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Malaria
RECOMMENDATIONS FOR MALARIA PREVENTION
GENERAL INFORMATION Malaria remains the most important infectious disease and most frequent infectious cause of death for persons traveling to countries in the tropics and subtropics. Even if your exposure will be brief, such as a 1-night stay in a malarious area, you should take protective measures. It is possible to contract malaria during brief stopovers at airports in malarious zones if health officials have not taken proper measures to rid the area of mosquitoes. Airports off the main international circuit are particularly suspect. Malaria is an infection caused by a single-celled blood parasite that is transmitted through the bite of the Anopheles mosquito. Malaria occurs in many parts of the world, including Central and South America, Africa, the Indian subcontinent, Southeast Asia, the Middle East, and islands of the South Pacific. The risk of malaria is highest between dusk and dawn, the time that Anopheles mosquitoes feed on humans. Malaria occasionally is acquired by drug addicts who use contaminated syringes, through blood transfusion from an infected person, or by transfer from mother to fetus during pregnancy. There are 4 different species of malaria: P. falciparum, P. vivax, P. ovale, and P. malariae. Of the 4 species, Plasmodium falciparum is the most dangerous and is the only one that can lead to death if not treated promptly. Malaria is characterized by fever and flu-like symptoms that may come and go, including chills, sweats, headache, muscle aches, and/or a vague feeling of illness. Vomiting, abdominal pain, diarrhea, and cough may occur. There may be anemia and jaundice (yellowing of the skin and the whites of the eyes). Malaria symptoms can develop as early as 7 to 8 days after being exposed and as late as months or even years after leaving a malarious area when use of preventive drugs has been stopped (see Preventive Therapy). If falciparum malaria is not treated properly, it can proceed to shock, lung and kidney failure, coma, and death. While illness caused by P. vivax, P. ovale, and P. malariae is not usually life-threatening, there may be serious health risks to very young or very old persons or to those with underlying illness. If malaria is left untreated, symptoms may recur intermittently for months or even years; prolonged symptoms also may occur in those who are partially immune to P. falciparum (that is, those who have been infected on numerous occasions).
DISEASE RISK The risk of getting malaria varies considerably according to your destination, itinerary, season, and style of travel. The highest risk of acquiring malaria is in Oceania (Papua New Guinea, Irian Jaya, Solomon Islands, etc.) followed in order by sub-Saharan Africa, the Indian subcontinent, Southeast Asia, South America, and Central America. In most parts of the world, malaria is a rural disease with minimal or no risk in urban areas. However, as a general rule, malaria risk occurs in both urban AND rural areas of sub-Saharan Africa and the Indian subcontinent. Malaria is less common at higher altitudes, during dry seasons, and among those who stay in air-conditioned and/or screened accommodations. Most cases of imported falciparum malaria among U.S. travelers have been acquired in Africa south of the Sahara. For persons not using drugs to prevent malaria, the relative risk of malaria in sub-Saharan Africa is 1:50 (1 out of every 50 persons) per month of stay. Vivax malaria, on the other hand, is most often acquired in India where the risk is approximately 1:250 travelers (1 out of every 250 travelers) not using preventive drugs. In some areas of the world, some drugs used against falciparum malaria are no longer effective because the parasite in those areas has become resistant to those drugs. Resistance of P. falciparum malaria to chloroquine is nearly universal, and chloroquine remains effective against P. falciparum only in Mexico, Central America, and the Caribbean. A drug called Fansidar is no longer recommended for use because P. falciparum resistance is so widespread and continues to spread. Resistance to mefloquine (Lariam) has been confirmed along the eastern and western borders of Thailand. If you are planning a trip to a malarious area, you should get expert medical advice about which preventive drugs to use and what personal protection measures to take to prevent mosquito bites. Travel medicine advisors are the most qualified to provide this advice. Although the use of preventive drugs and insect precautions will decrease your chances of getting malaria, such measures do not guarantee protection. Therefore, if you have traveled in a malarious area and think you might have symptoms of malaria (especially fever and/or "flu"-like symptoms), you should seek medical attention immediately. Delay of appropriate therapy can have serious—even fatal—consequences. Also, you should inform your health care provider that you might be at risk of malaria and request "thick and thin blood films" for diagnosis. One negative blood film does not rule out malaria, and, if symptoms persist, 2 additional films should be performed 12 to 24 hours apart.
