Eradication of Malaria

• So why did the campaign fail?

• 1) Insecticides (DDT)– Environmental damage!

Pesticide Resistance

• Rapid Reproduction

• Selection

DDT

DDT

Pesticide Resistance

• Rapid Reproduction

• Selection

Eradication of Malaria

• 2) Plasmodium– Wide use of chloroquine has led to drug

resistant strains!

Eradication of Malaria

• 3) Social/Political Reasons– Emerging nations in Africa were trying to be

free from external (Western European nations) domination; much of the monetary resources stopped flowing in!

• Genetic resistance to Plasmodium

• 2 examples

There are some general genotypes that are resistant to malaria

Duffy Blood Group

• Noticed in military groups in Vietnam.

• African Americans had less severe cases or no cases of malaria!

Genetic Resistance• Plasmodium vivax

• Duffy blood groups– Proteins on cell surface– 3 alleles

• A Dominant

• B Dominant

• y recessive

A =

B =

y = no proteins

Genetic Resistance• Plasmodium vivax

• Duffy blood groups– Proteins on cell surface– 3 alleles

• A Dominant

• B Dominant

• y recessive

A =

B =

y = no proteins

AB yyAA BB Ay

By

Genetic Resistance

• yy genotype has advantage– P. vivax malaria resistance– Only advantageous if P. vivax malaria

endemic

• 40% people of W. African decent

• 0.1% people of non-African decent

• P. vivax keeps the allele common in Africa.

Genetic Resistance

• Sickle celled anemia• Codominant trait (Allele “A” and “B”)

– AA have sickle celled anemia– AB have both types of cells

• Sickle cells don’t support species of Plasmodium well.

• Resistance to infection

Genetic Resistance

• AA selected against – Sickle celled anemia

• AB selected for– Both sickle and normal cells

• BB selected against– Normal cells

• If malaria not endemic, what alleles will be selected for? Against?

• Allele for sickle cells maintained in the population even though strongly disadvantageous to have both alleles.

Genetic Resistance

Sickle Celled Anemia

• In the US, 10% of African Americans have this allele!

Other forms of Resistance to Malaria

• Babies get antibodies from their moms breast milk; they are protected until weaned.

• Once weaned becomes susceptible again!

• What you need to have malaria spread within a population!

Epidemiological Models

Infected People

MosquitoesUninfected

People

contact contact

Habitat

Climate

Food

Source of Plasmodium

Source of New Hosts

Habitat

Behavior

Breaking the Chain

Infected People

MosquitoesUninfected

People

contact contact

Habitat

Climate

Food

Source of Plasmodium

Source of New Hosts

Habitat

Behavior

Eliminating Mosquitoes

• Mosquito Life Cycle

Eliminating Mosquitoes

Eliminating Mosquitoes

• Destroy habitat

• Insecticides

• Biological control

Eliminating Mosquitoes

• Destroy habitat

• Insecticides

• Biological control

• Why don’t these methods work?

Pesticide Resistance

• Rapid Reproduction

• Natural selection

Getting rid of the source of Plasmodium

Getting rid of the source of Plasmodium

• Drug treatment

• Transgenic mosquitoes

Getting rid of the source of Plasmodium

• Drug treatment

• Transgenic mosquitoes

• Why don’t these work?

Getting rid of the source of Plasmodium

• Drug treatment

• Transgenic mosquitoes

• Why don’t these work?

– Availability of drugs• Money

• Medical staff

– Recrudescense

– Drug resistance

– Reservoir hosts?

– Transgenic mosquitoes not a reality

– Expensive

How can we protect the uninfected population?

• Vaccines

• Prophylactic drugs

How can we protect the uninfected population?

• Vaccines

• Prophylactic drugs

• Why don’t these work?

How can we protect the uninfected population?

• Vaccines

• Prophylactic drugs

• Why don’t these work?– Vaccines unsuccessful– Prophylactic drugs expensive– Prophylactic drugs unpleasant

How can we prevent contact between people and mosquitoes?

• Insecticides

• Mosquito nets

• Long clothing

• Behavior

• Avoid mosquito habitat

• Screens on houses

How can we prevent contact between people and mosquitoes?

• Insecticides• Mosquito nets• Long clothing• Behavior• Avoid mosquito

habitat• Screens on houses

• Why don’t these work?

How can we prevent contact between people and mosquitoes?

• Insecticides• Mosquito nets• Long clothing• Behavior• Avoid mosquito

habitat• Screens on houses

• Why don’t these work?– Money

– Availability of materials

– Human behavior difficult to change

• "Everything about malaria is so molded by local conditions that it becomes a thousand epidemiological puzzles." Hackett (1937)

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

• Prevention of malaria in pregnancy

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

• Prevention of malaria in pregnancy

• Monitoring for epidemics – Rapid response

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

• Prevention of malaria in pregnancy • Monitoring for epidemics

– Rapid response

• New methods and tools

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

• Prevention of malaria in pregnancy • Monitoring for epidemics

– Rapid response• New methods and tools

• Improvement in existing tools through research and development

Roll Back Malaria (RBM) Strategy• Early diagnosis and prompt treatment • Prevention

– insecticide-treated materials– vector control measures

• indoor spraying• larvicide • environmental management

• Prevention of malaria in pregnancy • Monitoring for epidemics

– Rapid response• New methods and tools• Improvement in existing tools through research and development

• Coordinated action through establishing partnerships that utilize an optimal mix of measures adapted to local situations.