(a) Define the term "disease." (b) State the difference between resistance and susceptibility to diseases. (c) Enumerate four economic importance of animal ...

(a) Definition of disease

A disease is any departure from the normal state of health of an animal in which the body or some of its parts fail to function properly, usually caused by a pathogen, deficiency or disorder.

(b) Difference between resistance and susceptibility

Resistance is the natural ability of an animal to withstand or overcome infection by a disease-causing organism without becoming ill, whereas susceptibility is the inability of an animal to withstand infection, so that it easily falls sick when exposed to the pathogen.

(c) Four economic importance of animal disease

• It causes death of animals, leading to loss of stock and capital.
• It reduces productivity (lower milk, meat, egg and wool yield).
• It increases the cost of production through spending on drugs and veterinary care.
• It lowers the market value/quality of animals and their products; some diseases (zoonoses) are transmissible to man.

(d) Three factors that determine the degree of resistance

• The breed and heredity of the animal.
• The age and general health/nutritional status of the animal.
• Previous exposure or vaccination that confers immunity.

(e) Three conditions that may inactivate a pathogenic organism

• Exposure to high temperature/heat (e.g. boiling, pasteurisation).
• Application of disinfectants and antiseptics.
• Exposure to sunlight (ultraviolet radiation) and drying.