Tag Archives: transmission

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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Reducing disease transmission with signage

Just trying to do my part to make the world a safer place.  Print the PDF of the signage below and tape or glue in a bathroom near you.  In my experience, signs printed onto label paper look more official and thus have a longer half-life before being discovered by the bathroom signage czars. To see actual signage in use at a Swarthmore College bathroom, please refer to my previous post, “Dangerous bathroom design.”

Bathroom signage to reduce disease transmission

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Dangerous bathroom design

Flu season is coming, so here are some photographs to highlight one of my pet peeves, bathroom design that promotes disease transmission.  I post with the hope that somebody with true influence over architects will someday link to this post.  My pet peeve: bathroom doors hinged in a way that require people to touch the handle or knob to exit. I’m sure there are fire code reasons why architects specify for this, but it’s strange (remote risk of fire vs real and daily risk of disease).  I designed a graphic to highlight the issue:

In other words, when you touch the handle, you will most likely pick up viruses and bacteria left by the people who didn’t wash their hands (and those people might be really sick).  Really: research has shown that door handles have more bacteria than (gasp) toilet seats.  But even if architects are required by law to hinge doors to pull in, I think all bathrooms should be equipped with signage like the above, with perhaps additional verbiage about using a paper towel or shirt to open the door to educate people who don’t normally think about such things (you should do this if you don’t already; photo).

Compounding the above problem is the fad of equipping bathrooms with only electric hand dryers (“Saves the environment!”).  Because cheap hand dryers take about 3 minutes to dry your hands, many people opt to just exit the bathroom without washing their hands.  Or at least guys opt out…I don’t hang out in women’s restrooms that often.  This means that the handle or knob is going to get a lot more use from hands that are coated in microbial nasties. (Somebody needs to compare bacterial counts on handles in paper-free and paper-provided bathrooms…let me know what you find.) Here’s a graphic I designed for the machines:


So: my plea to people in power is for doors to be hinged so that mere pushing (e.g., with shoulder) allows exiting.  And for paper towels to be provided.  Or, if that is too costly, then for installation of signage that truly informs bathroom users about bad bathroom design and what they can do about it.  If you work in a hospital and have both MRSA and immune-suppressed patients, you definitely need signage like this. It’s cheaper than installing a door handle sanitizer, I’d wager.

If you like the idea of signage but are worried about selling it at your institution, here is a article to send to your colleagues and staff. Signage makes a difference, but edgy signage makes more of a difference.

If the Bathroom Signage Committee at your workplace is packed with people averse to anything novel, don’t worry, you can do it yourself!  Just download the door signage and hand dryer signage files (PDFs), then print onto 4 x 6″ paper.  I recommend 3M’s removable adhesive labels (#6200), which are essentially Post-Its you feed into your inkjet or laser writer. I love these sheets for stealth stickering projects when I don’t want to permanently annoy people. Then, of course, you need to sneak the stickers into the bathrooms at your workplace.  If you place them carefully and all at once, people will assume somebody in charge mandated the change and they will have a better chance of staying up.  Good luck, and have fun.

NOTE: the signage above was installed at Swarthmore College.  They lasted about a week before they take down by order from above.  Now they are back to zero signage, and are promoting disease transmission. Hey, I tried!

Please share with your friends, folks.

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