Any condition that causes deviation from the normal state of animal. It is a condition where the system of animal is not function properly.

• Disease may be infectious or non-infectious. 

INFECTIOUS DISEASE

 Are illness that are contagious , meaning they can be spread from one animal to another. infectious diseases are caused by microorganisms called pathogens. Bacterial and viral infections are common causes of infectious diseases.

• BACTERIA – are simple , single- celled  microorganisms . live in air , soil,  food , and on the bodies of animals and plants. Some bacteria injure cells by giving of poisons called toxins. Ex. Cholera , Tuberculosis , Tetanus , Diphtheria , Typhoid fever
• VIRUSES – are the  smallest pathogens . A virus can multiply only after entering in a living  cell . The virus then takes over the cell’s reproductive mechanisms, resulting in cell damage or death. Ex. Rabies , Foot and mouth disease, Lumpy skin disease , Hog cholera
• FUNGI- organisms such as yeast , moulds and mushrooms are known as fungi. Fungi grow in warm , dark, and moist areas. Ex.  Cryptococcosis , aspergillosis
• PROTOZOANS  –    have the ability to move through fluids in search of food. Ex. Trichomoniasis , coccidiosis

HOW PATHOGENS CAN SPREAD

Pathogens can spread through  contact with –

• An infected animal
• An infected person
• Contaminated food and water
• Contaminated soil 

Pathogens can enter into the body through breaks in skin or through the moist lining of the eyes , ear, nose , mouth, and other openings.

NON-INFECTIOUS DISEASE

  It is not spread by contagious. It is because of –

• Injuries
• Poisons
• Poor nutrition
• Birth defects