Health and Welfare of Farm Animals
Session 2 - The Causes of Ill-Health in Farm Animals
This resource is suitable to support Level 2 Agriculture courses.
Causes of Ill Health
Ill health in animals can be caused by:
- Viruses
- Bacteria
- Fungi
- Parasites
- Metabolic disorder
- Poisons
Prevention and Treatment of Ill Health
For diseases to be prevented or treated it is important that the
cause of ill health is known. For example:
A change in feeding system could prevent metabolic disorders,
whereas improved hygiene or vaccination may be appropriate
actions to take to prevent some viral or bacterial diseases.
Bacteria: Characteristics
Small disease causing organisms.
Range of types, shapes and sizes (round, rod shaped, spiral).
Can grow and multiply outside host cells.
Can live as spores for many years (these may be hard to kill
with disinfectants).
Can be seen with a light microscope Sometimes a disease will be
described by using the scientific name of the bacteria e.g.
Escherichia coli which is shortened to E. coli.
May respond to antibiotics.
Examples of Diseases Caused by Bacteria
Foot rot (Fusobacterium necrophorum and Dichelobacter nodosus).
Digital dermatitis in cattle.
Anthrax (Bacillus anthracis).
Joint ill.
Examples of Diseases Caused by Bacteria
Clostridial diseases, e.g.
Tetanus (Clostridium tetani).
Braxy (Clostridium septicum).
Pulpy kidney (Clostridium welchii).
Black disease (Clostridi um oedematiens).
Virus : Characteristics
Very small disease causing organism.
Can only multiply inside other living cells.
Often very contagious.
May be killed by disinfectants when outside the body.
Can’t be seen with an ordinary microscope.
Examples of Ill Health Caused by Viruses
Foot and Mouth diseases.
Orf.
IBR - Infectious Bovine Rhinitis.
BVD - Bovine Viral Diarrhoea.
Coronavirus scouring in calves.
Fungi Characteristics
These include moulds and yeasts.
Larger than bacteria.
Multiply rapidly under warm moist conditions.
Quite resistant to disinfection.
Example: Ringworm.
Parasite Characteristics
These are larger organisms that live at the expense of the host
(the animal they live on).
Internal parasite live inside the host (e.g. in the intestine,
liver, lungs).
External parasites live on the outside of the animal.
Some parasites only spend a short part of their life cycle with
the host (e.g. ticks).
Parasites such as tapeworms carry out most of their life cycle
inside the host.
Examples of Parasites
Round worms (Nematoda).
Tapeworms (Cestoda).
Liver Fluke (Trematoda).
Lice.
Blowfly.
Ticks.
Sheep scab.
Metabolic Disorders and Deficiencies
Metabolic disorders occur when there is an imbalance of energy
or minerals in the body tissues.
-
May be due to a lack of a mineral in the feed e.g. grass
staggers (hypomagnesaemia) in stock on spring grass.
-
May be brought on by stress e.g. weather or handling.
Examples of Metabolic Diseases and Disorders
Lack of calcium (Hypocalcaemia) - Milk fever.
Lack of magnesium (Hypomagnesaemia) - Grass staggers.
Lack of blood sugar (Hypoglycemia) - Twin lamb disease.
Lack of Copper - Swayback.
Poison Characteristics
May be due to animals eating poisonous plants.
Accidental overdosing e.g. giving sheep too much copper.
From farm chemicals.
