Malaria Plasmodium life cycle PRAKASH JHA M.Sc. BIOINFORMATICS Roll No. 25 prakash424@hotmail.com Plasmodium life cycle
Introduction: Malaria is a disease caused by protozoa & it is widespread in tropics, subtropics and certain areas of temperate zones. Malaria means bad air. Causative agent of malaria is Plasmodium. Plasmodium belongs to class Sporozoa of Phylum Protozoa. Out of 60, only 4 species of plasmodium cause malaria in men. Plasmodium vivax Plasmodium ovale Plasmodium malariae Plasmodium falciparum
History: Plasmodium, the causative agent of malaria, discovered by Charles Laveran. Lancisi suspected relationship b/w mosquito & malaria. Roland Ross(1897) discovered relationship b/w mosquito & malaria & got Nobel Prize in 1902.
Plasmodium- a digenetic parasite Plasmodium is protozoan parasite and spends its life in two hosts (Digenetic). The two hosts are: Man : Primary/definitive host (Adult parasite live & causes fever) Anopheles Mosquito(female) : Intermediate host. Anopheles carries the malarial parasite from infected human host to a fresh human host whom it bites, hence mosquito is also a vector.
Life cycle: in human(Asexual) Infected mosquito bites an individual Saliva rich in Sporozoites (infected stage) injected Sporozoites enter the circulation and then the liver Sporozoites multiplies in liver cell & forms merozoites Merozoites enter RBC forming trophozoites which mature to become Schizonts Merozoites discharged into blood stream when red cell degenerate This results in attack of malarial fever Red cell destroyed by spleen Some merozoites continue to develop in liver.
In Mosquito : sexual Some merozoites develop into male/female gametocytes. During mosquito bite , these gametocyte are ingested Gametocyte fertilize in mosquito intestine. Sporozoites enter human blood on mosquito bite. Sporozoites localizes in salivary glands of mosquito. Development of Sporozoites Completion of cycle.
Plasmodium life cycle
Phases of life cycle in human Pre- Erythrocytic Phase Sporozoites enter the liver and multiplies Erythrocytic Phase Merozoites enter RBC & forms trophozoites. Exo- Erythrocytic Phase Some Merozoites continue to develop in liver. This Phase absent in falciparum malaria.
Importance of mosquito as a vector Gametocytes (mega/micro) remain in blood for several weeks but are unable to develop further in human host because of the high body temperature of man. It is therefore necessary for them to be taken into the body of anopheles(female) as mosquito is cold blooded animal.
Fever cycle: In early stage, fever may persistent for several days but soon it develops into synchronous periodicity. A classical attack of fever has chill, rise in temp. to 40-41 °C headache & Myalgia. This is followed by several hour of profuse sweating & fall in temperature. These paroxysms occur every in: 48 hours(In vivax & ovale malaria) 72 hours(In quartan malaria) In falciparum malaria, the temperature is usually persistently elevated or may progress to 48 hour cycle.
Features of plasmodium species Malaria Types Incubation Period Striking Features Plasmodium ovale Mild tertian malaria 14 days Schizonts & gametocytes enlarge the infected erythrocytes Plasmodium vivax Benign tertian malaria Plasmodium malariae Quartan malaria 30 days Erythrocytes are not enlarged Plasmodium falciparum Cerebral malaria (fatal) 12 days Ring shaped trophozoites, Gametocytes are crescent shaped
Symptoms: High fever headache Liver is moderately enlarged Nausea Vomiting Diarrhea Rarely jaundice may occur anemia
Laboratory diagnosis: Thick & thin blood films are taken .The typical morphology of parasite within the erythrocyte allows differentiation of plasmodium species. It can also be demonstrated on bone marrow examination & by splenic puncture.
Treatment: Chloroquine for vivax, ovale & malariae Primaquine is important to destroy the liver hypnozoite stages of vivax & ovale. Quinine, mefloquine for falciparum Chloroquine Recently, Tu Youyou win nobel prize for her work in helping to create an antimalaria medicine ( Artemsinin).
prevention: Anopheles mosquitoes usually feed during the night so you can protect yourself by sleeping under a bed net. Indoor residual spraying of the walls and other surfaces can kill them reducing the chances that infected mosquitoes spread the disease from one household to another The number of mosquitoes may be controlled by eliminating mosquito larvae before they reach adulthood. Wear cloths that covers full body.
Sickle cell anemia (a gift of nature) In SCA there is replacement of Glu ß6 of HBA with Val in Hbs. Heterozygous for SCA lead a normal life even through their erythrocytes have shorter lifetime than normal individuals. The gene responsible for tendency of RBCs to sickle also alters the permeability of plasma membrane of sickle cell, causing potassium ions to leak out. Low levels of potassium kill malarial parasite.
Sca : example of balancing selection The sickle cell mainly occur in Africa where malaria is major cause of death. The women who are heterozygote have higher fertility; that’s why natural selection has not eliminated the allele. The loss of deleterious recessive genes through deaths of homozygotes is being balanced by the gain resulting from successful reproduction by heterozygotes . For this reason, the selection is called as balancing selection.
From where malaria came to humans?
Origin of malaria in humans: Gorilla was the original source of human infection by P. falciparum. Researchers revealed a genetic match b/w human P. falciparum organisms & those infecting wild gorillas. Using single genome amplification technique they identified DNA sequence from parasite found in fecal samples from wild gorillas This proved that parasite jumped species from gorillas to human.
References: http://www.malwest.gr/enus/malaria/informationforhealthcareprofessionals/plasmodiumlifecycle. aspx http://www.nature.com/nri/journal/v14/n11/fig_tab/nri3742_f1.html http://www.nhs.uk/conditions/malaria/pages/causes.aspx Allison , A.C., The discovery of resistance to malaria of sickle-cell heterozygotes, Biochem. Mol. Biol. Educ. 30, 279–287 (2002) Human malaria parasites may have originally come from gorillas Health News NHS Choices A Fresh Look at the Origin of Plasmodium falciparum , the Most Malignant Malaria Agent.
ANY QUESTIONS ?
Thank You