Study Points

Malaria and the International Traveler

Course #94363 - $15 • 3 Hours/Credits

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  1. The symptoms of malaria were first described

    INTRODUCTION

    The symptoms of malaria were first described around 2700 B.C.E. in ancient Chinese medical writings [1]. Thousands of years later, malaria continues to be one of the most significant infectious diseases. Approximately 3.2 billion people live in areas of malaria transmission, and an estimated 150 to 300 million cases of malaria are reported each year. Malaria is a leading cause of illness and death in the developing world, killing an estimated 430,000 people each year [2,58]. Young children and pregnant women are the groups most affected [2,37,58]. Although the transmission of malaria was successfully interrupted in the United States during the late 1940s, it continues to pose a challenging health threat to individuals who travel to and emigrate from malarious areas [5,54].

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  2. How many species of malaria parasites are known to infect humans?

    LIFE CYCLE OF MALARIA

    Malaria is a mosquito-borne disease caused by a parasite from the genus Plasmodium. Although there are more than 100 species of Plasmodium, only five are known to infect humans. These include P. falciparum, P. vivax, P. malariae, P. ovale, and the more recently discovered P. knowlesi (a simian malaria parasite), which has previously been misdiagnosed in humans as P. malariae [6,7,8,9,26]. P. falciparum and P. vivax cause the most infections worldwide. P. falciparum is the agent of severe, potentially fatal malaria due to its unique ability to invade and multiply inside erythrocytes. If treated promptly and effectively, however, it is almost always curable. P. vivax is the most geographically widespread of the species. Although it produces symptoms that are less severe, relapses of infection caused by P. vivax may occur up to three years after the initial infection. P. malariae produces long-lasting infections that have the ability to persist asymptomatically for years. Occurrences of infection from P. ovale are rare and generally limited to West Africa [3,10,11]. Little is known about the morphology of P. knowlesi parasites, but they do appear to have unique characteristics that can be identified through the use of light microscopy [12]. P. knowlesi appears to cause less severe clinical disease than P. falciparum; however, it may cause more severe and potentially fatal infections than P. vivax or P. malariae [6]. The severity of infection caused by P. knowlesi is the result of its rapid (i.e., 24-hour), targeted erythrocytic cycle. P. knowlesi is widespread throughout Malaysia, accounting for approximately 70% of human malaria infections in this area. Cases of infection with P. knowlesi have also been reported in Thailand, China, Singapore, and the Philippines [12,26].

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  3. Which of the following factors primarily influence where malaria is found?

    TRANSMISSION

    Malaria is transmitted in areas that allow the Anopheles mosquito to survive and multiply. This occurs mainly in tropical and subtropical areas where the temperature, humidity, and rainfall create an environment that allows malaria parasites to complete their growth cycle in the mosquitoes. Temperature is particularly critical to completion of the life cycle. For example, even within the areas where transmission is most common (i.e., tropical and subtropical regions), it does not occur at high altitudes, during cooler seasons in some areas, and in most desert areas. Transmission is most common in sub-Saharan Africa, with the highest case rates occurring among travelers returning from West Africa [15]. Although malaria has been eliminated in western Europe and the United States, the presence of the Anopheles mosquito in these regions poses a constant risk of reintroduction of the disease, especially in regions with temperate climates [2,53].

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  4. Following an infectious mosquito bite, the symptoms of malaria generally appear after an incubation period of

    SYMPTOMS AND DIAGNOSIS

    Following the infective mosquito bite, an incubation period of between 7 and 30 days usually passes before the first symptoms of disease appear. Shorter incubation periods are associated with P. falciparum; longer periods are characteristic of P. malariae. A string of recurrent attacks is typical and generally includes chills, fever, and sweating. In addition to these symptoms, headache, general malaise, fatigue, muscular pains, nausea, vomiting, and diarrhea are also common [3,10,18].

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  5. Common symptoms of uncomplicated malaria include all of the following, EXCEPT:

    SYMPTOMS AND DIAGNOSIS

    Following the infective mosquito bite, an incubation period of between 7 and 30 days usually passes before the first symptoms of disease appear. Shorter incubation periods are associated with P. falciparum; longer periods are characteristic of P. malariae. A string of recurrent attacks is typical and generally includes chills, fever, and sweating. In addition to these symptoms, headache, general malaise, fatigue, muscular pains, nausea, vomiting, and diarrhea are also common [3,10,18].

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  6. The manifestations of severe malaria include

    SYMPTOMS AND DIAGNOSIS

    Malaria infections with P. falciparum are categorized as severe when complicated by serious organ failure or abnormalities in the patient's blood or metabolism. Severe malaria occurs most frequently in persons either with no immunity or decreased immunity to the disease. The presence of one or more of the following clinical criteria indicates severe malaria [3]:

    • Seizures or other neurologic abnormalities

    • Impaired consciousness or coma

    • Abnormal behavior

    • Severe normocytic anemia

    • Pulmonary edema

    • Acute respiratory distress syndrome

    • Circulatory shock

    • Disseminated intravascular coagulation

    • Spontaneous bleeding

    • Acidosis

    • Hypoglycemia

    • Hemoglobinuria

    • Jaundice

    • Acute kidney failure

    • Repeated generalized convulsions

    • Parasitemia greater than 5%

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  7. Which of the following diagnostic techniques is the criterion standard for laboratory confirmation of malaria?

