字幕表 動画を再生する 英語字幕をプリント Do mosquitoes bite some people more than others? Maybe you're the type of person who's constantly itching when you're outside at night. Or you're the type that get hassled at all. According to the experts, mosquitoes are picky about who they bite. But do we know why? There's more than 300 species of mosquito in Australia, but only 20 pose a risk to human health through disease or nuisance biting. You may also be surprised to learn it's only female mosquitoes that bite and that's because they need an energy hit to develop their eggs. But how does she do this? When she has found an animal or a person to bite, she'll land on the skin and she'll start probing away at the skin with her proboscis and the proboscis isn't a sharp, needle-like device, it's actually a little bit flexible. So she can inject that into the skin, move around and find a source of that blood. But also, the feeding tubes in the proboscis, some of them spit and some of them suck. So the mosquito will inject some saliva into the skin - it has anti-coagulants, a little bit of anaesthetic, it helps the blood feeding go through much easier, and then in other tubes, the mosquito will suck up the blood. So how does a female mosquito choose her next meal? Researchers say she's initially attracted by the carbon dioxide we breathe out. Then, when the mosquito gets closer, they respond to the heat of our body - the higher your body temperature, the more likely you are to get bitten. Scientists think the key attractor is the chemical of our skin produced by bacteria and sweat, which signals how attractive, or not, we might be. But, it's very difficult to tell exactly what bacteria or smells are appealing, and every species of mosquito is slightly different in what it finds attractive. There's also other factors that come into play, like the colour of our clothing. Dark colours tend to attract mosquitoes more than light colours - perhaps they can see us moving around more in dark clothing. Scientists also recently discovered a gene in mosquitoes that leads them to bite some people over others, but they're yet to determine why. And there's a load of other theories out there, like eating garlic, or taking vitamin B will change how attractive we are to mosquitoes. But science has failed, so far, to show any evidence this works. We do know that some research shows that maybe diet has a subtle change to our attractiveness. We know from studies in Africa that drinking beer may make us more attractive to mosquitoes that spread malaria parasites. But it doesn't mean that avoiding drinking alcohol will prevent you from being bitten by any mosquitoes. Your blood type may also have an impact, though scientists think not as much as the smell of your skin. Studies in Africa investigating malaria transmission are examining whether type O blood attracts a few more mosquitoes than other types. But just because you don't itch, doesn't mean you weren't bitten at all. Everyone differs when it comes to their reaction to mosquitoes' saliva, just like we do with certain foods. But putting up with nuisance biting isn't the only worry when it comes to mosquitoes. They can also carry disease, with the World Health Organisation estimating there are more than 700,000 deaths every year from vector-borne disease. Mosquitoes are carriers, along with others including ticks, sand flies and fleas. It's for this reason that mosquitoes are considered the deadliest animals on the planet. Malaria is perhaps the best-known of these diseases and causes more than 400,000 deaths every year. Australia was declared free of malaria in 1981. The disease we're most worried about in Australia is caused by Ross River Virus. We get thousands of cases of human disease across Australia every year. It doesn't matter whether you're in Cairns, or Hobart or Sydney, or Perth, there's a chance that in some of those areas during some seasons you may be exposed to that virus. It's much more prevalent outside metropolitan areas and the reason for that is that the mosquitoes don't hatch out of the wetland infected with the virus. They have to bite an animal first, and typically that's a kangaroo or a wallaby. So it's in these rural, or semi-rural areas where the risk is much greater of mosquito-borne disease in Australia. Ross River Virus has no treatment or cure so the best way to prevent the illness is to stop mosquito bites. And there's plenty of ways you can do this. Wearing long sleeves and long pants to minimise access to skin is one of them. Using repellents, like sprays or lotions is another. Products containing DEET or picaridin or extract of lemon eucalyptus are most effective. The higher the concentration, the longer it will last on your skin and the less you will need to re-apply. Burn mosquito coils and candles containing insecticides in outdoor areas. They'll help protect you if you're within a few metres. Sitting under fans can also be useful as mosquitoes can't fly easily in windy conditions. Other measures, like sound-emitting devices and wristbands exist, but there's no evidence yet showing they work. Wearing a colourful band on your wrist, no matter how strongly it smells, it won't provide protection for the rest of your body. Cleaning up around the home is another important way of lowering mosquito numbers. They love breeding in pet water bowls or bird baths so change the water regularly, and check for common places water collects like pot plant drip trays, blocked gutters, toys, or old tyres.