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.


  1. Endoparasites:- These are parasites which live within the body of animals. Examples are liverfluke, tapeworm, roundworm etc.
  2. Ectoparasites:- These are parasites which live outside or on the host. Examples are ticks, lice, mites, fleas, insect bugs.



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 pig is the secondary host. The body segments called proglottides are arranged in 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.


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 pig where enzyme act on the egg and embryo is liberated. It finds its way to the blood stream 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.


  1. The effect on man varies. It may have so little effect on some people that they are unaware of its presence.
  2. Some may have abdominal pain or discomfort.
  3. Increase in appetite
  4. Weakness
  5. Loss of weight, dizziness and restlessness
  6. Poisonous substance produced by the worm may cause convulsion in some people.


  1. Sufficient cooking of meat to kill any larvae of the worm
  2. Prevention of the deposition of human excreta in such places that cattle and pig will not be able to eat them.
  3. Treatment of infected person by regular deworming.
  4. Inspection of animal before slaughtering
  5. Burning of infested pasture
  6. Proper meat inspection before selling.
  7. Rotational grazing.


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 are pass out with the faeces from the primary host(cattle,sheep,pig etc). if the eggs and faeces are passed out by the ruminant into 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 it way to the animal’s liver to the bile duct through the liver tissues.


  1. Destroys the liver tissues
  2. Causes general weakness of the animal
  3. Causes obstruction of the bile duct
  4. It inhibits the production of bile from the liver
  5. Lipid digestion is impaired
  6. It prevent the flow of bile from the gall bladder to the small intestine.
  7. Excessive blood from the liver causes anaemia
  8. It leads to death in extreme cases.


  1. Control snails on pasture using copper sulphate solution
  2. Regular deworming of animals
  3. Rotational grazing
  4. Avoid grazing near streams.

ROUNDWORM (Ascaris lumbricoides)

It is an elongated, cylindrical, whiteworm which is pointed at both ends. The body is smooth and covered by thick, tough cuticle of few centimeters long.


The eggs are fertilized in the female worm and the larva developed within the egg shell. The eggs are deposited in the intestine of pig from where they are passed out with the host faeces into soil where they can remain for years. When the eggs are picked up by pigs either through feeding or drinking, the egg shells are dissolved by digestive enzymes and the young larvae emerges. The larvae then pierces through 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 are swallowed through the gullet into the intestine. Here, the larva develop into mature worms and the life cycle is repeated all over again.


  1. Reduce growth of host animals
  2. High infestation can affect the respiration of host animals.
  3. Indigestion and constipation
  4. Loss of appetite and weakness result in death
  5. Destroy many organs during the migration of young worms.


  1. Regular deworming with piperazine drugs
  2. Good sanitation
  3. Provide clean and uncontaminated water to the pig


  1. State stages of roundworm.
  2. Discuss the life cycle of roundworm.
  3. List five examples of endoparasites.
  4. Distinguish between ecto and endo parasites


Tick:- This is an ectoparasite of livestock animals. The body is divided into head and abdominal region. It has four pairs of tough leathery integument. It possesses a toothed hypostome used for sucking blood from its host.


The life cycle of most ticks occur in four stages. These include the egg, the larvae, the nymph and the adult stages. Each of the stages normally requires a separate host.

Egg:- After the female tick has sucked blood and fully engorged, it drops from the host, lays its eggs in the  ground under grass and dies.

Larvae:- Each egg hatches into a larva with six legs. The larva crawls into the grass and attaches itself to the skin of passing animals or grazing animals. The larva feeds on the blood of the host and later falls to the ground.

Nymphs:- The larvae on the ground moults into nymphs with eight legs. The nymph crawls and attaches itself to a second host. It feeds on the host and later drops on the ground.

Adult:- Nymph on the ground finally moults into an adult tick which crawls into the grass and attaches itself onto a third host animal. If the adult tick is a female, it inserts its mouth to the body of the animal directly and sucks its blood. But, if the adult tick is a male, it does not fix itself to the host but crawls on the skin in search of a female tick to mate with. After mating with the female, the male dies. When the female has sucked enough blood, it falls on the ground, lay its eggs and dies and the whole cycle is repeated.

