In this essay we will discuss about manifestation of diseases in humans and its prevention.
Manifestations of Diseases:
Diseases are characterised by interference in the normal functioning of the body leading to impairment of health. These diseases show certain abnormal changes in the functioning or the appearance of one or more symptoms of the body, called disease symptoms, like headache, coughing, loose motions, wound with pus, etc.
Though these symptoms indicate some kinds of disease but do not indicate exact type of disease as these may be due to a number of diseases e.g., headache may be due to many causes like examination stress or meningitis or any other disease. So there is need of laboratory testing of blood or urine or stool or any other body tissue to pinpoint the disease further.
These disease symptoms are of two types:
1. Organ-specific and tissue-specific manifestations.
2. Common manifestations.
1. Organ-specific and tissue-specific manifestations depend on the target organ which the microbes target after their entry e.g:
2. Common manifestations:
These are observed in a number of diseases and generally occur due to activation of immune cells in response to infectious agents. These immune cells either produce antibodies or actually attack and kill the disease causing microbes.
This is manifested in the form of inflammation characterized by redness of the infected area, swelling, fever and increase in permeability of the capillaries of that area.
But there are certain diseases in which tissue- specificity of the infection leads to very general – seeming effects e.g., in AIDS, the HIV (Human Immunodeficiency Virus) attacks and kills the Helper – T cells of cell- mediated immune system so causes acquired immunodeficiency in which number of T-cells drops even below 200 in comparison to 500 – 1500 in a normal person.
So AIDS patients also become more susceptible to bacterial and viral infections of any system of body. In such cases, even minor infections may transform into fatal diseases e.g., common cold changing into pneumonia.
Severity of disease manifestations depends upon the following factors:
1. Number of microbes inside the body so the disease manifestations may be minor and unnoticeable when the number of microbes is very small while these symptoms may be large enough and life threatening when the infection is large. Number of surviving microbes inside the body depends upon the immune system.
2. Invasiveness (rate of successful penetration) and toxigenecity (rate of production of toxins inside the host) of the microbes.
3. On the tissue or organ which the microbes target e.g., HIV enters in the body through the sexual contact but spreads to lymph nodes through the body.
Similarly, virus causing Japanese encephalitis or brain fever enters into a person through the saliva of vector mosquitoes in the blood but attacks the brain.
Prevention of Diseases:
(A) General prophylactic measures to prevent:
i. Air-borne diseases like pneumonia, tuberculosis, common cold, influenza, etc., can be prevented by avoiding overcrowding and providing hygienic living conditions.
ii. Water-borne diseases like cholera, typhoid amoebiasis, ascariasis, etc. are preventable by providing safe drinking water or use of boiled water or treatment of water to kill any microbial contamination.
iii. Contagious diseases like chickenpox, measles, smallpox, leprosy, etc., can be prevented by isolating the infected persons to avoid their close contact with the healthy persons.
iv. Vector-borne diseases like malaria, dengue, cholera, etc., can be reduced by providing clean environment through public hygiene measures so as to prevent their breeding. This can be achieved through health education measures like proper sanitation of human faeces. Vectors can be killed by spraying of insecticides or through biological control e.g., Gambusia fish eats upon the mosquito larvae in water.
v. By providing proper and sufficient nourishment and food which is essential for the proper functioning and strengthening of individual’s immune system which produces antibodies to prevent the occurrence of diseases.
vi. Sexually transmitted diseases like syphilis, gonorrhea, AIDS, etc. can be prevented by having monogamous and faithful relationship, and using condoms.
vii. Other general measures of prevention of diseases are Proper coverage of eatables to prevent their contamination by the vectors; proper washing of fruits and vegetables before their use; keeping the food in clean containers; washing of hand before meals; proper diet to prevent diet-deficiency diseases like marasmus, kwashiorkor, etc.
So two important but simple methods of prevention and control of a number of infectious diseases are:
1. Personal hygiene.
2. Public hygiene.
1. Personal hygiene includes self-cleanliness by clean habits for maintaining good health, and adopting healthy habits which keep oneself free from contamination.
Clean habits include:
(i) Washing of hands with germicidal soap before and after the meal, and after toilets; and regular trimming of nails.
(ii) Taking regular bath which opens sweat pores and removes the body odour.
(iii) Proper washing of hair with mild soap or shampoo and their combing to prevent dandruff and lice infestation.
(iv) Regular brushing of teeth with a fluoride tooth paste to avoid bad breath and tooth decay.
