Host Lynsey McAnally (00:04):

Angus at Work, a podcast for the profit-minded cattleman. Brought to you by the Angus Beef Bulletin, we have news and information on health, nutrition, marketing, genetics and management. So let’s get to work, shall we?

Hello and welcome back to Angus at Work. As the weather begins to warm up and insects return, ranchers will again face the challenge of managing insect pressure, as well as concerns associated with complications caused by these tiny nuisances. I'm Lynsey McAnally, and on today’s episode, our host, Shauna Hermel, was joined at CattleCon2026 by Deana Hardee, veterinarian with Merck Animal Health, and Megan Silveira, managing editor with the Angus Journal, regarding New World screwworm, the Asian Longhorned Tick, and a conditionally approved product from Merck that could help protect U.S. cattle herds from future threats.

But before we get started, we wanted to take a moment to thank Superior Livestock for their sponsorship of this episode.

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Shauna Hermel (01:47):

Hello, and welcome to this edition of Angus at Work. I’m Shauna Hermel, editor of the Angus Beef Bulletin and host for today. I’m here talking at the CattleCon2026 with Deanna Hardee of Merck Animal Health. You all have a new product that you’re premiering here that I think a lot of our producers are going to take some interest in. Could you first tell us a little bit about what you do there at Merck? Then we’ll get into some product specifics.

Deana Hardee (02:16):

Thanks for having me, Shauna. So a couple of things: Like I said, my name is Deana Hardee. I’m a veterinarian on our cattle sales team. Essentially, I work with our technical services team members, our field sales force. I do both support for those teams as well as post-market launch studies. I try to be involved in the industry where I can and just a contact vets can reach out to as well or other folks in the industry as they have questions about new products like Exzolt™ Cattle-CA1.

Shauna Hermel (02:44):

You bet. Now this is targeted toward some problems that we haven’t had a lot of help with. I know being in northeast Missouri, there’s a lot of problems with ticks. There’s a lot of problems with flies and some of the diseases there and then, of course, we’re looking south of the border on some issues. How does this product ... how is it labeled to help with those issues?

Deana Hardee (03:09):

That’s a great question. As I mentioned, our new product is Exzolt Cattle-CA1. That CA1 standing for conditional approval. So we’ve worked collaboratively with FDA to get this product across the finish line in a way that can be useful for two imminent threats, right? New World screwworm, as well as the cattle fever tick. Because it’s a conditionally approved product, it won’t be used off-label, but we are of course trying to seek full approval with this product. I think it’s important to note: When we think about conditionally approved products, this is a product that has all the safety and data packages already approved. So that’s human food safety, as well as target animal safety. But what we were lacking to get that kind of across the finish line was our in-house studies or data, specifically as it relates to cattle fever tick and New World screwworm.

So we were able to utilize studies from our other global markets — Australia and Brazil specifically in these cases — to get that conditional approval here for the cattle industry as we think about those threats. So right now the product, like I said, is labeled for the prevention and treatment of New World screwworm myiasis and then for the control and treatment of the cattle fever tick.

Shauna Hermel (04:21):

Do you have people who are using the product now?

Deana Hardee (04:24):

So it just got released into distribution because it is a prescription product, right? Coming through your veterinary clinic. It is available to be purchased. We are obviously targeting our southern markets because that's where those threats are most likely to occur. And so again, [to use] this product a producer would need to reach out to a vet. Of course, if you have any other questions, you can always visit with our animal health representatives or visit our website, but it would be available through your veterinarian.

Shauna Hermel (04:52):

What would motivate [a producer] to go ahead and call their veterinarian to get some information on the product?

Deana Hardee (05:03):

I think it’s something that’s on all of our radars. As we mentioned, we’ve watched that northern progression of the screwworm, right? From Central America into Mexico. So as I’ve visited with veterinarians and ranches down across the border, they’re thinking next steps. If we happen to have a threat, we come into spring/summertime when we have a more prominent fly season, or even as we think about particular stressors in our industry that may promote flies to come in (calving, branding working where we're creating wounds, castrating, dehorning, etc.). They’re certainly thinking through their personal biosecurity. What does the ranch’s biosecurity look like? What's their plan? We’re very excited here at Merck to have a potential solution. Admittedly, we understand this is just a very small part of that entire integrated pest management idea.

