Preventing malaria

- [Voiceover] I think, when we talk about preventing malaria, it's useful to have an idea of what allows malaria to thrive in the first place. So, for malaria to be a problem in any given community, there usually has to be a combination of three things: a high human population density, a high Anopheles mosquito density, and high rates of transmission between the two groups. And so, if you lower any of these three variables sufficiently, malaria essentially disappears, and that's kind of what happened in North America and in Europe and in parts of the Middle East. And it's really important that we focus on these variables because there is no vaccine for malaria as of now, so we just kind of have to take precautions. So, how can we lower any of these variables? Well, we probably aren't going to lower the population density of humans, so I'll leave that one alone, but we do have ways to lower the population of mosquitoes in the areas that we live. And so, one of the ways we can do that is by using insecticides, chemicals that kill insects, in this case, mosquitoes. Probably the most common insecticide chemical is called a pyrethroid, and these work by being sprayed in the house or around your tent or whatever, let's say you're camping. And when mosquitoes come into contact with these pyrethroids, they get paralyzed, and then they die. It's kind of barbaric, but that's the most common insecticide, pyrethroids, that we find in just household insecticide sprays. So, those will lower the population density for sure. And you might have heard of two spray-on bug repellents, one called Picaridin, and one called DEET, D-E-E-T. So, these are chemicals that you can spray on your clothes or your skin to keep the mosquitoes away. Mosquitoes actually hate the smell of these chemicals. We can't really smell it, but mosquitoes do, so they stay away. So that's why these work so well as repellents, insect repellents. And you've also probably seen those green mosquito coils. Those are actually made with pyrethroids as their main ingredient as well. But these coils have more of a mosquito repellent role rather than a killing role. So, we've talked about how we can kill mosquitoes. We've talked about ways that we can sort of keep them away from us, repel them. What else can we do to lower the mosquito density? Well, one of the most effective things we can do is to eliminate their breeding sites. And what they do is they breed in standing water or stagnant water, old water that's maybe collecting outside of your house in a bucket or in a tire or something like that. So, we can drain the water or we can add chemicals to kill off or at least reduce the amount of mosquito larvae that can develop in that water. So, the byproduct would be, well, hopefully, fewer mosquitoes grow up and start buzzing around because they can't develop at the rate they'd like to. So, these are all things we can do to reduce mosquito density. Now, what can we do to reduce the rates of transmission? Well, we can change our behaviors a little bit, because, for example, we know that mosquitoes are more likely to be out and about in the evenings. So, we can just be extra careful when we go outside around then, and we can wear long-sleeved tops and long pants and cover our necks, and so on. And this kind of works for two reasons. So, we physically protect our skin from mosquito bites, right? We can, we can see that. But it turns out that mosquitoes are actually attracted to the smells from the oils in our skin. So, when we cover them up, we cover up the smell from our little skin oils as well. We can also do non-behavioral things, too. We can modify our house a little bit. So, we can put screens on our windows and screens on our doors to keep the mosquitoes out. And we can sleep in beds that are covered with mosquito-proof netting, so we're not getting bitten in the night while we're sleeping. And, you know, you can actually get netting material that's been soaked in a repellent or in an insecticide, and that makes them a lot more effective at preventing mosquito bites than if you just had the net alone. But the nets are still really effective. The other thing we can do to prevent transmission is to treat people with anti-malarial drugs as soon as we know that they're infected, because, you know, if you think about it, let's say an infected mosquito bites this guy and infects him. Well, having more infected people around means that uninfected mosquitoes that might come along, they can easily draw plasmodium from this infected person, and they can go on and infect another person with it. So, it's important to get treatment right away if there's a confirmed malaria infection. Now, before we finish up, there's just one more thing I wanted to touch on, and that's malaria prophylaxis medication, so, if you're traveling to an area of the world where malaria is endemic, in other words it's really sort of prevalent there, you can take a combination of medications to protect you from the malaria infections while you're there. So, depending on the drug resistances that exist in the parasites where you're going, that would kind of determine what drugs you'd use as prophylaxis. So, here's the timeline, right, and here's your trip. We're in the middle here. And so, the way that these prophylactic drugs work is that you'd take them for a period of time before your trip, maybe a week or so, depending on the drug, right? And then, you take them the whole time you're away. Let's say you've gone to Southeast Asia, for example. And then, you come home, and you continue taking them at home for some period of time. It could be a week, it could be a month. It kind of depends on the drug you're taking. So, I know you're probably thinking that these things sound awesome, right? I mean, and they are, they are awesome. But the downside is that this prophylaxis business only really works for people who don't live in these endemic areas, which is kind of ironic. So, the reason why is, well, there's a couple of reasons. So, one, they're not super expensive, but if you were taking them every single day, forever, the cost would probably add up to something really, really unreasonable. Two, there are side effects, right? So, for long-term use, there are side effects that make them a little less attractive to use. So, they're only really suitable for short-term use. And, you know, let's say that problems one and two didn't even exist. It still would be really difficult to get them transported to every malaria-endemic place in the world. So, I guess availability and transport is a consideration. And, last, using these drugs every single day, that would vastly increase the risk that the little malaria parasites would develop a resistance to them. And if that happened, then the people using them would kind of just be back at square one, because the drugs wouldn't work anymore. So, that's why the focus is on prevention by reducing these two variables here: the mosquito population density and transmission of the parasites.