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MacabreMikolaj 04-18-2010 02:16 AM

Worms? Ick!
Ok, so this is slightly disturbing and we were hoping someone could help. Shay-la's just turned 3 year old has just crapped out a rather unsightly bunch of worms. We usually pay fairly close attention to their manure, especially after deworming, and never encountered anything like this. In all the research I'm doing, they look EXACTLY like ascairds/large roundworms and yet everything I'm reading says that horses after the age of 18 months to 2 years old develop an immunity to them and you only see them in severely malnourished horses with immune problems.

So what's the deal? We JUST dewormed them yesterday and from what we can tell, everyone else looks fine. They were all dosed with ivermectin last fall, and then we just gave them a dose of pyrantel yesterday. Eve likely wasn't dewormed prior to Shay-la receiveing her, or very infrequently anyway, but that was almost TWO years ago. We use the strategic deworming plan as we live up north where deworming is unecessary from about October to April. Eve was actually dewormed quite heavily last year as Betty thought she looked shabby.

Eve has shown zero signs of worm infestation - she has good weight, good shedding, and a healthy spring shine to her coat as well as no signs of rubbing her tail.

Pic of the worms:


We are planning on grabbing a sample tomorrow and taking it to the vet to see if we can get tests done. I highly doubt it though, we are so completely and utterly incompetent in equine health care, our local vet office ACTUALLY doesn't sell anything but ivermection :? How messed up is that? We got BETTER advice from the local tack store then from the idiots that work behind the vet's desk!

Ryle 04-18-2010 10:44 AM

There's no sense in running a fecal now if you just dewormed yesterday. If you are going to run one, you should do it in 10-14 days though even that is going to be of very limited use since you don't know what the fecal egg count was prior to this deworming. You should be running Fecal Egg Counts rather than simple fecal floatations.

It is common for horses to develop a resistance to ascarids by the age of 2, however if she wasn't dewormed when she was young and already had an adult load it's possible that these worms have been there for some time. Use of products that ascarids are resistant to in the previous dewormings or under-dosing in the previous 2 wormings could have allowed them to remain.

You say she has been on a strategic deworming program. What products have been used? And how have you been assessing her weight prior to deworming?

MacabreMikolaj 04-18-2010 11:08 AM

We used ivermection almost constantly due to it being virtually the only product available to us. Occasionally we use pyrantel or moxidectin. To be perfectly honest, until recently, we didn't know much about appropriate deworming programs and just used ivermectin as I stated it was virtually the only dewormer available to us.

I could pretend I know what your talking about with fecal egg counts, but I really don't, so I suppose I can cross my fingers and hope that one of our vets in the area has a clue. Typically we deworm about 2-3 times a year, in April, July and October. Last year, we moved the horses to a boarding facility and she seemed to know better so she had us dose Eve with moxidectin immediately, with another dose following two weeks later. I believe after that Eve was dewormed with ivermectin every two months until fall, with a dose of pyrantel right after the moxidectin treatments.

As for underdosing, for any horses we have over 1,000lbs, we give them a full syringe. We tip their heads, all our girls are good, and absolutely minimal wormer is lost. We have never had an obvious worm problem before, both to physically look at the animal or to observe their manure. We use a weight tape everytime we deworm, and I am the one that takes their weight everytime to give ourselves a better consistancy.

kassierae 04-18-2010 11:44 AM

If you wormed them yesterday she excreted them because they are dead. It happens, and has happened for us too. Also, I think you should get a copy of Country Supply( or Valley Vet( and the next time you worm give them all a dose of Equimax. Also, even if you think they don't need to be wormed, they may very well need it. Our guys get done every 8-10 weeks. And always rotational, because worms can build up an immunity if you use the same thing over and over.

riccil0ve 04-18-2010 04:14 PM

I have nothing useful to say. Just this. Yuck! I hate worms, any kind of worm. Ugh.

Oh, it also isn't always necessary to de-worm every 8 to 10 weeks. In my opinion, that's a little much. The amount of de-worming should be based on your area, you're climate, etc. Seeing at it gets freakishly cold where you are, Macabre, I don't think any nasties would survive in the elements to be ingested. I could be wrong, but most bug-type creatures don't do well in cold. I de-worm every three months, and my girls are both just fine.

MacabreMikolaj 04-18-2010 06:54 PM

I get that they are dead. Obviously. That was not my question. My question was WHAT type of worms are they. That is a lot of very big dead worms to be coming out of a technically healthy horse and I am concerned if there is some proactive measure we should be taking, especially if they ARE roundworms which are supposed to be virtually impossible for horses over the age of 2 to contract unless they have compromised immune systems.

