Tag Archives: health

Using mosquitoes’ sweet tooth to control Zika transmission

Now that everyone wants to kill mosquitoes that transmit Zika virus, can somebody please make a transgenic plant that expresses mosquitocidal Bti (Bacillus thuringiensis subsp. israelensis) toxins? Just stick the Bti gene behind a phloem-specific promoter so that the protein gets pumped into the nectar. Then when males and female mosquitoes drink (and almost all do), they die. You could then plant acres of the modified plant nearby towns to protect people from Zika (and anything else transmitted by mosquitoes). The beauty of this method is that you could reduce populations of mosquitoes from an area without spraying, and do so for generations if you modified nectar-producing perennials. I know it’s trendy to dislike GMOs (like vaccines), but I think many people would support them under these circumstances.

And yes, apparently Bti toxins can kill adult mosquitoes (including Aedes aegypti), not just larvae. Klowden and Bulla 1984 demonstrated it, for example. And yes, Aedes aegypti drinks nectar (and probably fruit juice).

Of course, even if somebody had the incentive to make such a plant, it could take a decade to wade through the red tape involved in getting non-regulated status from governments. So if you want to do something today, leave out containers of sugar water (10%) that is laced with Bti (e.g., Mosquito Dunks, which you can buy online or at hardware stores). Maybe add something floral to attract them, too. (A review of olfactory cues suggests that imitation cherry and apple can work. If you don’t have those sitting around, I’d wager a few drops of jasmine flavoring or rose water would work, and those are easily found at local stores.) Even if the Bti doesn’t immediately kill the adult, adults sucking up a big sugar meal can transfer the bacteria to water where they lay eggs, and thus eventually cause the death of any larvae that develop. Note that bees and ants might get interested in your sugar water, but the Bti is completely harmless to them.

And if you don’t want to use Bti, there are plenty of articles on using sugar baits laced with insecticides (e.g., Qualis et al. 2013, Junilla et al. 2015). They really can work: mosquitoes absolutely love sugar and will drink up poisons in the process. These are great if you don’t want to use crop dusters to destroy all insects in the area.

If you have kids and want to entertain them, add food dyes to the sugar bait and then challenge them to find mosquitoes with bellies full of sugar water. For older kids that might be amused by actual science, use two dyes to test attractiveness of two different volatiles (or different sugars). It’s probably rare to recapture one right after a nectar meal, but when distended they reveal gut contents nicely.

Colin Purrington Photography: Insects &emdash; White-footed woods mosquito (Psorophora ferox) nectaring on goldenrod

FYI, the photograph above is a white-footed woods mosquito (Psorophora ferox), not Aedes aegypti. It doesn’t transmit Zika, but illustrates to the unbelieving that mosquitoes drink nectar. 

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Do antibiotics kill viruses?

Definition of antibioticIf you wonder why most people think antibiotics can treat viral diseases, one reason is that when people use search engines to understand what antibiotics do, they are informed that antibiotics do target viruses. Examples below.


antibiotic: a medicine (such as penicillin or its derivatives) that inhibits the growth of or destroys microorganisms.
microorganism: a microscopic organism, especially a bacterium, virus, or fungus.


antibiotic: any of a large group of chemical substances, as penicillin or streptomycin, produced by various microorganisms and fungi, having the capacity in dilute solutions to inhibit the growth of or to destroy bacteria and other microorganisms, used chiefly in the treatment of infectious diseases.
microorganism: any organism too small to be viewed by the unaided eye, as bacteria,protozoa, and some fungi and algae.


antibiotic: a substance produced by or a semisynthetic substance derived from a microorganism and able in dilute solution to inhibit or kill another microorganism.
microorganism: an extremely small living thing that can only be seen with a microscope.


antibiotic: A substance, such as penicillin or erythromycin, produced by or derived from certain microorganisms, including fungi and bacteria, that can destroy or inhibit the growth of other microorganisms, especially bacteria. Antibiotics are widely used in the prevention and treatment of infectious diseases.
microorganismany organism, such as a bacterium, protozoan, or virus, of microscopic size.

