Tag Archives: mosquitoes

So Make the Blood Hotter

In the latest issue of PNAS, researchers report that drinking body-temperature blood causes mosquitoes to undergo a classic heat-shock response:

The mosquito’s body temperature increases dramatically when it takes a blood meal from a warm-blooded, vertebrate host. By using the yellow fever mosquito, Aedes aegypti, we demonstrate that this boost in temperature following a blood meal prompts the synthesis of heat shock protein 70 (Hsp70). This response, elicited by the temperature of the blood meal, is most robust in the mosquito’s midgut.

Now we just need to develop some drug that will overload or exploit this response to prevent the mosquito from spreading disease. I’m imagining something like this:

Virologists Shouldn’t Bring Their Work Home

In a brilliantly titled Science Now story, Martin Enserink reports on a strange cluster of patients infected with an extremely odd virus:

A U.S. vector biologist appears to have accidentally written virological history simply by having sex with his wife after returning from a field trip to Senegal. A study just released in Emerging Infectious Diseases suggests that the researcher, Brian Foy of Colorado State University in Fort Collins, passed to his wife the Zika virus, an obscure pathogen that causes joint pains and extreme fatigue. If so, it would be the first documented case of sexual transmission of an insect-borne disease.

The paper coyly explains that “Patient 1″ and “Patient 2″ apparently acquired the virus from mosquito bites during their field studies in Africa. “Patient 3,” who didn’t go on the trip, and who lives in northern Colorado where Zika-carrying mosquitoes are nonexistent, seems to have gotten the pathogen by having sex with Patient 1.

Foy is the first author of the paper, which describes three anonymous patients. But in an interview with Science, he confirmed that he is the anonymous “patient 1″; his Ph.D. student Kevin Kobylinski, who accompanied him on the trip to Senegal and also got sick, is “patient 2.” Foy’s wife, Joy Chilson Foy, a nurse at the Poudre Valley Hospital in Fort Collins, is “patient 3″; she is also a co-author of the paper.

Well, at least she got authorship. Next time, Brian, just get her a t-shirt.

Oxitec: Biotech Geniuses, PR Morons

British biotech company Oxitec is
at it again
:

Some 6000 transgenic mosquitoes developed to help fight dengue were released in Malaysia on 21 December, according to a statement issued by the country’s Institute for Medical Research (IMR) in Kuala Lumpur yesterday. Just like the first releases ever of the mosquitoes, on the Caribbean island of Grand Cayman in 2009 and 2010, the news came as a surprise both to opponents of the insects and to scientists who support them.

As I said in a previous post, I’d classify myself among “scientists who support them,” so I’m chagrined to see that Oxitec still hasn’t figured out the most basic aspects of public relations. Someone needs to tell these guys that there is such a thing as bad publicity, especially when it comes to releasing genetically modified organisms into the wild. Indeed, the Malaysian experiment has given the company another black eye:

[Medical entomologist Bart] Knols worries that surprises such as the releases in Grand Cayman and Malaysia may erode public trust and provide anti-GM groups with ammunition. The two Malaysian groups, for instance, issued a statement yesterday saying they were “shocked … we condemn the apparently secretive manner in which the trials have been conducted.” Helen Wallace of the advocacy group GeneWatch UK says the lack of communication does little to instill confidence in Oxitec.

Oxitec executives respond that they got the necessary permits, so they weren’t doing anything illegal. That’s hardly the point. When you’re blazing a brand-new technological trail, and you know full well that vocal opponents of the new technology are trying to stop you, the only appropriate response is a large-scale public relations campaign. Open the doors to your labs. Call local radio and TV stations and offer to do interviews. Take out an ad in the paper. Run a blog and talk about the schedule for your activities: what you’re doing, where, and why. Be specific, and be impossible to ignore.

It doesn’t matter if your opponents are irrational, uninformed, or driven by their own hidden agendas – all distinct possibilities in this case. If the technology’s foes can credibly assert that you’re doing secret experiments on the public, you lose.

Please, Oxitec, get your PR game together.

Genetically Modified Mosquitoes: Available Now, Apparently

Count me among those surprised by this:

About a year ago, genetically modified (GM) mosquitoes were released into the wild—and they have been flying under the world’s radar screen until last week. On 11 November, British company Oxitec announced that it carried out the world’s first small outdoor trial with transgenic Aedes aegypti mosquitoes in the Caribbean island of Grand Cayman in the fall of 2009, followed by a larger study there last summer.

The trials were designed to test whether such designer mosquitoes could be successfully used to fight wild mosquitoes that transmit diseases like dengue fever. The announcement, made at a press briefing in London, has taken aback opponents of GM mosquitoes and surprised many researchers in the field of genetic control of insect vectors.

Some are questioning why the company stayed mum for so long, calling it a strategic mistake that provides critics of genetic modification with fresh ammunition. “I don’t think they did themselves a favor,” says Bart Knols, a medical entomologist at the University of Amsterdam. “This could well trigger a backlash.”

