Subject : Agricultural Science


Term : Second Term


Class : JSS 2


Week 3


Topic :





  1. Meaning of Disease
  2. Groups of Disease Causing Organisms of Livestock


Meaning of Disease

Disease means a change in the normal functions or well-being of farm animals which results in observable symptoms. OR

It is an illness, unhealthy or abnormal condition in the body of farm animals.

Groups of Disease Causing Organisms of Livestock

There are many types of disease causing organisms which attack farm animals.

These organisms include;

  1. bacteria,
  2. fungi,
  3. virus,
  4. protozoan and
  5. metazoan.

1. Bacterial Diseases

These are diseases caused by bacteria. Bacteria are single-celled micro-organisms. Examples of bacterial diseases of farm animals include:

S/nBacteria DiseasesAnimals Affected
1.MastitisCattle, sheep, goats, pigs
2.Contagious abortion/
Cattle, sheep, goats, pigs
3.AnthraxCattle, sheep, goats
4.TuberculosisCattle, sheep, goats, pigs
and Poultry birds
5.Fowl typhoidPoultry birds

2. Fungal Diseases

These are diseases caused by fungi. Fungi are lower plants which do not contain chlorophyll. They reproduce by spores and live by absorbing nutrients from organic matter.

Examples of fungal diseases:

S/nFungal DiseasesAnimals Affected
1.Ring wormAll animals
2.ScabiesCattle, sheep, goats
3.AspergillosisPoultry birds

3. Viral Diseases

These are diseases caused by viruses. Viruses are extremely small micro-organisms which can survive only inside living cells. They are much smaller than bacteria.

Examples of viral diseases of livestock are:

S/nViral DiseasesAnimals Affected
1.Foot & mouthCattle, sheep, goats, pigs
2.Rinderpest (cattle plague)Cattle, sheep, goats, pigs
3.New castle diseasePoultry birds
4.Fowl poxPoultry birds
5.Swine fever/Hog choleraPigs

4. Protozoan Diseases

These are diseases caused by protozoa. Protozoa are single-celled, majorly microscope and mostly water – dwelling organism which live independently or in colonies. They feed on organic compounds.

Examples of protozoa diseases of livestock are:

S/nProtozoan DiseasesAnimals Affected
1.TrypanosomiasisCattle, sheep, goats and pigs
2.CoccidiosisPoultry birds, rabbits
3.Babesiosis/Red water diseaseRuminants and pigs

Life Cycle of a Tapeworm

5. Metazoan Diseases (Parasitic Diseases)

Diseases caused by parasites are known as metazoan diseases. Those parasites which live externally on their host called ecto-parasites. Examples are lice, ticks and mites.

Those which live internally in their hosts are called endo-parasites. They are liver-flukes, roundworms and tapeworms.

Liver-flukes, roundworms and tapeworms affect all animals.

S/nParasitesDisease Conditions
2.Round wormAscarisis
4.TickEast coast fever; Babesiosis
5.Flies-tse-tseflies, stable
flies, black flies, warble,
nasal, house flies.

6. Nutrient-deficiency Disorders

Nutrient-deficiency disorders are those which occur when animals do not consume the right amounts of essential nutrients.

Examples of nutrient-deficiency disorders are:

S/nNutrient-deficiency DisorderAnimals Affected
1.BloatsAll ruminants
2.OsteomalaciaAll domestic animals
3.RicketsAll domestic animals
4.AnaemiaAll domestic animals



  1. Define the terms disease and pathogens.
  2. List three examples each of the following: (i) Viral disease (ii) Fungal disease (iii) Bacterial disease
  3. Mention four pathogenic organisms.