Tagged: research

Don’t throw your DEET Away!

deetfailThere’s been a lot of reporting about new research about the insect repellent DEET this week. Unfortunately, some of the media didn’t quite get it right.  Headlines like this one were common…and completely wrong.

The media coverage left a lot of people confused about DEET, and if it still worked. The results of the research were a lot more nuanced than “DEET suddenly stopped working so we are all screwed.”

Here is what the average person being bitten by mosquitoes needs to know, condensed:
DEET still works fine. It’s still one of the best insect repellents out there.  We know a way it might become less effective now, as demonstrated in the laboratory.

The un-condensed version:

DEET is one of our oldest and best insect repellents.  It’s universally acknowledged as the best repellent around, and has broad activity against several types of biting flies and ticks. This is why a problem with DEET is big news–it’s invaluable in preventing transmission of several different diseases.

Amazingly, scientists are just beginning to understand how DEET works, even though it’s been in widespread use for 50 years.  We know it stops ticks and mosquitoes from biting, but the exact mechanism of how that happens is still not clear.  Does it make us ‘invisible‘ by blocking mosquitoes from smelling? Does it smell horrible to biters? It’s still not settled science yet.

Martha Stuart says that's not a good thing

That’s important to know, since if we know how something works, we can copy it and try to make new and better controls.  There is always a concern with evolution of resistance in insects–they are commonly used to study genetics and mutations for a reason.   Insects breed fast, and they breed often–which means that small genetic changes, if they are helpful at keeping a bug alive and having sex, can spread quickly through a population.

Resistance to DEET, our most powerful and broad spectrum insect repellent, would be a very bad thing.  And so it makes sense that entomologists interested in human health would be studying how DEET works.

Evidence of genetic resistance to DEET in mosquitoes has actually been around since 1994.  In 2010, researchers found that they could increase the frequency of a gene that made mosquitoes ignore DEET to 50% in a couple of generations. That’s alarming, but that was in a laboratory-bred colony.

‘Laboratory-Bred’ is an important distinction for both that study and the recent one.  Mosquitoes in a cage have only one source of food (often the hapless graduate student that is rearing them).  They can’t fly off and look for other people or animals to bite.   It also means that their sexual choices are limited to other mozzies in the cage, so resistance can evolve more quickly that it would out in the wild where they have a wider choice of hookups.

Scientists use work in the lab to model the real world.  It helps us understand how organisms grow, change, and respond to their environment.  That  doesn’t mean that it’s a firm prediction of what will happen out in the larger world, especially with a group as diverse and wily as mosquitoes. That’s why I think headlines like the one at the top are irresponsible, and mangling the message of the research.

You can see an interview with one of the researchers here;  note she is careful to repeat that we should not discard DEET wholesale on the results of this research!

“What this work indicates is that there may potentially at some point in the future be some problems  with the repellents that we have, that we need to be aware of in advance.   Possibly we can use this information to  alter the repellent DEET to make it more effective, it may also help us in finding new repellents because we will know if [mosquitoes] are able to overcome certain things……Even though repellents are working fantastically at the moment, what this tells us is maybe how to prevent problems cropping up, and how to alter things for the future to make them more effective.” [emphasis mine]

Additional Resources:

Articles referenced in this post: 

  • Stanczyk N.M., Brookfield J.F.Y., Field L.M., Logan J.G. & Vontas J. (2013). Aedes aegypti Mosquitoes Exhibit Decreased Repellency by DEET following Previous Exposure, PLoS ONE, 8 (2) e54438. DOI:
  • Ditzen M., Pellegrino M. & Vosshall L.B. (2008). Insect Odorant Receptors Are Molecular Targets of the Insect Repellent DEET, Science, 319 (5871) 1838-1842. DOI:
  • Jaramillo Ramirez G.I., Logan J.G., Loza-Reyes E., Stashenko E., Moores G.D. & Vontas J. (2012). Repellents Inhibit P450 Enzymes in Stegomyia (Aedes) aegypti, PLoS ONE, 7 (11) e48698. DOI:
  • Rutledge L.C., Gupta R.K., Piper G.N. & Lowe C.A. Studies on the inheritance of repellent tolerances in Aedes aegypti., Journal of the American Mosquito Control Association, PMID:
  • Stanczyk N.M., Brookfield J.F.Y., Ignell R., Logan J.G. & Field L.M. (2010). Behavioral insensitivity to DEET in Aedes aegypti is a genetically determined trait residing in changes in sensillum function, Proceedings of the National Academy of Sciences, 107 (19) 8575-8580. DOI:

 

How to make a giant aluminum ants’ nest

The internets have been abuzz with this photo today:
ant nest

It’s a photo of an aluminum cast of an ant nest made by Walter Tschinkel, a Florida entomologist–but there haven’t been a lot of additional details.

