Genetic engineering of vectors? pt.1

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Из курса от партнера The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

626 оценки

The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

626 оценки

Not so long ago, it was almost guaranteed that you would die of an infectious disease. In fact, had you been born just 150 years ago, your chances of dying of an infectious disease before you've reached the tender age of 5 would have been extremely high. Since then, science has come a long way in understanding infectious diseases - what they are, how they spread, and how they can be prevented. But diseases like HIV/AIDS, Malaria, Tuberculosis, or the flu are still major killers worldwide, and novel emerging diseases are a constant threat to public health. In addition, the bugs are evolving. Antibiotics, our most potent weapon against bacterial infections, are losing their power because the bacteria are becoming resistant. In this course, we'll explore the major themes of infectious diseases dynamics. After we’ve covered the basics, we'll be looking at the dynamics of the flu, and why we're worried about flu pandemics. We'll be looking at the dynamics of childhood diseases such as measles and whooping cough, which were once considered almost eradicated, but are now making a comeback. We'll explore Malaria, and use it as a case study of the evolution of drug resistance. We'll even be looking at social networks - how diseases can spread from you to your friends to your friends' friends, and so on. And of course we’ll be talking about vaccination too. We’ll also be talking about how mobile phones, social media and crowdsourcing are revolutionizing disease surveillance, giving rise to a new field of digital epidemiology. And yes, we will be talking about Zombies - not human zombies, but zombie ants whose brains are hijacked by an infectious fungus. We're looking forward to having you join us for an exciting course!

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Ask Us Anything Videos

The videos accessible in this module are responses to questions that have been posed in previous sessions of this course. We invite you to look around here as an additional resource to answer questions you might have yourself or explore topics that pique your interest.

What can we do to minimize selection for resistance in vectors?8:43

Genetic engineering of vectors? pt.17:30

Genetic engineering of vectors? pt.27:21

What is the role of climate change in disease emergence?8:32

What can we learn from antibiotic and vaccine use in agriculture? 7:19

Познакомьтесь с преподавателями

Dr. Ottar N. Bjornstad
Professor of Entomology and Biology
Department of Biology
Dr. Rachel A. Smith
Associate Professor
Department of Communication Arts & Sciences and Human Development & Family Studies
Dr. Mary L. Poss
Professor of Biology
Department of Biology
Dr. David P. Hughes
Assistant Professor of Entomology and Biology
Department of Biology
Dr. Peter Hudson
Willaman Professor of Biology
Department of Biology
Dr. Matthew Ferrari
Assistant Professor of Biology
Department of Biology
Dr. Andrew Read
Alumni Professor in the Biological Sciences, and Professor of Entomology
Center for Infectious Disease Dynamics
Dr. Marcel Salathé
Assistant Professor of Biology
Department of Biology

So, one of the questions that's come up in the in the discussion forum,

particularly about vector borne diseases are, are strategies for

the genetic engineering of vectors.

In fact, this idea that we can change the pop, actually actively select for

changes in the vector population.

Either through the introduction of new genetic variance, or

through changes in selective pressures, to try select vectors that are, are either

just simply less effective at transmitting diseases or perhaps completely incapable.

And so these are strategies that have been applied in various different types of

insect pest management in the past and there are some trials going on currently

in in South America right now, looking towards prevention of both Dengue and

the prevention of the spread of Chikungunya.

Both are, are diseases that have come up quite a,

quite a bit in the discussion forums,

because we have a lot of learners who are actually experiencing those outbreaks-

>> Chikungunya also just got into Southern U.S. also, isn't that right?

Doesn't that mean, is there?

>> Yes there, so again, it's one, there are, there are, so

we have the vector now, where, there are two key vectors.

And often, sorry it is jibtie it is over pectus,

a is over pectus is a new invading mosquito, and so Chikungunya has sort of,

is probing the U.S. constantly, there have been a couple of cases I think of,

sort of on top, we'll talk the next transmission in Florida now.

>> Mm-hm.

>> So, so, well, one of the questions, these just to, to, to bring this to the,

to the, to the group who are perhaps more familiar with this,

how do we go about introducing genetic change or making use of

you know, artificial selection in this massive vector population?

How does it, how does this actually should work that these new,

that these new genetically engineered vectors can have an impact?

>> [COUGH] So they're, there are two parts to the technologies.

One is to introduce something with effects of change,

that is making your mosquito less competent to transmit malaria, and

that could be by manipulating its immune responses.

Most mosquito vectors, when they're challenged by the pathogen that they

transmit, still, that still evokes some sort of immune response, so

we might be able to boost that, and create ma,

make mosquitoes less competent, less able to transmit malaria.

Or we could play with a, like history trace of the mosquito themselves,

we could kill them, we could life shorten, we could stop them flying,

we could impact on their ability to search for blood meals or whatever.