We certainly encourage good fly control in general, paying attention, being aware, reporting if you think you have a case of New World screwworm is critically important, especially as we reach peak fly seasons. It’s just something we want everyone to have on their radar and then know that we’re trying to bring solutions to the industry's current needs and — certainly — a threat to our cattle industry.

Shauna Hermel (06:24):

One of the things that we heard this morning was a caution that we shouldn’t just think that this is a silver bullet to blanket and it could cause problems with maybe some resistance in some other parasites that we might also be controlled on if we tried to just megadose to get rid of the problem.

Deana Hardee (06:46):

Absolutely. That's why I think it’s so important to work with your veterinarian to use this product on all ectoparasiticides strategically. We are certainly not recommending a blanket protocol. We are wanting people to think about, again, those stress points and their processing systems that may create that open wound or utilize it in a way that makes sense for the biology of the pests that we’re targeting. I think we can speak on that with really any product, but especially our ectoparasiticides or even when we think about internal parasite control. This product though is an external parasite control product. And certainly, when I mentioned we have that label for the cattle fever tick, that is the Rhipicephalus (Boophilus) microplus species isolated.

Shauna Hermel (07:31):

Can you spell that?

Deana Hardee (07:32):

Nope, I can barely say it. But that is right there on our Texas-Mexico border in the cattle fever tick zone.

And that is something that is handled by a collaboration with Texas Animal Health Commission and USDA. They’re the ones that are in charge of that program and they have done a great job eradicating cattle fever ticks. And so we’re encouraging veterinarians ... That product, if it’s going to be used for that, would be under the guidance of the state animal health officials.

Again, we’re focusing more on trying to bring solutions to address needs, and this is a novel product. So it’s not just new, it’s really in a class of its own. The class of products is called isoxazolines. That one I can spell. But the active ingredient is fluralaner. We haven’t had a new class per se of ectoparasiticides in decades in the cattle industry. So when you ask about resistance, when we look globally and we look in other species, there’s no known resistance to specifically that fluralaner molecule today. But again, we can’t harp enough on be judicious and strategic. And, of course, include your veterinarian when you’re thinking about using these products.

Shauna Hermel (08:46):

So what’s the cost of the product?

Deana Hardee (08:48):

That one might be a little bit out of my wheelhouse; but, in general, it should be a little less or around a $1 per hundredweight. And when we look at the dosage, like I mentioned, it’s a pour-on product — a solution that goes from the withers essentially to the base of the tail. It’s 1 milliliter per 44 pounds. So again, that five-weight animal would probably be about $5 and so forth.

Shauna Hermel (09:14):

As far as when a veterinarian would prescribe it, in our case that we’re looking into as the New World screwworm, what would it take to have a veterinarian prescribe the product?

Deana Hardee (09:25):

That brings up a really great question. I can't encourage enough using a local veterinarian. To find a veterinarian that’s familiar with their operation. All producers should have that vet that has a [veterinarian-client-patient relationship (VCPR)]. That doesn’t necessarily mean they have to be on your ranch monthly. That just means they know what’s going on in your operation. They’re comfortable with your practices, how you do things, and they’re able to prescribe and have these conversations about when and where to use a product like Exzolt Cattle-CA1.

Shauna Hermel (09:56):

Would you use it for just one individual animal? If you found some larva in a wound, would you treat the whole herd?

Deana Hardee (10:05):

So that’s a great question. First, I would report. Make sure you report it to your statement officials. We do know this product, even though it’s a pour-on, there is a grooming component to it. So you want animals to lick each other. as well as themselves, but you can certainly treat an individual animal. When we think about animals that are maybe stalled more frequently — like a show calf that’s maybe tied up a large portion of the day — that’s just something I want us to think through. That self-grooming is an important part of that active ingredient reaching peak concentrations. But, again, I would work with your [veterinarian] to establish what makes most sense in that case. When we think about New World screwworm, we know there are other options that we have. Injectable products. But I just can't harp enough on those things that aren’t in a bottle, right?

So we know we have that sterile fly technique, which is so, so important for controlling the actual screwworm from getting here. And then even when it’s here, then I have to think about good just fly management practices. Of course, we deterring the new world’s groomers a little bit different than your common fly, but there’s still certain things we can do and be aware of. And then I think a large component of it, as well, is going to be management, making sure we don’t have facilities that create unnecessary wounds, again, making sure we’re strategic during the times where maybe we are creating an open wound. And then also watching our cattle closely, paying attention, being aware of this. So again, I think it comes down to your ranch and personal biosecurity, having that VCPR with a veterinarian and just practicing good pest management.

