Dr. Saundra TenBroek, from the University of Florida, and first time guest to the show, shares her advice on deworming horses with science and biology in mind. We've learned a lot over the years, and your parasite control program may look a bit different than it did a few years ago. Find out which horses may not need to be dewormed as much as we used to, and how to find out for yourself!
Dr. Saundra TenBroek, from the University of Florida, and first time guest to the show, shares her advice on deworming horses with science and biology in mind. We've learned a lot over the years, and your parasite control program may look a bit different than it did a few years ago. Find out which horses may not need to be dewormed as much as we used to, and how to find out for yourself!
Welcome to Extension Horses tack box talk series Horse stories with a purpose I'm your host doctor Kris Hiney with Oklahoma state university and our guest today is a first timer for the program Dr Sandra Tenobroeke Burke from university of Florida so welcome Sandra thank you so much I'm so happy to talk to you today so as a first time are you going to give us a little bit of background so what what do you do in Florida I'm an extension state horse specialists I've been in Florida since October of nineteen eighty five long time eighty five eighty yeah so I mean the short rows now of my career my time there's been spent predominantly doing youth work in extension the latter half of my career with horses specifically and I also teach in the undergraduate program so you're pretty busy trying to balance all that together right yeah that's what my life is interruptible and that's K. all right so our topic today it is actually going to be talking about strategic deworming in horses so strategic doesn't just mean that opposed to routine yeah so in the old days right not that long ago
a days we always just used to tell people to deworm their horses every two months because we really want to make sure they never had any worms that's not what were telling people to do today so tell us what in your definition strategically deworming a horse means okay happy to do that so the just even the way we landed on every two months was based on the life cycle from egg to adult that is capable of laying eggs so the call it the prepatent in period from the time the eggs laid until an adult is able to reproduce so thus the parasite the internal parasite it's that is the most persistent problem in horses is small strong gyles
and small strongyles have a sixty day prepatent period so that's where we really came up with the two every two months routine deworming and I would say way back in the
in ninety five when we talk equine health management we were talking then and all the parasitologist we're talking then about strategic deworming that is know what your problem is and D. worm only when you have a problem and the reason is concern over parasites developing resistance to the chemical classes that we have ivermectin or the avermectin to class of compounds came on to the market and it was a great boon for horse owners because it was available in paste form so we no longer had the stomach tube horses the pasty warmers are easy to give your horses and large strong gyles essentially went away so that was one of the great things because large strongyles have a migratory phase of their life cycle where they do damage and we had a lot of horses that colicked because of migrating large strong gyles well the avermectin compounds would kill the speed the migrating large strong so they are essentially gone thank goodness small strongyles persist because they can encyst in the lining of the gut wall and and no chemical class gets a hundred percent of the encystes small strong gyles so when the conditions are right they burst out and even though the horse was clear of parasites in theory they have another parasite load because they were hiding or hibernating so strategic deworming looks at the life cycle yes but also when there's the potential to reinfest and the idea of strategic deworming is to try to maintain a parasite population that has never been exposed to chemicals we call that population of parasites that have never been exposed to chemicals refugia R. E. F. U. G. I. A. so parasitologist promote maintaining some refuge of which means you don't deworm every horse on a regular schedule you D. worm when you have a problem and the way we know we have a problem is we collect fecal samples and we analyze the fecal samples for eggs per gram and dog owners are very familiar with that cat owners you go to the vet they take a fecal sample and they look at the eggs will now that has been become more commonplace with horse owners so that we can only de worms when the egg counts are high when the horses are shedding but let's be honest if you have to pay for the fecal exam your horse it is ten twenty times more expensive than it is just to go get the tube of dewormer so how am I going to make that sale to anybody that they should pay twenty times as much and then if find out they may still have to deworm the horse well I would say that is exactly what veterinarians told horse owners in the nineties when the parasitologist were screaming strategic strategic we're gonna run out of chemicals but over time we realized we have fewer and fewer chemical classes available that there is a parasite resistance to pretty much every chemical class we have and there are no new anthelmintics or chemicals to kill parasites coming on the market that we know of none are being developed so
the knowledge that we could lose the ability completely of being able to de worm our horses should be driver to tell us yes doing EPGs may cost you twenty Bucks and a dewormer only cost you five to eight dollars depending on which one you choose but at some point if we run out of dewormers that work it's worth taking the time and money so is it not a little bit about head and you know I I I'll be honest I advise people do that same thing but when you're fighting that well this is convenient for me versus doing strategic deworming and and trying to prevent parasite resistance is more of a hi and it's a bit more of an industry wide problem in it for an individual owner that doesn't see the effect on themselves right so often we tend to look at how does life effect me my farm yeah it's so why on earth should I care about somebody in a different state or down the road
