Why Do We Fall Ill
Category : 9th Class
Why Do We Fall ILL
Chapter Overview
Similarly, our body also has tissues, organs, and organ system. There are several specialized activities which keep on going all the time in these parts. For example, the heart beats to pump blood to all the body parts, the lungs breath to exchange gases, the kidneys filter the blood and separate urine and brain thinks. All these activities are interconnected. If our heart stops beating even for a while, the blood circulation will stop, thus the various parts of our body will not get nutrients and oxygen. This will adversely affect our body. Likewise, if our kidneys, stop filtering the blood, poisonous substances will accumulate in the body. Under such conditions, the brain will not be able to think properly.
For all such interconnected activities, body requires energy and also requires regular supply of raw materials from outside the body. In other words, regular supply of food is necessary to the body so that essential components are provided to the cells for proper working of the tissues and organs. Anything that prevents proper functioning the cells, tissues and organs will lead to lack of proper activity of the body. In this chapter, we will try to understand health and disease in this perspective.
The Significance of ‘Health'
We use the term’ health' many times in different ways, for example, my grandmother's health is not good, A person remarks, "this is not a healthy attitude’' we may even talk about healthy climate of an area or a town.
Then what is meant by the word health? When we consider the first statement the term health implies the idea of being well or functioning efficiently. For our grandmother, being able to walk around easily is being well and not being able to do so is being unwell' or 'unhealthy'
Second statement implies the healthy attitude as being interested in some particular work with positive feeling while not being interested is called the 'opposite5. In third statement we are referring to the environmental conditions that are congenial for disease-free, happy life.
Thus we can define health as "a state of being well enough to function physically, mentally and socially."
The World Health Organisation (WHO), in 1948, has defined health as "a state of complete physical, mental and social well-being, and not merely an absence of disease or infirmity." In other words, WHO recognises three dimensions of health-
(a) Physical health: It refers to the normal structure of the body and its functioning. There are several test by which the state of physical health can be determined.
(b) Mental Health: It implies harmony between the individual and its surroundings. A mentally sound person is free from tension, anxiety etc. and therefore, performs, his function in a better way in his environment. Unlike physical health, it is difficult to assess the mental health.
(c) Social Health: Man is a social animal. He lives and works with other people in the society. A person is said to be socially healthy, if he maintains good relations with others. A person is socially healthy if he has a good job, a good house, a happy family, good neighbours, and good friends.
Personal and Community Issues – Both Matter for Health
As described earlier, health is a state of physical; mental and social wellbeing. It cannot be achieved by an individual alone. The health of all organisms will depend on their surroundings or their environment. The environment includes physical as well as social environment. For example-Physical environment is related to temperature, humidity, storm, cyclones, floods, drought, etc, whereas social environment is the one created by the society in which one lives. In villages, towns, and cities, even the physical environment, is greatly determined by social environment. Social environment controls not only social health but also the physical health of the individual through public health services.
(i) clean environment around our dwellings and protection from outbreak of diseases
(ii) Proper removal and disposal of garbage,
(iii) proper drainage and sewage services,
(iv) clean drinking water and unadulterated food items
(v) Vector and pest control
(vi) Proper vaccination and other health care services etc. If these services are faulty or insufficient, the health of citizen is bound to be adversely affected despite taking the best balanced food and keeping the best personal hygiene. It is because, infection is connected with environmental cleanliness as well as uncontaminated food. Suppose there is a garbage littered around in your house or street or waste water overflows the drains, vectors and pests would breed in the area resulting in spread of disease.
Distinctions between Healthy’ and ‘Disease-free’
We have understood the meaning of health. Now we should also know the meaning of disease. The term disease (dis + ease = without comfort) is very much self-explanatory as it simply means—disturbed ease or being uncomfortable. However, this word is used in a more limited meaning.
Disease has been broadly defined as "A disease is a condition of the body or a part of it in which functions are disturbed or deranged". A disease is the malfunctioning of body organs due to one reasons or the others.
The terms 'disease free and 'healthy do not convey the same meaning. An individual is considered "disease free" if he does not have any discomfort or derangement of body functioning, However, a disease free person may have a poor health or good health. If a person is not suffering from a disease it does not mean he is healthy. For an individual, the word healthy' conveys different meanings under different situations, for example, for a dancer, healthy may mean he/she is able to stretch his/her body into difficult but graceful positions. On the other hand, for a musician playing flute, healthy may mean he/she has better breathing power in his/ her lungs to control the notes from his/her flute. Those who do not possess such a talent may not be considered healthy in this contest. Thus, a person may have a poor health without actually suffering from a particular disease. It is because when we think about health, we think about societies and communities. On the contrary, when we think about disease, we think about individual sufferers.
What does disease look-like?
The body of an individual is made up of a number of tissues which aggregate together to form organs, while a number of organs make an organ system. Each organ system performs a specific function. Each tissue/organ in the organ system also has a specific role to play. For example, in digestive system, teeth help in mastication, tongue helps in mixing of saliva in food, stomach and intestine help in digestion and absorption. Kidneys take part in filtration of blood and urine formation. Bone and muscles hold the body parts together to form a musculoskeletal system that helps the body to move.
When there is a disease, either the functioning or the appearance of one or more systems of the body will change for the worse. These changes give rise to symptoms and signs of disease.
Diseases are diagnosed with the help of symptoms and signs.
