Pest control

Cas-9-trated

Genetic engineering may help control disease-carrying mosquitoes



 

May 26th 2021 | words 684

 

 

 

 

EVERY YEAR, hundreds of millions of people catch mosquito-borne diseases like malaria and dengue fever. Hundreds of thousands die. Drug treatments are imperfect. And, despite decades of effort, vaccines have, for many of these diseases, proved tricky to develop.

 

Better, then, to stop those infections happening in the first place, by exterminatingor at least suppressingthe mosquitoes that carry the diseases. In a paper just published in the Proceedings of the National Academy of Sciences, a team of researchers led by Craig Montell, of the University of California, Santa Barbara, describe how CRISPR-Cas9, a new and powerful genetic-engineering process, could help to do just that.

 

Dr Montell and his colleagues used CRISPR to boost an existing control method called the sterile insect technique (SIT). This involves releasing lots of sterilised males into the wild. Females that mate with these males produce no offspring. Repeated releases can reduce populations dramatically. SIT has been used in North America to eliminate screwworm flies, an agricultural pest, and to suppress several species of crop-munching fruit flies.

 

It has been tried on mosquitoes, too, but with less success. One reason seems to be side-effects of the procedure. To sterilise them, males are zapped with radiation or exposed to toxic chemicals. This works, but it damages them in other ways, too. The result can be sickly individuals that struggle to compete in the mating game with their wild counterparts.

 

Dr Montell and his colleagues hoped that CRISPR might offer an alternative. Their first step was to look for genes which, when disabled, would render male mosquitoes infertile. They began their hunt in fruit flies, a stalwart of genetic research. They focused on a gene that, when removed, made male fruit flies sterileand which was present in a similar form in their target mosquito species, Aedes aegypti, which is the vector of, among other illnesses, yellow fever, dengue and Zika virus. Disabling the equivalent gene in male Aedes likewise left them infertile.

 

Crucially, the genetic tweak involved did not appear to hinder the modified mosquitoes in any other way. On every measure of healthiness they performed as well as their wild counterparts. And even though they were firing blanks, they were still able to mate with females in the laboratory.

 

Although the details are not fully understood, says Dr Montell, once female mosquitoes have mated a few times, they become less receptive to doing so again. Mating with an infertile male is therefore not only fruitless in itself, but should also leave a female less interested in unmodified males in future. Sure enough, a series of experiments conducted in cages suggested that releasing between five and six genetically modified males for each wild male was enough to cut the number of reproducing females by half. Upping that ratio to 15:1 dropped it by 80%.

 

There is more work to do before field trials, says Dr Montell. But having established the principle, he is excited to see where the work might lead. That the target gene is found in both fruit flies and Aedes suggests it is likely to exist in other disease-carrying mosquitoes, too. And that the engineered males leave no offspring means fewer worries about any unintended consequences which might arise from releasing millions of genetically modified organisms into the environment.

 

More speculatively, the team is pondering whether it might be possible to create males which can outplay their un-engineered cousins at the mating game, despite being infertile. Improving on millions of years of evolution would usually be hard. Even if researchers could find an alteration that improved a males attractiveness, it would probably reduce the animals overall fitness. Such a genetic tweak would ordinarily be winnowed out by natural selection over subsequent generations. But because each generation of males is created anew in a laboratory, says Dr Montell, there is no long run to worry about. If the team can find the right mutation, such genetically engineered hommes fatales could give mosquito-suppression efforts an even bigger boost. 

 



VOCABULARY



dengue

dengue / degi / (also 'dengue fever,'breakbone fever) 

noun [U]

a disease caused by a virus carried by mosquitoes , that is found in tropical areas and causes fever and severe pain in the joints

(,) 

 

exterminate

exterminate / ikstmineit; NAmE -strm- / 

verb [VN] to kill all the members of a group of people or animals

SYN wipe out 

 

sterile

sterile / sterail; NAmE sterl / 

adj. 

1. (of humans or animals ) not able to produce children or young animals

SYN infertile

2. completely clean and free from bacteria

sterile bandages   

 

sterile water   

 

3. (of a discussion, an argument, etc. ) not producing any useful result

SYN fruitless 

a sterile debate   

 

4. lacking individual personality, imagination or new ideas

 

The room felt cold and sterile.   

 

He felt creatively and emotionally sterile.  

 

5. (of land ) not good enough to produce crops

sterility / strilti / noun [U] : 

The disease can cause sterility in men and women.   

 

the meaningless sterility of statistics   

 

She contemplated the sterility of her existence.   

