2: malaria

Question 1

vector for malaria

Answer 1

anopheles freeborni mosquito

Question 2

what areas of the world do you see malaria?

Answer 2

tropical climates

Question 3

what map echoes the malaria map?

Answer 3

hemoglobinopathy - tells you selective pressures

Question 4

describe the plasmodium species that cause disease in humans

Answer 4

5 species:

• falciparum (most severe disease)
• vivax
• ovale
• malariae
• knowlesi

Question 5

key points of plasmodium lifecycle

Answer 5

1. bite of infected mosquito
2. plasmodium sporozoites have trophism for hepatocytes
3. asexual reproduction in hepatocytes
4. release into bloodstream
5. hijacking of RBC and degradation of Hb, formation of ring forms
6. lyse RBC and release merozoites to invade more RBC, or gametocytes to reinfect mosquitos [hemolytic anemia -> direct hyperbilirubinemia = jaundice]
7. P vivax and P ovale can produce dormant hypnozoites in hepatocytes, can reactivate in 3-12 months

Question 6

host response to malaria

Answer 6

splenic immune reaction and filtrative clearance -> leads to clinical appearance

Question 7

clinical presentation of malaria:

• general
• what features suggest falciparum over others?
• what features suggest vivax or ovale over others?

Answer 7

• exposure to endemic area
• lack of prophylactic treatment used by travelers
• headache
• fatigue
• myalgias
• abdominal pain
• *fever!

falciparum: seizures

vivax/ovale: paroxysmal chills, fever, rigors (hepatic sequestration and re-release)

Question 8

physical findings in malaria

Answer 8

• fever
• mild hepatomegaly
• palpable spleen
• mild icterus (jaundice)

-rash is very unusual

Question 9

why can falciparum cause cerebral malaria?

Answer 9

can cause sequestration and agglutination in vasculature, including CNS capillaries

Question 10

features of cerebral malaria

Answer 10

• seizures
• encephalopathy
• coma

Question 11

what causes hypoglycemia in malaria? significance of this sign?

Answer 11

due to decreased hepatic gluconeogenesis and increased systemic glucose utilization - poor prognostic sign

Question 12

what causes metabolic acidosis in malaria?

Answer 12

due to hypoperfusion, lactic acidemia

Question 13

what does noncardiogenic pulmonary edema of malaria look like?

Answer 13

ARDS- adult respiratory distress syndrome

Question 14

what causes renal impairment in malaria?

Answer 14

ATN (acute tubular necrosis)

Question 15

what hematologic abnormalities do you see in malaria?

Answer 15

anemia

Question 16

what liver dysfunction do you see in malaria?

Answer 16

• cholestasis

- acute hepatitis

Question 17

diagnostic testing for malaria: stains

Answer 17

• LM of Giemsa-stained blood smear**
• thick and thin blood smears (to evaluate for ring forms and estimate parasite load)
• thick smears concentrate parasites -> increases diagnostic sensitivity

Question 18

diagnosis of malaria: lab findings

Answer 18

• nonspecific
• normocytic normochromic anemia w/ evidence of hemolysis (high RDW - tells you size of RBCs)
• increased acute phase reactants (ESR, CRP)
• increased RDW (tells you the variability in size of the RBCs - increases with hemolytic anemia b/c get fragments along with regular red cells)

Question 19

treatment of malaria - non falciparum

Answer 19

-chloroquine is treatment of choice, if in chloroquine sensitive area

Question 20

treatment of malaria - falciparum

Answer 20

• if chloroquine sensitive, chloroquine

- if question chloroquine sensitivity, artemisinin-based combos preferred

Question 21

malaria prevention options

Answer 21

• mosquito tents
• insect repellents
• preventive treatment in travelers (drug choice based on destination)

Question 22

describe 4 drugs commonly used for malaria prophylaxis

Answer 22

• malarone (atovaquone-proguanil)
• doxycycline
• chloroquine phosphate
• mefloquine HCl

Question 23

prophylaxis regimen for malarone

Answer 23

• 250 mg atovaquone + 100mg proguanil
• one tablet p.o. daily
• start 1-2d before, through 7d after
• don’t use in pregnancy (insufficient data)
• easy to tolerate, generic, inexpensive

Question 24

prophylaxis regimen for doxycycline

Answer 24

• 100 mg
• one tablet p.o. daily
• start 102d before, through 4w after
• don’t use in pregnancy (teratogenic)
• used to be inexpensive

Question 25

prophylaxis regimen for chloroquine phosphate

Answer 25

- 500 mg salt (300 mg base) - one tablet p.o. weekly - start 1-2w before, through 4w after - safe for pregnancy - generic, inexpensive, easy to tolerate

Question 26

prophylaxis regimen for mefloquine HCl

Answer 26

- 250 mg salt (228 mg base) - one tablet p.o. weekly - start 2-3w before, through 4w after - safe for pregnancy * CNS side effects (hypersexual dreams/nightmares)