Environmentally Friendly Pest Control: An Overview of The Sterile Insect Technique

In many cases, we can use the insects themselves to aid us in their elimination. One method, called the Sterile Insect Technique (SIT) involves using sterilized insects to drive the population down.

First, insects are raised in rearing facilities to adulthood. Then, males are singled out with a variety of methods (which I won't go into here...feel free to dig up the sources via google scholar), sterilized and released into the field in droves. This is preferable to pesticides because the technique is generally very environmentally friendly and species specific-no chance innocent bugs getting caught in the crossfire or people accidentally being exposed to pesticide.

This technique has been used with great success against the tsetse fly of Africa and on the screw-worms of North America. The tsetse flies (Glossnia ssp.) are best known for transmitting trypanosomaisis, or sleeping sickness as it's commonly known. It's a horrible disease, and some of the treatments are fatal about 10% of the time. The disease is usually fatal in most people who remain untreated. Fortunately, we can control it's vector. If we control it's vector, it can't pass from person to person. If it can't pass from person to person, the disease dies out. Screwworms aren't disease vectors for humans...and don't really affect us but their effects on cattle are even more horrifying. Adults are attracted to open wounds, where they lay their eggs. The larvae hatch, start eating the living flesh, and the scents released while they feed attract more female screwworm flies. At the very least, the cattle lose value and lose weight. Infestations resulting in death weren't uncommon before the measures were taken to eradicate the pest.

In controlling trypanosomiasis and screwworm flies, scientists use radiation (usually Cobalt-60, but also X-rays) to sterilize male flies and release them on the wild population so they mate with females. Many insects mate only once, and this would cause the female to lay infertile eggs or in the case of tsetse flies whose larvae develop internally, expel dead larvae. This causes a drop in the population of the target insect species, and the process is repeated for the next generation. Sooner or later, the number of sterile males outnumber the wild-type fertile males and eventually the population goes extinct.

Unfortunately, there are some drawbacks to this procedure. For example, one has to know that there will not be much migration into an area. If outside females who have already mated can immigrate into an area on a regular basis and reproduce, this tactic only becomes good for suppression. One of the biggest drawbacks is the fact that it's simply not economical. It has to have backing from a wealthy country like the US or United Nations in many cases and it is very labor intensive. This technique has been used for some agricultural pests (pink bollworm and the Mediterranian fruit fly to name a few), but would be ineffective for parthenogenic sawflies and aphids because they do not rely on males to reproduce. So it's not a silver bullet...but for many species which reproduce sexually, it's definitely effective. Many areas of Africa are now free of tsetse flies because of this technique, and the US hasn't seen an infestation since 1966

Many times, the flies are sexed manually when pupae by trained professionals. Other times, insects may be genetically modified with a gene coding for insecticide resistance on the Y chromosome. After this, they need to be carted into packages, refrigerated and dispersed around the habitat...sometimes by air. Of course, the biggest problem is when the equipment breaks down. In one case, a facility using the SIT had it's irradiation equipment fail and accidentally released millions of fertile male screwworms into the environment. These types of mistakes would simply set the project back awhile, but not render it ineffective.

This technique creates a lot of waste in terms of insects. Only about half the insects produced by any given facility can be used for two reasons. One reason is that in many cases, it's the female and only the female who can transmit disease. A female with non-working reproductive parts can and will take blood meals, which means they can still be disease vectors. The second reason is that mixed releases are simply inneffective. The goal is to get the males to spread throughout the area. Unfortunately, male insects have the 'dude in a nightclub' mentality-they won't spread out if they're released with females.

Why go prowling if you can get laid right at home? I've stayed in many a crappy nightclub for no other reason than because I was having success with the women there...and the same principle applies here.

http://www.ars.usda.gov/is/pr/2002/020828.htm

Alphey, L. (2002). Re-engineering the sterile insect technique. Insect Biochemistry and Molecular Biology, 32(10), 1243-1247. DOI: 10.1016/S0965-1748(02)00087-5

Pedigo, Larry P., Rice, Marlin E. (2009). Entomology and Pest Management (6th ed). New Jersey: Pearson Education

Vreysen, M.B., Saleh, K.M., Ali, M.Y., Abdulla, A., Zhu, Z., Juma, K.G., Dyck, A., Atway, M.R., Mkonyi, P.A., , . (2000). Glossnia austeni (Diptera: Glossinidae) Eridicated on the Island of Unguja, Zanzibar Using the Sterile Insect Technique. Journal of Economic Entomology, 93(1), 123-135.

