Livestock Ectoparasites Life Cycles

Back to: AGRICULTURAL SCIENCE SS3

 

Welcome to class! 

In today’s class, we will be talking about livestock ectoparasites life cycles. Enjoy the class!

Livestock Ectoparasites Life Cycles

Tick

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

The life cycle of a tick

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

1. 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.
2.  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.
3.  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.
4.  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 bloodsucking.

The stages of development of ticks occurring 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.

Economic importance of ticks

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. Damage of the 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.

Control of ticks

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

Evaluation

1. What are ectoparasites?
2. State stages of tick.
3. Discuss the life cycle of tick.

Lice

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 mouthpart used for biting and sucking. They attack cattle, sheep, goat and poultry birds.

The life cycle of lice

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 become 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

Control of lice

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.

General evaluation

1. What are ectoparasites?
2. State stages of lice.
3. Discuss the life cycle of lice
4. List five ectoparasites
5. List five endoparasites 

Reading assignment

Essential Agric Science by O.A. Iwena, Chapter 41, Pages 394 – 396

Assignment

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     b. dipping   c. avoid overcrowding      d. spraying with  insecticide.
4. Regular sucking of blood of animals by ticks can lead to a disease called a. anaemia  b. trypanosomiasis     c. ringworm   d. coccidiosis
5. Trypanosomiasis affect the following animals except a. fowl b. goat c. cattle d. sheep

 Theory

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

 

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