3.5. In Defense of Normality

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Из курса от партнера University of Illinois at Urbana-Champaign

Sustainable Food Production Through Livestock Health Management

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University of Illinois at Urbana-Champaign

Sustainable Food Production Through Livestock Health Management

112 оценки

Learn about the impact of infectious disease on sustainable animal-based food production by understanding the science of growth, immunity, and infection and by learning the problem-solving skills needed to advance animal health and food production through optimal management practices. There is a growing global need in agricultural production for a workforce that is capable of integrating knowledge of animal health and production with an understanding of consumer preferences in the context of economic reality, business efficiency, and ethical constraint. However, current evidence suggests that there is a growing shortage of people with the knowledge and problem-solving skills required to match the rapid advances being made in animal health, science, and food production. The results of this shortage are wide-ranging and could lead to challenges in food security and agricultural economic competitiveness in some countries. In this course we will explore the effect of infectious disease on sustainable animal-based food production. The content and learning outcomes of this new course will be designed to be relevant across different food production sectors (i.e., beef, dairy, poultry, and pigs). While the instructors will provide the participants with a strong scientific base for understanding the impact of infectious disease in animal-based food production, the emphasis of the material will be on practical problem-solving and will be directed towards equipping participants with a platform for developing the skills needed to contribute to sustainable food production.

Из урока

Week 3: Animals' Response to Infectious Disease

This week we will introduce the concept of the farm and each production system as an ecosystem in which animals and microbes live in mutualistic relationships, and explain the beneficial impact of ecologically managing the microbes alongside the animals to enhance host defense, animal health, and production efficiency.

3.1. Microbes: Friend or Foe? 10:21

3.2. Promoting Friendly Farm Infections 7:46

3.3. Microbial Colonization in the Newborn World 8:35

3.4. The Farm: It’s a Bug’s World 8:51

3.5. In Defense of Normality 12:11

3.6. The Energetic Cost of Defense 7:37

3.7. When the Defense Cannot Defend 14:22

3.8. The War Within 7:27

3.9. Defending the Airways 7:51

3.10. Defending the Next Generation 8:45

Познакомьтесь с преподавателями

Dr. Jim Lowe, DVM, MS, Dip ABVP (Food Animal)
Associate Professor
Integrated Food Animal Management Systems, College of Veterinary Medicine
Dr. Brian Aldridge, BVSc, MS, PhD, Dip ACVIM (Large Animal), MRCVS
Clinical Professor
Integrated Food Animal Management Systems, College of Veterinary Medicine

[SOUND]

[MUSIC]

So we've spoken so much about infectious disease and

it's impact on production systems, and

as we consider the pathogen's side, the microbe side of infectious

disease would be remiss to not think about the host side.

You see, when we adopt certain management practices, and

we try and reduce disease, a lot of our practices are aimed

at shutting down the pathogen or killing the pathogen.

But in some ways a better way is to

make the hosts themselves more resistant to disease.

So to understand how we do that, we have to know the workings of the immune system.

The immune system is that part of the body,

that body system which interacts directly with microbes.

Whether they be bacteria, viruses, or parasites, endoparasites and

ectoparasites.

Our immune system is what prevents those microbes becoming established and

causing disease.

What I want to do is really give you a big overview and relate a little bit

to what's taking place inside the animal and what kind of signs you might see at

different stages of the immune response or particularly the inflammatory response,

the first response that a host will have against an invader.

Because if you understand that, then you can institute early detection systems

that the immune system, the inflammatory response is in place.

And that animal is in the midst of fighting an invader.

So the first thing the immune system does is recognize danger.

Really a pathogen becoming established or

the presence of a toxic component from a pathogen that enters the host.

For the host to produce any response to it,

it has to recognize that it's dangerous.

On cell surfaces around the body at strategic sites there a specific

receptors on the cell surfaces called pathogen recognition receptors or PRRs.

Those PRRs are designed to recognize specific signals from

the pathogens called PAMPs or pathogen associated molecular patterns.

So as soon as those PAMPs engage the PRRs or those receptors that is the signal for

danger, that then starts a whole series of processes,

in fact a cascade of processes by which the immune system is up regulated

to defend against the organism that danger signal has alerted the immune system to.

And the immune system also responds to other foreign, or

threatening events such as trauma, such as a damage to a cell, and they,

when a cell is damaged, they release certain elements called DAMPs,

and that is another, it's a danger signal which the immune system can recognize.

So the first stage in the immune response, is recognition of a danger signal.

So after that danger signal has been recognized,

the first response of the body is to try and neutralize that danger signal or

the organism that is expressing that danger signal.

So that can occur by a whole set of different mediators.

There can be cells, or

there can be chemicals that are secreted at the site which the pathogen exists.

Some of these are called a proteins, they're called antimicrobial peptides.

So as soon as the danger signal's been recognized, for instance,

in the nasal cavity or at a mucosal surface, that part of the body,

those lining cells will produce an anti-microbial peptide.

