Life cycle of malaria parasites – Asexual cycle in Humen

Life cycle of malaria parasites  involving three  living things.

• Mankind,  secondary vertibrate, intermidiate host.
• Mosquito, Primary invertibrate, definite host.
• Plasmodium parasites is gest or guest.

The malaria parasite complete it’s asexual cycle  in mankind and sexual cycle in mosquito .

Asexual cycle in human

The asexual life cycle takes place in the human body & it is divided into Two stages.  

a )  Pre-erythrocytic stage

b)  Erythrocytic stage

a ) Pre-erythrocytic   or Exo-erythrocytic  or Liver stage tissue phase cycle :-

         (  These cycle has  above three name ) :-  When an infective female anopheles mosquito  bites to human body  ( a healthy individuals ) many sporozoites enter  in the human body through saliva of moaquito , where saliva act as an anti- coagulation agent.

Sporozoites :- Sporozoites having spindle shaped  and they very motile. They get adjusted  ( circulate ) within 30 minutes and then they enter the parenchymal cells of liver .After entering the liver cell sporozoites becomes round body , again it develops and form globular mass having nucleus  (chromatin). Further this nucleus divided into number of nuclei. Each nuclei get cytoplasm and makes individual structure .This is called ‘Cryptozoites’ (  ie  Hepatic Schizonts ).

This cryptozoites  develop so pressure comes on the outer cell abd parenchymal cell burst and cryptozoites get released out .

                   In case of Pv – 10,000  Cryptozoites  forms         

                   In case of Pf – 40,000  Cryptozoites  forms 

                   In case of Pm – 2000  Cryptozoites  forms,

during the tissue phase cycle .

                   In case of  Pv  and  Po, some sporozoites not develop and they take rest or sleep  ( dormant stage ) and are called ‘Hypnozoites’. They develop after  3 to 6 months to develop into cryptozoites  which enter erythrocytes of peripheral blood circulation. Thes   Hypnozoite are  responsible for ‘relapse’ (re-attack), recurrences.

                 This pre-erythrocytic cycle or tissue -phase cycle requires in Pv 8  to  10  day’s  ,  in  Pf   5  & 1/2   to  6 day’s  and  in Pm    11  to   12    day’s 

  b )  Erythrocytic cycle :-

Cryptozoites  attack on new RBC in human blood and forms  ‘ Sydnet ‘ ring stucture .

              1 ) Ring stage: When cryptozoites attack red blood cells (RBCs) they develop and the cytoplasm forms a vacuole with a chromatin dot (nucleus). This is called the ring stage.

          2 ) Trophozoites stage :-  After ring stage stage chromatin expands in size, cytoplasm having vegetative growth with ameboid movement .

            3 )  Early Schizont :–  In this vacuole get deminishes , cytoplasm fused and chromatin devided into 8  to  32 small chromatin dots. Each   chromatin dots by the same cytoplasm.

         4 )  Mature   Schizont :-     Each chromatin dots   surrounded by cytoplasm and form merozoites .This merozoites  ( erythrocytic schizonts )  are formed in rbc .Pressure  created on the wall of rbc and merozoites comes -out through breaking of rbc .At this stage ,busting of rbc allergic reaction takes place because this dead rbc acts as a antigen and fever comes to the patient.

Then same merozoites again come to the cycle  and re-attack on fresh rbc and repeated this cycle for 2  to  3 times  or ( for many months , not exactly known ) , and remaining merozoites develop in male and female gametocytes , which are required  to further development by sexual cycle in mosquito .

   This  cycle takes variable time period in various species or  this cycle follow a ‘ cyclic pattern ‘ depending on the kind of species

Development Time of Malaria Parasites

• Plasmodium vivax (Pv): Completes its cycle in 48 hours (2 days).
• Plasmodium falciparum (Pf): Completes its cycle in 36 hours (1½ days).
• Plasmodium malariae (Pm): Completes its cycle in 72 hours (3 days).
• Plasmodium ovale (Po): Completes its cycle in 48 hours (2 days).
• Plasmodium knowlesi (Pk): Completes its cycle in 24 hours (1 day).

Incubation Period

The incubation period (time from infection until symptoms appear) usually takes 8 to 14 days to complete, depending on the species:

• Plasmodium vivax (Pv): 10 to 12 days (8 + 2 = 10 days to 10 + 2 = 12 days).
• Plasmodium falciparum (Pf): 7 to 8 days (5½ + 1½ = 7 days to 6 + 1½ = 8 days).
• Plasmodium malariae (Pm): 14 to 15 days (11 + 3 = 14 days to 12 + 3 = 15 days).
• Plasmodium ovale (Po): 10 to 12 days (8 + 2 = 10 days to 10 + 2 = 12 days).

                      Thus fever comes to the patient  on above mention period  . So at this time health worker need home visit  and  to take blood  sample for early detection ,and support to stop trasnsmition timely .

                   Thus time take  merozoites  to form gametocytes  are

.  In Pv  = 55 hours  ,  In Pf  = 110 hours  ,In Pm  = 100 hours .In Po =55hrs

 Hence total duration of  asxeual life cycle takes  12 to 18  day’s  for completion .

          In Pv = 10 +2.5  =   13 day’s

      In Pf  =  7  +  5  =  12  day’

      In Pm  = 14 + 4 = 18   day’s .

           In Po = 10 +2.5  =   13 day’s