Factors in theDevelopment 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 Development 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 HostMAN 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 HostEXAMPLE: Rabies – principal host is animal - occasional host is manThe host accidentally steps in the life cycle ofthe organisms.
Disease AgentsEFFECTS 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 AgentsTYPES OF AGENTS:• biological – amoebic dysentery• chemical – fluorosis• physical – trauma or accident• nutritional – anemia, goiter, beri-beri, etc.• psychological – stress, tension, neurosis, psychosis
EnvironmentTHE FAVORABLE ECOLOGICAL FACTORS:• good heredity• good environment• proper nutrition• adequate medical care• satisfying work and recreation• personal-social fulfillment• emotional maturity, etc.
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 Developmentof the Infection Process. Reservoir of Source of Infection Modes of Causative Escape Agent Susceptible Modes of Host Transmission Portals of Entry
Causative Agent1.) Bacteria – are microscopic organisms. Mostbacteria 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 THEIRSHAPE: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 THEIRSHAPE: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 animalor plant tissues. The fungi that cause disease inhumans grow either on skin surface or onmucous membranes. The fungi take nutrientsform the cells of these tissuesRingworm , athlete’s foot and tinea flavaARE COMMON HUMAN DISEASES CAUSED BY FUNGI.
Causative Agent3.) Rickettsiae – are small bacteria that can beproduced only within living cells. Rickettsiaeusually live in the cells of insects such aslice, mites, and ticks. Some rickettsiae cancause 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. Afew protozoans can cause diseases. They liveon or in other organisms known as hosts.Protozoans absorb food from these hosts.Some protozoans live part of their lives inhumans and part in other organism.LIFE CYCLE OF A MALARIA
Causative Agent5.) Viruses – are made up of genetic materialssurrounded by a protein shell. Viruses are NOTcells. 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 InfectionMAN....• 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 EscapeAs long as humans or animals serve only as reservoirs,new infection does not take place. These organismsmust be able to escape from their sources. The mostimportant ways by which microorganisms escape arethrough the following.1. respiratory tract2. gastrointestinal tract3. urinary tract4. skin5. mechanical escape like the sucking of insects that brings out the infected blood.