Britannica Library:

antibiotic:  chemical substance produced by a living organism, generally a microorganism, that is detrimental to other microorganisms. Antibiotics commonly are produced by soil microorganisms and probably represent a means by which organisms in a complex environment, such as soil, control the growth of competing microorganisms.
microorganisms: living things that are too small to be seen with the naked eye. They are normally viewed using a microscope. Bacteria, viruses, and some molds are examples of microorganisms.


antibiotic: Any substance that can destroy or inhibit the growth of bacteria and similar microorganisms.
microorganism: An organism that is too small to be seen by the unaided eye, especially a single-celled organism, such as a bacterium.

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A simple name change for antibiotics could save lives

In depressing medical news this week, the World Health Organization reported that 64% of adults believe that antibiotics can be used to treat flu and colds. That’s terrible because those 64% are likely to pressure their doctors for antibiotics when they don’t need them, which in turn will speed the evolution of bacteria resistant to the drugs … and then people die from bacterial infections that used to be treatable.

Cartoon image of Batman slapping robin for thinking antibiotics can treat common coldThere are several beliefs that contribute to this statistic, and I think it’s important to tease them apart so we can better craft outreach strategies. The one that gets the most attention, of course, is when people (e.g., Robin in the popular Batman meme I based on original by Dr Nick Bennett and his wife) think that colds are caused by bacteria. A second reason is that some people think viruses are a kind of bacteria and thus treatable with antibiotics.

But there’s a third, even more important explanation that gets almost no attention: people thinking antibiotics are effective against a wide range of microorganisms (i.e., not just bacteria). Why on Earth would people think this? I think kids are almost certainly to blame. When young kids are sick, they don’t really care about the whole virus-versus-bacteria thing … they just know something is infecting them and that the parents keep chanting “antibiotic” over and over again. So I think it’s unavoidable that kids construct a definition for antibiotics before they even start kindergarten (pollsters: can you ask?). Kids are also genius at figuring out word meanings when they don’t get full information from teachers or parents, so it is probable that many assume that the anti (against) and biotic (living) parts of “antibiotic” mean that the drug kills all life. (This is, indeed, what the word “antibiotic” used to mean before microbiologists commandeered it to mean something else.) Although kids might be told later in life (in high school, college) that antibiotics target only bacteria, the correction might not stick in the average person’s brain. In addition to the above, ignorance about antibiotic efficacy is probably increasingly pulled from the Internet. If you doubt me, just type “antibiotic definition” into Google and read the top five or so definitions: they all say that antibiotics can kill microorganisms.

If “antibiotic” (the word) is the source of so much confusion, replacing it with a better word might cause people to stop asking for it, which could save lives via preserving antibiotics. Luckily, the word “antibacterial” is just waiting there, perfect for the job. The anti and bacterial parts of the word convey its meaning unambiguously, plus it’s an old word (older than antibiotic!), and is already used by the general public. You can even Google the definition if you don’t believe me: all the definitions indicate it is a drug that kills bacteria (and only bacteria). It would join other words such as “antifungal” and “antiviral”, all of which tend to be used and understood by both doctors and patients.

Cartoon image of Batman slapping robin for thinking antibacterials can treat common coldThere would, of course, be a certain amount of work associated with the switch. For example, websites promoting antibiotic awareness would need to run a Search and Replace macro to insert “antibacterial” everywhere instead of “antibiotic”. That might take 10 minutes for a large site. And brochures and cartoonish wall art for waiting rooms would have to reprinted, but the result would be that waiting patients and parents would be measurably less confused on what antibacterials do. And once everything was converted to “antibacterial”, outreach organizations like WHO and CDC could focus on the more important issues such as making people understand what colds are (please see Batman comic #2) and making sure that the full course of antibacterials is taken.

Note that I’m not suggesting everyone stop using “antibiotic” altogether. But in terms of public outreach, discussion with patients, and the names on drug containers, we should give it a try.

