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Factors in the Development of Diseases
Reported by: Patrick Sagario and Ellyza Cua
III-Boyle
Contents:• Modern Concepts of Diseases• Factors that Cause Diseases - Host - Agent - Environment• Six Essential Factors in the Developm
ent of the Infection Process
The Modern Concepts of DiseasesDISEASES...• may be defined as a failure of the adaptive
mechanics of an organism to counteract adequately the stimuli and stress to which it is subjected, resulting in a disturbance in function or structure of some parts of the body.
• may be described as a departure from a positive state of health or well-being.
• exists whenever there is an impairment of the normal state of organisms that affect the performance of vital functions.
The Modern Concepts of DiseasesDISEASES...• results when, in the struggle between the
organism and the individual, there is a visible evidence of the interaction.
• is the detectable reaction of the individual, the human host to a parasite (an infectious agent in a particular environment).
Factors that Cause Disease
Host (man)
Agent Environment
The Host
MAN MAY...a) become an obligate host where the
microbiological agent has been established in man and only in man for its survival. Man is an obligate host to the virus of measles. Only in cells of man can the virus of measles survive. Man is its only reservoir.
b) be a principal host for some diseases where he is chiefly responsible for the propagation of the parasite as in salmonella infection (typhoid). Man is the reservoir of infection.
c) be an occasional host. Animals are the principal reservoir; man is an unimportant reservoir.
The Host
EXAMPLE:
Rabies – principal host is animal - occasional host is man
The host accidentally steps in the life cycle of the organisms.
Disease Agents
EFFECTS OF MICROORGANISMS ON THE BODY:1. Destroy body cells and tissues, e.g., boils,
tuberculosis2. Cause mechanical injury, e.g., due to rapid
multiplication3. Secrete toxins or poison, e.g., bacterial diseases,
sore throat, diphtheria, tetanus, typhoid fever4. Cause uncomfortable bodily reactions such as
fever and aching, e.g., influenza
Disease Agents
TYPES OF AGENTS:
• biological – amoebic dysentery• chemical – fluorosis• physical – trauma or accident• nutritional – anemia, goiter, beri-beri, etc.• psychological – stress, tension, neurosis,
psychosis
Environment
THE FAVORABLE ECOLOGICAL FACTORS:
• good heredity• good environment• proper nutrition• adequate medical care• satisfying work and recreation• personal-social fulfillment• emotional maturity, etc.
Environment
THE UNFAVORABLE ECOLOGICAL FACTORS:
• poor heredity• poor environment• low living standards• stress, pathogenic organisms• psychogenic-emotional factors• aging• unhealthful practices
KEEP IN MIND THAT...• Disease occurs when an imbalance exists
between the host and the disease agent as they interact in the environment.
• Health is maintained when a state of balance exists between the three forces.
• Infection is the successful entry, lodgement and multiplication of disease agents in the body.
• The presence of parasites alone do not result in disease, while disease results when the parasites overcome the resistance of the host and cause destruction or disturbance in the function of the body.
Six Essential Factors in the Development of the Infection Process.
Reservoir of Source of Infection
Causative Agent
Modes of Escape
Modes of Transmission
Portals of Entry
Susceptible Host
Causative Agent1.) Bacteria – are microscopic organisms. Most bacteria have one of three basic shapes: rod (bacilli), round (cocci), or spiral (spirilla).
Toxins – waste that poison the body.
Causative AgentCLASSIFICATION OF BACTERIA ACCORDING TO THEIR SHAPE:
1. Cocci or round shape – common diseases produced are tonsillitis, pharyngitis, rheumatic fever, septic sore throat, furuncles, pimples, gastroenteritis and pneumonia.
2. Bacilli or rod-shaped bacteria – common diseases produced are diphtheria, cholera/el tor, leprosy, tuberculosis, typhoid fever, dysentery.
Causative AgentCLASSIFICATION OF BACTERIA ACCORDING TO THEIR SHAPE:
3. Spirilla or spiral-shaped bacteria – common diseases produced are syphilis and tropical
ulcer.
ANTIBIOTICS-interfere w/ the growth of bacteria.
Causative Agent2.) Fungi – are organisms that feed on animal or plant tissues. The fungi that cause disease in humans grow either on skin surface or on mucous membranes. The fungi take nutrients form the cells of these tissuesRingworm , athlete’s foot and tinea flava ARE COMMON HUMAN DISEASES CAUSED BY FUNGI.
Causative Agent3.) Rickettsiae – are small bacteria that can be produced only within living cells. Rickettsiae usually live in the cells of insects such as lice, mites, and ticks. Some rickettsiae can cause disease in humans. • An infected organism, like a tick, spreads the
rickettsiae when it bites a human or an animal. The rickettsiae then spread and reproduced inside the cells of an animal / human.
• Rocky mountain spotted fever and typhoid fever are two diseases caused by rickettsiae. Untreated rickettsiae diseases may be fatal.
Causative Agent4.) Protozoans – are one-celled organisms. A few protozoans can cause diseases. They live on or in other organisms known as hosts. Protozoans absorb food from these hosts. Some protozoans live part of their lives in humans and part in other organism.
LIFE CYCLE OF A MALARIA
Causative Agent5.) Viruses – are made up of genetic materials surrounded by a protein shell. Viruses are NOT cells. They are smaller than any known cell.• Viruses must live inside cells in order to
reproduce.• Viruses are responsible for more diseases
as cold, influenza, mumps, measles, chicken pox, rabies, and lupus.
• Viruses are also suspected to cause some forms of cancer and arthritis.
Reservoir or Source of Infection
MAN....• is recognized as the most important reservoir and
source of infection at the same time. Reservoir of infection are man, animals, plants, soil or inanimate and organic matters, in which an infectious agent lives, multiplies, and depends primarily for survival.
• serves as a reservoir during an attack of a disease and during convalescence. He may be a carrier who carries the germs in his body for long duration sometimes throughout his lifetime but is unaware of his condition because no symptoms of the disease bother him.
Mode of Escape
As long as humans or animals serve only as reservoirs, new infection does not take place. These organisms must be able to escape from their sources. The most important ways by which microorganisms escape are through the following.
1. respiratory tract2. gastrointestinal tract3. urinary tract4. skin5. mechanical escape like the sucking of insects
that brings out the infected blood.
TONSILITIS & PHARYNGITIS
RHEUMATIC FEVER
FURUNCLES
PIMPLES
GASTROENTERITIS
PNEUMONIA
DIPHTHERIA
CHOLERA/EL TOR
LEPROSY
TUBERCULOSIS
TYPHOID FEVER
DYSENTERY
SYPHILIS
TROPICAL ULCER
LIFE CYCLE OF A MALARIA
prepared by: azylle
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