Friday, September 11, 2020

fogging the question


Life is made up of compromises and trade-offs.

Today's topic is about a small trade-off -- that may have larger consequences.

The area of Mexico where I live is home to one of nature's deadlier predators. Aedes aegypti -- to use its formal name. Or, as it is often commonly-known, the yellow fever mosquito.

The common name is not really fair. The mosquito does not cause disease. It is merely a carrier. Like those asymptomatic people who are infected with viruses, and unknowingly spread them to other people.

Aedes aegypti does exactly the same thing. It carries around viruses that it has picked up from feeding on the blood of people infected with the virus and it then spreads the virus when it sucks the blood of another person. Never being affected by the virus it carries.

Yellow fever is not a major threat where I live. But the mosquito does deliver three other viruses that are a problem here: dengue, zika, and chikungunya. Just like the novel coronavirus, there is no vaccine or treatment for any of them.

The non-blue areas are where Aedes egypti hangs out. Oddly enough, not in Egypt. Not coincidentally, those areas are also where viruses for dengue, zika, and chikungunya have their way with humans.


In our villages, we have had serious outbreaks of all three diseases since I have lived here. Because the treatments are limited, the best approach is preventative. DEET and other first defense lines offer some protection.

There is an additional defense here. The fogger truck. Mosquitoes take advantage of their environment. To breed, they need pools of clean, calm water. Our rainy seasons offers plenty of that. The small pools that form where palm fronds meet the palm trunk are perfect nurseries for wigglers.

The mosquitoes have bloomed this summer. So have the fogger trucks. They came through our neighborhood three times this week.

I do not know what chemical is in the fog they produce, but I do know that it is effective. After each fogging, my patio is filled with the corpses of butterflies, dragonflies, bees, and wasps (pictured above). What seems to be missing are the corpses of mosquitoes. Of course, they are small -- and my eyes (along with the rest of me) is aging. I may just not see them.

The proof is in the sitting, though. After the trucks pass through, I can sit for a couple of days on my patio DEET-free without becoming a mosquito buffet. But that soon passes and the mosquitoes return.

My friend Dan Patman reminded me of an experiment that was conducted in Brazil, Vietnam, and Indonesia. Scientists have isolated a bacteria that blocks the replication of pathogens carried by Aedes egypti. When the bacterium-infected mosquitoes are released into the wild, the bacterium infects native mosquitoes. Preliminary findings show a reduction of dengue, chikungunya, and zika in the area of release.

That may be a more benign way of dealing with the problem than fogger trucks. But it is still under study, and the mosquitoes will not wait. There is also something else to remember. If we learned anything from Jurassic Park, it is that nature will find a way to reproduce. Viruses are good at that.

I started to write that at least we are not being hunted by velociraptors -- until I recalled the wise words of H.G. Wells. After all, it was not to dinosaurs that the Martians succumbed in War of the Worlds, but to viruses. What humans often fail to do is to show some humility in the face of nature.

I will mourn the passing of the dragonflies and butterflies (not so much the wasps) in mankind's ongoing battle against viruses.

Fog on.

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