Long-Term Malaria Prophylaxis for Travelers

Jürgen Knobloch

In This Article

Principal Considerations

Long-term malaria prophylaxis is hampered by a lack of standardization and compliance. Advice should be individually optimized to achieve a high degree of protection and compliance. Individual risk assessment takes into consideration the duration of stay in the endemic area, the individual exposure, the seasonal transmission rates, and the drug-resistance situation. Methods for prevention of exposure may help reduce the reliance on chemoprophylactic drugs. Exposure-prevention methods may be combined with standby treatment in lower transmission areas if the traveler has been trained to take the antimalarials appropriately. Although suitable for long-term use, chloroquine and chloroquine-proguanil cannot be used as prophylaxis owing to high resistance rates in most endemic regions. Mefloquine is suitable for most malaria-endemic regions, although its use is restricted by neuropsychiatric side effects, particularly in women. Doxycycline is also appropriate; experience with long-term malaria prophylaxis is available for up to 6 months. The use of atovaquone-proguanil is restricted to 28 days in some countries, but clinical studies indicate that its use is suitable for at least 20 weeks. Primaquine is also effective for chemoprophylaxis; experience is limited to 1 year of protection against falciparum and vivax malaria. When giving individual recommendations to a traveler, special considerations for backpackers, expatriates, and frequent travelers may apply.

Travel, for business or pleasure, in malaria-endemic regions often lasts for up to only 4 weeks' duration. Those who travel for longer than 4 weeks are considered long-term travelers, such as backpackers, expatriates who more or less live in one place for months or years, and business travelers who frequently visit tropical areas. In the United Kingdom, long-term travelers are defined as those who are visiting or traveling through malaria-endemic countries for > 6 months.[1]

There is a negative correlation between compliance of prophylactic measurements and the duration of stay in the endemic area. Long-term travelers tend to adopt a nonchalant attitude toward malaria, as is observed in the local population, and therefore often disregard the recommendations of their physicians back home.

In general, the degree of compliance varies widely. It is by and large accepted that it is more appropriate to individualize rather than to standardize malaria prophylaxis recommendations for long-term travelers; however, expert recommendations are often vague. The German Society of Tropical Medicine, for instance, does not give any specific recommendation but stresses the need for experienced tropical doctors to give appropriate individual advice.[2] Publications from the Centers for Disease Control and Prevention (CDC) do not provide any specific recommendation for long-term travelers.[3] The World Health Organization (WHO) recommendations on drugs appropriate for long-term application are brief.[4] Recently, the Health Protection Agency Advisory Committee on Malaria Prevention for UK Travellers has provided a supplement to the guidelines for malaria prevention in travelers from the United Kingdom for 2003 titled "Malaria Prophylaxis for Long-Term Travellers."[1] This document contains a more complete description of antimalarials and additional preventive measures, together with recommendations for malaria chemoprophylaxis for individual countries, the latter of which are similar to the German guidelines, which also provide country-, region-, and season-specific recommendations for antimalarial drugs.[2]

Pretravel advice should provide information on individual risk assessment. It is essential to clarify that temporarily exposed travelers are at greater risk than the endemic population since they lack both genetic protective factors and immunity. Moreover, the statistical probability of being infected by sporozoites increases to nearly 100% when, for example, the stay in the endemic area exceeds 4 weeks and 10 bites per night are received, assuming that 1% of the bites are infective.[5]

An important factor for risk assessment is the drug-resistance situation in the travel area. Drugs that are known to be poorly effective should not be used since a grade 1 or 2 resistance breakthrough might further hamper a differential diagnosis when atypical clinical malaria occurs. This has been shown to be particularly true for travelers developing subclinical forms of falciparum malaria under chloroquine-proguanil prophylaxis.[6] This drug combination has been shown to have an average protective efficacy of < 70%, and it is therefore no longer considered adequate for most malaria-endemic areas.[7]