The nest you are looking at is one of a Florida harvester ant, and appeared with many other photos and casts in a 2004 paper about nest architecture in the Journal of Insect Science.  They are things of great beauty, and tell us a lot about how ants build.

The uppermost portions of a medium-small Pogonomyrmex badius nest

The uppermost portions of a medium-small Pogonomyrmex badius nest

This series of photos, for example, shows how the complexity of the nest structure grows as the colony adds workers.  You can find more amazing photos of different types of ant nest casts here in a 2012 article.

There is even a video of the process of making these casts! And yes, don’t do this at home. Even if Dr. Tschinkel did publish detailed instructions on all the different ways to make an ant nest cast.  I am looking at you, Mr. Treelobster.

I would be remiss if I did not also link to this older video that uses ten tons of cement to discover the extent of a much larger African South American ant nest. (I am told it’s Atta vollenweideri, and it was dug up in South America. Thanks for the correction!)

Tschinkel W.R. (2004). The nest architecture of the Florida harvester ant, Pogonomyrmex badius., Journal of insect science (Online), PMID:

Tschinkel W.R. (2010). Methods for Casting Subterranean Ant Nests, Journal of Insect Science, 10 (88) 1-17. DOI:

Crowd-sourcing Ant Science

Earlier this week, the internets were buzzing with a claim that Kickstarter is funding more projects than the National Endowment for the Arts.  It turns out that may not be strictly true, but it certainly is true that a lot of cool projects are being crowd-sourced that otherwise would never have made it off the ground.

I’ve mentioned some insecty Kickstarter projects before, like Meet The Beetle (a film about an endangered tiger beetle).  Unfortunately, Kickstarter is limited to arts and humanities. But now the concept of crowdsourcing has been harnessed for science!

Petridish.org is so new it hardly has a bacterial film growing on its website yet. Its first science crowd-sourcing project involves two awesome things: Insects and Madagascar.

“Unique” doesn’t begin to describe Madagascar. This giant island split from the African Continent over 160 million years ago, and over 90% of it’s mammal and reptile species occur no where else in the world.  Deforestation and erosion are critical threats to the island’s ecosystems, and many native species are endangered.

Brian Fisher, one of the folks behind AntWeb, is leading a project to document the ant species of a high remote preserve.   You might be wondering why you should care about ants in Madagascar.  You may especially be wondering this because you have figured out that at some point later in this post I’m going to hit you up for a donation.  I really like this statement from AntWeb that puts ants in context:

“At this moment, more than one thousand trillion ants are scurrying all over the Earth. If every human climbed aboard one side of a scale, and every ant crawled onto the other side, the scale would just about balance.”

Ants probably move more earth and recycle more dead things yearly than a whole army of human undertakers with bulldozers ever could.  Ants are a critical part of making the world’s living systems function.  The project description:

“Ants are the glue that hold forests together. But Madagascar’s hotspots of biodiversity are vanishing, and along with them unknown species. An estimated 40 percent of the island’s species, in fact, have already perished through human encroachment.

While ants aren’t as popular as furry and feathery animals, the insects turn over forest soil, breakdown debris, disperse crucial nutrients and otherwise support an unimaginable number of species both up, down and across the food chain. The insects are also a growing resource for antimicrobial and antifungal compound discovery, as many ants manufacture such chemicals to ward off disease and even farm food.

I need to reach one of the last standing pristine forests, called the Kasijy, before nearby populations burn them down to raise cattle. Researchers have visited the remote site only a handful of times because it’s a rugged, canyon-filled landscape resting on high blocks of limestone and sedimentary rock.Because Kasijy is so pristine, it also serves as a crucial data point of what Madagascar used to be like before the advent of modern civilization. The region and other forests are great places to understand the ongoing impacts of climate change on highly specialized ecosystems.

My expedition aims to:

  • Inventory Kasijy’s untold new species and document their roles in a pristine natural ecosystem.
  • Understand the biodiversity patterns of Madagascar and resolve our “bioilliteracy” of the Kasijy forest.
  • Set up more robust conservation plans for the island.
  • Raise awareness of Madagascar’s natural wonders and its ongoing plight.”