Knols is absolutely right. The company claims it publicized the trial among island residents (but see the comments after the Science piece for a different take on that). Even if they did have a good local information campaign, they clearly failed to tell the wider world about an experiment that they should have known would be highly controversial. I personally think the benefits of their strategy far outweigh the risks, but doing something like this without a full-blown global PR campaign ahead of time is just asking for trouble.

You’re Grounded, Girl

In a new twist on the elegant sterile insect technique, researchers have now made a strain of Aedes aegypti mosquitoes where the females can’t fly. As the accompanying press release explains:

UCI researchers and colleagues from Oxitec Ltd. and the University of Oxford created the new breed. Flightless females are expected to die quickly in the wild, curtailing the number of mosquitoes and reducing – or even eliminating – dengue transmission. Males of the strain can fly but do not bite or convey disease.

When genetically altered male mosquitoes mate with wild females and pass on their genes, females of the next generation are unable to fly. Scientists estimate that if released, the new breed could sustainably suppress the native mosquito population in six to nine months. The approach offers a safe, efficient alternative to harmful insecticides.

Mosquito on a mirror. Image by Schristia.

Mosquito on a mirror. Image by Schristia.

Because the flightless phenotype only affects females, and the males remain fertile, the selective pressure against it should be pretty mild. These bugs should also be a lot easier to breed than strains with inducible sterility; as long as they’re in captivity getting free blood meals and protection from predators, the females should be able to mate and reproduce just fine.

Aedes aegypti is a major vector for Dengue fever, a nasty virus which infects upwards of 50 million people a year, so if this strategy works in the field, it could be a huge boon to public health. It could be even bigger news if they do the same thing with Anopheles, which transmits the ninth leading cause of death worldwide.

The original paper is open access, for those who want the details.

Sterile Mosquitoes: The Next Big Antimalarial?

Catching up on some old news, I noticed that the November issue of the Malaria Journal has a supplement dedicated to the most elegant insecticide ever developed: the sterile insect technique (SIT). As the accompanying press release explains:

SIT involves the generation of ‘sterile’ male mosquitoes, which are incapable of producing offspring despite being sexually active. Because female mosquitoes only mate once during their lifetimes, a single mating with a sterile male can ensure that she will never breed. This leads to an increasing reduction in the population over time, in contrast to insecticides, which kill a certain fraction of the insect population. The supplement features articles reviewing the history of the technique; ethical, legal and social concerns that might arise from it; and detailed reviews of all of the elements required for a successful SIT programme.

The approach was originally developed by Edward Knipling and his colleagues in the 1950s, who used it successfully to eradicate a devastating cattle pest called Cochliomyia hominivorax, or the screwworm fly. It’s been somewhat harder to use against other pests, though, including mosquitoes. To find out why, and to see the state of the science in this nonchemical pest control technique, check out the supplement – it’s open-access.

Foreclosed Swimming Pools Attract Bottom-Feeders

Awhile back, I commented on the finding that abandoned swimming pools at foreclosed houses are producing a boom in mosquito-borne infections. Now, it seems, some Floridians have found a way to deal with at least one aspect of the abandoned pool problem:

Debra Mitchell, a code enforcement officer in Wellington, said the town is using catfish to clean pools in homes foreclosed on amid the devastated housing market. Officials were previously spending nearly $7,000 a month of taxpayer funds on chemicals to keep the stagnant pools sanitary.

“Some of us got clever and decided to try the fish-eating…er algae eating fish,” Mitchell told NBC affiliate WPTV-5.

At a typical home, the town drops 15 algae-eating fish in the pool to keep the water clean. In addition to being a potential health hazard, Mitchell believes that cleaner more sanitary pools will make the houses more attractive to buyers, as will the lower fees for upkeep.

The catfish aren’t likely to fix the mosquito problem, but if someone can encourage the town to add a few Gambusia to the mix, that would probably help.

As If Foreclosure Weren’t Bad Enough

In the summer of 2007, the incidence of West Nile virus cases in Bakersfield, CA shot up 276%. Simultaneously, the rate of home foreclosures in the area went up 300%. The two numbers are very similar, but obviously that’s just a coincidence – viruses don’t track real estate trends. Or do they?

Reporting in the November issue of Emerging Infectious Diseases, a team of researchers reveals a surprising consequence of the mushrooming foreclosure crisis:

Adjustable rate mortgages and the downturn in the California housing market caused a 300% increase in notices of delinquency in Bakersfield, Kern County. This led to large numbers of neglected swimming pools, which were associated with a 276% increase in the number of human West Nile virus cases during the summer of 2007.

The abandoned pools, which are clearly identifiable in aerial photos because they’re green with algae instead of light blue, become ideal mosquito breeding ponds. Pools are extremely popular backyard accessories in that part of the country, so the widespread foreclosures boosted the local mosquito population dramatically, with a corresponding increase in WNV infections. I’d predict that other pool-friendly areas with foreclosure epidemics, such as South Florida, will see similar vector increases.

By the way, I learned about this fascinating finding on This Week in Virology, a podcast my former thesis advisor just launched. Check it out.