Posted on 10/23/2011 7:15:22 AM PDT by PJ-Comix
Until about a decade ago, most people in the United States only knew about bedbugs through the seemingly dated phrase "Sleep tight, don’t let the bedbugs bite." But the bloodsucking parasites, which were largely eradicated by the mid-20th century, have roared back in all 50 states, and the bugs’ evolving resistance to insecticides is part of the reason for their resurgence. A new study gives the most complete picture so far of the adaptations some bedbugs have developed to thwart exterminators’ poisons.
The pesky bugs, it appears, can pump out a stew of enzymes that destroy insecticides, according to the study out this week in the journal PLoS ONE. This newly described neutralizing mechanism is in addition to a mutation, which scientists revealed a few years ago, that alters the structure of bedbugs’ nerve endings and prevents common insecticides from binding to their nerves. Together, these defenses could form a one-two punch that protects bedbugs from exterminators’ chemicals.
"The enzymes we discovered in the context of this paper are essentially the initial line of defense in breaking insecticide down before it reaches the nerve," Zach Adelman, lead author of the paper and an associate professor of entomology at Virginia Tech, says.
To figure out bedbugs’ defenses, Adelman and colleagues started by gathering a sample of bedbugs from Richmond, Va. The Richmond bugs had demonstrated strong resistance to a class of insecticides known as pyrethroids—the agents of choice for exterminators. Pyrethroids paralyze bedbugs by keeping open the sodium channels where nerves meet and communicate with one another. "The nerve will keep firing, and it can’t relax," Adelman explains. The result: paralysis and eventual death.
The researchers also used some bedbugs that had been reared in a lab in Fort Dix, N.J., for decades, and had not been exposed to chemicals. When Adelman’s team blasted both sets of bedbugs with two different pyrethroid insecticides—one called beta-cyfluthrin and another deltamethrin—they found that the Richmond bugs could withstand 111 times the dose of the beta-cyfluthrin insecticide compared with the Fort Dix bugs, and a whopping 5200 times the dose of deltamethrin.
Clearly, the hearty Richmond bugs had adapted some strong defenses. Adelman and company found that the bugs possessed one of the two mutations in genes coding for their sodium channels that researchers had previously seen in populations of New York bedbugs that were also resistant to this class of insecticide. The mutation is analogous to camouflage—it’s as if the insecticides can’t recognize the nerve endings they typically target. Adelson’s group also saw that the Richmond bugs were producing far higher levels of suspected insecticide-busting proteins in the cytochrome P450 monooxygenase and carboxylesterase families.
With these identifications, Subba Reddy Palli, an entomologist at the University of Kentucky, thinks the study will help in bringing bedbugs to heel. "This paper is good progress toward understanding insecticidal resistance," he says.
Now that his team has identified the genetic sequences bedbugs use to make these detoxifying compounds, Adelman says scientists can check populations worldwide to see how far this defensive capability extends. That will be important for establishing surveillance of growing resistance, as well as for creating new strategies for controlling the critters. For example, he says, if it seems that only the Richmond bedbugs have the genetic mutations needed to crank out this particularly powerful cocktail of enzymes, exterminators should engage in an all-out assault to try to wipe out that bedbug population before it spreads.
The arms race against bedbugs and other insects mirrors the battle with bacterial "superbugs" that have developed antibiotic resistance, such as those that cause staph and tuberculosis. Indeed, bedbugs have a long history of developing defenses against our chemical warfare agents. Bedbug "superbugs" first emerged in the 1950s. DDT (which was banned in 1972 because of human health concerns) wiped out most native bedbug populations in the U.S. by 1950. But some bedbugs survived, developing resistance to it, and later, organophosphate insecticides such as malathion.
Now pyrethroids are losing their effectiveness. "We have all these bedbugs we’ve chased from one chemistry to another," Dini Miller, a co-author of the study, an urban-pest management specialist for the state of Virginia, and a professor at Virginia Tech, says.
Yet the identification of bedbugs’ enzymatic countermeasures could ultimately provide exterminators with fresh ammunition. Besides insecticides, exterminators use a range of methods, including cold air, steam, and vacuums. But these repeated treatments can add up to hundreds or even thousands of dollars. Rejiggering conventional insecticides might still do enough damage to keep bedbugs at bay. "We can look at formulating things in new ways and get better penetration into these bedbugs," Miller says.
Down the road, scientists can base next-generation insecticides on chemicals substantially unlike those that bedbugs have already mastered disarming. Adelman says: "We can come back to the bugs and say, ‘We have a chemical you can no longer deal with given your arsenal. Now try this on for size.’"
New offensive weapons can’t come too soon, as the spread of these brownish or reddish bloodsucking insects has residents of heavy-hit urban areas such as New York City on edge. "Bedbugs don’t kill you," Adelman says, "but they can drive you crazy."
I contend that maybe it did [evolve into another creature]. The resistant kind.
So using that exact same logic, an albino or a hemophiliac isn't a homo-sapiens but is another species? Are you going to go against all biologists and claim that a poodle is not a dog because it has less genetic information for a dog than a mutt?
If you believe that a mutation is proof of Evolution, then you are a neo-Darwinist, which ironically enough was debunked back in 1967 at the Wistar Institute as a mathematical impossibility by a group of hard-core evolutionists and mathematicians.
The simple argument goes like this. A mutation has the odds of 107, which is rare but not that rare when you have a large population of reproducing cells. But for a series of mutations it becomes 1014 for that next one and for four mutations you need 1028 mutations and the world isn't large enough to contain all of those mutations, and even with billions of years there would never be enough time. So how did scientists explain how certain organisms developed immunity to four different kinds of man-made toxins? They quickly came to the conclusion that neo-Darwinism, or mutations plus natural selection could not explain evolution, and because they refused to even consider Creation, they left with no answers.
But mathematical impossibility is not really the best refutation, rather observational science serves better than your speculative non-science. The fact is that mutations are not beneficial. Mutations are corruptions in the genetic material, not improvements. This is observed by the fact that many diseases and cancers are formed by mutations, and I don't know anyone who thinks cancer is "evolving upwards".
Here is a thought experiment for you. Go stand in front of an operating X-ray machine for hours until your cells start to mutate. Do you suppose that prolonged exposure will transform you into a higher-level being? If not, why the cognitive dissonance?
Where did I claim that it was another species? ( HINT: I didn't).
I said it was a different creature. As in, "has different traits".
Sorry I wasn’t able to continue the discussion yesterday.
There is more genetic difference between an African bushman and a Norwegian basketball player than there is between a bed bug not resistant to pyrethrins and one that is.
Are the 2 human examples still the same species? or are they both evolving into something else?
Most mutations are neither positive nor negative. Whether a mutation is harmful or helpful depends on the environment. We are already seeing this with antibiotics - those that were considered no longer useful due to “evolved resistance” are being used again as current bacteria are resistant to newer antibiotics. It becomes a hysteresis loop, which is decidedly not evolution. Mutation does not result in an increase in information, which would be required.
The Peppered Moth is a good example of this. They have gone from light-colored to dark-colored back to light-colored as a response to the environment in the U.K. during the Industrial Revolution. Of course, no evolution occurred - the environment determined that a specific coloration let them avoid being eaten. That’s all. It provided no other benefit. Evolution isn’t merely selecting a characteristic (or rather having the birds select it for you). Evolution would be an effective defense mechanism against the birds.
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