Book Review: Only A Theory

When I was shopping for textbooks, something caught my eye. It was this:



One of the professors decided to make the book Only a Theory by Ken Miller required reading for the class. I've been wanting to read something by Miller despite the fact that I can't seem to find Finding Darwin's God in any of my local bookstores. So I decided to read this to see what I thought of it.

First off, I am an athiest under most definitions of god. I don't believe in any gods, but I don't see the need to spout on and on about it. I'm more interested in seeing how the real world works. However, I was afraid that most of the book would amount to an explanation of theistic evolution. Even I find this one of the more innocuous forms of religion, I still don't think it has a place in biology class.

However, considering all of the hullaballoo over creationism and intelligent design-especially here at Iowa State, I can certainly understand the decision.

A few years back, a professor by the name of Guillermo Gonzales attempted to get tenure here at ISU. He had a good study group and before he came to ISU, he had published quite a bit of research. However, he wrote a book called The Privileged Planet and devoted most of his efforts to Intelligent Design. As a result, he didn't publish much research and for this reason was denied tenure.

You can find out more about Gonzales and his book elsewhere online, I'm only mentioning this for background. Iowa State is one of the battlegrounds over ID, and it certianly makes sense that Iowa State would want to include reading material from a devoutly religious man who has spent much of his career defending evolution. Miller helps to cut through the stereotype that evolution is only accepted amongst athiests and helps to destroy the false dichotomy they try to create. In fact, the producers of Expelled were quoted as saying that Miller would 'unnecessarily confuse the audience'.

In the book, there were a lot of things I agreed with him about and many that I didn't...and not just about religion.

He begins the book by sharing some of his experiences defending evolution. He rightly points out that much of the opposition to evolution is based in religion and emphasizes that it is an emotional opposition at it's very core.

I've noticed this while speaking to crowds about why I don't believe in god. Religion is held sacred to many and I believe that the reason many religious people dislike athiests is because, in reality, they're afraid of us. They're afraid that we can disprove something they want to believe in. This is also why they're so afraid of evolution. I'll get to this later.

Next, he explores the many claims of the ID movement...many of which appeared in the 2005 Kitzmiller VS Pennsylvania trial. These include the flagellar/type III secretion systems, blood clotting pathways, information theory and such.

The examples he cites and explains are very good. The flagellum is undeniably the posterboy for ID, and any claim of irreducible complexity is quickly refuted by Miller. Same with the eye and blood clotting pathways. The explanations he gives are really quite good. And damning to ID.

However my one gripe about the examples he chose is that anybody who reads up on the subject (especially as much as me) will already be intamitely familiar with them. It's certainly not a bad thing. I know Miller didn't write the book for people like me who follow the literature or who have read every single page of the transcripts and decision of the trial (I'm such a nerd...). He wrote it for the laypeople who might be on the fence. And to laypeople, those examples are very good. Besides, the Cdesign Proponentists would just accuse him of 'ducking the punches' if he did.

So it's not really even a flaw...just something that annoyed me.

However, the one thing I really didn't agree with is that he thinks the reason for the prevalence of ID and creationism here in America is due to our rebellious nature.

The reason I don't agree with it is because I grew up knowing many people from Britian and Australia...young people like the type who become enamored with ID. They were just as rebellious as I was. Furthermore, the 2005 riots in France should lay his hypothesis to rest...especially for European culture. Suspicion of those who are in positions of authority is simply a part of human nature. Being American has nothing to do with it, although I'll agree with him that we like to think we're a renegade culture.

He believes that Americans want to look at the literature and decide for themselves. However, the literature is pretty conclusive in favor of evolution. Any amount of research on the Discovery Institute or Answers in Genesis reveals almost immediately that they are undeniably intellectually bankrupt and have nothing to offer.

Instead, I believe that it's not that Americans want to decide for themselves...it's that we as a culture tend to believe whatever we want to believe. There's a marked difference.

