Mosquitoes and Malaria

Malaria is a serious disease that not all traveling divers fully consider. Years ago, I was sitting in Ambua Lodge in Papua New Guinea, talking to a California diver who had just spent a week on a liveaboard. He was drinking a gin and tonic, while sweat rolled down his forehead and dripped off his nose. He thought he might have contracted malaria from mosquitoes along the shore, he said, and maybe the tonic would help. He had an another drink, but in less than an hour, he began shivering uncontrollably and headed off to get under the blankets. He was at the lodge four more days before he could travel. The quinine in that tonic water wasn't much help.

In 2015, there were about 214 million reported malaria cases. The tiny, insidious Anopheles mosquito spreads the malaria plasmodium, of which there are five known species. The plasmodium falciparum, the most difficult to treat, is prevalent in all areas of the Solomon Islands.

So where's the real risk to divers? Happily, there is no malaria present in the Caribbean islands, save Honduras Bay Islands, where in the past two decades we reported on two divers who contracted malaria. However, it's generally well controlled throughout these islands, though the CDC still says the threat to American travelers is "moderate."

Indian Ocean islands such as the Seychelles and the Maldives have no incidence of the disease. Small islands with dive resorts across the tropical belt from the Maldives to Raja Ampat and into the Pacific offer less risk than those that have local villages, yet divers passing through towns such as Sorong (West Papua) or Honiara in the Solomons (where a high proportion of the residents suffer from malaria) increase their risk.

Larger landmasses such as Papua New Guinea (where the risk is high) are a different matter. There is a moderate risk in the eastern islands of Indonesia, such as Sulawesi, Kalimantan, Lombok and Sumatra, but none reported in Bali or the Gili islands. In most of Equatorial Africa, malaria is a major concern.

In Ecuador, Guayaquil, Quito, and the Galápagos are free of malaria, but if you decide to make a trip inland, be aware of the risk.

Palau is malaria-free, as are the remote islands of Micronesia, and the Marianas have no malaria reported. There is a low risk in the rural areas of the Philippines, a low risk in Thailand, and a moderate risk in Vanuatu.

The question divers often ask us is whether they should take a malaria prophylaxis. The drugs tend to have few, if any, side effects, and if you've ever seen a person like the diver at Ambua swing from fire to ice, you will be tempted to take no risk and find a suitable drug. You'll need to get a prescription based on your destination, your age, your family history, and medication you might be taking and whether you are likely to be pregnant. Do your own research, because few North American physicians know about malaria and proper drug choices, and if you're concerned, see a tropical medical specialist. Available drugs include:

Atovane plus proguanil (Malarone). Taken once per day during possible exposure and for seven days after, it is suitable for short trips and last-minute trips, since it can be started the day before traveling. Some physicians discourage the use of this drug as a prophylaxis, preferring to reserve its efficacy for treatment of known cases.

Doxycycline (Vibramycin-D) is taken two days preceding a trip and for four weeks after return. It increases the risk of sunburn.

A combination of Chloroquine and proguanil is rarely recommended nowadays because it's largely ineffective against the most common and dangerous type of malaria parasite, although it may be suggested for areas where that particular strain is less common, such as India and Sri Lanka.

Primaquine is also a good choice for short trips and is the most effective medicine for the prevention of plasmodium vivax, mainly found in South America and Africa.

Mefloquine (Larium) was thought to be the miracle antimalarial with only one tablet taken weekly, until users reported anxiety disorders, panic attacks, depression and vivid hallucinations -- clearly a bad choice for divers! However, some divers in the South Pacific area carry a dose as an acute therapy in case they suffer a malaria attack, rather than as a regular antimalarial.

We won't dwell on how to prevent mosquito bites -- long sleeves, avoid being out at dusk, etc. --other than to say that the most effective mosquito repellents contain DEET. Consumer Reports says that a 25% solution is enough, but many prefer higher concentrations. It should not be used for more than three weeks running and may reduce the sun-protection factor of some sunscreens.

There are no vaccines against malaria. And, strains of malaria have become resistant to older drugs. It's an insidious disease and may recur through one's life. If you're making a diving trip to the tropics, you shouldn't just blow it off.

For more information go to: www.cdc.gov/malaria

- Ben Davison