Back to: AGRICULTURAL SCIENCE SS3
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In today’s class, we will be talking about livestock parasites. Enjoy the class!
A parasite is an organism that lives in or on another organism where it derives its nourishment without the host gaining anything from the association.
Forms of parasites
- Endoparasites: These are parasites which live within the body of animals. Examples are liver fluke, tapeworm, roundworm etc.
- Ectoparasites: These are parasites which live outside or on the host. Examples are ticks, lice, mites, fleas, insect bugs.
Life cycles of endoparasites
Tapeworm is composed of a very small head, neck and long segmented body. They belong to the group called Platyhelminthes. Taenia solium is found in pigs while Taenia saginata is found in cattle. The head called scolex consist of suckers and some times hooks as in Taenia solium. It holds on to its host by mean of these organs. Taenia solium may be about 4m to 12m long and can live inside man for many years, but only one can be present in a host at a time. Man is the primary host while the pig is the secondary host. The body segments called proglottides are arranged in a long row from the neck. The proglottides are small and young at the neck while those far from the neck are the largest and the oldest.
The life cycle of the tapeworm
Tapeworm is a hermaphrodite, that is, it has both male and female reproductive organs, so it can fertilize itself. A matured proglottid pulls off the body of the adult tapeworm, passed out with human faeces where pigs ingest it during feeding.
It goes to the intestine of the pig where enzyme act on the egg and embryo is liberated. It finds its way to the bloodstream by passing through the intestinal wall and finally deposited in the muscle or heart of the pig. Each embryo encycled itself by cyst to become bladderworm with an inverted head so that the sucker lies on the inside. When not well-cooked pork or beef containing the bladderworm is eaten, human digestive enzyme dissolves the bladderworm and young tapeworm with its head turn inside out emerges. They do not affect the health of the pig or cattle.
Economic importance of tapeworm
- The effect on man varies. It may have so little effect on some people that they are unaware of its presence.
- Some may have abdominal pain or discomfort.
- Increase in appetite
- Loss of weight, dizziness and restlessness
- A poisonous substance produced by the worm may cause convulsion in some people.
Control of tapeworm
- Sufficient cooking of meat to kill any larvae of the worm
- Prevention of the deposition of human excreta in such places that cattle and pig will not be able to eat them.
- Treatment of infected person by regular deworming.
- Inspection of an animal before slaughtering
- Burning of infested pasture
- Proper meat inspection before selling.
- Rotational grazing.
- What are endoparasites?
- Discuss the life cycle of tapeworm.
The life cycle of liver fluke (Fasciola hepatica)
The adult fluke is found in the bile duct of the animals where it feeds and reproduces. The adult fluke reproduces eggs in the bile duct of the animal which is passed out with the faeces from the primary host (cattle, sheep, pig, etc.). If the eggs and faeces are passed out by the ruminant into the water, they developed into a larva called miracidium which later hatches ten days. This larva swims in the water, looks for a snail –its secondary host (limnea trucatula)
It penetrates the snails’ skin or the pulmonary hole. It developed into a sporocyst within the snail. Through asexual reproduction, the sporocyst produces a larva called radial. The radial ruptures the sporocyst and migrate to the digestive gland of the snail. There it grows to the final larva called cercaria.
After six weeks, the cercaria leaves the snail through the pulmonary hole and swims to look for the final host in the water. The cercaria is ingested by the ruminant through infested pastures or water. Then in the animal’s stomach, it makes its way to the animal’s liver to the bile duct through the liver tissues.
Economic importance of liver fluke
- Destroys the liver tissues
- Causes general weakness of the animal
- Causes obstruction of the bile duct
- It inhibits the production of bile from the liver
- Lipid digestion is impaired
- It prevents the flow of bile from the gall bladder to the small intestine.
- Excessive blood from the liver causes anaemia
- It leads to death in extreme cases.
Control of liver fluke
- Control snails on pasture using copper sulphate solution
- Regular deworming of animals
- Rotational grazing
- Avoid grazing near streams.
Roundworm (Ascaris lumbricoides):
It is an elongated, cylindrical, white worm which is pointed at both ends. The body is smooth and covered by thick, tough cuticle of few centimetres long.
The life cycle of the roundworm
The eggs are fertilized in the female worm and the larva developed within the eggshell. The eggs are deposited in the intestine of pig from where they are passed out with the host faeces into the soil where they can remain for years. When the eggs are picked up by pigs either through feeding or drinking, the eggshells are dissolved by digestive enzymes and the young larvae emerge. The larvae then pierce through the intestinal wall to the blood, then to the liver, to the heart then to the lungs. From the lungs, then pierce into the mouth and throat of the pig. From the throat, the larva is swallowed through the gullet into the intestine. Here, the larva develops into mature worms and the life cycle is repeated all over again.
Economic importance of roundworm
- Reduce the growth of host animals
- High infestation can affect the respiration of host animals.
- Indigestion and constipation
- Loss of appetite and weakness results in death
- Destroy many organs during the migration of young worms.
Control of roundworm
- Regular deworming with piperazine drugs
- Good sanitation
- Provide clean and uncontaminated water to the pig.
- State stages of roundworm.
- Discuss the life cycle of roundworm.
- List five examples of endoparasites.
- Distinguish between ectoparasites and endoparasites
Essential Agric Science by O.A. Iwena, Chapter 41, Pages 390 – 395
- The following are endoparasites of livestock except a. insect bug b. roundworm c. liver fluke d. tapeworm
- The primary host of tapeworm is a. man b. sheep c. goat d. pig
- The head of a tapeworm is otherwise referred to as a. sucker b. scolex c. hook d. anchor
- The following are the economic importance of tapeworm except a. causing reduced growth b. causing indigestion c. causing death d. causing increased weight in animals
- Which of the following is not a method of preventing diseases? a. quarantine b. vaccination c. hygiene d. eating too much
- Explain briefly 5 economic importance of tapeworm in livestock production.
- Enumerate 5 methods of preventing livestock diseases.
In our next class, we will be talking about Bacterial Disease. We hope you enjoyed the class.
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