Welcome, in this module, we're going to talk about mastitis. A particular disease that relates to the mammary gland. And we're going to explore different aspects of mastitis. In this particular video, we're going to kind of start out with some background and some definitions and those kinds of things. So let's go ahead and go to the first slide. Mastitis is defined as an inflammation of the mammary gland, an inflammation of the mammary gland. And so it's an inflammatory response by the tissue to some, usually external, source of an insult to the tissue. There are several ways that that can happen. This can usually occur in response to intramammary infection, intra being inside the mammary gland. Intramammary infection, or IMI, sometimes it's abbreviated. Far and away, this is the major source of causing this inflammation in the mammary gland. But it's certainly not the only way that this can happen. We can have mechanical trauma. If the animal or the mammary gland gets say kicked or somehow physically damaged, mastitis can occur. Again, this inflammatory response in the mammary gland can occur. Thermal trauma, one example of that would be, say, in sheep. Any time sheep around the world will lamb, actually during winter or very, very early spring, the ground is very cold, the mammary gland is still kind of developing all those blood vessels and lymph vessels are really just kind of giving organized, and so the gland can become affected by the cold and the result can be potentially mastitis. And so that can occur in that particular species as, certainly, as well as other species. Chemical insult, if for some reason some caustic or toxic chemical actually gets up in the mammary gland, that can result in inflammation in the mammary gland as well. But again, far and away, the majority of time we're talking about an infection by some pathogenic organism. Usually, almost always, but not always, bacterial. So let's go ahead to the next slide. So, what animals can get mastitis? And fundamentally, the answer is any mammal can get mastitis. Go ahead to the next slide. Any animal with a mammary gland, and especially those that are lactating. And we'll kind of, as we go through this video and the next video or two, we'll start to understand why lactating animals in particular. But any animal with a mammary gland, if there's some internal infection there or some internal inflammation, by definition, that's then mastitis. This is especially important in dairy cattle, because clearly we are harvesting milk from dairy cattle. It is a very important disease in dairy cattle. In fact, we can go to the next slide and start to see that. It's the most costly disease in dairy cattle. In the US industry, US dairy industry, this number, about $2 billion lost annually, is a number we've seen for a lot of years now. The ability to control mastitis has gotten better. We've gotten better at controlling mastitis, but at the same time obviously, costs have gone up. So we're still seeing this annual loss of about $2 billion. So it's a big deal in this particular industry. Where do those losses come from? A variety of sources. Lost milk production. So the impact of the actual inflammation on the ability of the mammary gland to make milk, as well as discarded milk. So in this particular case, a lot of times where we have clinical mastitis, what they will do is they'll actually infuse antibiotic up in the mammary gland, through the streak canal of the teat, up into the mammary gland. And you have to dump that milk. You don't want that milk going into the food chain. Dump the milk for several milkings afterwards, depends upon the label of the antibiotic. So again, lost milk, these two top ones here, are far and away the major contributor to the losses of money. Veterinary costs, clearly associated with that. Additional labor costs to treat the animals. Many times you have to segregate those animals and milk them separately from the rest, so increased labor costs. Culling and loss of cattle, so mastitis is so bad that they know that cow's mammary gland is not going to recover well, they might cull that animal. At the same time, on occasion, cows can actually die from very, very, very severe cases of mastitis. And then, lost milk quality. And that is, again, this idea that the hydrolytic enzymes in the milk, and we'll talk about that here in just a moment, are degrading the quality of the milk so you don't get as much cheese manufactured from that. So, often does this disease occur in animals? And we'll take a look, particularly, at dairy cattle to start with. Well, actually, what we're going to do is we're going to look at some definitions. And this is an important distinction. Prevalence of this disease is percentage of animals infected at any given time. So if you go out into a population of animals, how many animals would you expect to have the disease? Incidence is the frequency or rate at which new infections occur. So new infections, how often does this happen? And the reason I bring out this distinction is that a lot of times researchers and people that report these things sometimes confuse these terms. So you have to be really careful in how you go and look and evaluate these kinds of terms. We're going to focus mostly on prevalence, and give you a few examples of that. Again, in dairy cattle, next slide there. These are actually 20-year-old numbers, so hopefully they're a little bit better than this, but it gives you a rough idea of where we are. So roughly the third of the cows, a little over a third of their quarters. Remember that cows have four quarters, most cows have four quarters, lactating quarters. So if we calculate that out, about 12% of all quarters in lactating animals are infected at any given time. So that gives you an idea of the prevalence. Let's then take a look at another species, our own species, and that is lactating women. And here, again, if you go in the literature, it gets a little bit fuzzy as to what's prevalence, what's incidence, people don't necessarily define it all that well. This is the number that you see fairly often, and roughly 10% or so of lactating women during a lactation will experience mastitis. I'll add one more to that, and that is in swine. In swine, granulomatous mastitis. That's the kind of mastitis where, after a lactation, you can actually palpate the gland and you can find scar tissue in there. The particular study I'm thinking of was done at the end of a lactation, so at weaning. So that mastitis may have occurred at any point during that lactation. Just to kind of give you a ballpark idea of numbers, first parity cells, that is after the end of their first lactation, about 5%. Later lactations, say, up to seven or greater lactations, up to 25%. So a big range in terms of the prevalence of mastitis depending upon parity, depending on stage of, or length of lactation that is, in terms of how long lactation is, and a bunch of other factors. So the take home message here is you really have to be extremely careful in comparing prevalence in different species. So you really have to kind of look at that species and look at how things happen in that particular species. Clearly, dairy cattle are managed differently than swine. Lactating women are going to manage their lactation differently than these other species. And so you can't necessarily just take this thing and say, okay, what is the incidence of mastitis in this species, and compare it directly to another one. You have to kind of look at the details in more detail.