We only de-worm 3 times a year typically. It's all that is necessary - we do not deworm from October to April. We give one last dose after the frost has killed everything, and then a dose in spring right when the bugs start. They also get a dose mid summer for bots. Most boarding barns around here will deworm every 2 months due to close quarters, which is what we're intending to start doing when we move. This will equal 4 times a year (April, June, August, October).

As stated in my first post, it is concerning because we have never encountered this before. I understand this may be normal in a living worm factory that's just been rescued, but these types of worms look ONLY like a type of worm she's not supposed to be able to have, hence our concern.

Ryle 04-18-2010 07:29 PM

1. While your new new barn manager may seem to know more, if she had you deworm again 2 weeks after using moxidectin she really doesn't know as much as she thinks. There is absolutely no reason to deworm that soon after using moxidectin.

2. The worms are likely ascarids from their appearance. There have been issues with ivermectin and pyrantel resistance in ascarids in different parts of north america so it's possible that you haven't done a good job in the past of getting rid of them.

3. So you give "the whole tube" to a horse that is over 1000 lbs, but how do you know that a horse is over or under 1000 lbs? And for those under 1000 lb s how do you estimate how much they weigh to plan your dosing?

4. Fecal egg counts are done by testing a set amount of feces each time and actually counting the number of parasite eggs seen on the whole slide. This is a much more informative sort of test. A plain old fecal float like most vets use is really only effective at telling what types of worms your horses have whereas an FEC gives an estimate of the kind of load they are carrying.

5. The fact that you've used moxidectin in this horse means that either this horse hasn't developed a resistance to ascarids, the ascarids have been immune to the type of dewormer you have used, or you haven't been dosing for an appropriate weight. (Or that these parasites are not ascarids and actually worms that have migrated up out of the ground into the feces---possible if the feces are more than a few minutes old.)

Ryle 04-18-2010 07:30 PM

Here is a bit of a run-down on deworming to help you understand a few things:

First, understand that you should always involve your vet in planning your deworming program and that's even more important now because strategic deworming should be done rather than following the old "deworm every 6-8 weeks rotating dewormers" which will no longer provide effective protection for your horse and will only help to build resistance. Along with the development of resistance is the fact that we now know that 20% of horses carry 80% of the parasites and those are the ones that need a more stringent deworming regimen while the other 80% of horses will need less frequent dewormings because they have a better resistance to parasites and thus don't carry big burdens even without frequent dewormings. . Add in the fact that environmental conditions vary all over the world and they have a direct affect on environmental contamination with parasite larve and on when infection rates are going to be highest in each situation. All of these facts mean that there is no "one-size-fits-all" deworming program. Some horses may only need deworming twice yearly while others like foals require much more frequent dewormings. So, rather than just following the old plan it's now recommended to practice strategic deworming--plan a program based upon the specifics of each horse and use diagnostic testing to ensure that the program is appropriate or to determine when deworming is necessary. This is to help reduce the number of dewormings to help slow the development of resistance while still providing adequate deworming for each horse. This is important because there aren't any new deworming drugs that will be hitting the market anytime soonIt is important to take all factors into account and know which horses are more resistant and which are less resistant in order to plan a deworming program that is going to be effective for minimizing parasite loads, minimizing the frequency of treatments and also minimizing the risk/rate of parasite resistance developing to the drugs in use.
So, rather than just following the old plan it's now recommended to practice strategic deworming--plan a program based upon the specifics of each horse and use diagnostic testing to ensure that the program is appropriate or to determine when deworming is necessary. This is to help reduce the number of dewormings to help slow the development of resistance while still providing adequate deworming for each horse. This is important because there aren't any new deworming drugs that will be hitting the market anytime soon.

There are 4 classes of dewormer on the market:
benzimendazoles --fenbendazole, oxibendazole, other chemicals that end in -azole (there is a long list)
pyrantels---pyrantel pamoate (paste) and pyrantel tartrate (daily dewormer)
avermectins---ivermectin and moxidectin

Of those 4 classes, all but praziquantel are "broad spectrum" meaning that they kill several types of parasites. It is not necessary (or at least was not prior to the developement of parasite resistance) to rotate dewormers using these products to kill the most common parasites of horses. The "rotate to kill the different types of parasites" was necessary when we only had the much older drugs which were often only effective against one or two types of parasites. Praziquantel is the only one of the current drugs that is not broad spectrum and it kills tapeworms which the other drugs are not effective against unless you use pyrantel at twice the normal dose.

But, these drugs are not all as effective as they used to be because they have been over-used and mis-used for many years. Now we have parasites that are becoming and have become resistant to these drugs so we have to change our deworming strategies to help slow the build up of resistance while still minimizing the parasite load in our horses.

