.
  • Humans can avoid the infection by thoroughly washing and adequately cooking the vegetables.



Liver flukes have undergone tremendous modifications both morphologically as well as physiologically to be able to suit themselves to their endoparasitic mode of life. The following are the parasitic adaptations of Fasciola sps.

  1. A thick and permeable tegument is present in liver flukes. This tegument protects the animal from the enzymatic actions of the digestive juices of the host. On the other hand this tegument is permeable to water to be able to get the nutrients from the surroundings
  2. Absence of locomotory organs as they are not needed by the animals. Some of the free swimming larval forms like miracidium has cilia which help in movement
  3. Alimentary canal is without anus as there is no undigested food to be egested. Branched intestine helps in distribution of the digested food to all parts of the body
  4. Oral sucker, acetabulum and spines of the body wall of the adult worm serve as the organs of attachment to the host tissues
  5. The adults lack, circulatory system, respiratory system, sensory organs as they are not necessary
  6. Nervous system is poorly developed as it is not completely utilized. But free swimming miracidium larva has sensory eye-spots
  7. Respiration is anaerobic type, due to the lack of free oxygen
  8. Of all the body systems, reproductive is well developed. It produces enormous number of eggs to increase mortality as their live is prone to several hazards
  9. Egg shells of these animals are resistant to protect the developing zygote from unfavorable environmental conditions
  10. Self-fertilization is ensured by hermaphroditism even in the absence of another companion for copulation.

  1. What is liver rot disease?
  2. Write about the treatment and preventive measurements of liver rot disease.
  3. What are the symptoms of liver rot disease.
  4. What are parasitic adaptations?
  5. Write all the adaptations of Fasiola as a Parasite.

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