Symptoms: They are manifestations or evidences of the presence of diseases. Symptoms of diseases are the things we feel as being wrong. They are in the form of structural and functional changes in the body or body parts. These symptoms provide important clues that help physicians and other health care professionals to make diagnosis of the disease, for example, wound with pus, cold, cough, fever, headache, loose motions etc. are some symptoms of diseases. Though they do not give any exact cause of the disease sometimes. Many times the symtoms point to several possible disorders. In those cases, doctors rely on medical tests, such as blood and urine tests and X-rays, to confirm the diagnosis.
Signs: They are definite indications of the disease. On the basis of symptoms, physicians search for definite clues or signs of the disease, using certain instruments. They even go for laboratory tests to pinpoint the cause of the disease.
Table 3.1. Differences between symptoms and signs of diseases
|
Symptoms |
Signs |
|
1. Symptoms indicate the presence of |
1. Signs provide information about the presence of particular disease. |
|
2. Symptoms are collective manifestation of a number of diseases of particular parts or organs. |
2. They are distinct for different diseases. |
Acute and Chronic Diseases
Acute diseases are characterised by abrupt or sudden onset, usually with severe symptoms.
Acute disease, as a rule, lasts in a comparatively short time-not more than a few weeks. For example, Common cold lasts only for a few days.
Chronic diseases are long duration diseases which generally develop slowly with a milder course in the beginning. They are usually associated with symptoms of less severe intensity.
The chronic diseases have drastic long term effects on patient's health. For example, asthma diabetes, tuberculosis, elephantiasis, cardio-vascular diseases, arthritis, cancer etc.
Table. 3.2: Differences between Acute disease and chronic disease
|
Acute disease |
Chronic disease |
|
1. Acute disease is of shorter duration. |
1. It is longer duration disease. |
|
2. They do not cause long term bad effects on human health. |
2. They cause drastic long term effects on human health. |
|
3. The recovery of acute disease is generally complete after the treatment, |
3. The recovery is seldom complete even after treatment. |
|
4. There is generally no loss of weight of the patient. Examples: Cold, Cough, etc. |
4. There is loss of weight of the patient. Examples: Tuberculosis, Arthritis etc. |
Chronic Diseases and Poor Health
Any disease that causes poor functioning of some part of the body will affect our general health. This is because all functions of the body are necessary for general health. But on acute disease, is of short duration and will not have time to cause major effects on general health, while a chronic disease will do so. We can understand it by following examples:
(i) During any acute disease, say cold and cough, no permanent bad effects occur on our health and we recover from the disease well within a week or so. Because of the shorter period of occurrence of the acute disease, we neither lose weight nor feel tired. We may not be able to go to school for a few days only if we have an attack of acute disease.
(ii) During a Chronic disease, say, elephantiasis or tuberculosis, some of the permanent bad effects like loss of weight and fatigue start appearing. A chronic disease may make us lethargic to understand and learn our lessons. In other words, we may have prolonged general Poor health if we have a chronic disease. Therefore, the chronic disease lead to drastic long- term effects as compared to acute diseases.
Causes of Diseases
Human health is affected by various factors. Most diseases have more than one cause.
These causes may be immediate as well as contributory. The causes or factors of diseases are of two types:
(i) Biological agents or pathogens: These includes viruses, bacteria, mycoplasma, fungi, protozoans, helminthes and other organisms. The biological agents are called pathogens (Gr. Pathos = disease, genus = producing). These pathogens are transmitted to the human body through air, contaminated water, food, soil, physical contact, sexual contact and animals.
(ii) Inadequate diet: Absence of nutrients such as carbohydrates, proteins, minerals, vitamins etc. in diet makes a person unhealthy. Unhealthy persons are more susceptible to infections. Deficiency of nutrients in the diet results in number of deficiency diseases in human beings, eg. Scurvy, ricketes, beriberi, kwashiorkor, marasmus, night blindness etc.
(iii) Environmental Pollutants: Various environmental pollutants such as gases (e.g. \[S{{O}_{2}},CO,N{{O}_{x}}\]etc.), particulate matter, industrial chemicals, heavy metals (e.g. cadmium, arsenic, lead, mercury), pesticides etc. also cause diseases.
(iv) Tobacco, alcohol and drugs: Continuous use of tobacco, alcohol and other drugs (narcotic drugs) results in harmful effects leading to chronic diseases.
(i) Improper functioning or malfunctioning of body parts such as heart, kidneys, liver etc.
(ii) Genetic disorders.
(iii) Hypo or hyper secretion of hormones
(iv) Improper functioning of body’s immune system
The factor that actually causes the disease is called immediate or primary cause. The factors which make an individual prone to catch the disease are known as contributing causes.
Poverty is a cause of poor nourishment and it can also function as one of the third level of causes. Poor persons generally live in unclean surroundings where basic amenities provided by municipality and public health services are lacking.
Human diseases are broadly classified into two categories-
These are also called inborn diseases because they occur since birth. Examples-Phenylketonuria, sickle cell anaemia, Haemophilia, Down's syndrome, Turner's syndrome, cleft palate etc.
(a) Infectious or communicable diseases
(b) Non-infectious or non-communicable diseases
(a) Infectious or Communicable Diseases: Diseases, where infectious agents are the immediate cause are called infectious or communicable diseases. These are caused by micro- organisms or pathogens such as viruses, bacteria, protozoa, fungi, worms etc. These diseases pass from an infected person to a healthy person and therefore, these are called communicable diseases. These are transmitted from one person to another person by air, water, food, physical contact and insects etc.
