Describe the life cycle of Plasmodium in man.

Life cycle of Plasmodium in man
Plasmodium vivax is a digenetic parasite.
It completes its life cycle in two hosts.
1) Man 2) Female Anopheles Mosquito
Human phase : Man is secondary host.
Plasmodium reproduces asexually by schizogony which is a type of multiple fission.
It is two types.
i) Hepatic schizogony
ii) Erythrocytic schizogony
i) Hepatic schizogony : When a mosquito bites a man sporozoites are released into blood of man through its saliva. They reach hepatocytes within half an hour.
It includes two types
1) Pre erythrocytic cycle
2) Exo erythocytic cycle
1) Pre erythrocytic cycle :
a) Trophozoites : The sprozoites reach liver cells and transform into trophozoites.
b) Schizont : Trophozoites assume spherical shape attain maximum size.
c) Schizogony : Schizont undergoes schizogony.
d) Cryptozoites : The division forms 12,000 daughter individuals called cryptozoites or first generation merozoites.
e) Now the cryptozoites may again attack liver cells and continue exo-erythrocytic cycle or they can start erythrocytic cycle.
Prepatent period :The time period between first entry of Plasmodium into the blood in the form of sporozoites and second entry of Plasmodium into the blood in the form of cryptozoites is called prepatent period. It is approximately 8 days.
ii. Erythrocytic cycle : Erythrocytic cycle was first described by Camillo Golgi. Hence it is called Golgi cycle.
a) Initiation of cycle : The cycle is initiated either by cryptozoites of pre-erythrocytic cycle or the micro meta cryptozoites of exoerythrocytic cycle.
b) Trophozoites : In fresh RBC these stages get spherical shape and transform into trophozoites.
c) Signet ring stage : Trophozoite develops a small vacuole which gradually increases in size and pushes the cytoplasm and nucleus to periphery. It is called signet ring stage.
d) Amoeboid stage : Signet ring stage loses vacuole and develops pseudopodia. It becomes amoeboid stage. RBC grows almost double in size. This process is called hypertrophy.
e) Haemozoin : The parasite digests globin part of hemoglobin & converts haeme into insoluble haemozoin.
f) Schuffner’s dots : Small red coloured Schuffner’s dots appear in cytoplasm of RBC.
g) Schizont : Parasite further grows in size becomes schizont
h) Schizogony: Schizont produces 12 to 24 erythrocytic merozoites.
i) Rosette stage : Merozoites arranged like petals of rose in RBC. Hence this stage called Rosette stage.
j) Burst of Erythrocytes : Erythrocytes burst and release merozoites along with haemozoin into blood.
k) Incubation period : Period between entry of Plasmodium in the form of sporozoites into blood and 1st appearance of Malarial Symptoms in man.
l) Formation of gametocytes : After repeated erythrocytic schizogony, some merozoites enter RBC & transform into gametocytes. Further Development of gametocytes takes place only in Female Anopheles mosquito.