Contagious Pathogens

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来自 University of Illinois at Urbana-Champaign 的课程

Lactation Biology

5 个评分

University of Illinois at Urbana-Champaign

Lactation Biology

5 个评分

Lactation and especially milk, which is the product of that unique mammalian process, are routinely encountered within our daily lives. Nevertheless, they often are poorly understood by many, even including many who are engaged in the business of producing milk. The overall course goal is to introduce fundamental concepts that form the basis for understanding the biology of lactation, the biology of the mammary gland, and the products of that important physiological process. As a learner in this course, you will be provided with a series of easily understood presentations that collectively will help you build a foundation for greater understanding of lactation. You will be able to engage with other learners so that you can extend your learning beyond the video presentations. Ultimately, you will be able to construct your own mental model for understanding the wide range of topics that relate to the biology of lactation. Upon completion of the course, you will be prepared to expand your knowledge and understanding of lactation from other sources and experiences as you pursue your individual interests. Before you start the course, I suggest that you identify a question or several questions about lactation that you already have on your mind. This could be from your own experiences, something you read about or saw, or something you have wondered about. Write down your question(s) and use that to help you decide how to engage with the content of this course. You might engage with the modules in the order they are presented, or start with a module that is of particular interest to you, or pick and choose modules in any order. I encourage you to engage in all of the types of learning activities that this course has to offer, including but not limited to, the discussion forums, quizzes, peer-review assignments, and concept maps and other learning aids.

从本节课中

Module 9: Mastitis

The mammary gland is an excretory gland, meaning that it produces a fluid that is secreted to the outside of the body. These secretions leave the gland through a series of ducts that eventually open to the outside of the skin. The presence of these openings not only means that the mammary secretion can leave the gland, it also means that microorganisms can enter the gland. When that happens, the gland may become infected and present as a disease known as mastitis. Mastitis is an inflammation of the mammary gland, the inflammation most commonly being caused by an infection by a pathogen. Mastitis is the most costly disease in dairy cattle, but is also prevalent in other species, including our own. We will examine many of the aspects of how this disease is manifested using the dairy cow as our primary example in this module. We will examine mastitis at the level of an individual cow, as well as at the whole herd level. And then to fully integrate and apply the knowledge gained about this disease, we will examine several real-life cases of herd-level mastitis problems faced by dairy producers.

Mastitis Syndromes11:12

Mastitis Types7:08

Contagious Pathogens7:32

Environmental Pathogens6:03

Other Pathogens5:39

与讲师见面

Dr. Walter Hurley, PhD
Professor Emeritus
Department of Animal Sciences

[SOUND]

In this video we want to keep examining this mastitis disease.

In this particular video we're going to focus on the pathogens, so, again, Mastitisis technically is an inflammation mammary gland.

it doesn't have to be caused by infection or a pathogen.

Most of the time we find it in fact there is some pathogen and usually a bacterium.

A few exceptions certainly that are causing this so we're going to take a look

at some of the major mechanisms and again using a cow as our main model.

But you'll find, in other species, as well.

That there are some similarities with the kinds of pathogens that you find.

So let's take a look at the first slide here.

And again, this is really to remind you of this relationship between the host.

The environment that that host is in, and the agent.

And in this particular case,

this is really what we're focusing on is the agent.

And in this particular case, talking about bacteria and other microorganisms.

Okay, next slide.

To remind you that we can think about types of mastitis,

although there are other types of mastitis these are the two major types.

Contagious mastitis, cow-to-cow, somehow that bacterium was in this mammary

gland and somehow it got transferred to another cow's mammary gland.

So how does this happen from cow-to-cow?

One way or the other, whether it's on the outside the mammary gland or

in the mammary gland, somehow it gets transferred to another cow.

And environmental mastitis, where those pathogens are out

in the environment of the cow and so she's always kind of exposed to those,

and again we'll break that down and think about some of those kinds of pathogens.

So we're going to focus first of all on several pathogens that are very typical in

dairy cattle that are causing contagious mastitis.

Again, keep in mind this is cow to cow.

[COUGH] And so we'll try to expand on that a little bit.

Let's take a look at the first one.

Staphylococcus aureus.

Staph aureus.

This is today.

In today's world this is the number one mastitis causing agent.

It's a gram-positive bacteria.