well that you don't really have to care about somebody is the parasites on your farm that your horses are suffering and you might develop a population of resistant parasites in your horse on your farm and and those similar species of parasites might not be resistant on another farm so let's say so we'll just use small strongyles for an example these the population of small strongyles on your farm might become resistant to ivermectin where's the small strongyle population on another farm might not so you're not we're not really worried about you fixing the world's problems were worried about you and your horses and the parasite population that are affecting your horses on your farm isn't that why a lot of owners will say okay I'm I am aware resistance issues and so I'll just do my part and I will rotate dewormers and therefore I won't have an issue the yeah well the rotation is getting harder to because there's very few we really have to classes of compounds that are still effective and the only broad spectrum that gets everything well there's nothing that gets everything the avermectin class gets pretty much everything except for tapeworms and so we use praziquantel for tapeworms that's what the the Zimectrin golden some of those others that have the tickets you get gold or plus yeah plus they have the the praziquantel but tape worms are not usually a huge issue the big issue for horse owners a small strong gyles and then the parental family still has some pretty good effectiveness parental tartrate and parental pamoate although there's quite a bit of resistance from to pamoate as well so that parental tartrate still works and if you triple dose it you can kill tapeworms with that as well but the benzimidazole class there's been huge resistance for years to the benzimadazole class and so there is one exception that when you use the power pack where you give a dose for five days in a row it's very expensive but that is one way to still use that class of compounds and the only way honestly to know whether or not to your dewormer is working which most horse owners are not gonna like here this is you have to have TWO fecal exams done right we got to have a before and after yes to know if it actually works sure well and there's been a lot of research done so this is a place where you can go to your state specialist and say what's been done in my state so for instance in the state of Florida we took fecal egg counts every two weeks on a group of ponies that were never D. worm for twelve months and we looked at we tracked egg shedding throughout the year and we learned that egg shedding was the highest in the month of April and in the month of September in the summertime the fecal egg counts dropped even below February because the infective stage of small strong gyles is a third stage larvae so they have to ingest a horse has to just a third stage large larvae to get infected and by doing that because of that in the Florida at least those are summers are so hot those larvae desiccated on the pasture so we learned through the research that we don't need to deworm at all in the summertime in the state of Florida because the horses are not going to re infest at a high enough level that it's a problem fall and spring the grass is short courses are still grazing the grass is short the temperatures are moderate egg shedding is really high so fall and spring big time re infestation time for the horses in the winter they're eating hay there's no grass so how did they infect by eating grass they're not gonna get parasites from hay so you're looking at getting rid of the parasites and not allowing them to re infest with the larvae and so de worming strategically in the state of Florida we recommend deworming everybody in the spring and everybody in the fall in because bots in our state or problem in September we make sure that we use a compound that get bots as well which the avermectin class does do that so that's right knowing what the egg shedding is throughout the year and when your horse is most likely to be reinfested grazing
moderate temperatures not too hot not too cold the larvae can survive on pasture and the horses will take commitment that grazing so if somebody has a horse that lives in a stall and a dry lot why should they ever deworm in their horse they probably don't have a problem and the only way they know they have a problem is that you do a fecal egg count the exceptions that might be pin worms because pin worm eggs can be on fences and posts and the horse can lick at and they can get the pin worms but they have a five to six month lifecycle so once or twice a year for pinworms okay so depending on your situation and then if you are grazing horses you have to be a little bit more concerned than our horses that seldom see the light of day
if you if you or with the help of your county agent your state specialists can if one of the three of you knows what is your parasite problem where do you live what is the opportunity for your horse to consume the egg or the larvae which is the infective stage and then the other concern is young horses versus mature horses young horses you do need to be more regular as opposed to strategic with young horses because if you have ascarids on your property those have migratory phases and you really wanna stay after that so if you have young horses up to the age of two or three you want to be more aggressive in your deworming program because of those particular pericytes adult horses become immune to them but young horses are not and because their migratory phase through the lungs you really don't want even microscopic damage to a horses lungs because he wanted to be an athlete later in life so we're much more aggressive in much more regular for young horses but older horses depending on your management support situation do you pick up the manure for your pastor and composted you know you're reinfestation maybe zero and and then the last thing is the researchers at the university of Georgia parasitologist there have learned that if you look at any group of horses