Shauna Hermel (11:42):

Tell me a little bit more about the state work with the Texas Animal Health Commission on the ticks.

Deana Hardee (11:49):

Yeah. So cattle fever tick is very much under their jurisdiction. We have a very well-recognized program. It’s a very effective program. So when it comes to cattle fever tick usage, even as an accredited veterinarian, I'm not writing a script for that. That is going through that program.

They are the ones that are in charge of the animal movements, when to treat and so forth. And we have a good working relationship with Texas Animal Health Commission and USDA and certainly are talking with them on if this is an option potentially. But we also know that's a well-oiled machine, and it has been highly effective for almost a century.

Shauna Hermel (12:26):

And so when it comes to producers using it, it would actually come from the direction of the Texas Animal Health Commission?

Deana Hardee (12:33):

If they are in that very specific quarantine zone, which is the only place in the country where cattle fever tick currently exists. They have not had a new treatment option for cattle fever tick in decades. So when we look in our foreign markets, that is a very large issue for them. It was very easy for us to get that approval because it is very effective against cattle fever ticks. How

Shauna Hermel (12:55):

How about the Asian Longhorned Tick? We've heard a lot about it today and how [Theileria orientalis] is becoming more of a widespread problem. Each little tick has its own little mischief.

Deana Hardee (13:07):

Oh, absolutely. Single hosts, multi-host ticks, some prefer certain climates. Ticks are interesting little parasites, for sure.

Shauna Hermel (13:17):

I think causing more problems than we probably give them credit for right now.

Deana Hardee (13:21):

That is a very large discussion. Again, I'm a little bit more in the feedyard space, but do a fair amount in the cow-calf and stocker segments, too. When we see cattle in the feedyard that come back positive or have titers for Theileria orientalis, we're certainly ... Is this part of contributing to the overall immune system for that calf and is it causing detrimental effects as we think about BRD and other things or is it just ... I think we’re still learning a lot, but today Exzolt Cattle-CA1 is only labeled for New World screwworm and the cattle fever tick. Of course, we’re seeking full approval of the product and we hope to be able to add additional label claims.

Shauna Hermel (14:01):

Okay. So you have research in the pipeline looking at some other vector-borne diseases and …

Deana Hardee (14:08):

Yeah, so that's one of the reasons Exzolt Cattle-CA1 was able to get to the market because it is a product we should have to the market soon-ish. We were able to expedite it because of the imminent threat here in the industry. When we think about what’s important to us stateside compared to our global colleagues, we have a little bit different set of vectors that we'll be targeting. Two of those are cattle fever tick and New World screwworm in addition to others.

Shauna Hermel (14:34):

How does it work? How does the product work?

Deana Hardee (14:37):

So that’s a great question. So Exzolt Cattle-CA1, like I said, an active ingredient is fluralaner. Fluralaner is a ligand-gated chloride antagonist of the channel specific to arthropods. So it's very safe in mammalian species. It specifically targets that ligand-gated channel [within], in this case, a tick or the larva of the New World screwworm, essentially causing some nervous damage. We can't stop flies from landing or laying a little eggpack, but we can stop that development of the early larval stages. In the case of the tick, we can kill those, both the small nymphs or seed ticks, but we do a really good job at the adult female ticks, too.

Shauna Hermel (15:21):

Okay. How long will it stay in the system? What's the half-life or ...

Deana Hardee (15:26):

That's a great question. When we think about half-life, I like to talk more about the efficacy of the product because it's going to be different for different species of ticks, for different flies, etc. Right now today, when we look at New World screwworm, our current research in Brazil only goes out to 14 days. So you'll see for prevention and treatment for 14 days. When we look at cattle fever ticks, we have research from pretty much every geographic region in Brazil and Australia. We see a range of 28 to 70 days.

Shauna Hermel (16:00):

Oh wow.

Deana Hardee (16:00):

Depends on the geography, the concentration of tick, what the environmental conditions are like ... When we one-on-one visit with our colleagues in these other countries, our veterinarian tech service colleagues, they feel really comfortable with that 50-56 day mark. That's most often kind of the average that they're using.

Shauna Hermel (16:21):

Okay. 50 to 56 days.

Megan Silveira (16:24):

You're kind of talking about the whole mindset that we're in right now with this new threat. What are a few big takeaways you wish all producers knew?

