Setting: office
CC: “I’m going on a trip to Africa for three weeks.”
VS: normal
HPI: A 24-year-old healthy medical student is going on a 3-week trip to Africa as part of a medical mission and vacation. She is here seeking advice about vaccinations and prophylaxis.
PMHx/Medications: none
PE: normal
Which of the following is not an appropriate preventive therapy for this type of traveler?
a. Ciprofloxacin daily
b. Hepatitis A vaccine
c. Malaria prophylaxis
d. Typhoid vaccine
Answer a. Ciprofloxacin daily
It is not necessary to use daily prophylactic antibiotics to prevent diarrhea. It is inappropriate to use antibiotics in advance of developing diarrhea, and if asked, you should specifically refuse to do so. The traveler should be careful to eat foods that are fully cooked or can be peeled, such as bananas or oranges. She should avoid street food as well. Hepatitis A and typhoid fever vaccinations are routine where the water supply is not safe. Malaria prophylaxis is advised in many places around the world.
CCS will not require you to memorize which specific countries need specific malaria regimens. No one will expect you to remember the chloroquine sensitivity or resistance levels in 190 separate countries in the world.
Which of these is not appropriate for malaria prophylaxis?
a. Mefloquine
b. Artemisinin
c. Atovaquone/Proguanil
d. Doxycycline
e. Netting
Answer b. Artemisinin
Artemisinin-containing combination therapy is used as a drug of choice in acute malaria. It is not a prophylactic medication. The two most commonly used preventive malaria treatments are mefloquine and atovaquone/proguanil. Both of these are equal in efficacy. Doxycycline is used in areas of mefloquine resistance in Southeast Asia. Doxycycline is not the best first choice because there is a risk of photosensitivity reaction. Chloroquine can be used in areas where there is clear chloroquine sensitivity. All of these kill blood schizonts of malaria. Mosquito netting at night is one of the most effective preventive measures you can do for malaria.
Trophozoites = Red Blood Cell (RBC) “Ring” Seen in Malaria Smear (Figure 10-8)
Figure 10-8. Malaria. Plasmodium falciparum. Blood film. Several red cells contain trophozoites (ring forms). The arrows point to a ring form and double-dot ring form. (Reproduced with permission from Lichtman MA, et al. Lichtman’s Atlas of Hematology, www.accessmedicine.com.)
Trophozoites develop into schizonts in RBCs.
Schizonts = RBCs “Pregnant” with Malaria = Burst = Spread
All of these kill blood schizonts of malaria.
Initial Orders:
Hepatitis A vaccine
Typhoid fever vaccine
Mefloquine
Mefloquine
• Must start 3 weeks before departure
• Safe in pregnancy
• Not for use with severe psychiatric illness
• Not for use with history of seizures
Atovaquone/Proguanil
• Active against liver schizonts of falciparum
• Prevent blood schizont release
Primaquine
• Kills liver schizonts of all species
• Kills blood schizonts of all species except Plasmodium falciparum
The patient is vaccinated against hepatitis A and is given the typhoid fever vaccine to take at home over several days. The prescription for mefloquine (or atovaquone/proguanil) is also given to her.
Genetic Protective Factors against Malaria
• No Duffy antigen on RBC
• Sickle cell trait
• Thalassemia trait
The patient calls you 2 months later. She returned from her trip 2 weeks ago and now has a fever. She did not remember to take preventive therapy for malaria.
Orders:
Transfer to ED
Thick and thin smear for malaria
Fingerstick for glucose on arrival
CBC
CHEM-7
All patients with malaria have some GI distress.
It is not dangerous.
Which of these indicates severe malaria?
a. Positive thick smear with elevated bilirubin
b. Positive rapid diagnostic test with enlarged spleen
c. Ten percent of cells with plasmodia present with hypoglycemia
d. Temperature 104°F and hematocrit 32%
Answer c. Ten percent of cells with plasmodia present with hypoglycemia
Malaria is complicated or dangerous when parasitemia goes above 5% to 10% of cells. At this parasite level, hypoglycemia develops as well as dangerous signs of disease, such as:
• Cerebral involvement
• Renal failure
• Metabolic acidosis
• Respiratory distress
Mechanism of Hypoglycemia in Severe Malaria
• There is decreased gluconeogenesis.
• There is decreased glycogen level.
• Parasites consume the glucose.
Hypovolemia + Hemoglobinuria = Renal Failure = Blackwater Fever
Mechanism of Acidosis
• There is increased lactate level from the parasite.
• There is decreased liver and renal clearance of the lactate.
• Parasites block the blood flow, which increases anaerobic glycolysis.
The patient comes to the ED. She has a temperature of 103°F with chills.
PE:
Neurologic: normal
Chest: normal, no respiratory distress
Reports:
Fingerstick: glucose 80 mg/dL
CHEM-7: total bilirubin 2.4 mg/dL (slight elevation); indirect bilirubin elevated
CBC: hematocrit 34%; platelets 128,000/μL
Reticulocytes 4%
Normal blood urea nitrogen (BUN) and creatinine levels
Thick and thin smear: positive for P. falciparum, 2% parasitemia
The thick smear detects malaria.
The thin smear speciates.
Rapid Diagnostic Tests for Malaria
• Antibody tests
• Detect histidine-rich protein
• Detect plasmodium antigens
Which of these is not appropriate for treating this patient?
a. Artemether/Lumefantrine
b. Atovaquone/Proguanil
c. Mefloquine and doxycycline
d. Quinine and doxycycline
e. Chloroquine
Answer e. Chloroquine
It is inappropriate to use chloroquine alone to treat malaria acquired in Africa, even if it is uncomplicated. The Center for Disease Control and Prevention (CDC) recommends artemisinin-containing regimens such as:
• Artesunate and amodiaquine or
• Artemether/Lumefantrine
However, any of the other regimens can be safely used.
On CCS, this patient has mild malaria. After treatment, she can be seen “as needed.”