A peptide which has the ability to eat and neutralize that agent or even destroy it.

So after recognition of the danger,

the second stage is to try neutralized the danger.

So, the third stage of the inflammatory response is a signalling activity.

So, with most immune responses, most inflammatory responses, those

first two events will have neutralized the infection to a certain site.

But, the body is also signaling

to a broader immune response that actually the danger is there.

So this signaling response occurs by the expression of

surface molecules at the inflamed site.

So, by recognition of the danger signal,

the cells that carry those recognition receptors will then

start to express molecules, which tell other immune cells

that that is the site in which infection is taking place.

Now, the body at this stage is trying to localize the infection.

What the body doesn't want is for those infections to become

established systemically to reach other parts of the body.

So the recognition, and the neutralization, and the signaling in

an attempt to bring other active elements of the immune system to that site in

the anticipation, in the hope of localizing because a localized infection

is much less damaging and has much less ramifications than a systemic infection.

The fourth element of this immune response or

inflammatory response is actually recruitment.

This is really an amplification stage, this is saying that all of those local

factors aren't enough to protect the body against this invading organism.

Either the organism is particularly strong and has certain virulent factors,

factors which make it a very dangerous organism or the number of

infectious agents are too great for those local mechanisms to neutralize it.

So this is a stage of amplification.

And this occurs by recruiting other parts of the immune system.

The immune system isn't just localized but all the time there are immune elements

circulating around the body in the blood system, at mucosal surfaces,

there's constant passage of sensitized immune factors moving around the body.

And they are, at any one time, able to exit

that circulation system and accumulate at a site of infection or inflammation.

So, these will recognize the signalling process.

The cells that are close to that damaged area, or

the area in which is being infected, they will express certain receptors.

The cells that are scanning that area will recognize those receptors,

and they will exit the bloodstream at that site, and accumulate there.

There are also, the release of a number of soluble mediators at that site as well.

And the net result of that is to increase the blood supply.

And this is now giving us some of the clinical signs that we'll be able to

recognize.

If you think about it now the immune system, instead of being neutralized at

one site, is beginning to signal that it's damaged and recruit other cells.

To do that it needs more blood cells, more blood, and more blood cells.

So what would that look like?

That might look like, imagine if an animal or you had cut your skin or

had an infected skin, you'll start to see swelling of that site, or

redness of that site.

Two of the main signs and early signs of the inflammation.

That's telling at what stage is taking place.

Neutralization hasn't been affected.

We're now amplifying recruiting other soluble and

cellular agents to that site to try and combat that infection.

So the next stage of the inflammatory response will be destruction of

those bacterial agents, or those viral agents, or those invading organisms.

So that takes place because now we've recruited all kinds of cell types and

all kinds of soluble mediators.

Some of those cells are called neutrophils, so

they particularly have an activity in which they can engulf invaders.

They can eat them.

They're called phagocytes.

They can take them into their cell cytoplasm and engulf and ingest them.

So, they're some of the first cells that are at those sites.

And there might be other soluble mediators, certain proteins.

That's also effective at destroying bacteria, rupturing their cell wall,

neutralizing viruses, aggregating them together so

that the phagocytes can eat more vermining, engulf them more easily.

So now, the blood system and the immune system is looking at destroying,

and not just destroying, but removing those agents as well, because there's

also a circulatory system which collects all of that debris and

removes them from the body.

So the immune system isn't just aimed at killing pathogens.

It's also aimed at removing them as well, and the body has all different sites

which are able to processed damaged cells and

cells which have collected microbial or pathogenic agents.

That occurs at the lymph nodes, that occurs in the liver,

that occurs in the spleen.

So, all of these are sites in which those bacteria can be finally dealt with and

digested and taken away so they cause no more damage to the body.

But the last stage of this inflammatory process that deals with most

infectious agents is healing.

So the immune system is really a homeostatic process.

The point of the immune system isn't to kill microbes,

it's actually to restore health, it restores normality.

So once that foreign agent has been recognized, once the neutralization

process has taken place the amplification steps and the recruitment of other cells,

the destructive processes, and the removal of those agents has taken place.

The cells that are left, or the damage that's been incurred needs to be healed,

and so the last part of this inflammatory response is to recruit cells and

to recruit soluble mediators.

That'll restore health to that damaged part of the body.

So healing is part of the inflammatory response.

And what we're looking about when we have an animal with a robust immune system,

we expect when it's exposed to an infectious agent

that it will heal within a certain period of time.

Within that period of time, if its immune system is working and

the infection hasn't won the battle, then you'll see healing.

That redness, that swelling will go away.

The pain associated with it will disappear.

And that should occur within 48 to 72 hours.

If you have an inflammatory response that goes beyond that,

that shows you that the immune system is now recruiting additional defenders,

as it were, the adaptive immune response.

And that's when other interventions are needed.

But by far, most infections are dealt by those seven stages of the inflammatory

response, and that's what you'll be looking for you in your animals.

[MUSIC]

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