Malaria(Plasmodium falciparum)- Epidemiology, Life Cycle, Prevention and Eradication

Malaria(Plasmodium falciparum)- Epidemiology,

Life Cycle, Prevention and

Eradication

Sarath

Epidemiological TriadHost1.Sex-Male2.Race-Sickle cell trait3.Occupation-Labourers,Farmers,Tribals4.Socio Economic status 5.Human Habits -Nomadism

Environment1.Seasons2.Temperature3.Humidity4.Rainfall5.Altitude

Agent Factors1.Parasites2.Reservoirs3.Relapses

VectorAnopheles Mosquito

Organism

Plasmodium Falciparum

Phylum : Apicomplexa

Class : Sporozoea

Subclass : Coccidia

Order : Eucoccidia

Suborder : Haemosporina

Features of plasmodium falciparum

Forms in the peripheral blood- Rings and crescents only.

Ring form- Cytoplasm fine and regular. Often with 2 nuclei. Form accole.

Merozoites- 18 to 24 or more. Arranged in a grape like cluster.

Gametocyte- Banana shaped. Larger than the red blood cell.

Life CycleExogenous Phase(in Mosquito)Sexual Cycle (sporogony)

Endogenous Phase(in Human)Asexual Cycle(Schizogony)

Sporozoites pass through body cavity,salivary glands

Exoerythrocytic cycle multiplication in liver parenchymal cells

Merozoites

Enter RBC

Ring Trophozoite

Mature Trophozoite

Immature Schizont

Mature Schizont

Microgametocyte(differentiation)Macrogametocyte

Human blood enters mosquito

Microgamete(fertilization)Macrogamete

Zygote

Ookinete(motile Zygote)

Penetrates to outer layer of stomach wall of mosquito and encysts

Oocyst grows(multiple division stage: cyst bursts to release sporozoites

Sporozoites in saliva injected into human host

Malaria Life Cycle in Humans

ReservoirConditions :

1. The person must harbour both sexes of gametocyte in blood

2. Gametocytes must be mature

3. Gametocytes must be viable

4. Gametocytes must be present in suffcientquantity

Reservoir Contd…

Humans

1. One who harbours the sexual forms of parasite.

2. Children are more likely to be gametocyte carriers than adults. Hence better reservoir.

Transmission

1. Vector Transmission

Anopheles culicifacies – Rural and per urban areasAnapheles stephensi -- Urban and Industrial areasAnopheles fluviatilis -- Hilly areasAnopheles epiroticus -- Only in Andaman and Nicobar

2. Direct Transmission

By sharing syringes, blood transfusion etc.

Parasites keep their infective activity during at least 14 days in bottles stored at -4 0C

Persons who have lived in endemic area and anyone who has had malaria should not be accepted as a blood donor until 3 years afterwards.

3. Congenital Malaria

Congenital infection from mother to newborn also occur, but it is comparatively rare

Prevention

All that we have to do is to break this chain

Insecticide treated nets

Repellents protective clothing screening of houses

Environmental sanitation

water management

drainage

Larviciding of water surfaces

intermittent irrigation slucing, biological control

Indoor residual spraying

Space spraying

Ultra low volume sprays

Health education

Community participation

Prophylaxis for susceptible population

Gametocidaldrugs

Prevention

Action For Individual and Family protection

Reduction of Human-Mosquito contact Insecticide treated nets, repellents, protective clothing, screening of houses

Destruction of mosquito larva Peri-Domestic sanitation

Source reduction Small scale drainage

Social participation Motivation for personal and family protection

Destruction of Adult Mosquitoes Indoor residual spraying

Prevention

Action For Community protection

Reduction of Human-Mosquito contact Insecticide treated nets, zooprophylaxis

Destruction of mosquito larva Larviciding of water surfaces, intermittent irrigation, sluicing, biological control

Source reduction Environmental sanitation, water management, drainage

Destruction of Adult Mosquitoes Indoor residual spraying, Space spraying, ultra low volume sprays

Social participation Health Education, Community participation

Biological Control-Gambusia

Insecticide treated nets

Can malaria be Eradicated???

AgentSource

SusceptiblePopulation

Vector

Eradication Elimination Control

Current answer is NO Why??

Despite progress, the burden of malaria is still great and it is widespread.

Drug and insecticide resistance are on the rise. In South East Asian countries, resistance of Plasmodium falciparum, to Artemisinin, has been detected.

Although new drugs and insecticides are being sought, none are expected to be available in the near future.

Ref: Malaria eradication:Is it possible?Is it worth it?Should we do it?Should we do it?Jenny Liu,Sepideh Modrek,Roly D Gosling,Richard GA Feachem

Increased mobility of people not only makes containment of resistance difficult, but also threatens the introduction or reintroduction of malaria parasites to receptive areas.

New strains are emerging- ex. Plasmodium knowlesi

Zoonotic reservoirs

Ref: Malaria eradication:Is it possible?Is it worth it?Should we do it?Should we do it?Jenny Liu,Sepideh Modrek,Roly D Gosling,Richard GA Feachem

How can we bring eradication in the future???

Malaria is biologically and ecologically different throughout the world. So Malaria eradication strategies should be developed and implemented on a local or regional level.

Eradication can be accelerated by new drug regimens and strategies that lead to complete parasitologiccure of the individual.

The majority of malaria infections occur in asymptomatic people, who are a source of continued transmission. A successful and accelerated eradication effort will target asymptomatic infections through community-based efforts.

Thank You