there are high shedders horses that have a large number eggs that they produce and there are low shedders and and they call it the eighty twenty it's we've use the eighty twenty principle in life in many ways eighty percent of the horses on a property don't shed a lot of eggs the eighty twenty principle relative to egg shedding is 20 percent of the horses out of a hundred produce eighty percent of the parasite eggs so if you can identify those horses that are high shedders and maybe just do fecal egg counts on those horses and deworm horses according their problem or your other horses may not have to even be checked regularly so definitely want to circle back just as a little bit a reminder for people to when we talk about you know your older horses that's kind of mature horses but then when they get older and their immune systems don't work quite as well it might be worth
checking those horses as well because as we said the immune system believe it or not the immune system does more than just bacteria and viruses it actually also fights internal parasites your immune system's pretty cool but as it declines just like older people are more susceptible to diseases horses that are older maybe more susceptible to parasites as well absolutely that's a great point but again look at what are they eating what is their chief their grazing if they still have their teeth in their grazing yeah they could pick up ascarid eggs which are may be a problem an older horse or they could certainly pick up larvae from the grass so it's I don't think it's worth mentioning a little bit online at parasites because we don't get these guys enough credit I think they're really pretty incredible so we talked about that really cool part of that small strongyles life cycle is that they can hide and so that's so neat they actually can essentially be dormant within the intestinal wall the horse waiting their turn to come out so what are those triggers that say Hey it's my turn to be an adult worms
empirically I don't see I don't know what the date is on this but from observational perspective if the parasite load in the gut is high you see more of those parasites ski in C. Y. S. T. encyst in the gut lining so they put a little wall around themselves when you D. worm now there's no competition and that de worming and the gut being vacated of the adult worms that seems to be a trigger for those insisted small strong Giles to come out and begin to start laying eggs grazing on the mucosa and laying eggs yeah so how they do it I don't know maybe some expert parasitologist know how worms know what the heck is yeah
so they have to be talking to each other somehow and even the fact that the worms know what time of year it is to actually shed eggs into the intestinal tract to be passed out like that's incredible to think about how little worm on the inside of your horse knows up at spring good weather it let's go
you know it's pretty common that that horses live at boarding stable and there's a lot of horses coming and going right that's not really a stable population did haha the people have to think about things a little bit differently if your horse lives at a facility where there's a lot more newcomers to the property absolutely
ideally you know for bio security purposes whether you're talking parasites bacterial infections viral infections new horses is coming on the property should be isolated and or quarantine for a period of time and then you deworm them when they come on to the place or at least do fecal egg counts if the place you're boarding house horses coming and going without doing that and then you know you might want to talk about their bio security issues the other thing is look at how much turn out they haven't how much grazing the act actually do if they turn out in the dry lot the probably not going pick up any parasite eggs or in these in the pear larvae because they're not grazing so there's a lot of things that go into it if you if they do have pastor but they're managing that pastor through rotation dragging in warm weather picking up the manure composting it before they spread it there's a lot of ways that you can use the integrated pest management to reduce the parasite load on your property so those are all things worth looking at and talking to management about so if somebody is really interested in this can you just go ahead and do a fecal egg count on your horse absolutely it's not that hard and even if if the simplest thing to do would be do a direct flotation which is kind of what they do at the vet clinic most the time there's recipes for fecal float you can just use hypertonic sugar or hypertonic salt and that sounds fancy and chemical but you can take distilled water and stir sugar into it until it stops dissolving and then it's got enough sugar in it or you can do it scientifically and weigh it and put unknown amount of sugar into unknown amount of water but really if you just stir sugar or salt into distilled water until it will no longer going to solution you're good you take some of that and put it into a test tube and you mix a little fecal sample in it and fill it up to let's just above the edge of the test tube lay it later the cover slip on it and leave the eggs will float to the top you can lift that cover slip off and put it on the slide to look at under scope that has ten times magnification you should be able to see those eggs so it's really easy to do if you want to do an actual eggs per gram you have to use what's called a Mc master slide you can buy them on the internet they're not very expensive you still need fecal float and you do need to weigh so you put known amount like one gram of feces into this
tube filled with fecal float you draw up your solution and not put it under this slide and you can it's got a little grid on it that you see under the microscope and you can do a physical count so make those master slides come with instructions they're not expensive Mike microscopes can be expensive but ten X. is not that much four X. even for X. is doable but ten X. is the best and so with just a little bit of equipment you can do your own either directly floatation which tells you what kind of worms you have it's qualitative or Mc masters which is quantitative tells you how many you have and really you're right the scope that you need to do this are are the low and so this isn't lighted stage compound microscope your identifying types of bacteria like we're talking real simple
