What are Other Determinants of Susceptibility?

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Do curso por The Pennsylvania State University

Epidemias - A Dinâmica das Doenças Infecciosas

605 classificações

The Pennsylvania State University

Epidemias - A Dinâmica das Doenças Infecciosas

605 classificações

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.

Marilyn Roosinck and What’s Different about Plant Epidemiology?8:19

Can Plants be Vectors of Disease?4:33

What are Other Determinants of Susceptibility?5:56

Can Pathogens Change Host Function?5:57

Immune System Conflict6:08

Conheça os instrutores

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 in, in this week's lectures we talked about the hosts and we talked about,

quite a few mechanisms of susceptibility in the host and, in particular we covered,

genetic sources of susceptibility the microbiome, nutrition among other things.

And so one of the questions that was posed was is that a comprehensive list?

Are there other important determinants of susceptibility that, that maybe we

haven't, covered entirely in the course, or that are novel areas of research?

So, [CROSSTALK] [LAUGH] exactly.

So, well one thing that I'm not sure that we covered very explicitly in

the lectures last week, were, or this current week, were co-infections.

There was some discussion about the microbiome as this whole ecology

of organisms that live within you.

But, particularly, pre-existing pathogenic infection, infections with pathogenic

organisms, can very much affect your susceptibility to invading infections.

And, in fact, we're going to have, some videos coming up in the coming weeks,

both by some case study videos by Eric Cardhell here at Penn State and

Isabella Covendori are going to tell some stories about the impact of co-infections.

>> Hm. >> On susceptibility to both,

bact, bacterial and viral and infections, right?

>> I would add that apathogenic infections,.

>> can also, as Marilyn pointed out, over 90% of our infections are apathogenic and

they are certainly modulating our response to the, the pathogens.

And so, don't, don't forget the apathogenic infections here.

And I get to tell this story because I haven't told one yet.

>> [LAUGH].

>> You know it's interesting, we have been talking a bit about these

unusual relationships between, between or among different microbes.

And one of the coolest ones I think,

are course the retroviruses, those are the viruses that I work on.

>> [LAUGH]. >> But the, most of,

ten percent of our genome is, is made up of these viral sequences.

And, one, one way that these can, increase in frequency,

at some point they have to be acquired, is because, you know,

there's, there's an outbreak of a retrovirus infection going on and

by chance one of them is viruses, infects the neighbor's sperm and

now all prodigy will then carry the virus, it's transmitted vertically.

>> Right. >> And it has the virus in all cells.

But having an infectious, formally infectious,

virus in your genome is one way to protect yourself from the infectious viruses.

>> Mm-hm. >> So you know that's

a wonderful symbiotic.

>> And there's some very good examples this hasn't occurred just once but

independently in sheep and mice,

there's multiple, examples of that, that type of relationship occurring.

>> So that behavior can be [INAUDIBLE] susceptibility.

It can influence exposure, but,uh, even just scratching yourself is a form

of sort of an immune response to removing fleas and ticks and things like that.

That's of course, your mucus and the way you produce your mucus, particularly for

[INAUDIBLE] nematodes, is a really important response and,

in helping to flush out parasites and tapeworms and things like that.

>> I, I think in our modern era, with modern medicine,

you kind of focus on what in-the-body defenses, either from our own cells,.

>> or that of the immune system, or Trudy uses some vaccine, but of course,

you're right, behavior is a really crucial element there, and

it's a first priority of defense.

And there hasn't been that much, much study, but, but,

in some cases where we have seen studies, for

example the Howler monkeys, where they're trying to remove ectoparasites, what they

found there was as much as 24, 24 percent, all the energy that that monkey uses.

>> What? >> In a single day goes into defending-

>> Against this.

We see baboons, they'll use, plants, certain plants from the rainforest to

get rid of schistosomiasis and they have that adapted immune system, we.

You see this in ants and caterpillars.

So a lot of behavior where it's ingesting a product that kills the parasite or

just simply moving away or, or, or grooming these are all very useful.

>> Mm.

So I've got to play my card and tell a story now.

But, so it, I was doing a lot of work on grass and

ticks, the ticks bite the grass and give them an infection.

>> And it didn't quite add up because they didn't have many ticks and

yet they were all getting infected at a high rate.

So I spent some time in the field just watching them and,

other chicks were removing the ticks as they got on their siblings.

So there was a huge amount of allopreening of their each siblings and

the mother taking the ticks off when they got on.

And that individual then swallowed the ticks,

and when they swallowed the ticks they became infected with the virus.

So, it isn't that, it's the consumption of the factor that's causing infection,

not the biting of the factor, is it?

>> No.

>> But of course once it's been eaten it can't pass the virus on, it's dead.

>> So, I would say also changes in the host behavior, ecology [COUGH] might, for

example, polio in humans, right?

Everybody got polio as an,

as a newborn infant or a very young infant until we started cleaning up water, and

then people didn't get polio until they were much older.

So when you get it as a really young baby, you get lifelong immunity and you, and

you never get any disease.

But, when you get it when you're older, you can get poliomyelitis.

Which is a, an obviously devastating disease.

So, changes in host ecology really can change the susceptibility too.

>> Interesting.

>> And probably a timely example right now is with Ebola.

And, and the role of, you know,

behavioral, cultural practices in that case.

>> Yes.

>> In the.

>> And really how difficult it is for people to change their cultural practices.

That's their very deepest fear right now.

>> But, again, these are, these are practices that largely affect exposure

explicitly rather than susceptibility.

>> Absolutely.

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