(b) Non-infectious or Non-Communicable diseases: These are diseases which are not caused by any pathogen or living organism and do not spread from infected person to a healthy person.
These are of following types.
(i) Deficiency diseases,
(ii) Metabolic diseases
(iii) Degenerative diseases
(iv) Allergies Cancer
(vi) Injury
(vii) Genetic disease.
(i) Deficiency Diseases: These diseases are caused by deficiency of nutrients like minerals, vitamins etc., e.g., Beri-beri, Kwashiorkor, Marasmus, Scurvy etc.
(ii) Metabolic diseases: These diseases are caused due to the defect in metabolic reactions and are called metabolic disorders, e.g., Alkeptonuria.
(iii) Degenerative Diseases: These diseases develop due to malfunctioning of some of the important organs e.g. heart disease, epilepsy. Heart disease results from the abnormal working some parts of this vital organ. Epilepsy may result from abnormal pressure on regions of the brain.
(iv) Allergy: These diseases are caused due to hypersensitivity of body to certain external foreign substances, called allergen, e.g. Asthma and hay fever.
(v) Cancer: This is caused by uncontrolled growth and division of cells in certain body tissues leading to tumor formation.
(vi) Injury: It is caused due to physical damage e.g., breaking of bones (Bone fracture).
(vii) Genetic diseases: These are caused by defective genes passed on from parents to offspring e.g. Haemophilia, cystic fibrosis etc.
Table 4.1: Common human Infectious diseases.
|
Causal organism/agents |
Diseases |
|
1. Viruses
SARS: virus seen coming out of cells |
(i) Common cold (ii) Chicken pox (iii) Small Pox (iv) Influenza (v) Poliomyelitis (vi) Measles (vii) Mumps (viii) AIDS (Acquired Immuno Deficiency Syndrome) (ix) SARS (Severe Acute Respiratory Syndrome) (xi) Rabies (ixi) Trachoma (xii) Swine flue (HINI) (xiii) German measles (xiv) Japanese encephalitis |
|
2. Bacteria
Staphylococcus, the bacterium causing acne |
(i) Cholera (ii) Diptheria (iii) Tuberculosis (iv) Leprosy (v) Tetanus (vi) Typhoid (vii) Plague (viii) Whooping cough (ix) Dysentery (x) Diarrhoea (xi) Pneumonia (xii) Anthrax (xiii) Food poisoning (xiv) Acne |
|
3. Fungi |
(i) Ring worm (ii) Athlete's foot (iii) Histoplasmosis (iv) Aspergillosis |
|
4. Protozoa
|
(i) Malaria (ii) Amoebiasis (iii) Kala-azar (iv) Diarrhoea (v) Sleeping sickness/Gambian fever (vi) Pyorrhoea |
|
5. Worms
Ascaris lumbricodides, the common round worn of small intestine. |
(i) Filariasis/Elephantiasis (ii) Taeniasis (iii) Ascariasis (iv) Anterobiasis |
Table 4.2: Common Deficiency Diseases
|
|
Deficient Nutrient |
Diseases |
|
1. |
Protein
|
Kwashiorkor
|
|
2. |
Protein and total food calories
|
Marasmus
|
|
3. |
Vitamin-A
|
Xerophthalmia, Nigh blindness
|
|
4. |
Vitamin-
|
Beri-beri
|
|
5. |
Vitamm-
|
Cheilosis
|
|
6. |
Niacin
|
Pellagra
|
|
7. |
Vitamin
|
Pernicious anaemia
|
|
8. |
Vitamin C
|
Scurvy
|
|
9. |
Vitamin-D |
Rickets (in children), Osteomalacia (in adults) |
|
10. |
Vitamin-K
|
Bleeding diseases
|
|
11. |
Iron
|
Microcytic anaemia
|
|
12. |
Fluorine
|
Dental Caries
|
|
13. |
Iodine |
Goitre |
Table. 4.3: Few common diseases due to hypo or hyper secretion of hormones.
|
|
Disease |
|
Hormone involved |
|
Level of hormone |
|
1. |
Diabetes mellitus |
1. |
Insulin |
1. |
Hyposecretion |
|
2. |
Addison's diseases |
2. |
Aldosterone |
2. |
Hyposecretion |
|
3. |
Grave's disease (Exophthalmic goitre) |
3. |
Thyroid Hormone |
3. |
Hypersecretion |
|
4. |
Cretinism (in children) |
4. |
Thyroid Hormone |
4. |
Hyprosecretion |
|
5. |
Myxodema (in adults) |
5. |
Thyroid Hormone |
5. |
Hyprosecretion |
Infectious Agents
Infectious diseases are caused by a variety of micro-organisms such as viruses, bacteria, protozoans, fungi or worms.
(a) Viruses: They are sub-microscopic crystalline organisms. They cannot multiply on their own because they do not have their own cellular and metabolic machinery. They utilize metabolic machinery of the host cell and multiply only inside the cell. The various diseases caused by viruses are common cold, influenza, SARS, AIDS, Mumps, Chicken Pox, Small Pox Swine flu etc.
(b) Bacteria: They are unicellular prokaryotic, microscopic organisms. They reproduce very quickly. Some common bacterial diseases are typhoid, cholera, tuberculosis, anthrax diphtheria, tetanus, etc.