When planning a deworming program for adult horses, your main concerns are strongyles, tapeworms and bots in that order. (And this is where you can really see the big problem with deworming based on that link above.) Strongyles are the parasite with the most resistance issues--in more than 90% of areas tested these parasites are now resistant to fenbendazole and in more than 40% they are resistant to pyrantel. There has even been 1 study showing strongyles becomeing resistant to ivermectin. So, the standard rotation in that link you are likely not going to be effectively killing strongyles for 1, maybe 2 and even as many as 3 out of 3 dewormings.

For foals, your main concerns are ascarids, strongyles, tapes and bots. So you have the same concerns as with adults---resistant strongyles, but you also have the added concern of ascarids which are shown to be resistant to ivermectin in some areas of the country. Rotating is still a good idea in foals so that you balance possibly not killing ascarids with one treatment and then the next treatment killing ascarids but possibly not killing strongyles. However, it's probably best to stick to rotating either pyrantel or fenbendazole with ivermectin.

So, rotation options are limited at best and it's really not the rotation that is most important for preventing parasite resistance but appropriate dosing and treatment intervals.

You need to be SURE you are not under dosing your horses so always use a weight tape or measure your horse and calculate his weight. In studies even many vets were way off on weight estimations and they have the benefit of spending a few years working in situations where they get to walk horses onto scales daily to see what 900 lbs LOOKS LIKE.

Weight calculation information:
Body Weight Estimation of Horses
KG calculation shown as well as a chart based upon heart girth measure (remember, the heart girth only assessment may be off by as much as 200 lbs just like weight tapes)
Horse Weight: Estimate It Easily
How to calculate in pounds

Ryle 04-18-2010 07:31 PM

As for appropriate dosing intervals, you want to treat according to the egg reappearance period so that you are dosing to prevent continual recontamination of your pastures. This means that you won't be deworming at a time when there are no parasites in the system that will be susceptible to the product you are using next which happens if you dose too soon after ivermectin or moxidectin with pyrantel or fenbendazole because at normal doses these two chemicals only kill adults in the GI tract and if you've dewormed with moxidectin last 8 weeks ago there aren't adults there to kill and you've missed the migrating larva which will then start shedding eggs 4 weeks after you treat with either of these drugs and shed for the 4 weeks until you deworm again. Or if you dewormed with ivermectin 6 weeks ago and treat with either pyrantel or fenbendazole you will start seeing egg shedding into your pasture in 2 weeks because you didn't have adults in the GI tract when you dewormed last but they will be there in a couple of weeks. Or in the case where you actually do have adults for the pyrantel or fenbendazole (which again is not likely to be working) to affect because it's been 8 weeks since your last dose of ivermectin you will again have parasite ova being shed in 4 weeks because that is how long after the use of either of those drugs you start seeing adult egg shedding parasites in the GI tract. So deworming based upon Egg Reappearance Periods, you would deworm and then deworm again based upon what drug you used last--4 weeks later for pyrantel (or Fenbendazole, though the next day would probably be more useful LOL), 8 weeks after ivermectin or 12 weeks after moxidectin. In this manner, you can significantly reduce the parasite load on your pastures in a year's time.

Besides deworming, there are pasture maintenance practices that can help to minimize pasture contamination with parasite larva. Rotating pastures with other types of livestock (cattle, sheep, goats) can allow time for the parasite larva to die off before you put horses back on it but you have to have many months between rotations. Picking up feces at least every 2-3 days will also greatly reduce the parasite load on your pastures. (Doing this daily will keep the amount of feces you have to shovel at one time down ) Dragging pastures to break up feces during the very hot, dry southern summers will also help lower parasite burden on pastures, but if you do it during moderate weather it will only help to spread the larva around.

Whatever deworming information you read, make sure it's up-to-date. Many articles and recommendations are based upon old information and that can lead to wasting money and providing poor parasite control for your horses.

Here are some questions to help you and your vet determine the risk of re-exposure and re-infection for your horse’s particular situation.
1. How old is your horse?
2. Is she turned out or stalled?
3. If turned out is it a dry lot or pasture? How much acreage?
4. Do you pick up feces out of the turnout every 2-3 days?
5. Are other horses in the pasture too? If so do they get dewormed regularly? What are their ages?
6. Do you have extreme weather---summers over 100 degrees for extended periods or winters below 40 degrees for extended periods?

For detailed instructions on planning a deworming program that is appropriate for your horse, check out this 1 hour webinar (have pen and paper ready!):

tealamutt 04-18-2010 10:54 PM

once again Ryle, excellent info. Though it seems like a lot to slog through, I strongly suggest that folks read everything she has posted as this is very important information, as well as accurate. My parasitology professor would be so impressed!

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