Causes of Diseases
When a person is affected by a disease either the normal functioning or the appearance of one or more systems of the body changes for the worse. These changes give rise to signs of the disease called symptoms. On the basis of the symptoms the physicians look for the signs of a particular disease and conduct tests to confirm the disease. Microscopic living things (known as germs) are all around us. Some of these germs can cause disease in people (Watch Disease Causes Video to learn more).
Diseases are caused by :-
i) Pathogens like virus, bacteria, fungi, protozoans or
ii) Poor health and under nourishment.
iii) Malfunctioning of body parts.
iv) Environmental pollution.
v) Genetic disorders.
Infectious diseases are caused by exposure to living organisms not normally present in the animal. Animals are exposed directly or indirectly to infectious organisms in many ways, including breath, urine, or manure of other animals, and from arthropods. Infectious agents enter the individual through the skin, mucous membranes, lungs, mouth, or reproductive tract. Agents, such as germs (bacteria, viruses, fungi, rickettsiae) and parasites (worms, protozoa, arthropods), infect or infest various tissues and organs of animals and humans. The germs and protozoa invade and multiply inside or outside of tissue cells, while worms (helminths) and arthropods invade and develop in the lumen of hollow organs and between cells of tissues. Tissue damage results from increased pressure, adverse reactions, toxins, or feeding by the disease agents.
Risk Factors: Risk factors may predispose an animal to disease. Multiple causative factors increase the probability of disease in the individual. Protective measures such as immunizations, husbandry, management practices, and crossbreeding decrease the risk that disease will occur.
Disease Causes Video
Useful for CBSE, ICSE, NCERT & International Students
Grade : 9
Subject : Biology
Lesson : Why Do We Fall Ill?
Topic: Disease Causes Video
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