Malaria & Vector Borne Disease

Things to Note:

1. The most important arthropod vector for human disease is the mosquito (but there are others)
2. The most important mosquito borne disease is malaria (but there are lots more)
3. Where and how people live is critical in determining vector exposure
4. Vector control using pesticides raises complex question environmental, trade, justice
5. Environmental change at local and global scales impacts on vector density and distribution
6. Vector borne disease has major economic consequences that indirectly impact health

Malaria

1. Plasmodium falciparum
2. P. vivax
3. P. malariae
4. P. ovale
5. P. knowlesi

 

Transmission of Malaria

Anopheline mosquito → Black white strips

Malaria and poverty are closely linked → highest occurrence in “developing countries”

 

Diagnosis & Therapy of malaria

1. Patient Travel History; Malaria “rich” areas
2. Microscope:
   • Malaria parasites can be identified by examining under the microscope a drop of the patient’s blood, spread out as a “blood smear” on a microscope slide.
3. Rapid Diagnostic Tests
   • detect malaria antigens (proteins) in a sample of a person’s blood (usually a fingerstick) and indicate a positive result by a color change on the testing strip

 

Why is knowing the exact species (out of the 5) important?

• The most severe form is caused by P. falciparum
  • should immediately seek diagnosis and effective treatment, and inform medical personnel of the possible exposure to malaria infection.
• Other Plasmodium species cause significant morbidity but are rarely life-threatening.

 

Facts:

Malaria mortality Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under 5.	Preventive treatment for pregnant women: 25 million pregnant women annually.
Annual cases of malaria 2015 214 million malaria cases About 438 000 malaria deaths. Africa: vast majority (about 90%) About 80% deaths are in children <5 years In 2015, about 305 000 African children died before their fifth birthdays. A lot of that was malaria	Population at risk 3.4 billion (half of the world population) 97: Number of countries with ongoing transmission in 2013 80% of deaths in 18 countries 40% in Nigeria and the Democratic Republic of the Congo

 

 

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Malaria incurs Health Care Costs: Malaria & Humanitarian Crisis:

Around 40% of public health spending in sub-Saharan Africa 20-50% of inpatient admissions Up to 50% of outpatient visits Average household spending Over 10% of yearly spending in Africa

Up to 30% of malaria deaths in Africa occur in the wake of war, local violence or natural disasters. Cause infrastructure damage and spread of diseases

Large amount of which (health issues) are Malaria-caused.

 

What are the resources Required? (in this malaria crisis)

1. Diagnostic tests: approximately 1.5 billion annually.
2. Drugs: 228 million doses of ACTs are needed to treat P. falciparum annually;
   1. 19 million doses of chloroquine and primaquine are needed annually for P.vivax.

How do we control the spread of Malaria?

1. ITNets

2. Indoor Residual Spraying

3. Intermittent Preventive Therapy

4. Effective Diagnosis and Treatment (ACT)

5. Vector control

6. Minimising exposure to vector

7. Drug prophylaxis (not quite the same as intermittent preventive therapy)

 

Where do we find the money to fund these Malaria Programs?

• Tax?
• Businesses?
• Government?
• Individuals?
• WHO?

 

Development & Economic Impact:

• Loss of education
• Loss of productivity
• Health care costs
  • Poor families in hyper-endemic areas may spend 25% of their income on treatment for malaria
  • Impact on publicly funded/NGO funded health care

• Business: Loss of opportunity
  • Areas of low lying potentially very productive land may be relatively unattractive for settlement because of mosquito infestation (Economist July 17th 2004)

• Loss of foreign Investment
  • Malaria transmission deters investors
  • Risks to non-indigenous employees
  • Continuity of labour supply

 

Direct economic costs:

• USD 12 billion per year in direct losses,
• Lost 1.3% of GDP growth per year for Africa.
• Burden: 35.4 million Disability Adjusted Life Years (sub-Saharan Africa)
• Cost per DALY averted USD 2-24 (sub-Saharan Africa)

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Prevention of Malaria

DDT: Dichlorodiphenyltrichloroethane

is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochlorine, originally developed as an insecticide, and ultimately becoming infamous for its environmental impacts.

• Indoor Residual Spraying: DDT for Malaria
  • Bans the use of DDT; except for malaria control~ POPs May 17th 2004

 

Spraying DDT

Indoor Residual Spraying (with DDT) to combat malaria

Questions:

1. What is the environmental cost (of using DDT) → killed large amounts of bumblebees
2. How does environmental risk equate with the health benefit (of malaria eradication)?
3. Impact on Exports? (especially agriculture)

Cases:

Uganda

The ministry launched indoor residual spraying in northern Uganda in February 2008. It was planning to roll out the campaign to other parts of the country when the High Court halted the exercise in May 2008, after a petition from environmental activists. Case subsequently dismissed For and Against arguments: http://www.newvision.co.ug/new_vision/news/1324275/ddt-save-lives-uganda http://www.observer.ug/viewpoint/guest-writers/29572-ddt-is-not-our-solution-for-malaria-

Long Lasting Insecticidal Nets (LLIN)

 

Finance: (providence)

1. Free or
2. Subsidized ?

 

 

 

Immunity and Vaccines?

• There’s currently no vaccine available that offers protection against malaria, so it’s very important to take antimalarial medication to reduce your chances of getting the disease. However, antimalarials only reduce your risk of infection by about 90%, so taking steps to avoid bites is also important.

• After repeated attacks of malaria a person may develop a partially protective immunity. Such “semi-immune” persons often can still be infected by malaria parasites but may not develop severe disease, and, in fact, frequently lack any typical malaria symptoms.
  • Residents of hyperendemic areas who move to non endemic areas gradually lose immunity; The risk of going home!
  • Hence traveling to malaria prone areas is dangerous
    • High risk of symptomatic/severe infection on holidays home

• Those with sickle cell anemia are resistant to the parasite that causes malaria. A small genetic change in hemoglobin both causes sickle cell anemia and protects against malaria.
  • That is why sickle cell anemia recessive gene is prevalent in africa
  • You either died of sickle cell anemia (full) or of malaria or
    • Have “mild” sickle cell anemia and is resistant to malaria… (½ s)

 

 

Vaccine Research Programs

• In May 2009, RTS,S began large-scale Phase 3 clinical testing,
• 11 clinical trial sites in seven African countries – Burkina Faso, Gabon, Ghana, Kenya, Malawi, Mozambique, and Tanzania.
• completed enrollment in January 2011, with a total of 15,460 confirmed participants.

• The RTS,S/AS01 vaccine provided protection against both clinical and severe malaria in African children. (Funded by GlaxoSmithKline Biologicals and the PATH Malaria Vaccine Initiative; RTS,S ClinicalTrials.gov number, NCT00866619.)

The RTS,S Clinical Trials Partnership

N Engl J Med 2011;366

 

Seasonal Malaria Chemoprophylaxis MSF
SMC uses sulfadoxine/pyrimethamine (Fansidar®), reduced the number of cases of simple malaria by 66 percent during trials in Mali and Chad between July and October last year.

 

 

To Sum Things Up:

1. The most important arthropod vector for human disease is the mosquito (but there are others)
2. The most important mosquito borne disease is malaria (but there are lots more)

1. Where and how people live is critical in determining vector exposure
2. Vector control using pesticides raises complex question environmental, trade, justice

1. Environmental change at local and global scales impacts on vector density and distribution
2. Vector borne disease has major economic consequences that indirectly impact health