Young Earth Creationists have to overlook the fact that there are nesting sites of terrestrial dinosaurs in the strata they claim were underwater during the 'Noacean Deuluge'. They have to ignore most of physics to assert the universe is a few thousand years old and they have to overlook the fact that pathologists need to use the same techniques to study diseases such as Community Acquired MRSA (which according to any of the AIG bacterial resistance articles, should not exist)...amongst other things. People who want to decide for themselves should see these as fatal flaws-nay-falsifications of the young-earth hypothesis.

I think that for many people, the various forms of creationism lack abandonability. They simply equate them with religion and hold it sacred...willing to overlook the flaws in their worldviews because they're unwilling to abandon them or view things in a different light.

I wouldn't consider our culture really all that rebellious. Much of our so-called rebellion in popular culture is packaged up in the form of pop-punk bands and singers like Avril Lavigne and Sum-41 and marketed to the masses.

Instead, I think that the problem is the way science is taught in the US. Science, when properly taught as Miller points out, is nothing more than common sense laid out. It builds on itself, sure...but once you get the basics down there's not a whole lot that's not easily understood. Unfortunately, as Miller also points out, this is where the Cdesign Proponentists are winning. They're making evolution too controversial (even though I don't really believe it is) and the officials who are elected by popular vote are hesitant to teach it for fear of being replaced.

If it's not properly taught, or taught in an over-simplistic form, students don't develop the understanding needed to reconcile their beliefs with science. Their beliefs lack abandonability and the cycle starts over and over.

The rebelliousness of American society is a major theme in the book...and it's one that I don't agree with at all. Other than that, however I think the rest of the book is perfectly solid. It is...and should be required reading for all incoming biology major freshmen.

Buy Only a Theory from Amazon.com

Bacterial endosymbiont is a major causative agent of morbidity associated with filarial nematode infections.

Wolbachia is one of my favorite bacteria, I've actually given it it's own label on the blog. It does all sorts of strange things, like dictate the gender of the host’s offspring. Wolbachia lives in the eggs of it’s insect hosts, being passed on from mother to daughter. If they end up in a male, they dead-end because they cannot be passed on through sperm. Instead, they kill any potential male offspring the female has or makes infected males unable to have offspring with uninfected females depending on what species they infect.

However, Wolbachia is actually a somewhat common endosymbiont in insects and nematodes. Although it’s famous for the effects on insects I mentioned earlier, Wolbachia actually has a major role in medicine despite not actually being a human pathogen.

200 million people around the world suffer from a disease called river blindness. This disease is spread by parasitic flies through the bite. When a fly bites a human, it injects nematode larvae in it’s saliva. Once inside the body, these nematodes form nodules under the skin. They mate and then produce larvae which migrate through the skin, looking to be taken up again by a Simulium host.

The larvae when alive don’t really cause a whole lot of damage. Being a parasite, they’ve evolved ways to become invisible to the host’s immune system. The damage from river blindness comes from when the nematodes die. When they die, they become visible to the host’s immune system which subsequently responds, with many different responses but inflammation is the response responsible for the damage that causes the blindness. If the larva happens to be in the eye when this happens, then this can be very serious.

However, the nematode’s body isn’t the only thing that causes the immune response. Scientists studying Onchocerca volvulus have discovered that the effects of the dying larvae are greatly excasterbated by their Wolbachia endosymbiont.

Scientists took extracts from nematodes, nematodes treated with an antibiotic and nematodes that didn’t harbor Wolbachia and injected them into the eyes of mice. Nematodes treated with the antibiotic doxycycline as well as nematodes which don’t harbor Wolbachia triggered less of an immune response than did nematodes who had Wolbachia endosymbionts. To the scientists, this indicated that something in the Wolbachia cells and not the nematode cells caused the inflammation and other immune responses.

But what in the Wolbachia cells could trigger a response?

Wolbachia are a gram-negative bacteria, which means that a major portion of their outer cell wall is formed from a macromolecule called bacterial lipopolysaccaride (LPS). A receptor called Toll Like Receptor 4 (TLR4) is a major part of response to bacterial infection. Since TLR4 responds to LPS, it was a natural candidate for testing.

To test the link between the Wolbachia LPS and the immune response, the researchers used mice with a mutation in the TLR4 gene that made them less sensitive to LPS to determine if this was the cause. Once again, extracts containing Wolbachia were injected into the mice and their immune responses measured.

As one would expect, those mice with an underresponsive TLR4 receptor displayed less severe symptoms than did mice with a normal TLR4 gene. This means that instead of the nematodes causing the inflammation and other immune responses associated with river blindness, it’s actually their endosymbionts that cause those types of problems.