What would also be great is if pollsters could replace “antibiotic” with “antibacterial” for half of the survey participants. Currently, most physicians and “antibiotic awareness week” coordinators LOVE the word “antibiotic” and can see no fault in it; they blame ignorance levels on the educated, ignorant masses. But if poll data could show them that ignorance goes down by (say) 50% after adoption of “antibacterial,” they might rethink their opposition to change.

BONUS FACT: Alexander Fleming used the word “antibacterial” 19 times in his paper describing the isolation of penicillin. He used “antibiotic” 0 times. He got a Nobel prize for the work.

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Teaching kids about sugar content of beverages

One out of three kids these days is overweight or obese, and consumption of sugary drinks is a big reason why. Sugary drinks also cause tooth decay (I know, big surprise there), and might even cause kids to be aggressive (or if kids think sugar has that effect, it might have a placebo effect). So I got to wondering what public schools could do … and I think that making a “sugar content” poster in kindergarten is is the way to go. The idea is to construct a display for the hallway or classroom wall that visually shows how much sugar is hidden in common beverages. Here’s an example:

Sugar in drinksThis project would fit in perfectly with most state standards (for example, see page 10 in Health Education Content Standards for California Public Schools). And because it includes numbers (of teaspoons), teachers can use the poster content to visually drive discussions about addition and subtraction. If this poster was done in a fun way, the experience might vaccinate kids against over-consumption of sugary drinks for the remainder of their lives. The parallel to brushing teeth might be appropriate: you teach kids how to do it before school … even though the chemistry of decay is beyond their understanding: if you don’t brush and floss, your breath will be nasty and you’ll lose your teeth. Like many health lessons, that’s best taught to young kids.

There are lots of ways to make the poster, but what I like about the one above is that water (no sugar) and plain milk (contains lactose … which is a sugar) are included. There should also be a sampling of common juices (apple, orange, e.g.) because they are loaded with sugar. And just for scale, it might be good to show how many teaspoons of sugar are in a typical bag of candy (e.g., Skittles).

Poster titles matter here, just like they do at a scientific meeting, in that they can provide a take-home message. “Rethink your drink” is a popular title (it rhymes), but I prefer something that confronts the point more directly. Here are some ideas: “Don’t drink dessert all day”, “Don’t drink your dessert”, or “Sugary drinks are candy drinks”. If snark is allowed in your district, then something like, “Sugary drinks are a sweet way to gain weight and rot teeth!” The idea is to be direct and memorable and to not shy away from the point: sugary drinks can (and do!) make kids fat.

If you want some background information relevant to lesson plans on sugar for K-3 levels, here are some resources from BrainPOP. If you’re looking for more examples of posters, here’s a Pinterest board where I collect them:

Pinterest board Educating kindergartners about sugary drinks on Pinterest.

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Junk food vending machines in public schools

I’m amazed that we are well into 2014 and schools can still sell junk food to students in vending machines. Below are four photographs just in case you haven’t been to school recently.  In first, some breakfast cereals: Frosted Flakes, Cocoa Krispies, and Apple Jacks, with 37%, 40%, and 43% sugar, respectively.  I’m sure that the Vending Machine Committee for this school decided that if they avoided Kellogg’s Honey Smacks (55.6% sugar), they could argue that the actual offerings are “healthier options.”  Photographs 2 and 3 show candy and chips.  Photograph 4 is for viewers interested in obesity among minorities.

In Pennsylvania (where photographs were taken), 15.9% of high school students are overweight.  11.8% of adolescents are obese.  With rates that high, many students don’t even need healthier forms of calories — they need to stop snacking.  Vending machines promote snacking.

Colin Purrington Photography: Obesity &emdash; junk-food-vending

Colin Purrington Photography: Obesity &emdash; public-school-vending-machine-radnor

Colin Purrington Photography: Obesity &emdash; junk-food-school-vending-machine

Colin Purrington Photography: Obesity &emdash; public-school-vending-machines

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