    SYMPTOMS AND DIAGNOSIS

    The criterion standard of microscopic diagnosis involves examination of thick and thin blood smears. (Thick smears are more sensitive but more difficult to read.) The smears are stained, usually with the Giemsa stain, which gives the parasites a distinctive appearance. A negative blood smear usually indicates no presence of infection. However, because nonimmune individuals may be symptomatic at very low parasite densities that are initially undetectable, the CDC has recommended that smears be repeated every 12 to 24 hours for 48 to 72 hours [4,19,20].

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  8. The first-line treatment for P. malariae malaria is

    TREATMENT

    TREATMENT RECOMMENDATIONS FOR UNCOMPLICATED MALARIA

    Plasmodium speciesDrugDosingComments
    P. falciparum or "species not identified" in areas without chloroquine-resistant strains Chloroquine
    Initial oral dose: 600 mg base (1,000 mg salt), followed with 300 mg base (500 mg salt) at 6, 24, and 48 hours
    Maximum dose: 1,500 mg base (2,500 mg salt)
    Use adult dosing in pregnancy.
    Adjust pediatric dosing by patient weight; do not exceed recommended adult dosing.
    Consider atovaquone-proguanil (preferred) or mefloquine if quinine is unavailable.
    Quinine and atovaquone-proguanil are recommended for use in children 8 years of age and younger.
    Hydroxychloroquine (Second-line alternative)
    Initial oral dose: 620 mg base (800 mg salt), given immediately, followed with 310 mg base (400 mg salt) at 6, 24, and 48 hours
    Maximum dose: 1,550 mg base (2,000 mg salt)
    P. falciparum or "species not identified" in areas with chloroquine-resistant strains (choose one of the following four options)Atovaquone/proguanil1 g/400 mg as a single dose, once daily for three daysThese are fixed-dose combination medicines that may be used for nonpregnant adult and pediatric patients. Both have been found to be very effective.
    Artemether/lumefantrine
    Patients 25 to <35 kg: Three tablets at hour 0 and hour 8 on the first day, then three tablets twice daily on days 2 and 3
    Patients ≥35 kg: Four tablets at hour 0 and hour 8 on the first day, then four tablets twice daily on days 2 and 3
    Quinine sulfate plus doxycycline, tetracycline, or clindamycin648 mg every eight hours for three to seven days
    MefloquineaFive tablets (1,250 mg) as a single dose daily
    P. malariaeChloroquineSame as for P. falciparumThere is little evidence of chloroquine resistance in P. malariae. May be used during pregnancy.
    Hydroxychloroquine (Second-line alternative)Same as for P. falciparum
    P. vivax acquired in all areas except Papua New Guinea or IndonesiaChloroquineSame as for P. falciparumIf patient is nonresponsive, change treatment to one of the three options listed for treatment of P. vivax malaria acquired in Papua New Guinea and notify state health department and the CDC.
    Hydroxychloroquine (Second-line alternative)Same as for P. falciparum
    P. vivax acquired in Papua New Guinea or Indonesia (choose one of the following three options)Quinine sulfate plus doxycycline or tetracycline648 mg every eight hours for three to seven daysHigh possibility of chloroquine-resistant strains. Options are equally recommended. During pregnancy, treat with quinine for seven days, regardless of area of acquisition. Risk/benefit of adding doxycycline or tetracycline (pregnancy category D) to quinine should be carefully evaluated. Risk/benefit of using atovaquone-proguanil or mefloquine (both pregnancy category C) should be carefully evaluated.
    Atovaquone/proguanil1 g/400 mg as a single dose, once daily for three consecutive days
    MefloquineaFive tablets (1,250 mg) as a single dose daily
    P. ovaleChloroquineSame as for P. falciparumMay be used during pregnancy
    Hydroxychloroquine (Second-line alternative)Same as for P. falciparum
    P. knowlesiAtovaquone/proguanil250 mg/100 mg, four times per day for three daysThere is little evidence comparing various medications for the treatment of this relatively new strain.
    aUse only when other options are unavailable.
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  9. Which of the following personal protective measures has been recommended by the CDC for individuals traveling outside the United States?

    PREVENTION

    The CDC and the Infectious Diseases Society of America have recommended that individuals traveling outside the United States be aware of and employ the following personal protective measures [30,33]:

    • Avoid travel to known malaria-endemic areas, when possible.

    • Be aware of peak exposure times and places, usually outdoors at dawn and dusk.

    • Wear clothing that minimizes skin exposure.

    • Use bed nets and ensure that they completely cover the sleeping area. Nets pretreated with insecticides or repellents may be purchased prior to travel. Nets may also be treated after purchase.

    • Use insecticides (with caution and as directed). N,N-diethyl-meta-toluamide (DEET) is an ingredient in many commercially available products and is the most effective repellent.

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  10. Travelers to malaria-endemic areas should be advised to take a presumptive self-treatment course of antimalarials if they

    PREVENTION

    Malaria may be effectively treated early in the course of the disease; however, delay of appropriate treatment may have serious, even fatal, consequences. Travelers who choose not to take an antimalarial drug, who are on a less than effective regimen (e.g., chloroquine in a chloroquine-resistant risk area), whose medical history dictates a suboptimal drug, or who may be traveling to very remote areas may be prescribed a presumptive self-treatment course (Table 4). Travelers should be advised to take the treatment promptly if fever, chills, or other influenza-like illness occurs. This is particularly important if the traveler is unable to access professional medical care within 24 hours. Travelers should also be advised to seek medical care as soon as possible after self-treatment [15,35].

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  • Back to Course Home
  • Participation Instructions
    • Review the course material online or in print.
    • Complete the course evaluation.
    • Review your Transcript to view and print your Certificate of Completion. Your date of completion will be the date (Pacific Time) the course was electronically submitted for credit, with no exceptions. Partial credit is not available.