Animal Health I – SS2 Livestock Farming Lesson Note (Second Term)

A parasite is a living thing that lives on or inside another animal, called the host, and takes its food, sucks its blood or makes it sick. External parasites, such as ticks, lice and mites, live on the skin or hair. Internal parasites, such as roundworms, tapeworms and liver flukes, live inside the body.

Behavioural objectives

By the end of the lesson, students should be able to:

• define a parasite and a host;
• name the two groups of parasites and give examples of each;
• describe the damage or symptoms caused by ticks, lice, mites, roundworms, tapeworms and liver flukes;
• state four ways parasites spread;
• list methods of preventing and controlling external and internal parasites.

What is a parasite?

In our previous lessons, we talked about feeding and housing. But even the best-fed cow can become thin and weak if it has “uninvited guests.” These guests are called parasites.

A parasite is a living thing that lives on or inside another animal (the host). The parasite pays no rent. It steals the animal’s food, sucks its blood and makes it sick.

What are the groups of parasites?

There are two main groups of parasites:

1. External parasites (ectoparasites): These live on the skin or hair of the animal (e.g. ticks, lice).
2. Internal parasites (endoparasites): These live inside the animal’s body, usually in the stomach, lungs or liver (e.g. tapeworms, roundworms).

What are the common external parasites?

These are the parasites you can usually see with your eyes when you look closely at a goat or a cow. They are the skin attackers.

Ticks

Ticks are the “vampires” of the farm. They attach themselves to the soft parts of the animal (like the ears or under the tail) and suck blood.

• Damage: They cause anaemia (blood loss), ruin the quality of the animal’s hide (skin) and spread dangerous diseases like heartwater.

Lice

These are tiny insects that crawl through the hair or feathers.

• Damage: They make the animal very itchy. You will see the animal rubbing its body against walls or trees. This causes the hair to fall off and the skin to become sore.

Mites

These are so small you can barely see them. They burrow into the skin.

• Damage: They cause a disease called mange, where the skin becomes crusty, thick and rough.

What are the common internal parasites?

These are dangerous because they are hidden. A farmer might think his pig is eating well, but the worms inside are actually the ones getting fat!

Roundworms

These look like pieces of white string or spaghetti. They live in the intestines.

• Symptoms: The animal develops a “potbelly”, loses weight and might have diarrhoea.

Tapeworms

These are flat and can grow very long. They have “hooks” on their heads to grab onto the animal’s gut.

• Symptoms: You might see white, seed-like segments in the animal’s droppings.

Liver flukes

These are leaf-shaped and live in the liver of cattle and sheep. They usually come from animals eating grass near swampy areas where snails live.

• Symptoms: The animal becomes very weak, and the area under its jaw might swell up (called “bottle jaw”).

How do parasites spread?

If you want to stop parasites, you have to know their “secret routes.”

1. Contaminated pasture: When a sick animal passes droppings, the eggs of the worms come out. When a healthy animal eats grass from that same spot, it swallows the eggs.
2. Dirty water: Many parasites live in stagnant (still) water or muddy areas.
3. Physical contact: Lice and mites pass from one animal to another when they huddle together in a crowded pen.
4. Intermediate hosts: Some parasites use “middlemen.” For example, a snail helps the liver fluke get into the cow, and a fly can carry parasites from one pig to another.

How can parasites be prevented and controlled?

You do not have to sit back and watch your animals suffer. Here is how the farmer fights back.

For external parasites

• Dipping: The animals walk through a deep pool of water mixed with chemicals (acaricides).
• Spraying: Using a knapsack sprayer to “bath” the animal with medicine.
• Hand-picking: On small farms, you can manually pull ticks off (but be careful not to leave the head in the skin!).

For internal parasites

• Deworming: Giving the animal medicine (pills or liquids) to kill the worms inside. This should be done every 3 months.
• Rotational grazing: Do not let your animals stay on one piece of land for too long. Move them so the parasite eggs left in the droppings die before the animals return.
• Clean water: Provide water from a borehole or a clean tank, not a muddy pond.

Farmer’s advice: A clean pen is the best medicine. If you sweep out the droppings and keep the floor dry, most parasites will have nowhere to hide!

Evaluation

1. Why do we say a parasite is like a “thief”?
2. If your goat is always scratching its body against a wooden pole, what parasite do you think it has?
3. Why should we avoid grazing our sheep near swampy areas?
4. Name two ways of controlling external parasites.

Assignment

1. List two external parasites and two internal parasites. State one damage or symptom caused by each.
2. Explain how rotational grazing helps to control internal parasites.