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Parasites in Livestock - Agriculture Form 2

Suggested Practical Activities in Livestock Parasites

Activity 1
Visit a livestock yard collect in a safe container the following parasites.
Ticks, Lice, Fleas, Keds and Tsetse flies

Activity 2
Visit a slaughter house collect in a safe container the following internal parasites Tapeworms, roundworms and Liver-flukes. (It is important to seek the assistance of the slaughter staff)


Background Information

In your previous studies it was clear to you that livestock diseases and parasites have high economic effects in livestock production. Parasites vectors to various livestock, damage organs of animals and predisposes them to secondary infections.
Parasites have the following effects on livestock:

  • They are vectors for animal diseases
  • Damage and block organs making the inefficient
  • Predispose livestock to diseases
  • Lower quality of products

The living organisms that cause diseases in livestock include:

  • pathogens
  • parasites



- A reduction in the number of red blood cells. Limits the ability of the blood to carry oxygen and its necessary for the completion of a parasite's life cycle.


- Lack or loss of appetite for food.


- A taxonomic class within the arthropoda phylum made up of invertebrates with two segments.


- A phylum in the animal kingdom consisting of invertebrate animals having an association.


- A means of giving liquid medicine by mouth to animals to control internal


- An organism that affects the external surfaces of an organism e.g. ticks


- Extreme weight loss due to illness or starvation.


- An organism that lives inside the body of an organism; such as a tapeworm


- (external skeleton), a segmented body, and jointed appendages. Includes crustaceans;
exoskeleton, a three-part body (head, thorax, and abdomen), three pairs of jointed.


-An organism that nourishes and supports a parasite; it does not benefit and is often harmed by the parasite.


- A taxonomic class within the phylum arthropod made up of invertebrates that have a chitinous insects; millipedes; centipedes.

Intermediate host

- An organism that harbors a parasite typically providing nourishment and shelter


- Swelling from excessive accumulation of watery fluid in cells, tissues, or serous cavities other nutrients around the body, and excretion of waste products.


-An organism that lives in or on another and obtains nourishment and/or shelter from the host without benefiting or killing the host.


is an association between two organisms in which one is called a parasite and the other a host in the content of the association. The parasite benefits by nourishing itself at the expense of the host.


- Any of the segments of a tapeworm; they contain both male and female reproductive organs their body and four pairs of legs but no antennae.


Topic objectives

By the end of this topic, you should be able to:

  • describe host-parasite relationship.
  • identify different parasites.
  • describe the lifecycles of parasites.
  • explain methods of parasite control in livestock.

Livestock Health II (Parasites)

Introduction to parasitism in livestock

Parasites cause considerable damage to livestock and loss of income to farmers. In this lesson, we shall explore the effects of parasites on livestock and the most susceptible stage of their lifecycle in order to successfully control them.
Parasitism is an association between two organisms in which one is called a parasite and the other a host in the context of the association. The parasite benefits by nourishing itself at the expense of the host.


Host-parasite relationship

Apart from deriving nourishment and protection from the livestock, other effects of parasites include;
1.Irritate their hosts, reducing feeding time
2.Affect growth rate
3.Reduce production in these animals.
Parasites derive nourishment and / or protection from a host while the host derive nothing in return.
Host usually loses blood becoming anaemic and gets exposed to secondary infections as well as destruction of its organs.


External parasites

They refer to parasites found on outside the body of the livestock on or under the skin of the host. Most of the ectoparasites belong to the class Arthropoda with two distinct classes namely (i) Insecta for example Tsetse flies, Lice, Keds, Fleas.

(ii) Arachnida like Ticks and Mites Various microenvironments eg. under the tail, belly region, anal region around the neck among other areas, favour the proliferation for different types of external parasites. This affects the distribution of the parasites and livestock production in general.

Control of tsetse flies

Methods of controlling tsetse flies include:

  • Chemical method for example use of insecticides.
  • Biological method for example sterilization of males flies.
  • Physical method for example use of fly traps.
  • Cultural method for example destruction of breeding grounds.
  • Creation of buffers areas.