PREVENTIVE THERAPY Also see Insect Precautions. Using preventive medications (chemoprophylaxis) in addition to personal protection measures against mosquito bites is an important safeguard for persons traveling to malarious areas. It should be remembered that no matter which medication is used to prevent malaria there is always the risk of potential side effects. However, the risk of antimalarial medications must always be weighed against the risk of severe and potentially fatal infection with Plasmodium falciparum. For those traveling to areas where chloroquine is still effective, this drug is recommended. For those traveling to areas of chloroquine-resistant malaria, there are 3 drugs that are considered to be equally effective for the prevention of P. falciparum malaria: atovaquone/proguanil, mefloquine, and doxycycline — each drug with different advantages and disadvantages. (While information on the drug primaquine is included in this article, primaquine is not considered to be one of the drugs of choice in the US and is rarely used.) It is important to note that there is no consensus globally or even among physicians within one's own country as to the optimal drug to prevent malaria. For example, in some countries, notably the United Kingdom, unwarranted and exaggerated media reports concerning mefloquine have led to decreased usage. However, in North America it has remained an important drug for the prevention of malaria. Therefore, when confronted with conflicting views concerning your antimalarial drug, it is wise to smile politely and ignore the advice of fellow travelers and overseas health providers. Let your doctor know if you have any serious underlying health problems (such as kidney, heart, or liver disease, or allergies) so that such problems can be taken into consideration in the choice of an appropriate drug for malaria prevention. If you have a serious, unusual, or unexpected reaction after taking an antimalarial drug, seek medical attention promptly and indicate to your health care provider that you have taken such medication. An overdose of antimalarial drugs (particularly chloroquine) can be fatal. Medicine should be stored in childproof containers, out of children's reach. TIMING OF ANTIMALARIAL DRUGS Malaria chemoprophylaxis should begin 1 week before traveling to risk areas—except for doxycycline, atovaquone/proguanil, and primaquine, which should begin 1 day before travel. A pre-travel dosage period allows the drug's concentration in the body's tissue to build up to an effective level and gives the physician time to evaluate any side effects. Antimalarials should be taken for as long as malaria risk occurs, in some cases months or even years. It is important to continue taking your antimalarial drugs for a period of time after you leave the risk area. If you have been taking chloroquine, chloroquine/proguanil, mefloquine, or doxycycline for malaria prevention, you must continue taking these drugs for 4 weeks after leaving the risk area. If you have been taking atovaquone/proguanil or primaquine, you must continue these drugs for 1 week after leaving the risk area. ANTIMALARIAL DRUGS Atovaquone and proguanil (Malarone) Malarone, a combination of atovaquone and proguanil in a single tablet, is licensed in the United States for malaria prevention and for treatment of P. falciparum malaria, particularly chloroquine-resistant Plasmodium falciparum. Malarone must be taken daily. This drug works equally as well as mefloquine, doxycycyline, or primaquine. It appears to be very safe and effective but somewhat expensive for a long-stay traveler. For many practitioners, Malarone has become the drug of choice for malaria prevention among short-term travelers and for self-treatment of malaria. It is recommended for all areas of the world where chloroquine-resistant P. falciparum is a risk. Malarone is also effective along the borders of Thailand where both chloroquine resistance and mefloquine resistance occur. (Doxycycline is an equally effective option.) The recommended dose of atovaquone/proguanil (Malarone) is a 250 mg/100 mg tablet, taken orally once a day, starting 1 day before travel and continuing for 1 week after you leave the malarious area. When Malarone is used for malaria prevention, no definite side effects are evident. However, nausea, vomiting, abdominal pain, and diarrhea occur when higher doses of the drug are used for treatment. Convulsions and rash have rarely been reported. Malarone should not be used by pregnant women or by any person with an allergy to the drug. The adverse effects of mefloquine have received considerable media attention, much of it exaggerated and unwarranted. Minor side effects of mefloquine include headache, stomach upset, dizziness, and bad dreams which tend to be mild or temporary. Approximately 1:200 to 1:500 users (one person out of 200 to 500 persons) will develop disabling anxiety, dizziness, depression, insomnia, or irritability sufficient to cause discontinuance of the drug. However, it is important to remember that more than 97% of mefloquine users will be able to tolerate the drug without discontinuing it. Severe adverse events, psychosis and epilepsy, may occur in 1:10,000 to 1:13,000 users, most of whom will have had a previous history of one of these problems. Mefloquine is not recommended for travelers who have an allergy to the drug, history of epilepsy, current depression, or a history of depression, anxiety disorder, psychosis, schizophrenia, or other major psychiatric disorder. The manufacturer recommends discontinuing the drug if the following symptoms appear during its use for malaria prevention: acute anxiety, depression, restlessness, or confusion; in this case, an alternative medication will be substituted by the health care provider.