This opens up a whole new avenue of potential research into new treatments for river blindness. Since we now know that it is not the larvae that cause river blindness we can focus on the real culprit, Wolbachia. The Wolbachia are vital endosymbionts-the nematodes don’t properly develop without the bacteria in the system. This means by focusing our efforts on Wolbachia we not only prevent the LPS from the Wolbachia being released when the filarae die, we drastically reduce the numbers of said filarae because without the Wolbachia the nematodes are unable to reproduce.

Saint Andre, A.V., Blackwell, N.M., Hall, L.R., Hoerauf, A., Brattig, N.W., Volkmann, L., Taylor, M.J., Ford, L., Hise, A.G., Lass, J.H. (2002). The Role of Endosymbiotic Wolbachia Bacteria in the Pathogenesis of River Blindness. Science, 295(5561), 1892-1895.

Hymenorrhaphy

This blog is mostly an entomology/evolution/general science blog because political/human rights bloggers are a dime a dozen, but I do dip into culture and politics every once and awhile. I'm also not a medical blogger, so this is also kind of new for me. Aside from reading about science, I also read up on human rights and such. The rights of women are important to me and they should be important to anyone who reads this.

One of the things that's always puzzled me about religion is the concept of virginity until marriage. I've always lived in a culture where it was considered unrealistic. According to the CDC, well over half of people are sexually active by their twenties. And here in America, it's usually considered a surprise if you're a virgin when you exit high school. If you're a male, it's considered a dishonor.

It's always struck me as just a way for men to stake their territory. While great significance is placed a woman's virginity, a male's virginity is considered a burden. Examples of double standards abound and there's no reason to expound on them.

Virginity is a very important part of many cultures in the world, but nowhere else is it more important than the Mideast. Women who have sexual relations before marriage risk being disowned by their families, or worse.

In many parts of the world, women are still treated as nothing but property...and little valued property at that. Nobody would beat their motorcycle because somebody has ridden it, however in many parts of the world women are beaten to death for precisely this reason. There have been cases in middle eastern countries where women were beaten to death for talking to westerners. Women have been beaten to death for standing up to or leaving their abusive husbands.

As late as 1994, virginity tests for schoolgirls were still common in Turkey.

Usually, virginity is determined by inspecting the hymen. The hymen is a thin, collagenous membrane that covers the vagina at birth. Many people believe that the hymen breaks during the first insertion, however this may not be necessarily true. It can break from trauma, strenuous physical activity such as gymnastics or biking or a multitude of other things. Some women may be born without one.

This creates a problem for women in cultures similar to the examples I mentioned previously. Women in Europe experience less stringent sexual norms than we have here in America, and since the population of Muslim families is increasing this results in women who may feel like they're caught between the worlds of their family and the culture they know. Similar pressures are felt by women in America who hail from places in Central and South America.

If the hymen breaks, either through excersize or intercourse, this could create a problem for women in hyper-conservative cultures. They risk dishonor, violence and death. In some cultures, this will go so far as to force the women to marry her attacker to maintain her honor.

Fortunately for them there is a solution in the form of hymenorrhaphy, or 'hymen reconstruction' in laymen's terms. This surgery, in some parts of the world, can literally save the lives of women in many cases.

The surgery is a relatively minor procedure. Patients may remain conscious after being given a local anesthetic or may be unconscious during the procedure after being given a general anesthetic.

In many cases, the hymen is barely damaged and can be reconstructed by simply stitching the remnants together with dissolveable sutures. In surgeries such as this, gelatin capsules may be inserted to simulate post-coitus bleeding.

In other cases, a flap of the vaginal lining may be used to create a new hymen. In this case, the new hymen will have it's own blood supply and the capsule will not be needed.

In many countries, these procedures are banned because they're viewed as dishonest. Many feminists also scoff at the notion of procedures used to restore the appearance of virginity. Moreover, these procedures aren't cheap...the cost can be between $2,000 and $4,000 in Europe.

Works cited/more information:

http://www.reuters.com/article/worldNews/idUSL2532025120070430
http://www.tcclinic.com/hymen-restoration-toronto.php
http://www.miklosandmoore.com/hymen.php
http://www.obgyn.net/english/pubs/features/presentations/hennawy13/hymenorrhaphy.ppt