Fig. 5.1: Cholera, typhoid and tuberculosis are caused by bacteria
(c) Protozoans: They are microscopic unicellular, eukaryotic organisms. They multiply rapidly. The various diseases caused by protozoans are malaria (by Plasmodium), sleeping sickness (by Trypanosoma), kala-azar (by Leishmania), amoebic dysentery (by Entamoeba), giardiasis (by Giardia) etc.
Fig. 5.2: Trypanosoma, the protozoan Fig. 5.3: Leishmania, the oval-shaped that causes sleeping sickness protozoan that causes kala-azar
(d) Fungi: They are multicellular, eukaryotic, heterotrophic organisms. They cause ring- worm, athlete's foot and other skin infections.
Fig. 5.4: Candida albicans, a saprophytic fungus, causes thrush disease
(e) Helminth: They are also multicellular worms which are mostly present in intestine.
They cause taeniasis (by Tapeworm), ascariasis (by Roundworm or Ascaris), elephantiasis (by filaria worm, hence also known as Filariasis) etc.
Fig. 5.5: Round worms cause Ascariasis in humans
Why we categorise Infectious Agents?
It is important to categorise infectious agents because each group of organisms have some common traits and many similar biochemical pathways. Proper knowledge of the category of micro-organism causing a disease is necessary for prevention and treatment of a disease. For example, members of each groups of viruses, bacteria and so on have many biological characteristics in common.
We can understand this by taking some examples. All viruses live inside the host cell whereas, bacteria do so very rarely. Taxonomically all members of group bacteria are very closely related to each other than to viruses and so on. Thus, many life processes are similar in the members belonging to group bacteria, but not shared with members belonging to group viruses.
All viruses as well as bacteria multiply fast while worms and protozoans multiply slowly.
Thus, based on differences in the characteristics amongst the members of different groups and similarities amongst the members of same group, we can design the control measures against them. For example, a drug or medicine which checks life processes in the members of one group will we effective against the other members of same group.
Let us take another example to understand this. The antibiotics are drugs that commonly block biochemical pathways important for bacteria. Several bacteria make a cell wall around them to protect them salve. Penicillin is an antibiotic that blocks the biochemical pathways by which bacteria build a cell wall around them. As a result, the bacteria cannot produce a cell wall and dies, on the other hand, human cell do not have a cell wall. Therefore, penicillin will not have such effect on human cells.
However, since viruses do not use such pathways, antibiotics do not work against viral infections.
Means of Spread (Mode of Transmission)
Infectious diseases are also called communicable diseases because they can spread from an infected person to a healthy person, infectious diseases spread by means of various method.
1. Through air: Infectious agents transferred from infected person to healthy person through air, dust and droplets (emitted on coughing, sneezing or spitting), e.g., common cold, Pneumonia, tuberculosis etc. This takes place through the little droplets thrown out by infected person who sneezes or coughs. Someone standing close can breathe in these droplets and the microbes enter in his body. It is a general experience that if someone having bad cold is close to you, you are likely to catch the same. In crowded living conditions, the air borne diseases are likely to spread rapidly.
Fig. 5.6: Air transmitted droplet infection?overcrowded and poorly ventilated housing is a major factor in the spread of airborne infections
2. Through Contaminated food/Water: Some diseases spread through contaminated food and water. This takes place if the excreta from a person suffering from an infectious diseases, such as cholera, typhoid, etc. gets mixed with the drinking water used by the people living nearby. The typhoid and cholera causing microbes enter the body of new hosts through contaminated water and cause disease in them. Such diseases are much more likely to spread in the absence of safe supplies of drinking water. Other water-borne diseases are amaebiasis or amoebic dysentery and hepatitis A.
Fig. 5.7: Common modes of transmission of diseases
For example, females of many species of mosquitoes feed on blood of many warm blooded animals including human beings to enable them to lay mature eggs. In performing this act they become potential carries i.e., they can transfer diseases from person to person. Female Anopheles is a vector for malarial parasite, sand fly (Phleobotomus) is a vector for Kala-azar and Housefly (Musca domestica) is a vector for cholera and typhoid. Like these human body louse spreads typhus, rat flea transmits bubonic plague, tse-tse fly spreads sleeping sickness etc.
4. For mite Borne: Some diseases are transmitted through the use of contaminated articles such as towels, clothes, handkerchiefs, utensils, toys, taps, door handles, soaps, syringes and surgical instruments.
Table. 5.8: Common Human diseases Transmitted by Insects
|
Insect Vectors |
Diseases Transmitted |
|
1. Mesquitoes
|
|
|
(i) Anopheles (ii) Culex (iii) Aedes |
Malaria Filariasis Dengue, Filariasis, Yellow fever |
|
2. Flies (i) House fly (ii) Tse-tse fly (iii) Sand fly |
Cholera, Typhoid, Diarrhoea, Dysentery, T.B., conjunctivitis Sleeping sickness Kala-azar, oriental sore |
|
3. Louse |
Epidemic typhus |
|
4. Rat Flea |
Bubonic Plague |
Organ Specific and Tissue Specific Manifestation
Human body is quite large in comparison to any type of disease causing microbe. So there are many possible areas, tissues or organs within our body where microbes may reside. Each pathogen has developed adaptation to infect a particular organ, tissue or system. In some cases the infected organ or tissue specificity depends upon the portal of entry while in others it is not so. Pathogenicity or severity of harm depends upon the tissue destroyed and the release of toxins by the parasites.