It grows in the teat canal, on teat lesions, on teat end lesions and so on.

So it's kind of on the teat, outside the teat, in the street canal of the teat,

and then somehow manages to get up in the gland.

Or contaminate the milking machine, that's then transferred to another cow.

Again transmitted as I just said,

by teat cup liners, udder wash cloths, milker's hands.

Staph aureus likes skin, it likes to be on the skin.

Now this is one reason why we encourage people to wear

those plastic gloves now when they're milking cows.

Droplet impacts by liner slips.

We'll kind of get into that in another video.

But the idea is that the milking machine's on and if there's contaminated milk in

the milking machine If there's air getting down in there,

sometimes that air can actually blow little impacts, or

little droplets of milk, back into another quarter of a cow.

So again, if that bacteria is in there,

it can potentially colonize that mammary gland.

This is the primary cause of chronic mastitis.

So if we recall,

the chronic mastitis is the one where it's subclinical, no clear signs.

We get these clinical cases, and then it goes back to being subclinical.

And so Staph aureus is a major, it's not the only cause but

is a major cause of chronic mastitis.

So when we see situations in a herd which we have a lot of chronic mastitis,

it's a very good chance.

Not absolute, but a very good chance that Staph aureus is the cause of that.

Causes development of scar tissue in the mammary gland so

obviously that scar tissue will not produce milk and

even in the next lactation it won't produce milk and it's very difficult.

It's not very responsive to antibiotic therapy.

So another type of contagious mastitis, another pathogen that we

associate with contagious mastitis is Streptococcus agalactiae.

Gram-positive.

Again, sole reservoir.

It really only lives in milk or in the mammary gland.

So again this is where you get contaminated milk

In a tea cup or something.

You transfer that to another cow potentially get into the mammary gland

of the other cow.

Again, it really only survives in the mammary gland or

in the milk in the mammary gland.

So it spread to unaffected quarter occurs during milking so you really,

with this particular pathogen, if that's what it is,

you look at the milking process, because that's where this thing is happening.

It can spread rapidly throughout a herd if it's not kept under control.

It's, If you have cows with

this pathogen, it is susceptible to antibiotic therapy.

You can cure that.

Or get rid of the cows.

Once it's out of the herd, it should be gone.

So it's not like environmental pathogens that are always there.

It's not like Staphylococcus aureus that's very often around.

This one, once you get it out of the herd and keep it out of the herd,

you shouldn't have any problem with this one again.

In the olden days, so go back 30, 40, 50 years ago, something like this,

this was the major pathogen that we found.

But again, what we found is that by using teat dipping,

this routine teat dipping, either in post-dipping milking or

at least post-milking teat dip with a germicide and

dry cow antibiotic therapy when you draw the cow out at the end of lactation.

Those two things are really a pretty well take care of it, controlling it.

And again, antibiotic therapy can pretty much eradicate this one.

With the Staph aureus that does not respond very well to antibiotics

this guy does and so this one can be controlled pretty well and heard.

So the third contagious passage that we going to consider is Mycoplasma,

Mycoplasma bovis.

This particular there other Mycoplasmas too that can cause mastitis,

this particular one is the most common.

Species of mycoplasma that would cause this.

It's very slow growing, and so therefore it's a bit difficult to identify.

You have to use special media.

It takes longer to grow a culture.

It's a little bit more difficult to identify in terms of bacterial culture,

bacteriological structure, then your staph aureus or your strep egg.

Usually, the sudden onset, purulent secretion.

So it gets clinically over quickly and get you into that acute,

and potentially peracute, but acute mastitis level or syndrome.

Rapidly can spread throughout the herd,

very rapidly could spread throughout a herd.

Decreased milk yield.

Very resistant to antibiotic therapy.

So once you get this into the herd, if you want to get rid of it,

you're basically going to have to call those cows.

It's what it amounts to.

Or do something else to accommodate the fact that those cows are infected because

you really cannot get rid of it with antibiotic therapy.

And there's really no other good way to get it out of the herd.

So this particular one again, is been around for a while in this country.

It's spread a lot so it's fairly prevalent around the country now.

In times past it was more regionalized.

But it's really spread a lot so this is again,

a major pathogen that we have to consider in terms of contagious pathogens.

[SOUND]

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