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INTRODUCTION OF MALARIA

INTRODUCTION OF MALARIA  

Malaria is a disease caused by a plasmodium parasite transmitted by the bite of infected mosquito named female anopheles mosquito.

This is communicable disease means when infected mosquito bites person and person gets infected. Now when uninfected mosquito bites this infected person then this uninfected mosquito gets infected and this infected mosquito bites another person, this is how the disease transmit person to person via bites of infected mosquito. And in such a way this cycle goes.


LIFE CYCLE OF PLASMODIUM PARASITE 
 
Life cycle of plasmodium is completed in two hosts and it is called digenetic. These are two hosts given below.
1) female anopheles mosquito
2) human beings

  
Here female anopheles mosquito is a primary or definitive host as a sexual phase of the malaria parasite occurs in the mosquito, while human beings are secondary or intermediate host as asexual phase of malaria parasite occur in the man.

Half cycle of plasmodium parasite is completed in human beings and other half cycle is completed in female anopheles mosquito. 

Now we see stages of cycle of plasmodium parasite in human beings and female anopheles mosquito.  


STAGES OF LIFE CYCLE IN HUMANS

When infected female anopheles mosquito attracted towards us and bites, then infected mosquito release its saliva in our blood. Along with saliva it releases plasmodium parasite in the form of sporozoites into the bloodstream. Sporozoites are infective stage of plasmodium parasite. 

Saliva contains anticoagulant anophelin and this is the reason blood clot does not form in our body when infected mosquito bites us.

Now this thousands of sporozoites reach liver cell through blood circulation and reproduces asexually (schizogony) in liver cell and converted into schizonts stage.

Over the next 1-2 weeks each schizonts rupture and multiplies into thousands of crypto merozoites (asexual division of the schizonts) that is further divided into different stages such as micro meta crypto merozoites and macro meta crypto merozoites. 

Only micro meta crypto merozoites break out of the liver and re-enter into the bloodstream where it invades the red blood cells and feeds on haemoglobin. This feeding stage of plasmodium is called trophozoite.

Now in the red blood cell, this merozoite reproduces asexually. Therefore, a large number of merozoites are formed whose results is that the RBC bursts.

Hence, newly formed merozoites invade other RBCs and this cycle is repeated in the bloodstream. All the stages of parasite cycle is done here or we can also say that half cycle of parasite is done in human body. 

But some certain merozoites change into sexual stages that is called gametocytes and it is responsible for the transmission of this malaria parasite from humans to mosquitoes.

RBCs containing gametocyte stage migrate to superficial blood vessels of skin. When uninfected anopheles mosquito suck human's blood, all the stages of parasite enters into mosquito's body.

[NOTE : if the mosquito is not anopheles, the cycle does not complete.]  

Now we see other half life cycle has to be completed in female anopheles mosquito.     

STAGES OF LIFE CYCLE IN FEMALE ANOPHELES

Gametocyte, male gametocyte (microgametes) female gametocyte (macrogametes) are ingested by an anopheles mosquito during blood shucking. 

Now in the stomach wall of mosquito, microgametes penetrate the macrogametes generating zygotes which become elongates and motile (ookinetes). This is called sexual phase of parasite.


Ookinete invade the midgut wall of the mosquito and changes to oocyst. 
The ooscyst grow, rapture and released sporozoites which are released in the body cavity (haemocoel) of the anopheles mosquito that travels to mosquito's salivary gland.This is how uninfected anopheles mosquito gets infected and now this infected mosquito is ready to bite second person. 

The cycle of human infection begins again when the infected mosquito bites another person.

SPECIES OF PLASMODIUM 

Five species of plasmodium parasite can infect human and cause malaria disease. 
  1. Plasmodium vivax
  2. Plasmodium falciparum
  3. Plasmodium malariae
  4. Plasmodium ovale
Mainly two plasmodium species in India are plasmodium falciparum and plasmodium vivax , in which plasmodium falciparum is very dangerous. It is responsible for the majority of malaria deaths globally.

Plasmodium Vivax that causes benign tertian malaria and Plasmodium falciparum causes malignant tertian malaria.

SYMPTOMS OF MALARIA

  • Headache
  • Diarrhoea
  • Vomiting
  • High fever
  • Shivering or sweating
  • fast heart rate 
  • Mental confusion

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