Doxycycline Travelers to areas where chloroquine resistance has been documented may consider the use of doxycycline. Doxycycline and the atovaquone/proguanil combination (Malarone) are the only effective preventive drugs for travelers to the eastern and western borders of Thailand where mefloquine resistance has been documented. Doxycycline is contraindicated in pregnant women, children younger than 8 years of age, and persons with allergy to doxycycline or tetracycline. The adult dose of doxycycline is a 100 mg tablet, taken orally once a day. Doxycycline must be started 1 day before travel and continued for 4 weeks after you leave the malarious area. Skin photosensitivity is an uncommon but annoying side effect that can lead to severe sunburn. Risk of this complication can be lowered by using a sunscreen that blocks UVA rays, avoiding prolonged exposure to sunlight, and by wearing protective clothing. Women who take doxycycline may develop vaginal yeast infections and therefore may wish to carry an antifungal drug for self-treatment. Doxycycline should be taken while sitting or standing in an upright position, and it should be taken with food or a liberal amount of fluid to prevent the tablet from sticking in the esophagus (swallowing tube). Both Pepto Bismol and antacids may interfere with the absorption of doxycycline and therefore should not be used simultaneously.
Primaquine While not one of the 4 primary drugs of choice, primaquine can be used in 2 different ways to prevent malaria:
Primaquine should be taken with food in order to reduce stomach upset. The drug should not be taken during pregnancy. It should not be taken by persons with low levels of Glucose-6-phosphate dehydrogenase (G6PD) as it can severe anemia in those who are deficient in this blood enzyme. This enzyme deficiency is most commonly seen among African Americans, Mediterraneans, South Asians, and Orientals. Primaquine may be used only after a blood test for G6PD deficiency has been performed and found to be normal. Persons with a genetic deficiency of methemoglobin reductase may experience a condition called methemoglobinemia when taking primaquine. PREGNANCY In general, pregnant women should not travel to a malarious area unless the travel is absolutely necessary, because malaria poses a very serious threat both to the pregnant woman and her fetus. In fact, it can cause more severe problems in pregnant women than in those who are not pregnant. Malaria increases the risk of maternal death and fetal prematurity, miscarriage, and stillbirth, making it very important that a pregnant traveler going to a malaria risk area consult her health care provider or travel medicine advisor and take preventive medication. In malaria risk areas where chloroquine is still effective, it is the preferred drug for pregnant women. Chloroquine has not been shown to be harmful to the fetus during pregnancy. In areas of chloroquine-resistance, mefloquine should be considered and is considered safe; however, there are not extensive data on its safe use during pregnancy, especially during the first trimester. Doxycycline, atovaquone/proguanil, and primaquine should not be used during pregnancy. (Proguanil is not available in the USA.) An alternative to mefloquine is the combination of chloroquine and proguanil. However, this alternative regimen has relatively low efficacy and therefore should be avoided if possible.
BREAST FEEDING Small amounts of antimalarial drugs may be passed on to infants who are breast-fed. The very small amount of drug in the breast milk received by the infant is not thought to be harmful. However, it is also not enough to protect infants against malaria; therefore, infants need to be given appropriate drugs in dosages according to their weight. Each malaria attack must be treated promptly.
INFANTS AND CHIDREN All children (including young infants) who travel to malaria risk areas should be protected against insects and should take drugs to prevent malaria. The dosage will depend on the child's age and/or weight. Doxycycline is not indicated for infants and children younger than 8 years of age. If a physician prescribes chloroquine or mefloquine for a child, the pharmacist may be willing to crush the tablets (which have a bitter flavor) and place the powder in gelatin capsules with calculated pediatric doses. Children may tolerate antimalarial medications more readily if crushed powder is mixed in food (for example, ice cream or chocolate sauce) or drink. It should be noted that Malarone now comes in a pediatric tablet that is one-fourth of the strength of the adult tablet. Using pediatric-strength tablets the dos
SELF-TREATMENT OF PRESUMPTIVE MALARIA In general, most travelers will not need to carry standby self-treatment drugs when using an appropriate, recommended medication to prevent malaria. However, in rare situations where the traveler must use a less effective medication or may not have access to medical care within 48 hours of developing a fever while in a malarious area, it may be prudent to carry a drug for self-treatment. The treatment drug should not be the same as the prevention drug. Malarone is the drug of choice for self-treatment when it is not being used for prevention. One alternative to Malarone for self-treatment is quinine plus doxycycline. Mefloquine is not routinely recommended for self-treatment because its side effects are much more common when the drug is used for treatment than when it is used to prevent malaria; seizures and/or psychosis occur in 1:100 to 1:1500 who use the drug for treatment. The adult self-treatment regimen of Malarone is 4 tablets taken orally once daily for 3 days. However, when self-treatment is administered, it is a temporary measure and medical attention should be sought as soon as possible. Taken from Travel Health Online |
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