There is sexual dimorphism (two distinct forms) that is the male is different from the female. While the male tick does not suck blood, the female is blood sucking.

The stages of development of ticks occuring on the host depend on the type of tick. For example, in the three-host tick e.g. Ixodes  ricinus, Amblyomma sp, the larvae feed on one host, the nymphs on another and the adult feeds on a third host.

In the two-host tick exemplified Rhipicephalus evertsi (dog tick), the larvae and nymphs develop on the same host while the adult feeds on the second host.

In the one-host tick e.g. Boophilus decoloratus, all the three stages are completed on one individual host.

Methods of Diseases Transmission

The one-host tick transmits disease through the egg, that is, it is transovarian.

The two-host and three-host ticks transmit diseases by infecting their different hosts.


  1. They remove or suck appreciable quantities of blood from their host thus leading to anaemia.
  2. Their bite cause serious skin irritation which may lead to wounds.
  3. Transmission of diseases such as east coast fever (Theileriasis)
  4. Damages of skin by tick which reduces the quality of hide.
  5. Too much loss of blood may lead to loss of weight and death of host animal.


  1. Keep animals in clean surroundings
  2. Regular dipping of animals to destroy ticks or spraying with acaricide solution.
  3. Practice rotational grazing or paddocking.
  4. Isolation of new stock to ensure they are free from infection.
  5. Change of animal bedding regularly.
  6. Handpick ticks from the body of host animals


These are wingless insects with flattened bodies. They are remarkably specific to their hosts, that is, each species is parasitic on only one kind of animal. The lice of poultry or cattle for instance, cannot live successfully on man and vice versa. The body is divided into three-head, thorax and abdomen. Their bodies are made up of exoskeleton with mouth part used for biting and sucking. They attack cattle, sheep, goat and poultry birds.


All lice pass their life cycle on the surface of the host and they cannot live long away from a host. They attach their eggs called nits to the hair or feather of the host and the young ones called nymphs emerged from the hatched eggs. This is an incomplete metamorphosis. The nymphs after a series of moults of its skin becomes the adult male or female louse. The life cycle takes about three to four weeks.

Economic importance of lice

  1. Bites cause considerable irritation which results in scratching and restlessness.
  2. Scratching may result in sores which may be infested with bacteria
  3. Restlessness can result in low productivity of the stocks
  4. They act as vectors of disease
  5. They suck the blood of host thus leading to anaemia, loss of weight and death.

Mode of Transmission

By body contact


  1. Overcrowding should be avoided to reduce the incidence of contact.
  2. The parasite can be killed with insecticide.
  3. Keep animals in clean environment.
  4. Regular dipping of animals in acaricide solution.


  1. The following are ectoparasites of livestock except a. tick b. louse c. flea d. roundworm
  2. Which of the following is not an endoparasite of livestock? a. Earthworm b. tapeworm   c. roundworm  d. liverfluke.
  3. Attack of lice on animals can be controlled by the following except. a. vaccination
  4. dipping c. avoid overcrowding   d. spraying with  insecticide.
  5. Regular sucking of blood of animals by ticks can lead to a disease called a. anaemia
  6. trypanosomiasis c. ringworm   d. coccidiosis
  7. Trypanosomiasis affect the following animals except a. fowl b. goat c. cattle d. sheep


  1. Describe briefly the life history of tick.
  2. Compare and contrast the features of ticks and lice


  1. List  5  economic importance of lice
  2. What are parasites?
  3. List five endo parasites.
  4. How can lice be controlled?
  5. How can tick be controlled?


  1. List  five  economic importance of tick
  2. List  five  economic importance of lice


  1. List  three controls of  Lice
  2. What is animal disease?
  3. What are pathogens?
  4. List five disease causing organism.
  5. How can you control ticks
  6. List four economic importance of tick.

See also






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