>> Or reproduce.

>> Or reproduce.

So, so there are ways of reducing the capacity of the mosquito to transmit.

And the second component of that is, how do you get it to spread?

>> I mean you can create that in the lab, it's perfect.

You can create a perfect refactory strain, and then you want to throw that out

the door, and get that to spread across Africa or spread through Central America.

So you need some sort of drive mechanism.

And there are you can sort of do, in a way you can sort of achieve that in two ways.

One, one you can actually have, a genetic drive mechanism,

something which causes a genes to spread and in Non-Mendelian ways,

something that gives it an advantage.

And there are a range of sort of techniques that can do that, and

the other is actually you sort of do it by brute force, you do it by numbers.

And, if you've got a low background relatively low density vector population,

and you can mass produce millions and

millions of vectors that carry this trait that you're interested in.

Particularly, if it was one that makes that sort of converts to relativity or

something, you can actually mass release millions and millions of these things,

get them to swamp out your resident vector population, and cause local elimination.

So, both of those things have strategies, I think the, the people have looked at

this for a number of years, have been researching this for

a number of years and then there are a range of candidate techniques for

which we can reduce capacity of the vectors to transmit.

>> Mm-hm.

>> Marrying those on the appropriate drive system,

is actually where the challenge is.

The, the the sort of two that have gotten most traction for 80s, and

80s mosquitoes and certainly 80s aegypti for transmitting Dengue and Chikungunya.

There's, one is through Wolbachia, which is a bacteria and

a parasite which has the advantage of it, it, it [COUGH] it basically has

Non-Mendelian drive mechanism built in so, it's able to spread through populations.

There's sort of an interesting twist that most mosquitoes, most, most mosquitoes,

actually most insects carry Wolbachia, but the ones we really really care about,

the, the key vectors like Aedes aegypti and the Anopheles don't have Wolbachia.

So, big part of the research program has been to try and introgress Wolbachia into

these populations, and then allow the Wolbachia to spread.

>> Mm-hm. >> So we haven't actually,

I don't think we haven't talked much about Wolbachia in the in the course so far, and

I, so I don't recognize, particularly it's incredibly interesting, but

I'll look these up.

>> Mm-hm. >> So, I don't know if you, or

Andrew maybe can, can just talk a little bit more about the wonders of Wolbachia.

>> So it spreads, so it spreads through the-

>> What is it to begin with?

>> So it's a, it's a bacterial endosymbiont, most and

it's generally maternally transmitted, so

if you get it into your germ line, and basically it's, you maintain it.

There's some rare horizontal germs between species, and it spreads through a,

it can have a range of sort of consequences for the organism carrying it

which could include life shortening, could include sterility,

could include changing sex even, and it spreads through-

>> But in some cases it actually prevents, mosquitoes from,

even from being susceptible to [COUGH] to the, to some-

>> So that was the interesting thing about the discovery of, the original approach,

in trying to introduce Wolbachia into these mosquitoes which didn't have any,

the idea was that it would carry a cost and

it would shorten the life of the mosquito.

And if the mosquito doesn't live very long, it reduces it's chance of

transmitting the disease, all of these diseases like Dengue and

malaria, have a long incubation period in the mosquitoes.

So, they don't simply act like passing syringes so if they would pick malaria up

from you, it would then take them about two weeks for that mosquito to

incubate and pass like for it could fly on and transmit somebody else.

So, if you could stop mosquitoes living for

two weeks, there would be no more malaria and no more danger,

that's all we need to do, or we need to do.

[LAUGH].

>> [LAUGH].

>> And in fact, most mosquitoes don't live for two weeks, it's only a small tail,

only a small portion of the population which live for that two weeks,

three weeks, three weeks plus, that are responsible for the transmission.

>> Mm-hm.

>> So if you could introduce something which had a fitness cost, that

slightly shortened life, then you would stop mosquitoes transmitting malaria, and

that was the original idea.

And, they found a Wolbachia strain which they have managed to

integrated into the mosquito population, which had this life-shortening effect.

>> Mm-hm.

>> The problem is, that the more life-shortening you are,

the harder it is for the parasite to spread, the more re-

>> Mm-hm. >> The more cost it has,

the more difficult it is to get it integrated within the population.

>> Mm-hm. >> So

there was this tension between life-shortening, and fitness cost, and

actually getting it into something to spread.

And, it was relatively fortuitous that they hit across another strain of

Wolbachia, which didn't have such strong life shortening effects, but

had very big transmission blocking effects.

So if, it turned out that if you were infected simultaneous, if

you were infected with the Wolbachia, you couldn't then become infected with Dengue.

>> Mm-hm.

>> So that's now changed the strategy.

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