The guidelines recommend continuous prophylaxis in Papua New Guinea, nearly all of sub-Saharan Africa, and in several provinces of Brazil. Continuous prophylaxis with mefloquine, doxycycline, or Malarone can be more than 90% effective if they are chosen correctly, but they cause “perceived or real” adverse events in more than 80% of patients.
Many patients also fail to adhere to the dosing regimen for continuous prophylaxis and find it difficult to get the drug they need if they are traveling for more than a year, Dr. Schlagenhauf-Lawlor said.
The nonspecific symptoms of malaria make it difficult for patients to self-diagnose the disease, Dr. Schlagenhauf-Lawlor said. In a study of 1,187 Swiss travelers who carried medication for SBET, about 10% became ill with fever while traveling. Even though only nine of the travelers were out of the reach of medical attention, most of those who were ill reacted to their illness contrary to SBET instructions and delayed in seeking medical attention (Bull. World Health Organ. 1995;73:215–21).
A combination of SBET and rapid malaria tests “could be useful for certain selected long-term travelers,” she said. Studies have reported that 68%–91% of travelers were able to use the tests successfully. However, the tests can generate false-positive results and have been difficult for travelers to read at low levels of parasitemia.
Seasonal Prophylaxis
In all but a few countries “it's almost impossible for an adviser to say in advance how the season will be at the destination,” Dr. Schlagenhauf-Lawlor said.
In the sub-Saharan countries of South Africa, Namibia, and Botswana, the transmission seasons are fairly stable, but can shift, she noted.
In South Africa, travelers may want to use continuous prophylaxis during the high-risk season of October through May and revert to SBET during the low-risk season of June through September. But travelers should always use personal protective measures.
Blood-feeding Anopheles gambiae mosquito, a leading malaria vector. CDC