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/n Bacteria Diseases Animals Affected
1. Mastitis Cattle, sheep, goats, pigs
2. Contagious abortion/
Cattle, sheep, goats, pigs
3. Anthrax Cattle, sheep, goats
4. Tuberculosis Cattle, sheep, goats, pigs
and Poultry birds
5. Fowl typhoid Poultry 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/n Fungal Diseases Animals Affected
1. Ring worm All animals
2. Scabies Cattle, sheep, goats
3. Aspergillosis Poultry 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/n Viral Diseases Animals Affected
1. Foot & mouth Cattle, sheep, goats, pigs
2. Rinderpest (cattle plague) Cattle, sheep, goats, pigs
3. New castle disease Poultry birds
4. Fowl pox Poultry birds
5. Swine fever/Hog cholera Pigs

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/n Protozoan Diseases Animals Affected
1. Trypanosomiasis Cattle, sheep, goats and pigs
2. Coccidiosis Poultry birds, rabbits
3. Babesiosis/Red water disease Ruminants 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/n Parasites Disease Conditions
1. Tapeworm Taeniasis
2. Round worm Ascarisis
3. Trypanosome Trypanosomiasis
4. Tick East coast fever; Babesiosis
5. Flies-tse-tseflies, stable
flies, black flies, warble,
nasal, house flies.
6. Mites Mange

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/n Nutrient-deficiency Disorder Animals Affected
1. Bloats All ruminants
2. Osteomalacia All domestic animals
3. Rickets All domestic animals
4. Anaemia All 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.