There are 39 days left to fund this project–I hope you can spare a dollar or two to help a researcher out!  Note that a large gift gets you acknowledged in any manuscripts published from this research.

Donate!

Roaches with JetPacks

You might have noticed a lot of news lately about robot designs based on insects.  Insects are great models for robots because bugs have an extremely stable and efficient model of locomotion: the tripod gait.  At any time, roaches have 3 feet on the ground–even when they’re running.   This tripod structure makes insects extra-resistant to tripping or tipping over.

Biomimetics is the fancy name for engineering systems that copy principles found in nature. Basing robots that need to scamper over rough terrain on an insect model that’s successfully lasted millions of years makes a lot of sense. But just how, exactly, do insects keep all those legs going in the right direction?  How can they respond so quickly to an approaching rolled-up newspaper?  How do insects manage this advanced scuttling with such a tiny brain?  And how can insects keep running even after their head is removed?

Jet propelled roach

(Yes, insects can live for quite a while without a head. They eventually die from dehydration or starvation because they can’t drink or eat anymore, but remain able to run away and respond to environmental stimuli. It’s really quite disturbing.)

In order to build a biomimetic robot, one has to first understand the mechanics at work in insects.  The engineering explanation for insect locomotion is hidden in equations about viscoelastic spring mass oscillation and tiny insect-mounted cannons.

Yes.

ROACHES WITH JETPACKS.

This is not a photoshopped picture; it’s from a 2002 research paper in which researchers attempted to mathematically work out the principles of roach locomotion. You can see the jet-pack at work in this movie:

So. Um, WHY did they put jetpacks on roaches? Aside from it just being a totally freakin’ COOL thing to do?

Remember I mentioned how stable the tripod gait is?   The researchers suspected that the roach wasn’t using just its brain to keep itself balanced and running.  They created a mathematical model of a roach with legs that were springs.

Just the mechanical properties of springy legs were able to explain how a roach kept on track and at full speed, despite obstacles.  They called these “preflexive” mechanisms, to indicate that the exoskeleton and muscles stabilize roaches without involvement of the nervous system.

They had an explanation on paper, with a lot of big words and calculations of lateral velocity.  The next step was to test their lovely model by poking a roach while it was running.   That…was about as difficult to do as you might imagine, based on your experience chasing roaches around your kitchen.

The researchers needed to have a precisely measured force disturbing the roaches, so that they could plug it into their model and see if it was accurate.  Hence, a tiny exploding cannon mounted on a roach. Or, to give it the gizmo it’s proper name, the rapid impulsive perturbation (RIP) device.  (That name is doubly clever, since they were experimenting with the death’s head cockroach, Blaberus discoidalis.)

They calculated the lateral force generated by the RIP explosion was equal to 85% of the insect’s forward motion.  If you were jogging along, and I ran into you with a force that was 85% of your forward momentum, I don’t think either of us would be standing up.  (Ok, yes, there’s mass involved in this too, but just work with me here.)  The roaches hardly even break stride.   In fact, it took just 13 miliseconds for a roach to begin to respond to the explosion and get back on track.  The roaches completely recovered from that RIP explosion within 31 miliseconds. 

Insects are indeed pretty damn amazing animals, and a great model for robotics.  The authors have continued their work on the hexapod gait, and have proposed several models of ways in which legs might be built–in both roaches and robots–to respond quickly to problems.

Science is awesome.

ResearchBlogging.org

Citation: Jindrich DL, & Full RJ (2002). Dynamic stabilization of rapid hexapedal locomotion. The Journal of experimental biology, 205 (Pt 18), 2803-23 PMID: 12177146

Revzen S, Koditschek DE, & Full RJ (2009). Towards testable neuromechanical control architectures for running. Advances in experimental medicine and biology, 629, 25-55 PMID: 19227494

Also: Just look at how easily the Star Wars AT-AT or AT-STs were destroyed by the rebels! Tripod-gait woud have saved the empire!

No, Bounce Fabric Softener will NOT protect you from bugs

I usually like Lifehacker, but in this case, FAIL.  Here’s a story they ran 2 weeks ago:

Bounce Fabric Softener Keeps Mosquitoes and Gnats Away

Some people have sworn by the power of Bounce dryer sheets—and specifically Bounce, too—to keep mosquitoes away from them, and gnats out of their garden. Now scientists have proven the power of fluffy white sheets as an insect repellent.

Lifehacker wasn’t the only media group that picked up on this story; and pretty much all of them made the same mistake.

