Class 9- Malaria

Question 1

Malaria background

Answer 1

• Mosquito borne disease
  
  • Only transmitted by female anopheline mosquitoes
• There were roughly 198 million cases (124-283 million) of malaria in 2013, resulting in an estimated 584,000 deaths (367,000-755,000)
  
  • 89% occur in Sub-Saharan Africa.
    
    • Over 20% of all child deaths in Africa can be attributed to malaria
• 5th highest cause of death from infectious diseases worldwide.

Question 2

Malaria Symptoms – Complicated vs Uncomplicated

Answer 2

• Complicated (severe malaria)
  
  • Cerebral malaria
  • Severe anemia
  • Acute respiratory distress syndrome (ARDS)
    
    • Parasites invading your lungs
  • Hyperparasitemia (5%> of RBCs are infected)
• Uncomplicated
  
  • Cyclical fever
    
    • Fever comes in cycles because every 48 hours a new batch of p. falciparum is released

Question 3

Types of Malaria parasite

Answer 3

• There are 4 primary malaria parasites that affect humans
  
  • Plasmodium Vivax
  • P. Ovale
  • P. Malariae
  • P. falciparum
  • P. Knowlesi
    
    • a primate form of malaria that has recently been found in humans.
• Plasmodium falciparum is the most common species and the most deadly.

Question 4

How much does risk of infection increase when bitten by an infected mosquito?

Answer 4

• It is estimated that your risk of becoming infected when bitten by a infected mosquito is 50%
  
  • More mosquitoes, more bites = more risk
    
    • Level or risk greatly influenced by malaria endemicity
    • The more infected people around, the more frequently the parasite will be spread

Question 5

What influences a mosquitoes competency in transmitting infectious diseases?

Answer 5

• Anthrophilic (prefer to feed on humans)
  
  • Zoophilic (prefer to feed on animals)
• Time of day (some feed at day, some feed at night)
• Indoor vs. Outdoor feeder
• How easily can the mosquitos lay eggs
• Pesticide resistance

Question 6

Calculating R0 for malaria

Answer 6

• Based on Entomological Inoculation Rate (EIR) and Vectorial Capacity (VC)
• Entomological Inoculation Rate (EIR)
  
  • Number of infected bites that each person receives per night
  • How is that calculated?
    
    • Human Landing Rate (HLR) multiplied by Sporozoite Rate (SR)
      
      • SR number of captured mosquitoes with infected salivary glands
• VC measures the rate of potentially infective contacts using the following variables
  
  • Vector density
  • Human biting habit (portion of human meals vs. animal)
  • Daily survival of the vector
    
    • Every Day there is X percent chance a mosquito will die
  • Overall life expectancy

Question 7

EIR and VC – specific control strategies

Answer 7

• EIR
  
  • Limiting exposure to bites (HLR)
  • Reducing Sporozoite Rates
• VC
  
  • Reducing vector density
  • Reducing vector life span
  • Influencing vector feeding preference

Question 8

Terms for Malaria endemicity

Answer 8

• Holo-endemic
  
  • Intense, everyone has malaria parasites all the time
  • >20%
• Hyper-endemic
  
  • Regular, often seasonal, transmission
  • 5 - 20%
• Meso-endemic
  
  • Regular but much lower than hyper-endemic. Danger of occasional epidemics with fairly high morbiidity and mortality
  • 10%
• Hypo-endemic
  
  • Population will have little or no immunity. Danger of severe epidemics involving all age groups
  • Not detectable except during epidemics

Question 9

What is the Malaria Hypothesis

Answer 9

• In 1948 J.B.S. Haldane proposed the high frequency of thalassemia (blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin) in Mediterranean races might be resulting from malaria
  
  • Basically we have been co-evolving with the parasite to prevent infection for millions of years.
• Other protective factors?
  
  • Sickle cell anemia
  • Glucose-6-phosphate dehydrogenase
  • Duffy antigen negative erythroid expression

Question 10

Malaria control strategies

Answer 10

• Reducing vegetation
• Separating animal and human living quarters
• Building homes with proper material
• Sanitation, sanitation, sanitation
  
  • The influence waste disposal has on ID
• Having enough space
  
  • TB, flea, diarrheal disease (fecal droplets) and mosquito born illnesses, airborne diseases (drop let nuclei)

Question 11

Fred Soper

Answer 11

• Led the charge to destroy mosquitos using DDT
  
  • Extreme hard-ass
    
    • Military level discipline
• Successful in Brazil and Italy so was putin charge of global effort
  
  • Didn’t succeed and the harms of DDT were eventually realized

Question 12

Malaria Treatments

Answer 12

• Mefloquine
• Sulfa drugs
• Chlorquine
• Doxycycline
• Artemisinin
  
  • Has been used in Chinese herbal medicine for centuries
  • When used alone, resistance can develop quickly
• ACTs
  
  • Artemisinin-based combination therapy
  • We aren’t actually using new drugs, but rather old drugs in combination