Portal Related Organ and Tissue Specificity: The pathogens or microbes enter the body through various routes. If the microbes enter from air via the nose, they are likely to go to the lungs and cause respiratory diseases such as tuberculosis, pneumonia etc. If microbes enter through the mouth, they pass into digestive tract and may cause typhoid, diarrhoea, taeniasis etc. Some microbes like viruses reach liver and cause jaundice. However, it is not necessary that the infectious agent reaches a particular organ depending upon route of entry.
Non-Portal Organ and Tissue Specificity: Malaria causing protozoans (Plasmodium sp.) enter through female mosquito bite and go to the liver via blood and then to the red blood cells of the whole body. Likewise the virus causing Japanese encephalitis or brain fever enters through a mosquito bite and, then infects the brain.
Sign and Symptoms: They are manifestations of the disease. The signs and symptoms of a disease will depend upon the tissue or organ which the microbe targets. For example.
(i) If the brain is infected, there will be headaches, vomiting, fits or unconsciousness.
(ii) If the liver is infected, there will be jaundice.
(iii) If the lungs are infected, there will be cough and breathlessness.
(iv) If alimentary canal is targeted by the pathogens then loss of appetite, abdominal pain loose motion, vomiting etc. may take place.
(v) If the lymph nodes are targeted, -there may be swelling of nodes, the lymphocytes production may go up.
Severity of Disease: The severity of disease depends on the number of microbes in the body because it has been found that if the number of infecting microbes is very small, the disease manifestation may be minor or unnoticed. But if the number of the same microbe is large, the disease can be life-threatening. The immune system is the greatest factor to determine the number of microbes surviving in the body.
Common effects: A causal organism does not get easy foothold due to presence of body defense system. The latter consists of protective coverings, germicidal secretions, friendly micro- organisms, phagocytes and immune system. Most of the common effects depend on immune system of our body which gets activated in response to any infection. Immune system is a complex of special cells and antibodies that is able to distinguish foreign organism and foreign
Substance. It immobilizes, detoxifies and kills the same.
The Pathogens are prevented from entering the body by intact skin, hair and mucus in nose, sweat, tear (contain lysozyme) and HCl (in stomach kills the germs). If microbes are able to enter the body, they may be killed by leucocytes (WBCs) or phagocytes in the process of phagocytosis. However, some pathogens escape phagocytosis and enter the tissue releasing certain toxic substances to kill the cells. The damaged cells release histamine and S'-hydroxyl tryptoamine which cause inflammation characterised by dilation of blood capillaries and small blood vessels surrounding the place of injury. The infected area becomes painful, red and swollen- There are some general effects like fever. Inflammation is the recruitment process which activates the immune system. T-cells, B-cells and their antibodies appear in the region Antibodies hold antigens while T-cells hold pathogens. Both antigens and pathogens are immobilized. Phagocytes then engulf them.
In HIV infection, the virus affects the body's immune system and damages its function.
Many of the symptoms of HIV-AIDS are due to weakened immune system. Due to the weak immune system, many minor infections that we face every day starts developing. For example:
(i) Minor cold can become pneumonia;
(ii) Minor gut infection can start producing major diarrhoea with blood loss.
(iii) All the other infections also, become fatal.
There are two ways to treat an infectious disease:
(a) Symptomatic Treatment: The medicines reduce the symptoms (e.g. bring down fever, reduce pain or loose motions or cough) which are mainly because of inflammation caused by infection.
(b) Bed rest: The bed rest enables us to conserve more energy which could be made available for causing healing during infections.
Similarly, there are drugs that kill protozoans, e.g., malarial parasites.
Do You Know
Antibiotics
Antibiotics are the chemicals produced by micro-organisms (e.g., bacteria and fungi) which kill or prevent the growth of other microbes. They can block the biochemical reactions of harmful microbes without harming human cells. Sir Alexander Fleming, in 1928, first discovered penicillin. Fleming noticed that an agar plate inoculated with the Staphylococcus aureus bacterium had become contaminated with a mold. He observed a clear zone in the agar plate devoid of bacterial cells. Detailed studies revealed the isolation of an inhibitory substances from the clear zone which was produced by the mold. The mold was Penicillium and its secretion was named as Penicillin. Other known antibiotics include tetracycline, streptomycin, Chloromycetin, chloramphenicol etc.
Antibiotics are characterised by their range of effectiveness and mode of action against the pathogens.
(i) Broad spectrum antibiotics kill a wide range of bacteria.
(ii) Narrow spectrum antibiotics are effective against a few types of bacteria.
Why antibiotics do not work against viral infection?
The answer to this question lies in the fact that the viruses do not use pathways which are followed by the bacteria or fungi against which the antibiotics are mainly effective. Hence during any viral infection such as common cold or influenza, taking antibiotics does not reduce the severity or the duration of the disease. But, if we get viral infection a secondary bacterial infection may also develop in this case taking antibiotics will help. In that case too, the particular antibiotics will act only against the bacteria but not against the virus.
While treating an infectious or communicable disease, following three limitations are normally confronted:
(a) When we have any disease, our body functions are damaged and may never recover completely.
(b) The treatment of the disease always takes time and hence the patient will have to take bed rest for some time even if we can give proper treatment.
(c) The patient may serve as a potential source of infection of the disease to other healthy people.
Keeping in view these limitations, prevention of diseases is considered far better than their cure. Preventing measures are precautionary steps taken to check the transmission of infectious diseases.