 

 

zap

zap / zp / 

verb (-pp-) (informal) 1. [VN] ~ sb / sth (with sth) to destroy, kill or hit sb / sth suddenly and with force

(),,

The monster got zapped by a flying saucer (= in a computer game).  

 

It's vital to zap stress fast.   

 

He jumped like a man who'd been zapped with 1 000 volts.   

1 000

2. [V +adv. / prep.] to do sth very fast

I'm zapping through (= reading very fast) some modern novels at the moment.  

3. [V , VN] to use the remote control to change television channels quickly

()

4. [+adv. / prep.] to move, or make sb / sth move, very fast in the direction mentioned

()

SYN zip :

 

stalwart

stalwart / stlwt; NAmE -wrt / 

noun 

~ (of sth) a loyal supporter who does a lot of work for an organization, especially a political party

(),

 

vector

vector / vekt(r) /

noun 1. (mathematics ) a quantity that has both size and direction

Acceleration and velocity are both vectors.   

-- compare scalar 

2. (biology ) an insect, etc. that carries a particular disease from six living thing to another

(),

3. (technical ) a course taken by an aircraft

() 

 

Zika virus

a flavivirus (species Zika virus of the genus Flavivirus) typically transmitted by aedes mosquitoes (especially Aedes aegypti and A. albopictus) that causes a usually mild illness marked chiefly by fever, joint pain, rash, and conjunctivitis and that has been associated with an increased incidence of microcephaly in infants born to pregnant women infected with the virus

 

receptive

receptive / riseptiv / 

adj. 

~ (to sth) willing to listen to or to accept new ideas or suggestions

(),

SYN responsive 

She was always receptive to new ideas.   

 

He gave an impressive speech to a receptive audience.   

,


winnow

winnow / winu; NAmE -nou / 

verb [VN] to blow air through grain in order to remove its outer covering (called the chaff )

,,()

PHR V

 winnow sb / sth 'out (of sth) 

(formal) to remove people or things from a group so that only the best ones are left

SYN sift out 

 

mutation

mutation / mjutein / 

noun 

1. [U, C] (biology ) a process in which the genetic material of a person, a plant or an animal changes in structure when it is passed on to children, etc., causing different physical characteristics to develop; a change of this kind

(),

cells affected by mutation   

 

genetic mutations   

 

2. [U, C] a change in the form or structure of sth

(),: (linguistics )  

vowel mutation   

 

 





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Economist | Pest control


 

Pest control

Cas-9-trated

Genetic engineering may help control disease-carrying mosquitoes



 

May 26th 2021 | words 684

 

 

 

 

EVERY YEAR, hundreds of millions of people catch mosquito-borne diseases like malaria and dengue fever. Hundreds of thousands die. Drug treatments are imperfect. And, despite decades of effort, vaccines have, for many of these diseases, proved tricky to develop.

 

Better, then, to stop those infections happening in the first place, by exterminatingor at least suppressingthe mosquitoes that carry the diseases. In a paper just published in the Proceedings of the National Academy of Sciences, a team of researchers led by Craig Montell, of the University of California, Santa Barbara, describe how CRISPR-Cas9, a new and powerful genetic-engineering process, could help to do just that.

 

Dr Montell and his colleagues used CRISPR to boost an existing control method called the sterile insect technique (SIT). This involves releasing lots of sterilised males into the wild. Females that mate with these males produce no offspring. Repeated releases can reduce populations dramatically. SIT has been used in North America to eliminate screwworm flies, an agricultural pest, and to suppress several species of crop-munching fruit flies.

 

It has been tried on mosquitoes, too, but with less success. One reason seems to be side-effects of the procedure. To sterilise them, males are zapped with radiation or exposed to toxic chemicals. This works, but it damages them in other ways, too. The result can be sickly individuals that struggle to compete in the mating game with their wild counterparts.

 

Dr Montell and his colleagues hoped that CRISPR might offer an alternative. Their first step was to look for genes which, when disabled, would render male mosquitoes infertile. They began their hunt in fruit flies, a stalwart of genetic research. They focused on a gene that, when removed, made male fruit flies sterileand which was present in a similar form in their target mosquito species, Aedes aegypti, which is the vector of, among other illnesses, yellow fever, dengue and Zika virus. Disabling the equivalent gene in male Aedes likewise left them infertile.

 

Crucially, the genetic tweak involved did not appear to hinder the modified mosquitoes in any other way. On every measure of healthiness they performed as well as their wild counterparts. And even though they were firing blanks, they were still able to mate with females in the laboratory.