When you look at the actual research paper, what you see is that some of what was reported was correct.  There actually WAS a paper that examined the repellency of Bounce dryer sheets to insects.ResearchBlogging.org

Raymond A. Cloyd, et al. (2010). Bounce® Fabric Softener Dryer Sheets Repel Fungus Gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), Adults.
HortScience, 45, 1830-1833

However.
There is a very large difference between a fungus gnat and a mosquito.  That’s rather like reporting that the care and feeding of cats and humans are interchangeable. Since, you know, we’re all mammals, right?

Let’s start with what a fungus gnat is, and when you’d be likely to encounter them.
Basically, fungus gnats don’t bite. They just annoy.  They’re likely to be the tiny things flitting around the soil of your potted plants.  They can be a commercial pest in greenhouses, but generally they are just a nuisance. They breed in moist soil and nibble on roots.

I think everyone knows what mosquitoes are–a biting fly that can carry major human diseases. They breed in water and adult females require a blood meal from a host to reproduce.

Not. The. Same.

This is an important difference, and it is a difference that has human health implications. If you go out in an area where there are disease-carrying mosquitoes with just a pocket full of dryer sheets as your protection, you are taking a risk with your health.

Media make mistakes covering science news all the time–but in this case, it’s a taxonomic mistake that could literally cost someone their life.  (Ok, I’m overstating it a bit. But, in THEORY, I’m right.)

Now that I’ve impressed upon you what’s at stake, let’s look at the actual experiment, shall we?

The authors tested the repellency of the dryer sheets in a very controlled situation, and were successful at reducing the number of fungus gnats in test chambers containing a dryer sheet.  At the end of their paper there is this caveat:

However, there are still important issues that need to be resolved, including the residual effects (based on age of dryer sheets) and effective distance of repellency, response in a no-choice situation (if dryer sheets are placed into each petri dish), impact on fungus gnat larval populations, and ultimately plant damage.

Now, every scientific paper ends this way. Here’s what we did, and here’s how it’s uncovered a whole host of new questions for us to answer! Continued employment, yay!

What I, as a gardener, would draw from this experiment is that it certainly couldn’t hurt to put a Bounce fabric sheet near my potted plants, if I happened to have a fabric sheet laying around.

But I would not, in a bajilion years, jump to the conclusion that it would protect me from all biting insects.

Sigh.

—

Long link to the paper, since the Researchblogging code keeps messing up blog code :(

Raymond A. Cloyd, et al. (2010). Bounce® Fabric Softener Dryer Sheets Repel Fungus Gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), Adults. HortScience, 45, 1830-1833

Lousebusters!

A fabulous new development in louse control! I’ve written before about the problem of head lice becoming resistant to commonly used pesticides, making treatment much more difficult.  A new device received approval from the FDA to be this year–and it’s a lot of hot air.
No, really:

Goates, B., Atkin, J., Wilding, K., Birch, K., Cottam, M., Bush, S., & Clayton, D. (2006). An Effective Nonchemical Treatment for Head Lice: A Lot of Hot Air. PEDIATRICS, 118 (5), 1962-1970 DOI: 10.1542/peds.2005-1847

ResearchBlogging.org

This device is a great story of how basic ecological research can lead to improvements in human health.  It all starts with birds.

Those of us who keep chickens or work with wild birds know that they have an amazing assortment of ectoparasites–parasites that live on the outside of the body (“ecto” = external). Most of these are called “feather lice.”

Feather lice are a fascinating group of animals; the researchers in this lab have studied, among other things, how lice have evolved to match the color of their host birds.  I think it’s safe to say that Dr. Dale Clayton, the lead researcher in this story, is Mr. Bird Lice.   Over the last 2 decades, he’s published a steady stream of fascinating papers (and books!) about lice and their co-evolutionary relationships with their hosts.

It was because of Clayton’s research that the University of Utah lured him away from his job at Oxford in the late 1990s.  Unfortunately, Clayton discovered exchanging  jolly old (damp) England for Utah’s arid climate made keeping his lousy subjects alive extremely difficult.  In fact, his lice colonies dried out and died.
Having dead research subjects will put a serious dent in one’s research productivity.