View the video to appreciate methods of tsetse flies control



This is the single most important ecto-parasite in tropical Africa of all the known external parasites.
Ticks have an incomplete life cycle comprising of the following developmental stages;

  • Egg
  • Six legged larva
  • Eight legged larva
  • Eightlegged adult

The most common harmful effects of ticks on livestock include

  • Cause injury to the animal
  • Spread very dangerous diseases
  • Cause irritation that leads to scratching and self-inflicted wounds in sheep lowering the quality of wool.

Life cycle of one-host tick

These are ticks that require only one host to complete their life cycle. The developmental stages of a one-host tick are completed on one animal. The lifecycle of one host tick is spent on same host. Eggs on the ground hatch into larvae.

The larvae climbs on the host suck blood and become engorged. The larva then moults into nymph. This feeds and changes in to adult.
Examples include: blue tick, Cattle tick, and the Texas fever tick

Lifecycle of two-host tick

These are ticks that require two different hosts to complete their life cycle
The lifecycle of two host tick is spent on two hosts. Eggs on the ground hatch into larvae. The larvae climbs on the host suck blood and become engorged. The larva then mounts into nymph and climbs on second host. The nymph feeds and changes in to adult.

Anaplasmosis is example of disease transmitted by two host ticks in cattle

Life cycle of a three-host tick

These are ticks that require three different hosts to complete their life cycle

Chemical control of Ticks

This involves application of Acaricides to livestock using various method eg Dipping, spraying, or manual hand dressing

A good acaricide should have the following characteristics

  • Have the ability to kill ticks
  • Be harmless to both human and livestock
  • Be chemically stable
  • Remain effective even when fouled by dung, mud or hair

Parasites Control

View the video to appreciate methods of tick control

Cultural methods of tick control

  • Burning infested pastures
  • Ploughing infested pastures
  • Rotational grazing
  • Double fencing
  • Hand picking and killing

General methods of controlling external parasites

Other examples of external parasites methods of control include

  • Shearing wool to reduce Lice, Keds and Fleas
  • Hand spraying with acaricides Keds Lice, Fleas
  • House Hygiene to reduce to break life cycle Mites, Fleas
  • Application of petroleum jelly Lice, Fleas to reduce Irritation caused by parasites
  • Dusting to kill Lice, Fleas,Keds

Hand spraying

Lice, fleas, keds and mites cause considerable loses in livestock. Animal houses should be cleaned and dusted regularly.


Internal parasites

They are parasites that are found in the body of the livestock eg. Tapeworms, roundworms, Liver-flukes.
Livestock houses should not only provide protection against elements of environment but also must allow ease in maintenance of high standards of hygiene. Dirty environments promote infection by internal parasites.

Heavy infestation by internal parasites leads to damage of body organs.

Proper disposal of human faeces and animal droppings plays a vital role in the management of internal parasites.
Proper drainage disturbs and breaks the microclimates suitable for the various developmental stages of various parasites.

General methods of controlling internal parasites

The following factors should be considered in the control of internal parasites;
1.Nutritional status,
2.Size of the animal,
3.The environment of livestock.
The stock person should ensure that all predisposing factors to infection are controlled, these include,

  • Overcrowding of animals in the house is avoided.
  • Manure or dung is removed frequently and clean bedding provided.
  • A high plane of nutrition is maintained.
  • High standards of hygiene are observed.



Roundworms attack common livestock animals for example Sheep, Goats, Cattle, Pigs, Donkeys and Poultry among others.
Heavy infestation by roundworms leads to anorexia, diarrhea, potbelly, eggs and adults in faeces, general body emaciation, starry coat and anaemia.
The eggs of roundworms must be ingested by the host animal for its life cycle to completed.


Life cycle of tapeworms

A typical life cycle starts with ingestion of infective eggs found in human faeces. Whereas tapeworms have similar lifecycles, Taenia solium must be ingested by pigs, while Taenia saginata must be ingested by cattle in order to complete their lifecycles. Proglottides or segments can be seen in faeces, animals become ravenous and characteristic oedematous swelling appear under the jaw.


Liver flukes

These are parasites that are found localized in the liver of animals
There are many species of flukes that attack livestock,

Fasciola hepatica

in sheep and

Fasciola gigantica

in cattle are the most common.
Liver flukes attack many types of livestock, especially cattle, sheep and goats. Water snail Lymnaea species, is the intermediate host.
Control liver fluke basically involves drenching of livestock animals with Antihelminthic drugs and elimination of the intermediate host by draining swampy area.

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