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Types Of Diseases

Human Health And Diseases of Class 10

Diseases are broadly grouped into two categories:

  • Congenital diseases
  • Acquired diseases

Type of Disease

(a) Congenital Diseases: Congenital diseases are present right from the birth. They are caused due to either genetic disorders or environmental factors during development or due to combination of these factors. These diseases pass on from generation to generation e.g. haemophilia, colour blindness, sickle cell anaemia, down's syndrome, albinism etc.

(b) Acquired Diseases :These disease are acquired by an organism after birth and are not inheritable i.e., do not pass on from one generation to another. These are further classified into two categories:

  • Communicable or Infectious diseases: These diseases are caused by pathogens/infectious agents such as bacteria, viruses, fungi, protozoans, worms, etc. These diseases can spread from diseased person to healthy person by means of air (droplet method), water, food, insects, physical contact, etc., e.g. tuberculosis, malaria, diarrhoea etc.
  • Non-Communicable or Non-Infectious diseases: These diseases can't be spread through infected persons to healthy persons. e.g. Scurvy
       

Table : Various Pathogens and Diseases caused by them

S.No:

Type of Pathogens

Common diseases caused by them

1

Viruses

Common cold, Influenza, Measles, Mumps, Poliomyelitis, Rabies,Small pox, Chicken pox, Yellow fever, AIDS etc.

2

Bacteria

Cholera, Typhoid, Tuberculosis, Tetanus, Diphtheria, Pneumonia,Syphilis, Gonorrhoea, Leprosy etc.

3

Rickettsiae

Typhus fever, Tick fever etc.

4

Protozoa

Malaria, Amoebic dysentery, Sleeping sickness etc.

5

Fungi

Ringworm, Athlete's foot etc.

6

Worms

Filaria, Ascariasis, Cysticercosis, Pinworm

7

Mites

Scabies

INFECTIOUS   DISEASES:

(a) Infectious Agents :The various infectious agents are - bacteria, viruses, protozoans, helminthes (worms) and fungi.

(i) Bacteria: They are unicellular, prokaryotic, microscopic organisms. They reproduce very quickly. Some common diseases caused by bacteria are typhoid, cholera, tuberculosis, anthrax, diphtheria, tetanus, etc.

(ii) Viruses: They are submicroscopic organisms. They cannot reproduce by themselves because they do not have their own metabolic machinery. They utilize the metabolic machinery of the host cell and multiply. The various diseases caused by viruses are common cold, influenza, dengue fever, AIDS, measles, mumps, polio, small pox, chicken pox, etc.

(iii) Protozoans: They are microscopic unicellular, eukaryotic organisms.The various diseases caused by protozoa are malaria (caused by Plasmodium), kala-azar (caused by Leishmania), etc.

(iv) Helminthes: Helminthes are multicellularworms which are mostly present in intestine.They cause taeniasis (caused by tapeworm), ascariasis (caused by round worm), filariasis (caused by filaria worm) etc.

(v) Fungi: They are also muiticellular, eukaryotic, heterotrophic organisms. They cause ringworm, athlete's foot and other skin infections.

(b) Means of Spread: Infectious diseases are called communicable diseases because they can spread from affected persons to a healthy person. The means of communication or spread are different for different pathogens.

The diseases are spread to the healthy person in two ways :

  • Direct transmission
  • Indirect transmission

DIRECT TRANSMISSION

Pathogens are transmitted from an infected person to a healthy person directly without an intermediate agents.

Its occur in following ways :

  • By direct contact with an infected person e.g. contagious diseases like chicken pox, smallpox, athlete’s foot, measles, leprosy, ringworm, gonorrhoea, syphilis etc.
  • Droplet infection (through coughing, sneezing and spitting of infected persons) e.g. diphtheria, influenza, tuberculosis, measles, mumps, whooping cough, etc.
  • Contact with soil, e.g. bacterial cysts of tetanus.
  • Animal bites e.g., rabies viruses.

Transplacental transmission : The viruses of German measles and AIDS; and bacteria of syphilis can be transmitted from the maternal blood into foetal through placenta.

INDIRECT TRANSMISSION

When the pathogens can be transmitted from the reservoir of infection to a healthy person through some intermediate agents.

It occurs in following ways :

  • Vector borne diseases : e.g. malaria (female Anopheles), dengue (Aedes mosquito), kalaazar (sandfly), cholera (housefly), etc.
  • Vehicle borne : Pathogens of cholera, dysentery, typhoid etc. are transmitted by agencies like food, water etc. AIDS is spread by blood or semen of suffering donors.
  • Air borne : e.g. influenza, epidemic typhus.
  • Formite borne : In this, the pathogens are spread through contaminated articles like handkerchiefs, towels, garments, utensils, crockery, surgical instruments, books, toys, door handles syringes, (fomiteborne, i.e., through inaminate articles other than water and food).
  • Unclean hands : e.g. Ascaris(Ascarislumbricoides) and Enterobiasis(Enterobiusvermicularis).

Carriers are organisms which harbour disease causing germs without showing any signs of the disease themselves, but have the ability to infect other individuals.

Carriers of specific germs are called vectors. e.g., female insect Anopheles is the vector of Plasmodium (which causes malaria).

