Malaria is an import from the Old World, and in fact is a major concern for the indigenous tribes in this rainforest region. However, for the casual visitor to Puerto Ayacucho, the drainage engineering is not too bad, and the actual chance of getting bitten by a malaria mosquito is certainly much lower than in tropical Africa, for example, where I've also been. The American CDC will recommend a regime of anti-malarial medications, beginning a month in advance of arrival, and continuing for a month after departure from the area. I took these pills along, and the locals just laughed. So, I decided to skip them, and I'm glad did as I learned during the trip to Africa that this medication is not without its side effects. I'm not a doctor, but I recommend listening to educated locals when you arrive as they generally are more familiar with the situation than you GP in America or Europe. I do recommend washing a set of clothes with the DEET formula, and wearing mosquito repellent. But, just because you get bitten doesn't mean that you'll get malaria. For some of my sunrise photos, I jumped up early from bed wearing only my swim trunks, and headed to the bank of the Orinoco in thongs. I got terribly bitten and was scatching my ankles for weeks afterward, but I didn't get malaria. If you are planning a trip into the rainforest interior for more than a week, then maybe the malaria pills will help, but basically stopping mosquitoes from biting will be the best method of avoiding malaria.
Tourists are restricted from visiting some parts of the upper Orinoco and it's tributaries because of the Venezuelan government's effort to protect the Yanomami and other isolated tribes. These tribal groups are being run over not only by hunters with rifles, miners with explosives, loggers with chain saws, petroleum engineers with helicopters, missionaries with bibles, anthropologists with notebooks, and tourists with t-shirts. All these visitors bring the junk of civilization, including diseases like malaria, flu, measles, and the common cold. The forest dwelling Yanomami are a stone age people long isolated and not immune to the dangers of the industrial world. Permits are given for visits to the outlying villages that have routine contact with Puerto Ayacucho, but unfortunately, wealthy and corrupt Venezuelan officials have been known to skip the permitting process to allow access into more remote parts of the rainforest. Ideally, these indigenous people should remain apart from all contact, even casual contact, for their continued lifestyle is more valuable than the need to provide them the lifestyle of the industrial world. The knowledge about how these people live can be easily learned by those occasional individuals who wander out of the forest into society. At this point, those individuals can be incorportated into the villages for purposes of retaining important aspects of their forest lifestyle. Please leave the Yanomami alone and learn from the existing body of knowledge and the products that stream into the souvenir marketplace from the village cooperatives.