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Welcome, Dr. Payne, and thank you for joining us today. Let's go ahead and get started. Can you tell us a little bit about yourself and what you do?
SPEAKER_02
Sure. My current role is an extension veterinarian with the University of Missouri, and I primarily focus on beef cattle. A brief history. In 2005, I went to the King Ranch Institute for Ranch Management and got a master's degree in agribusiness from there, and then joined University of Missouri Extension in this role I'm currently in in 2007.
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Dr.
SPEAKER_01
Payne, how did Tyleria arrive in Missouri and what factors are driving its spread into the western United States?
SPEAKER_02
To answer that question, we may talk a little bit about the history of Tyleria Orientalis here in the United States, and well, primarily focus on the Aikeda genotype. But we've had two Tyleria orientalis genotypes in U.S. cattle populations in certain parts of the country for several years. One of those genotypes is called bufeli, the other one's called kaitose or chitosi, just depending on who you listen to, is how they will say that. But the reason why most people probably haven't heard of those genotypes before is because those cause very little disease in the cattle that they infect. However, when that Aikeda genotype showed up in the U.S. for the first time in 2017, we knew it was going to be a little bit different situation because of the genotypes that I've already talked about. The Aikida genotype is by far the most pathogenic of the three. And so our first recorded case of the Aikita genotype was in a cow calf herd in Virginia in 2017. And since then, we've seen that protozoa move from east to west in the United States. Now, it's really hard for me to know what states that IKEA genotype has been detected in. I recently saw a map that had been developed by Kevin Lawmers, who's a veterinary pathologist at Virginia, Maryland College of Veterinary Medicine. And if I counted the states right, there were 27 states where that IKEA genotype had been recognized. Now I don't know if that was uh in native cattle only, or if that's probably a combination of native and imported cattle. How did it get from the eastern part of the United States to pretty much Midwest part of the United States in a matter of nine years? Well, there's a couple of reasons for that. And one is the Asian Longhorn tick. It can be infected with that Chiluria protozoa. And once it's infected, it's infected for life, and that protozoa completes part of its life cycle in that tick. So when that tick feeds on an uninfected animal, it's going to introduce that organism. Well, that tick is a highly invasive tick species, and ironically, it was first recognized in the U.S. or first detected in the U.S. in 2017 as well. That tick has again migrated east to west, and it's now also in 27 states in a matter of you know a decade or so. And so that's that tick species itself and its movement east to west has brought that protozoa with it. And then I think the other component of the answer to that question is that any cattle that are infected with this Tyleria protozoa that we're talking about, regardless of whether they show clinical signs or not, those animals are going to be infected for the rest of their life. And we call them chronic carriers. Now, majority of these animals are not going to show clinical disease from that protozoa once they go into this chronic carrier state. And so because these animals are appear normal, and also because they're carrying this organism, we and we know how frequently cattle are moved in the U.S. As that as our population of cattle in the eastern part of the U.S. Um has become infected with this protozoa and establish that chronic carrier state, and then as as they have moved west, um they brought that protozoa with them as well.
SPEAKER_01
So are ticks the only route of transmission for Tyleria?
SPEAKER_02
So the primary vector for transmitting chilaria, at least the IKEA genotype, and maybe some of these other genotypes that we've talked about, but it's going to be ticks, and specifically with the IKEA genotype, it's going to be the Asian longhorn tick. With that being said, there's several other ways in which it can be transmitted. And the other methods that we think about are taking red blood cells from an animal that is infected with that protozoa and passing those red blood cells to an uninfected animal. So when we think about some ways in which that occurs, one thing that comes to top of mind for most people is blood-contaminated equipment. And so that could be needles, uh, that could be castration equipment, dehorning equipment, tagging pliers, so on and so forth. Now, there's also some insect vectors that have been implicated in being able to transmit these infected red blood cells from a chronic carrier to an unaffected animal, and those would include things like horseflies. And so most people are familiar with anaplasmosis and the role that horseflies play in the transmission of that disease, and it would be the same with pileuria as well. Biting other biting flies, such as stable flies, there's some pretty strong evidence that they may contribute to the spread of this disease or transmission of the organism. And so those are some of the major um pathways by which this organism is being transmitted from infected to uninfected animals.
SPEAKER_01
If a pregnant hei or a cow is infected, what are the potential implications for the calf both pre- and postpartum?
SPEAKER_02
So the potential implications for an animal that is pregnant that is acutely infected with this organism, is there's a risk of abortion, and that's going to be dependent upon how severe the infection is. And so let me frame it up this way for those of the listeners that may not be familiar with what's going on during a chilirial infection, at least in the acute phase. So what we see is we have red blood cells become infected with this protozoa, and because those red blood cells are damaged, those are going to be lost in circulation, and so that's going to create an anemia. And the severity of the clinical disease that we see associated with chilaria is going to be related to the severity of that anemia. And one of those consequences, again, depending upon how severe this acute infection is, is going to be abortion. The other question that I will often receive as I'm talking to producers or veterinarians about chilaria is in relation to this chronic carrier state and whether or not a calf born to a chronic carrier cow will be a chronic carrier or at least infected at birth itself. And so, but all that to say is that most people that I've talked to in relation to this issue is maybe less than 2% of the calves born to a chronic carrier cow will be uh infected themselves at birth. So it's probably not a big contributor to the epidemiology of this disease. What should producers know about chilaria and what actions should they take? I think the biggest thing I would like producers to recognize about the Aikeda genotype is that the biggest impact it's going to have in a cattle population is when it's first introduced into a naive population of cattle that have not been exposed to this organism before. And even then, uh during that initial exposure or that first infection, the number or percentage of animals that we see come down with clinical disease is limited. Sometimes this protozoa gets into a population of cattle, such as a cow calf operation, and producers never see one animal uh develop clinical disease because of that infection. The other thing I think it's also important to recognize is that there is a potential for death loss associated with this disease. Um but fortunately, in most cases, it's typically going to run around one to five percent. Now I understand that in this day and age, when cattle prices are the way they are, any loss can be financially significant. But in the end, when this protozoa first gets into a population of naive cattle, again, is when you're gonna see the majority of the impact. Now, there's gonna be situations where, you know, for instance, if you're bringing naive cattle into your operation, such as replacement heifers, breeding bulls, those animals are gonna be at risk if Tyleria is in your system and there's transmission going on. The other thing I think cow calf producers have to be mindful of, even though we don't see a tremendous amount of problems with it, but every year cow calf producers are going to have a new calf crop, and for the most part, that calf crop is gonna be naive. It could have anemia, it may look like they have a form of pneumonia, because sometimes with chiluria we will not only see pneumonia but increased respiratory rates, fever, cattle may be a little bit depressed, so that reminds folks sometimes of what pneumonia looks like, but those impacts are often minimal as well. So that's the big take-home message is that first exposure is going to be where most of the challenges are gonna be, and from that point forward it's manageable. Um, so what actions producers can take, because each operation is different, their goals are different, um, their management practices are different. I think it's important regardless of whether you've got Tyler in your herd currently, or you're just trying to be proactive and come up with a management plan or a plan to maybe address potential exposure in the future. By all means, you need to work with your local veterinarian to come up with the best plan to do that, but I'm not sure.
