Malaria Awareness

Though malaria has long been a consideration for divers traveling to Pacific destinations, those heading to Honduras and Belize usually don’t think much about it. That era of complacency may be at an end. A CDC representative recently told Undercurrent that there have been confirmed malaria cases among tourists whose only recent travel had been to Roatán, and they said that they now recommend that travelers to the Bay Islands take chloroquine (Aralen). Other areas of central America are also considered malaria risks, although the Caribbean (except areas of Haiti and the Dominican Republic) is still basically malaria-free.

World Health Organization statistics breaking down malaria infections by country reveal some startling trends. While divers have long thought of destinations like Papua New Guinea as significant malaria risks, in WHO’s most recent stats actual annual per capita rates of infection in PNG (14.84 cases/1000 population) were less than half what they were in Belize (38.33 cases/1000 population). Similarly, rates of infection in Thailand (1.95 cases/ 1000 population) and Malaysia (1.90 cases/1000 population) were a fraction of those that occurred in Honduras (7.44 cases/1000 population). Of course, these Central American rates still pale in comparison with the malaria risk in Vanuatu (58.3 cases/1000 population) and the Solomon Islands (a staggering 312.19 cases/1000 population), but they’ve nonetheless become significant.

While the bulk of Central American malaria infections occur in the interior, malaria is a confirmed presence in resort areas in Belize, Honduras, and the Bay Islands, according to the CDC. For divers taking side trips into the interior or traveling through mainland airports, malaria risk may be significant. But in spite of the CDC warnings, none of the travel information that’s come our way from Belize resorts makes any mention of malaria risk or recommends that guests take chloroquine. (Note that malaria prophylaxis must begin well in advance of exposure to the parasite to be effective, so divers planning trips should see their doctors early.)

As if the increase in infections weren’t enough, the lethal P. falciparum species of malaria is becoming increasingly resistant to medications such as chloroquine. In fact, chloroquine-resistant malarial parasites are fast becoming the norm. Chloroquine has been so ineffective in Kenya that the government recently banned use of the drug. Chloroquine-resistant malarial parasites are now found in tropical South America and are spreading, with chloroquineresistant infection currently a risk as far north as southern Panama. If the northward movement continues, chloroquine-resistant malaria may soon become a threat to divers visiting Central America. The risk of contracting chloroquine-resistant malaria is still endemic in areas of the Pacific, including Papua New Guinea, the Solomon Islands, Vanuatu, Indonesia, Thailand, and other areas of southeastern Asia.

Despite its high toxicity and unpleasant side effects, including nausea, dizziness, and insomnia, the CDC still generally recommends treatment with mefloquine (Lariam) for travelers where chloroquine-resistant malaria is common. But even Lariam is losing its punch. Recent CDC reports confirm that mefloquine-resistant malaria has been reported in Thailand. Our first-hand reports from divers taking Lariam who returned from PNG with malaria suggests that the problem of mefloquine-resistant malaria may be becoming more widespread.

An effective vaccine certainly seems long overdue, but, despite ongoing research, vaccines have proved elusive. Some recentlydeveloped vaccines may prove more successful. A genetically engineered DNA vaccine is the most exciting prospect. One has already passed initial human tests; the vaccine was well-tolerated and produced an immune response in almost half the recipients. Plans are underway to test a second experimental vaccine designed to take a new tack by targeting P. falciparum, the deadliest malaria parasite, at each stage of its life cycle within its human host. Perhaps the era of nasty antimalarials will soon be history and we can return to simpler drugs like coffee, kava kava, and nitrogen on our dive trips.