1. Malarial life cycle… Dr.Shelke A.N. Assist.professor
Mrs.K.S.K.College,beed

2. Plasmodium specie which infect humans
Plasmodium vivax (tertian)
I am giving the old names for these malarias in parentheses to give some historical perspective in case you see these terms again. I will also explain how these old terms relate to the pathogenesis of these respective diseases and the associated fever patterns.

3. Malaria Life Cycle Life Cycle Sporogony Schizogony Oocyst Sporozoites
Mosquito Salivary
Gland
Zygote
Hypnozoites
(for P. vivax and P. ovale)
Gametocytes
Exo-
erythrocytic
(hepatic) cycle
The life cycle of all species that infect humans is basically the same. There is an exogenous asexual phase in the mosquito called sporogony during which the parasite multiplies. There is also an endogenous asexual phase that takes place in the vertebrate or human host that is called schizogeny. This phase includes the parasite development that takes place in the red blood cell, called the erythrocytic cycle and the phase tthat takes place in the parencymal cells in the liver, called the exo-erythrocytic phase. The exo-erthrocytic phase is also called the tissue phase. The schizogeny that takes place here can occur without delay during the primary infection or can be delayed in the case of relapses of malaria. I will focus on the development of the parasite in the human host.
Erythrocytic
Cycle
Schizogony

4. Malaria Transmission Cycle
Exo-erythrocytic (hepatic) Cycle: Sporozoites infect liver cells and develop into schizonts, which release merozoites into the blood
Sporozoires injected into human host during blood meal
Parasites mature in mosquito midgut and migrate to salivary glands
Dormant liver stages (hypnozoites) of P. vivax and P. ovale
MOSQUITO
HUMAN
Erythrocytic Cycle: Merozoites infect red blood cells to form schizonts
Some merozoites differentiate into male or female gametocyctes
Parasite undergoes sexual reproduction in the mosquito

5. Components of the Malaria Life Cycle
Sporogonic cycle
Infective Period
Mosquito bites
uninfected
person
Mosquito Vector
Parasites visible
Human Host
Mosquito bites
gametocytemic
person
Symptom onset
Prepatent Period
Recovery
Incubation Period
Clinical Illness

6. Exo-erythrocytic phase
Blood is infected with sporozoites about 30 minutes after the mosquito bite
The sporozoites are eaten by macrophages or enter the liver cells where they multiply –
pre-erythrocytic schizogeny
P. vivax sporozoites form parasites in the liver called hypnozoites

7. Malaria Life Cycle Life Cycle Sporogony Schizogony Oocyst Sporozoites
Mosquito Salivary
Gland
Zygote
Hypnozoites
(for P. vivax and P. ovale)
Gametocytes
Exo-
erythrocytic
(hepatic) cycle
The life cycle of all species that infect humans is basically the same. There is an exogenous asexual phase in the mosquito called sporogony during which the parasite multiplies. There is also an endogenous asexual phase that takes place in the vertebrate or human host that is called schizogeny. This phase includes the parasite development that takes place in the red blood cell, called the erythrocytic cycle and the phase tthat takes place in the parencymal cells in the liver, called the exo-erythrocytic phase. The exo-erthrocytic phase is also called the tissue phase. The schizogeny that takes place here can occur without delay during the primary infection or can be delayed in the case of relapses of malaria. I will focus on the development of the parasite in the human host.
Erythrocytic
Cycle
Schizogony

8. Exo-erythrocytic phase
P. vivax and P. ovale hypnozoites remain dormant for months
They develop and undergoe pre-erythrocytic sporogeny
The schizonts rupture, releasing merozoites and producing clinical relapse

9. Erythrocytic phase
Pre-patent period – interval between date of infection and detection of parasites in peripheral blood
Incubation period – time between infection and first appearance of clinical symptoms
Merozoites from liver invade peripheral (RBC) and develop causing changes in the RBC
There is variability in all 3 of these features depending on species of malaria

10. Erythrocytic phase stages of parasite in RBC
Trophozoites are early stages with ring form the youngest
Tropohozoite nucleus and cytoplasm divide forming a schizont
Segmentation of schizont’s nucleus and cytoplasm forms merozoites
Schizogeny complete when schizont ruptures, releasing merozoites into blood stream, causing fever
These are asexual forms

11. Erythrocytic phase stages of parasite in RBC
Merozoites invade other RBCs and schizongeny is repeated
Parasite density increases until host’s immune response slows it down
Merozoites may develop into gametocytes, the sexual forms of the parasite

12. Symptoms of malaria Early symptoms
Headache
Malaise
Fatigue
Nausea
Muscular pains
Slight diarrhea
Slight fever, usually not intermittent
Could mistake for influenza or gastrointestinal infection

13. Symptoms of malaria
Acute febrile illness, may have periodic febrile paroxysms every 48 – 72 hours with
Afebrile asymptomatic intervals
Tendency to recrudesce or relapse over months to years
Anemia, thrombocytopenia, jaundice, hepatosplenomegaly, respiratory distress syndrome, renal dysfunction, hypoglycemia, mental status changes, tropical splenomegaly syndrome

14. Symptoms of malaria Early symptoms
Headache
Malaise
Fatigue
Nausea
Muscular pains
Slight diarrhea
Slight fever, usually not intermittent
Could mistake for influenza or gastrointestinal infection

15. Common features of P.vivax infections
Incubation period in non-immunes days but can be 8-9 months or longer
Some strains from temperate zones show longer incubation periods, days
First presentation of imported cases – 1 month – over 1 year post return from endemic area
Typical prodromal and acute symptoms
Can be severe
However, acute mortality is very low