There are mainly two ways to prevent any particular infectious disease.
A General Ways of Prevention of Infectious Diseases: These includes:
This way of prevention of infectious diseases is related to a peculiar property of the immune system that generally fights off microbial infections. This is also the basis of immunization or vaccination. Let us take an example of small pox (an infectious, disease) and try to understand this property. Now-a-days small pox has been eradicated from the world. However, nearly hundred years ago, small pox epidemics were very common. During such an epidemic, people used to be afraid of meeting the small pox patient since they feared of catching the disease. There were also some persons who were not afraid of the epidemic. These people also provide nursing care to the smallpox patients. This group of people had suffered from small pox earlier and survived it, although with a lot of scars on their body. There was no chance of repeating small pox in those people who had it once. Hence, we may conclude that if the disease occurs once, then subsequent attacks of the same disease are prevented automatically.
Reason of the above prevention of disease is that the small pox could not occur in those people who faced the disease once because their immune system became trained to fight the subsequent attack by the same pathogen. In such cases, the immune system responds in the lowing manner:
(i) When the immune system is attacked for the first time by an infectious microbe, it spends against it and then remembers it specifically. When the particular pathogen re-enters he body, immune system responds with even greater strength. Thus, the infection is eliminated given more quickly than the first time around. This is also the basis of the principle of immunization.
(ii) Immunization or Vaccination is the method of stimulating resistance in the human body to specific diseases using micro-organism (bacteria or viruses) that have been modified or killed. These treated micron-organisms do not cause the disease, but rather trigger the body's immune system to build a defense mechanism that continuously protects against the disease. If person immunized against a particular disease later comes into contact with the disease causing agent, the immune system immediately able to responds defensively.
We can now see that, as a general principle we can Tool the immune system into developing a memory for a particular infection by putting something that mimics the microbe, we want to vaccinate against, into the body. This does not actually cause the disease but this would prevent any subsequent exposure to the infecting microbe from turning into actual disease.
Do You Know Immunisation or Vaccination
It is a technique in which antigenic proteins of pathogens or weakened or dead pathogens are injected into a person to develop immunity in him without infection. The pathogens, given in a vaccine, are unable to cause a disease but are sufficient to generate the primary immune response.
The credit of the discovery of the immune system goes to Edward Jenner (1749-1823). He observed that milkmaids did not get small pox infection apparently because they were exposed to a similar but milder form of disease called cowpox in earlier age. Jenner injected first James Phipps, a healthy boy of 8 years with cowpox virus and two months later he injected the I boy with small pox pathogen. The body did not suffer from small pox infection. Jenner proposed
I that an induced mild form of a disease would protect a person from a virulent form. Jenner was the first to discover a safe and effective means of producing artificial immunity against small pox. Edward Jenner is regarded as "Father of immunology". The term vaccine was given by Edward Jenner. In Latin, cow means vacca and cowpox means vaccinia. It is how the word vaccination has come into usage. Later on Louis Pasture prepared the vaccine for Rabies
And Anthrax.
Vaccine: They are antigenic proteins of pathogens or weakened or dead microbes which not able to cause the disease but stimulate the production of antibodies for a particular disease. Now vaccines are available for preventing many infectious diseases, e.g.. Polio, measles, tan us, diphtheria, hepatitis-B, tuberculosis, whooping cough, cholera, plague, mumps, measles
These form the public health programme of childhood Immunisation for preventing infectious diseases.
Table 5.9: Important vaccines for infants and children
|
Vaccine |
Disease |
Age group |
Safety level |
|
1. DTP.Hib |
Diphtheria, Tetanus, Pertussis (whooping cough) and Homophiles influenza type-B Poliomyelitis |
To all infants of 1, 2 and 3 month age |
90%-99% |
|
2. Polio |
|
All infants up to 5 years of age minimum of three doses at one month interval |
|
|
3. Hepatitis-B |
Hepatitis |
All infants, children and even adults |
Not yet confirmed |
|
4. BCG |
Tuberculosis |
All infants |
Nearly 70% |
Viral Diseases (Jaundice, Rabies AIDS and Polio)
Hepatitis results in jaundice which is of characterised by yellowness of sclera of eyes and skin. Jaundice occurs due to release of bile pigments (bilirubin) from damaged liver cells which gets excessively deposited in sclera (white parts of the eyes) and skin.
The various types of hepatitis are-Hepatitis A, B, C, D, E or G. Hepatitis-A (infectious or short-incubation hepatitis) and hepatitis-B (serum hepatitis or long-incubation hepatitis) are more prevalent in human population affecting both children and adults.
Modes of Transmission (i) Hepatitis. A spreads through contaminated water and food.
(ii) Hepatitis-B is transmitted by contact with infected person's secretions such as saliva, sweat, tears, etc. and also blood.
Symptoms: The common symptoms are:
(i) Fever and loss of appetite
(ii) Nausea and vomiting
(iii) Yellowness of white parts of eyes and skin (Jaundice)
(iv) Dark yellow coloured urine and light-colored stools after 3-10 days of infection.
(v) Itching of skin, headache and joint pains.
Preventive measures: These include:
Eating hygienic food and clean drinking water.
Hepatitis-A and Hepatitis-B-Vaccines should be taken to prevent the disease.
Use of disposable syringes and blood should be tested before transfusion.
Properly clean the hands after handling bed and utensils of the patient.