(v) Washing of eyes with clean water to keep them free from dirt and germs.
(vi) Clothes should be washed regularly to remove bad odour and dirt.
(vii) Only soft swabs should be used to remove the ear wax from the ears.
Healthy habits include:
(i) Avoiding alcohol, tobacco-smoking and drug addiction as these have serious ill-effects like liver damage (alcohol), lung cancer (smoking) and mental disorders (LSD).
(ii) Regular exercise and proper sleep.
(iii) Washing of vegetables and fruits before use.
(iv) Proper coverage of eatables to avoid their contamination.
(v) Breathing through nose as it cleans and conditions the air.
(vi) Keeping proper distance and posture during reading.
2. Public hygiene includes all those measures which prevent the spread of infectious diseases in the community and include:
(i) Proper disposal of garbage.
(ii) Proper system for disposal of human and animal excreta e.g., sewerage, compost pits, gobar gas plants, etc.
(iii) Use of smokeless chullah to avoid air pollution.
(iv) Protection of food articles from pollutants, dust and mechanical vectors like flies and cockroaches.
(v) Periodic cleaning and disinfection of water reservoirs.
(vi) Provision of safe and germ-free drinking water.
(vii) Occasional spraying of insecticides and disinfectants for killing germs and their carriers.
(viii) Avoiding stagnation of water in and around residential areas to eliminate the vectors and their breeding places. These measures have become more important due to wide spread incidences of vector-borne diseases like malaria dengue and chikungunya in many parts of India including Delhi.
(ix) Provision of health, education, efficient health services and immunisation.
(B) Specific Prophylactic Measure:
There are two ways of treatment of infectious diseases:
A. Symptom-Directed Treatment:
This treatment is directed to reduce the effects of the diseases which are generally due to inflammation of certain body tissues characterized by fever, pain, sneezing, vomiting, loose motions, redness of skin, etc. It involves taking of medicines like antihistamine (to reduce inflammatory reactions because inflammation is generally caused by histamine), antipyretics like aspirin, crocin, etc., (to quickly bring down the temperature), analgesics (to reduce pain), etc. Though these drugs may provide some relief from the symptoms but do not bring cure from the disease so are temporary and short-lived measures and need to be taken at regular intervals.
B. Pathogen – Directed Treatment:
This treatment is directed to kill the microbes with the help of certain chemicals. Different types of microbes have different and specific biochemical metabolic pathways e.g., metabolic pathways of bacteria may be different from those of higher organisms. The medicinal chemicals are aimed to block these pathways so as to inhibit the synthesis of toxic products or respiration so as to lower the energy production.
But the medicines used to block the metabolic pathways of bacteria may not block the metabolic pathways of other organisms. Most important therapeutic chemicals are antibiotics.
Antibiotics are the substances, primarily produced by certain useful micro-organisms which in low concentrations are antagonistic to the growth of harmful micro-organisms such as pathogenic bacteria. This property of antibiotics to kill the pathogenic microorganisms is called antibiosis. Medicinally important antibiotics have quick and broad-spectrum therapeutic effects but with minimum side effects.
Some medicinally important antibiotics are Penicillin (first discovered antibiotic by Alexander Fleming), aureomycin, erythromycin, neomycin, streptomycin, terramycin, Chloromycetin, etc.
Every antibiotic is known to block some specific step of specific metabolic pathway and will be effective against all those microbes which have similar biochemical mechanisms. This is the reason that most antibiotics work against many species of bacteria which have similar metabolic pathways rather than working against one e.g. Penicillin is a broad-spectrum antibiotic and inhibits the growth of a number of bacterial pathogens as it blocks the metabolic processes that build the cell wall in bacteria but is not much effective on human cells as these do not have cell wall.
But the antibiotics used to treat the bacterial diseases may not be useful against the viral infections. It is so because the viruses have different types of biochemical pathways than those of bacteria and secondly the viruses cannot be cultured in vitro (artificial media). Viruses have only a few biochemical reactions of their own and can survive only within the specific host cells. These use the host’s raw materials and machinery to multiply themselves.
So the antibiotics cannot be used to treat the viral infections like influeriza. This is the reason that making anti-viral medicines is difficult than making antibacterial medicines. But recently advances have been made to prepare a number of anti-viral vaccines against viral infections like measles, mumps, rubeolla, polio and hepatitis. Certain anti-retroviral drugs like Azidothymidine, Lamivudine, Nevirapine, Protease inhibitors, etc. have also been developed to keep HIV- infection under control.