His travails in lice-rearing, however, were what set a lightbulb off when his children came home with head lice. If his research lice dessicated and died, could he make head lice dry out and die too?  Alas, it proved to be a much harder puzzle than he thought:

“Over the next several years a variety of methods were tested in Clayton’s lab, ranging from the use of chemical desiccants, to heat caps fitted with electrodes, to rice bag caps heated in a microwave, to various hair dryers and blowers up to the size of a leaf blower “

His lab website says that “student volunteers” were used as his guinea pigs. Once again, a novel use for graduate students is discovered!graph of results

After almost 20 years of tinkering, the Lousebuster is now FDA approved and on the market. It also happens does a really, really good job of killing the insects using only hot air!

I know what you are thinking–unfortunately, it is not enough to have a blow-dryer, as you can see here in the results comparing the percent of lice being killed with different methods.  (I also am rather relieved that wall-mounted hand driers were not effective.  I can only imagine the lines at the airport bathroom if families traveling decided to do a little de–lousing between connections.)

The other nice item is that the company selling the Lousebuster requires that anyone purchasing them be certified in their use.  That means that no one should have a scalded scalp, and it should actually perform at the 95-99% louse mortality levels reported in various publications.

A newer version released December 2010 is quieter and “works on curly hair”.

So hoist one to toast Dr. Clayton and his lab in their demonstration of how basic research  pays off for all of us!!

Bedbugs and Condoms

I’ve covered how ectoparasitic insects are cultured (and fed) before here at the Bug Blog. It gets discussed in this interesting article from NYT:

“The classic bedbug strain that all newly caught bugs are compared against is a colony originally from Fort Dix, N.J., that a researcher kept alive for 30 years by letting it feed on him.  But Stephen A. Kells, a University of Minnesota entomologist, said he “prefers not to play with that risk.”  He feeds his bugs expired blood-bank blood through parafilm, which he describes as “waxy Saran Wrap.”

I think this is one of my favorite quotes EVAR from a news story:

“Coby Schal of North Carolina State said he formerly used condoms filled with rabbit blood, but switched to parafilm because his condom budget raised eyebrows with university auditors.”

Even better, I know the guy that invented the now-defunct condom system!   The article ends with questions asked of Dini Miller:

Well, he was asked — can you feel them bite?  “No,” he said. “If I put them on my arm and close my eyes, I never feel them. But I once got my children to put them on my face, and I did. Maybe there are more nerve endings.”

Why in the world, he was asked, would he ask his kids to do that?
“Oh, you know,” he said. “Bug people are crazy.”

Bees, Cell phones, and BS (again)

The interwebs are all abuzz (ha!) with a new report that cellphones might be responsible for the losses in honeybee populations. ResearchBlogging.orgSpecifically, the news stories reference this paper:

Ved Parkash Sharma and Neelima R. Kumar (2010). Changes in honeybee behaviour and biology under the influence of cellphone radiations Current Science, 98 (10), 1376-1378

It’s a peer reviewed paper…but frankly, I think the journal editor has a lot of questions to answer about letting this paper be published.

There are many things wrong with this paper that make me discount all of its findings. A short list:

1. They tested only FOUR hives–and each hive had a different treatment. This means that there was NO replication for their treatments!!
Basically, they put cell phones in two hives, cellphones with no batteries in another hive, and left another hive alone.  Because multiple hives were not tested, this calls all the measurements reported into question. For example, one of the things measured was the egg laying rate of the queen bee in each hive. Because there is only one queen per hive….and one hive per treatment….if one of the queens happened to be substandard, or just have a bad day, that would skew the results.  And there is no way to say what really caused the differences without a SAMPLE of many hives, each with the same treatments, or lack of treatment.

2. Because the sample size was so small, the claim of “significant” statistical results is invalid. Essentially, they had a sample size of one. You can’t do statistics on that. No statistical values were presented in the paper, although the word “significant” was used and the phrase “(p<0.05)” was in the abstract.  This is an inappropriate use of these numbers.

3. They used an EMF monitor in a way that (as best as I can tell) it was not meant to be used (see photo). EMF monitors are finicky things, and are supposed to be used in carefully calibrated conditions. Walking around with it and plopping it on a beehive are NOT part of standard procedure.

Additionally, there was no shielding on the other two hives that were NOT treated with cellphones–so they really received a background dose of whatever the cellphones in the region were producing, not a true control.

4. They put the cell phones in the freakin’ hive (see photo). Now, granted, maybe that is where Eddie Izzard takes his phone calls. But most people do not stand inside–or next to–active beehives when they are chatting about what to get for dinner.  This design is rather analogous to strapping cellphones to your scrotum. I’m betting you’ll get an effect–but is it a real one that the average scrotum owner needs to worry about?