Treatment: The basic concept behind the treatment process is to target the biochemical pathways occurring inside an organism. For this certain drugs like antibiotics are prepared to alter or stop the biochemical reaction of the microbes at some stages to stop them to produce infections, toxins or to kill them or to check their further growth and multiplication. There are two ways in which these diseases are treated they are:

(i) Reducing the symptoms: By this, infection is not cured but some of the symptoms like fever, pain, aches, inflammation can be reduced to make the patient comfortable. This is done by medicines like painkillers etc.

(ii) Killing infectious agents: This can be done by targeting the biochemical pathways of infectious agents using specific drugs.

  • Drugs: Chemical compounds that targets a particular reaction among the chain of reactions involved in the biochemical pathway by reacting with some substrates of that reaction and resulting in an undesirable product so that reaction cannot proceed further and stop infections by killing the microbes. They do not affect human cells.
  • Antibiotics: Antibiotic are chemicals that kill or stop the growth of certain kinds of microbes. They help our body to fight against diseases. The development of antibiotics began with the discovery of penicillin by Sir Alexander Flemming in 1928.FIemming noticed that an agar plate inoculated with bacterium Staphylococcus aureus had become contaminated with a mould. He further noticed the presence of a clear zone in the agar plate in which breakdown of the bacterial cells had occurred. Detailed studies led to the isolation of an inhibitory substance from the mould. As the mould was identified as Penicillium, Flemming called the antibiotic penicillin. Soon other antibiotics were isolated. Some well known antibiotics are streptomycin, gramicidin and tetracycline. The antibiotics have been obtained from either bacteria or fungi.
  • These are the drugs specific for curing bacterial diseases.They either cease the formation of cell wall or interfere in their metabolic activities like production of proteins.This kills or stops the growth of bacteria.
  • Antibiotics are not effective for viruses or it is difficult to make antiviral antibiotics because viruses are acellular entities, which only have nucleic acid and protein but lack cytoplasm, cell wall and cell organelles they do not have their own metabolic system, but they use the host's metabolic machinery to grow & multiply so drugs are not effective for them.
  •  Prevention from Infectious Diseases:Preventive measures are categorized into two distinct groups:

General preventive measures:

  • Safe drinking water: Drinking water should be filtered to remove suspended particles. It must be boiled, ozonized and treated with chlorine before drinking to avoid water borne diseases like typhoid, cholera, hepatitis etc.
  • Proper disposal of waste: Garbage should not be dumped here and there rather it should be thrown in covered garbage cans and burnt or buried for disposal. Sewage carrying drains should be covered for proper treatment of diseases of stomach and intestine.
  •  Control of vectors: Growth and breeding of animals like mosquitoes, rats, flies, cockroaches should be controlled, by keeping surroundings clean, spraying insecticides, removing stagnant water from populated areas.
  • Strong immune system: It helps to defense our body against invading microbes and can be made strong by proper diet and nourishment.
  •  Immune system: Our body possesses a special type of defense mechanism called immune system.lt provides resistance against disease causing microorganisms. Immunity is the ability of the body to resist the infections. Two specific types of cells are present in our body that provides immunity.
  • They are WBC (leucocytes) in blood and lymphocytes in lymph when any foreign body attacks our body these cells are released to all parts of body, they isolate, engulf, kill and digest the infectious agents and thus defend our body against any type of infection.

Specific preventive measures :This can be done by two ways :

  •  Immunization: Stimulating the body to produce antibodieby artificial means. Our immune system is misleaded, to develope a memory against particular infection by introducing something into the bodythat mimics the specific microbe. Specific prevention is provided by the immune system It produces specific molecules called antibodies that fight against the invading microorganisms or their products called antigens. Antibodies are proteinaceous molecules made by WBC's and lymphocytes to fight against foreign bodies or other harmful chemicals. Antigens are also proteins or other harmful chemicals that are present on surface of invaders. Whenever there occurs attack of a foreign body specific antibodies are produced corresponding to that antigen and an antigen antibody reaction occurs. It either engulfs and phagocyte it or makes it harmless and then makes it unable to grow and multiply. Besides this, immune system also possesses memory. Once antibodies are produced, they remain in the body and at the second infection, they recognize the antigens and show a much faster response.
  • Vaccination: A vaccine is a suspension of disease - producing micro-organisms, which is modified by killing or weakening (attenuated) so that the suspension will not cause disease. Rather it stimulates the formation of antibodies upon inoculation. The antibodies remain in blood for long and when the germs of a particular disease enter the body, the antibodies destroy them.This is the basis of immunization.

Some common vaccines:

  •  DPT vaccine, for protection against diphtheria, whooping cough and tetanus
  • BCG vaccine, for protection against tuberculosis
  • Polio (OPV) vaccine
  • Typhoid vaccine
  • Measles vaccine
  • TT vaccine, against tetanus
  • Pulse polio programme: The aim of this programme it to eradicate polio from our country. It was first held in our country in December, 1995. Polio vaccine called Oral Polio Vaccine (OPV) is given to children orally (through the mouth) , as per the National Immunisation Schedule (NIS).
       

Schedule of Immunisation

Benificiaries

Age

Vaccine

No. of doses

(a) pregnant woman

16 −36 weeks

TT

2 at intervals of 4−8 weeks

(b) infants

3−9 months

DPT

3 dose at intervals of 1−2 months

Polio

−do −

BCG

1

9 − 12months

Measles

1

18−24 months

DPT

1( booster)

Polio

1 (booster)

(c) Children

5−6 years

Typhoid

2

10 years

TT

1 (booster)

Typhoid

1 (booster)

16 years

TT

1 (booster)

Typhoid

1 (booster)

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