had for a little science projects maybe and it makes a great science projects usually so definitely something that people can learn and I definitely recommend contact your county educator state specialist we love teaching people how to do this and I'm sure there is some sort of work shop in your state that will help you figure out how to do these on your own and if there's not one plan call your agents say Hey can you guys do a workshop on doing fecal egg counts in the end they can find the expertise to get it done even your veterinarian who usually does it on dogs and cats they could teach you how to do it yes super super simple and again if you're worried about resistance if you want to know Hey is my dewormer actually working that's the only way you're ever going to yeah that's right yeah because certainly you know I maybe we should talk about this a little bit
by the time you can see of horse with visible parasite issues like it that's a lot worms and by the time the horses look in the US yeah I would on a positive side of this I mean we don't want a horse that worms because it's like but honestly small strong Giles don't do a lot of damage they make a horse inefficient because they they graze on the mucosa so they they're they're called blood worms because they drink blood so they're sharing the nutrients you're feeding your horse but they don't migrate so the good news in all of this is the most prevalent parasite that we battle in the horse industry is small strong gels they consume the larvae the larvae matures grazes on the mucosa lays eggs but they don't migrate industry tissues so the big negative is inefficiency feeding worms along with your horse so thank goodness the aspirants this the large strongyles there's others that migrating cause problems but small strongyles are a lot less damaging so that's the big positive in all of this and I'm gonna put you on on the spot here and ask your your your opinion okay daily dewormers
honestly they are excellent but I they're very expensive and there's really not a good reason to do it three or sixty five days of the year so
I personally I mean the daily dewormers will take care tape forms and tapeworms really hard to find in fecal samples you have to do a double centrifugation to even find out and so let's say you had horses teeth done and they're still poor you know they don't have strongyles and you just can't figure it out it's very possible they have a tape worm so you need to use the praziquantel with them but in general
one protocol that we used to recommend was to use ivermectin and then put him on thirty days of the daily D. warmer strategically so in the spring when you know all the re infestation rate is really high maybe mid March use ivermectin then do a thirty day protocol of the daily D. warmer and then you're good through the summer and then in September do the same thing ivermectin and take care of the bots and thirty days of the daily dewormer and then don't deworm for the rest of the winter that's an excellent protocol so you had mentioned previously the idea that we always need to refugia so it we've we've gone from there should be no parasites near your horse ever to now thinking about Hey some parasites are okay so how did we get from they are our enemy to now thinking about Hey I want to have some worms on my property okay well I'm trying to think I'm trying to think of something as an example of the concept help you understand this there was a time in the United States where we had something called screw worms they are really really bad and and screw worms did a lot of damage in the livestock industry and so the way we control them as we took the the male flies and we expose them to radiation and release those flies out into the population and those sterile males competed with the non sterile males mating with the females and they only mate one time so we were able to completely eradicate screw worms by having those sterile males competing with the monster so it's kind of the opposite if you have
parasites that are resistant that are breeding and you have some parasites that are never exposed to the chemicals so other non resistant you have this competitive inhibition going on where you have some that when you get ready to de worm because you have the genetics from those non chemically exposed worms in the population those chemicals will still work I hope that sense hopefully so so the whole ideas we don't need to deworm everybody all the time because let's face it you know it nature adapts sets that's how we all work right so L. survival right so the worms that are able to live through and somebody is right it's not there's never a hundred percent only the strong survive and then go they've got great genes to pass on to the next generation and so you don't want to be breeding these like Hercules worms right exactly see one of the few weaklings left a lot
to tone it down a bit this so is there anything that we haven't covered with this I mean I think we really do want to get people thinking about Hey just don't follow the same pattern all the time think logically and strategically about when and where to deworm your horse yes de worming regularly used to be what we recommend that now we we recommend D. worm strategically that is only there's a problem so always want to pay attention on your young horses always want to pay attention on your brood mares I'd like to D. were my mare that day that she foals so that she's not passing thread worms to her baby through the milk but in terms of the other population make sure you have a problem before you try to fix it because the concept of having no parasites that's never gonna happen so the parasites we do have it be nice if they weren't already exposed to chemicals and then the whole saying cleanliness is next to godliness there's a lot you can do in terms of pasture management pasture rotation composting you know picking up the manure composting and so you kill weed seeds as well as parasite eggs all those things are positive and part of an integrated pest management system so you don't have to just rely on chemicals to manage your parasites and remember people D. for horses not for you
thank you so much for spending some time chat about worms on actually a cold snowy day here in Kentucky right now so you may not be called snowing on some other day when you listen to this but right now we're huddled here and hotel trying to stay warm so well that has been our tech box talk horse stories for the purpose thanks