 

Although the details are not fully understood, says Dr Montell, once female mosquitoes have mated a few times, they become less receptive to doing so again. Mating with an infertile male is therefore not only fruitless in itself, but should also leave a female less interested in unmodified males in future. Sure enough, a series of experiments conducted in cages suggested that releasing between five and six genetically modified males for each wild male was enough to cut the number of reproducing females by half. Upping that ratio to 15:1 dropped it by 80%.

 

There is more work to do before field trials, says Dr Montell. But having established the principle, he is excited to see where the work might lead. That the target gene is found in both fruit flies and Aedes suggests it is likely to exist in other disease-carrying mosquitoes, too. And that the engineered males leave no offspring means fewer worries about any unintended consequences which might arise from releasing millions of genetically modified organisms into the environment.

 

More speculatively, the team is pondering whether it might be possible to create males which can outplay their un-engineered cousins at the mating game, despite being infertile. Improving on millions of years of evolution would usually be hard. Even if researchers could find an alteration that improved a males attractiveness, it would probably reduce the animals overall fitness. Such a genetic tweak would ordinarily be winnowed out by natural selection over subsequent generations. But because each generation of males is created anew in a laboratory, says Dr Montell, there is no long run to worry about. If the team can find the right mutation, such genetically engineered hommes fatales could give mosquito-suppression efforts an even bigger boost. 

 



VOCABULARY



dengue

dengue / degi / (also 'dengue fever,'breakbone fever) 

noun [U]

a disease caused by a virus carried by mosquitoes , that is found in tropical areas and causes fever and severe pain in the joints

(,) 

 

exterminate

exterminate / ikstmineit; NAmE -strm- / 

verb [VN] to kill all the members of a group of people or animals

SYN wipe out 

 

sterile

sterile / sterail; NAmE sterl / 

adj. 

1. (of humans or animals ) not able to produce children or young animals

SYN infertile

2. completely clean and free from bacteria

sterile bandages   

 

sterile water   

 

3. (of a discussion, an argument, etc. ) not producing any useful result

SYN fruitless 

a sterile debate   

 

4. lacking individual personality, imagination or new ideas

 

The room felt cold and sterile.   

 

He felt creatively and emotionally sterile.  

 

5. (of land ) not good enough to produce crops

sterility / strilti / noun [U] : 

The disease can cause sterility in men and women.   

 

the meaningless sterility of statistics   

 

She contemplated the sterility of her existence.   

 

 

zap

zap / zp / 

verb (-pp-) (informal) 1. [VN] ~ sb / sth (with sth) to destroy, kill or hit sb / sth suddenly and with force

(),,

The monster got zapped by a flying saucer (= in a computer game).  

 

It's vital to zap stress fast.   

 

He jumped like a man who'd been zapped with 1 000 volts.   

1 000

2. [V +adv. / prep.] to do sth very fast

I'm zapping through (= reading very fast) some modern novels at the moment.  

3. [V , VN] to use the remote control to change television channels quickly

()

4. [+adv. / prep.] to move, or make sb / sth move, very fast in the direction mentioned

()

SYN zip :

 

stalwart

stalwart / stlwt; NAmE -wrt / 

noun 

~ (of sth) a loyal supporter who does a lot of work for an organization, especially a political party

(),

 

vector

vector / vekt(r) /

noun 1. (mathematics ) a quantity that has both size and direction

Acceleration and velocity are both vectors.   

-- compare scalar 

2. (biology ) an insect, etc. that carries a particular disease from six living thing to another

(),

3. (technical ) a course taken by an aircraft

() 

 

Zika virus

a flavivirus (species Zika virus of the genus Flavivirus) typically transmitted by aedes mosquitoes (especially Aedes aegypti and A. albopictus) that causes a usually mild illness marked chiefly by fever, joint pain, rash, and conjunctivitis and that has been associated with an increased incidence of microcephaly in infants born to pregnant women infected with the virus

 

receptive

receptive / riseptiv / 

adj. 

~ (to sth) willing to listen to or to accept new ideas or suggestions

(),

SYN responsive 

She was always receptive to new ideas.   

 

He gave an impressive speech to a receptive audience.   

,


winnow

winnow / winu; NAmE -nou / 

verb [VN] to blow air through grain in order to remove its outer covering (called the chaff )

,,()

PHR V

 winnow sb / sth 'out (of sth) 

(formal) to remove people or things from a group so that only the best ones are left

SYN sift out 

 

mutation

mutation / mjutein / 

noun 

1. [U, C] (biology ) a process in which the genetic material of a person, a plant or an animal changes in structure when it is passed on to children, etc., causing different physical characteristics to develop; a change of this kind

(),

cells affected by mutation   

 

genetic mutations   

 

2. [U, C] a change in the form or structure of sth

(),: (linguistics )  

vowel mutation   

 

 





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