Deana Hardee (16:34):

To be aware, to pay attention, certainly understand that this is being very actively monitored and to report. It is so critical that we report if we see something. Oftentimes the New World screwworm eggpack or those larvae can be buried in a wound very deep and you can have your traditional blowfly (or maggots as we commonly refer to them) on the top. So again, I was not here during the time of the first New World screwworm outbreak, but I hear that there's a very distinct smell and those lesions.Certainly, we just can't be scared to report it. I think it's better for our entire industry if we know if it gets here, where it's at and we're able to mitigate it and hopefully shut it down before it spreads further.

Shauna Hermel (17:23):

So who do you report it to?

Deana Hardee (17:25):

That's a great question. It kind of varies state to state, but I always say you can reach out to your local veterinarian. You can also reach out to any state animal health official. So online, that would be through either a Department of Ag, a state veterinarian's office, or even through a local USDA website. My broad answer is [through your] state animal health official. Contacting a local veterinarian or a state animal health official. Everybody has their own names for different folks.

Shauna Hermel (17:53):

What are you all doing as far as education goes beyond talking to us and ... ?

Deana Hardee (18:00):

Especially in the zones or areas where we know it's most likely to be, they're very well versed on this subject, right? So we're trying to find opportunities to collaborate and support. We're, again, hoping to do more research to better answer the questions that we have here in the U.S. When we think about that 14-day duration, that is simply because the study ended at 14 days. So our goal is to see what is the actual extended efficacy or persistent efficacy, I should say, of New World screwworm. That research obviously would be done in countries endemic with New World screwworm. The same with cattle fever tick. We're trying to work collaboratively and see where that product fits, or if it fits, in any protocol as it relates to cattle fever tick.

Megan Silveira (18:42):

Are there any misconceptions, particularly with producers, that you think they might need to be aware of and actively not be falling into when it comes to problems like this?

Deana Hardee (18:52):

I mean, I do like to reiterate this is conditionally approved. With that, this product is not allowed to be used off-label as it sits today. That's kind of the big one in my mind. When it comes to any ectoparasiticide or pour-on product, I think it's also very appropriate to use the correct dosage. As we think about resistance or not adequately dosing, I always say producers at sale time like to overestimate what they think their animals would cost. When it comes to using products in the chute, we tend to underestimate. This is one time where we want to be as accurate as possible and certainly don't underdose an animal with a pour-on product.

Shauna Hermel (19:31):

What are the problems with underdosing?

Deana Hardee (19:33):

Again, we just don't know the efficacy there and we do worry about resistance. I think that's just good judicious practice. Give the product at the correct labeled dose. It's very common for us to take an average, but we all know when we think about our cow herd or calves that we're going to have some outliers. This product comes in either a one liter presentation that's a squeeze bottle that you individually dose or the draw-off gun. I just encourage people to move that number to best fit the animal that's in the chute at the time.

Shauna Hermel (20:00):

Okay. Anything else that you want to add on? Have we missed something on the New World screwworm?

Deana Hardee (20:07):

No. Again, I think we're just excited to be able to share Exzolt Cattle-CA1. Like I said, it's a novel and new class of drug that we just like to have as a tool in the toolbox. It might not be the entire solution, but I think it's a good option and something to consider as we think about this imminent threat.

Shauna Hermel (20:23):

Excellent. Well, one of the things that we like to do with the Angus at Work podcast is end on a positive note. So I would like to ask for you to share, do you have something on a personal or a professional level that would just be something really fun and uplifting?

Deana Hardee (20:38):

Man, my world has been very heavy ectoparasites, which is not the most exciting.

Shauna Hermel (20:45):

Developing a solution is!

Deana Hardee (20:47):

Absolutely. It's been a really fun time, not just because it's a new product, but as we think about an industry and be able to respond to needs, it's just fun. It's fun to be involved with a company like Merck that's innovative, that has research, supports this kind of thing. And being fairly new in my career, I've really enjoyed the ride.

Host Lynsey McAnally (21:15):

Listeners, for more information on making Angus work for you, check out the Angus Beef Bulletin and the Angus Beef Bulletin EXTRA. You can subscribe to both publications in the show notes. If you have questions or comments, let us know at abbeditorial@angus.org and we would appreciate it if you would leave us a review on Apple Podcasts and share this episode with any other profit-minded cattlemen. Thanks for listening. This has been Angus at Work!