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

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Из курса от партнера The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

614 оценок

The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

614 оценок

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

All right, hi and welcome back to the seventh week of the epidemics MOOC and

our AUI session for this week.

This week we've been focusing explicitly on emergence and evolutionary pathways,

but we also have been talking about mechanisms of control following on some of

the discussion from last week.

And this week the guest we have along, along is Matt Thomas who works in

the Entomology department here at Penn State, who has, a lot of experience,

particularly in vector borne diseases and, and control of vectors.

>> Yeah, so, [COUGH] so my interest is in,

insect pests and historically that was a lot of work in agriculture.

Basically trying to understand what makes a pest a pest.

Not all insects are pests.

But then some become pests.

And then what are we going to do about it?

How are we going to control them?

And then in the last few years, that the,

the pests have become increasingly interested in our, our mosquitos.

And particularly those that transmit diseases like malaria and dengue.

So, the work in our lab tries to understand, again, why,

why certain pests are more problematic than others.

Why is there is more malaria in one place than another place?

How might that change in the future?

And, what can we do about it?

What are the new tools that we might be able to develop to try and

combat these diseases?

>> So, where last week and this week converge is in the, how control for pests.

Whether they're vectors or insect pests or

pathogens themselves, can respond and cause selective pressure, right?

We've talked quite a bit about evolution of resistance and,

and and evolut, evolution variance in this week's lectures.

So I wanted to pose.

What, what, what can we learn about, the experience with,

ev, with resistance evolution in vectors or in insects in general and

how well does that translate to, how we might develop controls for, resistance

evolution or, or management of resistance evolution in pathogens themselves.

>> So I think with, [COUGH] so I think with vectors if you look at the history

of, of insect control, and if you look at agriculture in the first place and

how that's now taken a, sort of extend those lessons into, into public health.

And one thing we know is that if you try and

hit something hard with some lethal agent to by a side.

And, and you use a sort of simple magical approach then you're going to

get evolution as a response.

And if you look at, you know there was talk back in the 1940s and

50's with the advent of modern chemistry.

There was discussion around pestry agriculture.

This was you know, people had been living with pests for years.

Intensifying agriculture leading to new pest insects.

And the advent of DDT and organiphospites organichlorate,

created this prospect that we could actually get rid of pests.

>> Mm-hm.

>> Mm. >> And, you know, ten or

15 years of trying, increasing ratcheting up more insecticides, more insecticides.

Basically created some sort of insecticide treadmill,

left everybody to realize actually we can't do that.

Because what we're going to see is we'll apply insecticide,

we'll add back resistance.

We'll apply more insecticides.

We'll get more resistance, either stronger resistance or

resistance to another compound.

And that basically led to, it was one of the main drivers.

That and concerned around environmental contamination.

So there were two drivers.

The evolution resistance, concern around environmental contamination and the likes

of Rachel Carson Silent Spring led to the development of integrated pest management.

The idea to use insecticides judiciously still a key part of

the toolbox but only one tool.

And to use a suite of other tools with which you could try and combat diseases.

And rather than focus on eradication, it went away it,

it, it was a sort of transition from pest eradication to pest management.

How can we manage these things at levels we can live with?

>> Mm-hm. And so- >> So it seems there is also an important difference there, right.

In an agricultural setting, there's an economic trade off and

we can live with a certain amount of loss.

But in public health, we don't want to.

Many of us don't want to live with any disease.

>> Yet so that is one of the differences.

I mean, there are.

There are some clear parallels in how the use of of,

of sort of interventions, particularly insecticides based interventions.

And those are still the front line technologies against mosquito vectors like

Malaria vectors and Dhengi vectors.

Still reliant on, in fact the very same products.

A lot of the products are being taken from agriculture,

there's no new public health insecticides.

They all come from agriculture.

They're only four classes of insecticides approved for use in public health.

They all come from agriculture, and there hasn't been a new one,

for the last 20 years, 20, 30 years.

So it's still very much based on using insecticides high doses.

And trying to eliminate or eradicate the disease.

And I think it creates an interesting tension as to whether,

in fact, we should be looking at management.

>> Mm-hm.

>> And how we manage the issues, public health and

perhaps ethical issues of maintaining a disease at a low level.

Reducing disease burden, reducing mortality and morbidity.

But maintaining that potentially at a low sustainable level.

Rather than shooting for some goal of eradication, and

what comes with eradication may be increased cost, increase challenges.

Diversion of funds away from something that we know that works and

can keep things at a low level, towards trying to go for

something which perhaps, is, is more aspirational then realistic.

I mean, it's very hard, I'm not saying that we shouldn't go for

malaria eradication, clearly that's a good thing, who would argue against that?

And we have tools, we've shown that we can do that in various places.

There's no malaria in the US, there used to be.

There's no malaria in Italy, there used to be.

There's no malaria in Australia, there used to be.

So we can do eradication.

Trying to do that in settings like parts of,

of, of, of tropical Africa with much more challenging infrastructure.

Is really where is really what's makes it very, very difficult.

And I think that, I think some of the difficulties in,

I think there is a tension between do we shoot for eradication,

do we have the tools available to do that, how much do we invest in creating those

tools such that we can achieve that goal perhaps 30 years down the line,

rather than taking it down to a minimum level now.

>> And one of the very interesting concepts that's come out of integrated,

integrated pest management is the use of management strategies that will

prolong the useful life of existing technologies.

>> Yup.

>> Right? >> So

that we can prevent things from rebounding in the future as a consequence of

resistance evolution, or buy us some time, perhaps to develop something cl,

a slightly more silver bullet, right?

Or something with a little, at least a little bit more sheen on it.

>> If we gave you a limitless budget, well, it can't be limitless, can it?

That's not possible.

If we gave you a huge budget and asked you to eradicate malaria from Africa.

Could you do it?

>> On a timeframe of what?

>> Ten years?

>> Ten years.

That would need to be quite a bit budget.

>> So here's the season.

>> So, yeah, yeah, no, I think we could eradicate from.

With the current tools, I think we still might need new tools.

Mm-hm.

>> But I think there are areas where we could absolutely replicate it, and

there are areas where we could drive it down to very very low levels.

One of the challenges in eradication is,

if you do it locally, and you have this Island where you've eradicated it,

and you're surrounded by this intense area where there's still lots of malaria.

You constantly got this spill over.

This in fill and it's very, very difficult.

>> And that's the mosquitos, that's not people moving in-

>> No it would be both.

>> Both. >> People particularly.

But if you don't, if you, if you leave, if you don't.

I mean you can get rid of the disease but

if you still have a conducive environment, you still have the vectors in place.

And that's what we have in the US, right?

>> Mm hm. >> So we've got no malaria.

But there are still vectors here.

People come into the US.

We have about 1,000 cases or

so, something like that, in the US each year of imported malaria.

Very, very occasionally we get the small, stuttering chains of.

Somebody brings it into an airport, and

they get bitten, and they get bitten, and it carries on.

But then, it peters out because we have, basically, So, try to do that.

You could create islands like that and

you could shrink the malaria map, I think, in parts of Africa.

It creates a tension between, where's the biggest disease burden.

And should you be better of reducing disease burden by 90%

where there's a lot of disease or using those resources to try and shrink the map

where there's actually rather less disease but your focus is on eradication.

And that actually, that's a tension.

Andrew and I have a project in India,

and that was real tension, actually, with, for the.

Naturally, I see the malarial research.

Eh, what's their position on eradication?

Well, it's very difficult, because you've got areas where we can reduce the burden

of disease, or we can focus on eradication.

But we don't actually have resources to try and do both.

>> Interesting.

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