Control: Hepatitis is a viral disease and, therefore, is self-limited by body defenses. General measures of control include:
(i) Complete bed rest
(ii) Intake of carbohydrate rich diet.
(iii) Limited intake of proteins and fats in the diet
Modes of Transmission: The virus of rabies enters the human body with saliva of an infected (rabid) animal, generally by the bite of a dog of cat. A number of wild animals like mongoose, foxes, jackals, rabbits, bats, wolves, monkeys etc. also carry rabies virus. From the site of entry into the body, the virus travels via peripheral nerves to the spinal cord and the brain where it multiplies. It destroys the brain and spinal cord cells. The viruses then move through efferent nerves to the salivary glands, and pass into the saliva. Incubation period of this disease is usually
1-3 months, the long period of incubation makes it possible for a rabies vaccination, after a bite, to develop immunity and prevent the appearance of the disease.
Symptoms: Common symptoms of rabies are:
(i) Severe headache and high fever
(ii) Painful contraction of muscles of throat and chest, restlessness and inability to swallow even fluids due to choked throat. This phase is followed by convulsive seizures and death.
(iii) Infected person is afraid of water, and is called hydrophobia.
Preventive Measures:
(i) Pet dogs, cats and rabbits should be vaccinated with anti-rabies vaccine. In fact immunization of Such animals should be made compulsory.
(ii) Rabid animals should be killed, if they show excessive salivation and try to seek isolation.
Wash the wound with carbolic soap and clean running water, immediately after the bite. Now, apply antiseptic cream and consult a doctor for anti-rabies vaccines, as soon as possible.
(ii) Rabies can be treated by five doses of anti-rabies vaccine given at an interval of O, 3, 7, 14 and 30th day of bite.
Control: Till date, there is no treatment for rabies.
AIDS is a fast spreading, incurable disease. It is a serious health problem that threatens he entire human population and is caused by retrovirus-HIV (Human Immune-deficiency virus) it was first detected in June 1981 in USA. This virus weakens the human body's immunity or If-defense mechanism. Since the AIDS virus reduces the natural immunity of the human body, the person having AIDS becomes prone to many other infections.
Modes of Transmission: AIDS is transmitted only by
(i) Unprotected sexual contact with an infected partner. So it is a sexually transmitted tease.
(ii) Use of contaminated unsterile needles and syringes
(iii) Transfusion of infected blood or blood products.
(iv) Parturition (child birth) from infected mothers to offspring during pregnancy, birth due "ruptured blood vessels and breast feeding.
Fig. 5.10
Contrary to widespread fear, AIDS does not spread by casual contact, such as shaking hands, sharing towels, sharing utilities and telephones, coughing and sneezing, dry kissing, embracing, crowded transport, swimming pools and toilets etc.
Fig. 5.11: Structure of HIV or AIDS virus
Do You Know
AIDS is considered as a 'Syndrome' and not just as a disease. It is because disease causing virus after entering the body of healthy person spreads to lymph nodes all over the body.
It destroys body's immunity and therefore, body is no longer able to fight off many minor infections. Even a small cold infection can turn into pneumonia or a minor gut infection may lead to severe diarrhea with blood loss. The effect of minor diseases becomes too severe that they kill the patient suffering from AIDS. In other words, there are no specific disease symptoms for AIDS and the patient develops complex diseases and symptoms. So AIDS is considered to be a syndrome and not merely a disease.
Symptoms: The important symptoms of disease are:
(i) Low grade fever with cough, nausea and repeated diarrhea.
(ii) Susceptibility to other infections.
(iii) Sweating at night and weight loss.
(iv) Swollen lymph nodes.
Preventive Measures: No absolute vaccine is yet available. So we can prevent this disease only by following preventive measures:
(i) Use of disposable needles and syringes.
(ii) Protected sex.
(iii) Blood test must be done in pregnant women, blood donors, organ donors, etc.
(iv) The common razor at the barber's shop should not be used.
(v) People should be educated about AIDS.
Do You Know
Control: Till date, there is no specific treatment available against HIV infection. Some medicines are available to increase the number of resistance providing cells in the body. This treatment is known as Immunostimulative therapy.
Polio: It is common viral disease that generally affects children. It is caused by Poliovirus.
It occurs generally during warmer summer months and may cause paralysis of limbs. This disease has been eradicated from our country recently.
Mode of Transmission: Infection of polio occurs through faeco-oral route. In alimentary canal the virus multiplies and reaches the nervous system through the blood stream.
Its incubation period is 7-14 days. Polio was regarded as a disease of infants and children.
Hence, this disease was called infantile paralysis. But it is now known that this disease may occur at any age.
Symptoms: Common symptoms of polio are:
(i) Headache and fever followed by loss of head support.
(ii) Stiffness of the neck and convulsions.
(iii) As the virus damages the motor neurons of spinal cord, legs become paralysed.
(iv) Respiratory failure.
Preventive Measures: Immunization with oral polio vaccine provides immunity against Polio.
Pulse Polio Programme: Pulse Polio Programme was launched in 1995-1996 with an aim eradicate polio disease from the country. It involves simultaneous administration of Polio drops (Polio vaccine) to whole of the high risk population (i.e. children under five years of age) a single day throughout the nation. In this programme, polio vaccine is given to children twice apart 4-6 weeks.
Bacterial Diseases. (Diarrhea, Typhoid, Tuberculosis)
Mode of Transmission: The disease spreads through:
Symptoms: Common symptoms of diarrhoea infections are:
Abnormally frequent discharge of semisolid or fluid faucal matter with or without blood mucus leading to dehydration.
