They’re tiny, they’re easy to miss, and they have very little physical strength. But they have the power to knock you flat and bring big changes to our way of life.
Who are these miniature troublemakers? There are any number of small beasties that can spread havoc in a human population, but one of the most efficient is the mosquito. In the U.S. we are well aquainted with mosquito bites. Every region has some legendary enclaves of these bloodthirsty suckers. In recent times though, the bites they administer have for the most part only delivered a maddeningly itchy welt. Since the turn of the century (the one about 16 years ago), West Nile virus has become a concern in our country. It’s now been detected in 48 states. St. Louis encephalitis, first recognized here in 1975, is also carried by mosquitos, and both of these diseases can be fatal. But the really big killer, yellow fever, has been out of the picture. The last North American yellow fever epidemic was in 1905. Vaccinations ended yellow fever here and until fairly recently, only sproradic cases brought here by international travellers have been seen.
Things are changing. The Asian Tiger mosquito (Aedes albopictus) and yellow fever mosquito (Aedes aegypti) are showing up in California, on a continent to which they are not native. It’s not their first appearance in the Golden State but populations appear to be settling in to stay. Possibly riding in on egg cases stuck to bamboo plants imported from Southeast Asia or even sneaking in from humid states such as Florida, these guys can carry not only yellow fever, but dengue fever and chikungunya as well. That last disease may be new to you, but you’re going to hear more and more about it. That’s because these mosquitos are not only here, they’re reproducing quickly in the heat we’ve been experiencing more of recently. The fact that it’s been dry doesn’t deter them much — they need very little water to lay their eggs in or near. The heat, on the other hand, creates more humidity in agricultural or landscaped areas and that muggy air makes them feel very much at home. Researchers say the drought may make for even better conditions as some people water their lawns more and the excess moisture makes good egg-laying conditions. Amazingly, some mosquito eggs can even stand to sit around for two years waiting for a return of water.
So far, these new neighbors haven’t spread any of the diseases they can carry, at least in California (Texas and Florida have suffered some dengue fever and chikungunya cases). But unlike the whining biters we are used to swatting away in the early evening and morning hours, the newcomers are much smaller, more aggressive, and day-long hunters. If one of them should happen to bite an infected visitor from another country or a newly-returned traveller carrying yellow or dengue fever or chikungunya, we’d be on our way to widespread circulation, given the close proximity of so many human bodies in large California cities. In the grand scheme of threats we face, there are many much more likely disasters, but a small possibility does exist and public health officials are keeping tabs on mosquito populations and reported cases of exotic diseases. Wearing longsleeve shirts and long pants, putting on repellant, keeping screens in good repair, and eliminating standing water help cut back on mosquito success. The world gets ever smaller, and changes in weather and climate can alter the rules of safe living such that they resemble the daily precautions required in faraway places.