Malaria

Question 1

Vectors

Answer 1

biological (more efficient) or mechanical. Many insects, esp mosquitoes. Controlling vector = controlling disease. Introducing a new vector somewhere can result in a new outbreak

Question 2

How to tell which mosquito is which

Answer 2

Anopheles: resting position is pointing up, vector for malaria. Culex: resting position is more parallel, vector for west nile virus

Question 3

Distribution of malaria

Answer 3

Generally closer to the equator. Some strains are resistant to certain drugs. Affects 40% of world pop, 3 million deaths/year. 90% in sub-saharan Africa.

Question 4

Malaria fatalities in travellers

Answer 4

usually 1-5%, >20% in severe (can occur within 36-48 hours). Usually death results when people don’t recognize it’s malaria.

Question 5

P faciparum

Answer 5

infects all RBC stages. High mortality in non immune. Cannot relapse after treatment.

Question 6

P vivax

Answer 6

Only reticulocytes. relapses due to residual hepatic phase (an adaption for transmission in temperate climates)

Question 7

Life cycle of malaria**

Answer 7

Sexual reproduction in mosquito. Enters human bloodstream, goes to liver, reproduces asexually and progeny infect RBC. P. falciparum infects young and old RBC and causes lysis with its asexual reproduction (note there is no liver stage after this). P vivax infects young RBC (reticulocytes) and because it has a hypnozoite liver phase after the RBC phase (falciparum does NOT have this stage), relapses are possible after weeks/months symptom free.

Question 8

Genetic immunity to malaria

Answer 8

People with sickle cell anemia are less likely to get malaria. Thallasemia diseases and G6PD deficiency are also protective

Question 9

Malaria in pregnancy

Answer 9

Usually fatal to fetus. Parasite evade immune system in placenta. AB transfered to child (if it survives) only last so long too.

Question 10

Categories of malaria vaccine

Answer 10

Classify by parasite stages that are targeted: 1. pre-erythrocytic. 2. asexual blood stages. 3. mosquito stages

Question 11

Clinical effects of malaria

Answer 11

Asymptomatic or intermittently symptomatic in “immune” hosts. Febrile illness with temporary disability. Anemia, multiple mechanisms. Adverse pregnancy outcomes. Effects on other diseases (Burkitt’s lymphoma, HIV). *Organ failure b/c RBC get stuck (brain, kidney, lung etc.). *mortality 20% in severe malaria, even with optimal treatment. *Death (stars indicate falciparum)

Question 12

Common symptoms

Answer 12

Fever, chills, sweats, headaches, nausea, vomiting, malaise. Fairly non-specific, can be confused for other things.

Question 13

Severe malaria

Answer 13

Caused by P falciparum. Can cause RBCs to stick to endothelium, block small vessels, and cause organ damage. Life-threatening!

Question 14

Diagnosing malaria

Answer 14

Travel Hx! Lots of non specific symptoms, fever, spelenomegaly, thrombocytopenia. Look under microscope at blood smear. Hematuria, signs of anemia or hemolysis. PCR

Question 15

How to treat malaria

Answer 15

If unsure which species, assume the worst! Treat with atovaquone proguanil or if the symptoms are severe (unconscious, severe anemia, kidney failure, respiratory distress, acidosis, seizures, parasitemia >5%), use artesunate or quinine. For P. vivax, do follow up therapy with primaquine for hypnozoite stage

Question 16

Malaria control - personal and public

Answer 16

Health infrastructure strengthening. Mosquito Control Measures (*Insecticide—impregnated bed nets, Spraying programs). Vaccine - Someday…. Damage Reduction: Prompt diagnosis and treatment of acute cases. Chemoprophylaxis of selected groups (pregnant women, possibly young children, *travellers, specifically including Visiting friends and relative (VFR’s))

Question 17

WHO 3 pillars for control of malaria

Answer 17

diagnosis of malaria cases and effective treatment; distribution of insecticide-treated nets to populations at risk of malaria (especially children/pregnant women); indoor residual spraying - DDT - to reduce and eliminate malaria transmission.

Question 18

Info for travelers

Answer 18

A – Awareness of malaria risk B – Bite prevention C – Chemoprophylaxis D – prompt Diagnosis and Treatment. **If pregnant, avoid travel to malaria endemic areas

Question 19

Why important to take the malaria drugs before and after travel?

Answer 19

Prevent infection and kill anything still left inside you (hypnozoite)

Question 20

Cases - which travellers should you worry about most?

Answer 20

All are concerns, but anyone to West Africa is a concern b/c of the high density of infection.