(i) Abdominal cramps, vomiting and nausea
(ii) Due to rapid loss of water, eyes appear sunken, cheeks hollow, the inner side of cheeks appears dry, sudden loss of weight, fever, deep breathing etc.
(iii) Diminished appetite.
(iv) Noisy movement of gas in the intestine.
Preventive Measures: These include:
(i) Proper personal and community hygiene.
(ii) Underground sewers for disposal of human excreta.
(iii) Proper covering of eatable to prevent contamination.
(iv) Use of only disinfected water or boiled water for drinking.
(v) Use of fly proof doors and windows.
Control: It includes:
(i) Use of oral rehydration solution (ORS) (one teaspoon of sugar and a pinch of salt to 200 ml of water)
(ii) Glucose drip may be given intravenously.
(iii) Isabgol (husk of Plantago ovata seeds) should be given with curd to the patient to provide relief.
(iv) Pulp of boiled unripe banana along with required quantity of turmeric powder, salt and lime, also help in controlling diarrhoea.
(v) Antibiotics are effective in bacterial infection.
Mode of Transmission: The disease is transmitted by food and water contaminated with faces of the patient. Houseflies may carry the pathogens from the faces to the food, milk and water.
Symptoms: Its main symptoms are:
(i) Common symptom of typhoid is high temperature about\[103{}^\circ -104{}^\circ F\]. Typhoid fever rises to the maximum in the afternoon. In first week, it increases with each day. Fever remains high in second week, but in third and fourth week, it gradually decreases.
(ii) Coated tongue headache, extreme weakness.
(iii) Loss of appetite, constipation, stomach pain, inflammation in ileum and colon.
(iv) Rashes on the body (Rosy spots).
Preventive Measures
(i) Personal cleanliness, proper community hygiene
(ii) Nutritious diet.
(iii) Screening of water supply and food from contamination by flies.
(iv) TAB-Vaccine provides immunity for about three years.
It is a serious disease caused by a bacterium, Mycobacterium tuberculosis and was first discovered by Robert Koch (1882). It most commonly affects the lungs, brain, intestine, eyes etc.
It is especially common among the under nourished people who live in dingy, congested parts of large cities. A toxic substance known as Tuberculin is released by bacterium.
Mode of Transmission
It spreads by droplet infection. Disease causing bacteria enter into human body through coughing, sneezing, spitting and by direct contact or by food, water and air.
Symptoms: The symptoms of disease vary depending on the site of the infection in the body. Two specific sites of infections are:
(a) Lymph gland T.B: The main symptom of infection is swelling and tenderness of lymph glands, in neck, armpits or legs which may discharge secretions through the skin.
(b) Pulmonary (Lung) TB: It includes:
(i) Characteristic low grade fever in the evening
(ii) Coughing
(iii) Chest pain and breathlessness
(iv) Sputum containing blood
(v) Loss of weight and weakness.
Preventive Measures
(i) Personal and community hygiene
(ii) Nutritious diet.
(iii) BCG (bacillus Calmatte Guerins) vaccine provides immunity.
(iv) Directly observed treatment short course is very effective in drug resistant T.B. (DOTS)
Control: (i) Complete Anti-tubercular therapy can treat the disease.
(ii) Proper test, diet, rehabilitation and surgery helps in controlling disease.
Malaria is caused by malarial parasite Plasmodium. There are four types of malaria caused by different species of Plasmodium.
|
Types of Malaria |
Species |
|
1. Benign tertain Malaria |
Plasmodium vivax |
|
2. Malignant tertain (cerebral malaria) |
P. falciparum |
|
3. Mild tertain |
P. ovale |
|
4. Quartan |
P. malariae |
Falciparum malaria is most serious type of malaria.
Presence of malarial parasite can be checked by blood test. Here, Plasmodium vivax is described in brief.
Mode of Transmission: Plasmodium is transmitted by female Anpheles mosquito. When female mosquito bites man to suck blood, it introduces its saliva containing the malarial parasite into the blood stream of the man.
Symptoms: The attack of malaria is proceeded by headache, nausea and muscular pain.
Total period of malarial attack is of 6-10 hours and can be divided into three stages.
(i) Cold Stage: Characterised by chill and shivering.
(ii) Hot stage: Characterised by high fever (104 - 106° F), faster breathing rate and heart beat etc.
Sweating stage: It is characterised by sweating and lowering down of temperature to normal.
After the malarial attack, the patient feels weak, exhausted and anaemic. The malaria may secondly cause enlargement of liver and spleen.
Preventive Measures: These include:
(i) Use of mosquito repellants to prevent mosquito bites.
(ii) Wire gauzing of doors, windows and ventilators to check the entry of mosquitoes into the houses.
(iii) Periodic spray of insecticides to kill adult mosquitoes as well as spray of kerosene oil or insecticides in ponds, ditches etc. to kill the larvae of mosquitoes
(iv) Introducing carnivorous fishes (e.g. Gambusia, Minnow), (trauts) in water bodies. These fishes feed on mosquito larvae.
Control: Malaria can be controlled by taking antimalarial drugs. The commonest antimalarial drug is quinine (extracted from the bark of Cinchona tree). Other drugs for malaria are-Atebrine Bosoquine, Camoquine, Nivaquine etc.
Do You Know
Chapter at a Glance and Glossary
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