5. The references cited include newspaper articles and advocacy websites, which are not authoritative sources for a scientific paper. An article on X-rays, (which are not the same as cell phone emissions!), was cited as a reference showing cell phones could cause elevated drone production.  Additionally, that paper was published in 1986, much earlier than cellphones were in common production or use.

This paper (which for a student research paper would be questionable) should not have been in a journal.
It definitely should not have postulated a connection to Colony Collapse Disorder.
And it should never have made the levels of press exposure that it did. Shame on all of you newsies.

This is a classic example of Bad Science Reporting.  OMG RADIATION IN MAI BEEZ!!!

(I’M IN UR BEEZ, NUKIN UR DNA?)

The idea that cellphones affect bees has been around since 2007–and it wasn’t legit that time, either. You might also find this discussion of electromagnetic fields at the Skeptic’s Dictionary helpful.

BTW, this paper would be a great exercise for a classroom–take one of the press reports I cited above, and have your students evaluate this paper. Can they spot the ways in which it’s not quite proper science?

Migratory Butterfly Research in Europe

I’m still super busy, so how about you visit LabLit and read about the amazing migration of the Painted Lady Butterfly.  The article is written by a researcher that is putting the butterflies into a flight simulator (!) to determine how they orient.  In other words, how do they know in which direction to fly?

The Painted Lady migrates from Africa all the way to Britain and northern Europe.  I suspect Nesbit’s work is related to further elaboration on this recent paper, that described two layers of migration: One at the ground level, relatively independent of wind movement, and another at very high altitudes, where prevailing winds would move the butterflies without much effort very great distances.

Nesbit works in the Chapman lab, which has done a great deal of work on butterfly migration.

Full citation of paper:

Stefanescu C, Alarcón M, Avila A. (2007). Migration of the painted lady butterfly, Vanessa cardui, to north-eastern Spain is aided by African wind currents. J. Animal Ecology, 76 (5), 888-898

Not all mosquitoes are the same

ResearchBlogging.org
Welcome to the second day of World Malaria Day [week] at the Bug Blog! I’ve talked several times about the way in which different mosquitoes respond differently to pesticides for malarial control, but here’s a new twist.

In a recent study to compare different species of mosquito in their ability to be a malarial vector, there were very large differences!

As a review– a disease vector is an organism that does not cause disease itself, but transmits an infection by transporting pathogens from one host to another. The malarial parasite is alive inside the mosquito, although they don’t get malaria–but they can give it to us, the host. In this research, different mosquitoes were compared in their abilities to serve as a vector for malaria.

One of the claims frequently made by the “DDT will solve everything” crowd is that just spraying enough DDT will kill all the malarial mosquitoes.  This ignores that mosquitoes vary widely from population to population, and species to species, in their ability to resist DDT.  They aren’t all the same, and there is no one size-fits-all control method.

The research I discussed yesterday is another good example of the variability problem–predicting malaria using weather and other environmental data in different areas of Africa required different solutions.

In this experiment, you can get a sense of another layer of difficulty in controlling malaria. The experiments looked at two different strains of malarial parasite (Thai and Korean), and 3 different mosquito species.  That’s a lot of potential variation!

What did they find out?malaria_lifecycle

I won’t go into the specifics–you can read the paper if you want to see technical words like “sporogony”–but basically, not all of the mosquito species were able to support the malarial parasites’ life cycle.  (BTW, this diagram is probably the single greatest cause of drinking in invertebrate zoology students. The names! The stages! Ugh!)

Infecting a mosquito with the malarial parasite isn’t enough–the parasite has to change, migrate out of the gut of the mosquito, and into its salivary glands.  Not all mosquito bodies are equally friendly to this process–there were large differences between the 3 mosquitoes tested in this experiment.

Hopefully this gives you a sense of the complex layers of difficulty surrounding malarial control–in addition to the environmental variability  from location to location discussed yesterday, and variation in pesticide resistance which I’ve discussed before, there are also large genetic differences within mosquito species, mosquito populations, and malarial parasites. It’s a spaghetti tangle of variables, many of which we have no control over.

This is why there is no easy solution to malaria, and why after centuries, we are only now beginning to make progress.

But we are making progress! Just not as fast as we’d like.

Citation:
Joshi, D., Choochote, W., Park, M., Kim, J., Kim, T., Suwonkerd, W., & Min, G. (2009). The susceptibility of Anopheles lesteri to infection with Korean strain of Plasmodium vivax Malaria Journal, 8 (1) DOI: 10.1186/1475-2875-8-42