10 Human Health and Diseases - part 03 - Malaria

 

10 Human Health and Diseases - part 03 - Malaria

Common Human Diseases:
  • Disease is defined as condition of disturbed or deranged functioning of one or more organs or organ systems of the body, caused due to infections, defective diet or heredity. 
  • All human diseases can be broadly categorized into - 
  1. Congenital diseases and 
  2. Acquired diseases.
Congenital diseases :
  • Are present from birth.
  • May be caused by genetic abnormality or metabolic disorder. 
  • May be permanent and were practically incurable. 
  • However, modern research has helped to cure some inborn diseases through gene therapy, enzyme replacement therapy, etc.
Acquired diseases :
  • Develop after the birth
  • Can be sub divided into - 
  1. Communicable or infectious diseases 
  2. Non- Communicable or Non-infectious diseases.
Communicable or infectious diseases 
  • Diseases which are transmitted from infected person to another healthy person either directly or indirectly, are known as Communicable or Infectious diseases. 
  • eg. Malaria 
  • Caused by pathogens like viruses, bacteria, fungi, helminth worms, etc.
Non- Communicable or Non - Infectious diseases
  • The diseases that cannot be transmitted from infected person to another healthy one either directly or indirectly are known as Non- Communicable or Non - Infectious diseases. 
  • eg. Cancer 
Pathogens :
  • All the disease causing organisms are called ‘Pathogens’.
Vector : 
  • Many pathogens use another organism, the ‘Vector’ to reach us. 
  • These vectors are actually parasites which we regularly come across. 
Parasite :
  • Parasite is an organism that lives in or on the body of another organism and derives its nutrition from that of host organism. 
  • Parasites are two catagories viz - 
  1. Ectoparasite E.g. bedbug 
  2. Endoparasite. E.g. Plasmodium is a protozoan endoparasite of the mosquito (vector) and human beings.
Malaria :

  • It is a vector (mosquito) borne infectious disease caused by protist - Plasmodium.
  • There are four species of Plasmodium as - 
  1. P. vivax 
  2. P. ovale
  3. P. malariae
  4. P. falciparum.
  • Only P. falciparum causes serious illness while others are rarely fatal. 
  • Based on the species, there are 4 - types of malaria.
Signs and symptoms of malaria :-
  • Symptoms begin to appear about 7 to 15 days after the bite of infective mosquito.
  • Initial symptom :fever, headache, and chills, may be difficult to recognize as malaria.
  • Classical symptoms : cyclic occurrence of high fever followed by sweating and sudden shievering. Such entire episode lasts for four to six hours and recurs every two days or three days.
  • Vomiting and convulsions.
  • Arthralgia ( joint pain), aneamia due to rupturing of RBCs.
  • Haemoglobinuria, hepatomegaly (liver enlargement).
  • Retinal damage (eye).
  • Cerebral malaria (brain infection).
Mode of transmission :

  • Plasmodium is transmitted from one person to other through an insect vector- female Anopheles mosquito.
  • When infected female Anopheles sucks the human blood, it may transfer sporozoites to human circulation. 
  • Sporozoites reproduce asexually through fission (schizogony) in the liver cells or erythrocytes. 
  • The cells formed are now called merozoites. 
  • The cells formed within erythrocytes function as gametocytes (gamogony). 
  • Besides, it forms gametocytes within erythrocytes (gamogony).
  • Gametocytes if taken up by female Anopheles, fertilization occurs in its gut.
  • Diploid zygote is formed which transforms into oocyst. 
  • Oocyst forms large number of haploid sporozoites through meiosis (sporogony).
  • Sporozoites migrate to salivary glands and are ready to infect new human host.

Diagnosis and Treatment :
  • Malaria can diagnosed by microscopic study of blood smear. 
  • Besides, other rapid diagnostic tests based on nucleic acid amplification techniques are also used.
  • Treatment of malaria includes Artemisinin based combination therapies (ACTs). 
  • WHO has recommended 5 different ACTs which includes various combinations of artesunate, sulfadoxine, pyrimethamine, etc. 
  • In addition, quinine is also used.

Prevention and Control :
  • Prevention of mosquito bite by using mosquito nets and insect repellents.
  • Spraying insecticides and draining stagnant water where mosquito lays eggs.
  • Mosquito larve can be controlled by using Gambusia fresh water fish (biocontrol).

Always Remember
  • The time interval from the invasion of a pathogen to the development of clinical manifestations, is known as Incubation period.

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