Absolutely! We started reduction testing last year. It will be interesting to see any progression or changes as time goes by.
My fear, as is many of ours, what will we do when we approach a dangerous level of Moxidectin resistance. I haven’t been up on the research but last I checked, there is nothing with the same level of efficacy on the horizon.
Absolutely, it’s truly terrifying. So we really need to be cautious and conservative in how we use it.
I have no personal experience but I’ve read of cases in sheep and goats where there is just … no treatment for a particular load of internal parasites. You do what you can and watch your stock die or cull them. I cannot even imagine what’s going to happen if we get to that point in equines 
I know, ugh…
Our much smaller fields aren’t harrowed or picked, just mowed, and most horses in our herd still have very low fecal loads, with one or two exceptions (treated accordingly). In case that helps…
I agree on all that’s been said about resistance. Scary stuff… and a threat to animals and humans alike with indiscriminate use of antibiotics, antiparasitics, etc. Wish we knew then what we know now when I was growing up and we threw wormer at them like it was candy without a second thought.
It’s reassuring to hear the various reports of low counts from horses in fields that aren’t picked etc. I continue to find that certain horses always have some sort of load, whereas the others always don’t (so far).
Yes, I remember the old days and cringe about how we used to deworm every 4-6 weeks on schedule. Yikes.
If you’re using Equimax 1x and Quest Plus 1x, and getting low/clean FECsthere’s no need to worry about a hidden encysted strongyles of any significance.
If you’re dragging in the heat of Summer, you’re affecting the death of a lot of strongyle eggs as well.
Increasing deworming frequency is exactly how we ended up in this resistance pickle to begin with!
As counterintuitive as it sounds, letting horses carry a low parasite burden is healthier in the long run than trying to eradicate everything. Aiming for zero parasites is impossible, and what will happen is you will create a breeding population of only the most resistant individuals.
ETA: I don’t pick my fields. I drag periodically, but not in agreement with the weather. My formerly high shedders’ FECs have remained low for more than a decade. Some of them are constantly zero. I only deworm 2x annually: fall Equimax and spring Q/QP. If someone has a high FEC (this has only happened when I’ve brought home new horses), I will add a third deworming for that individual, usually Strongid/Anthelcide in combination.
have you validated that’s effective? That is definitely much more likely to be effective than either one on its own. Most people don’t know about combinations - how did you find that out?
I think I have only done a FECRT after it… twice? On 2 different horses; EPG from over 1000 to 0 in both instances. One horse remained at zero indefinitely after. So I’d say for my population it has been effective.
I know you know this, but researching anthelmintic combinations has been one of the few areas of hope for the last decade.
I just want to say this entire thread makes my equine parasitologist heart fill with pride 
Everyone doing their fecal egg counts, using the correct products (other than the comment about someone using the daily Strongid. Please don’t use that product), and having good knowledge. I’ve only been in this game for six years, but am well versed in how incredibly difficult it is to get people on this parasite control bandwagon. Just… thank you, everyone. So much. It makes my PhD feel mildly less worthless. I’d love to work on finding a new product, but funding is tough to get. I promise we’re trying 
If you don’t mind encapsulating why daily Strongid 2x should be avoided I’ll pass the info on to them… ty! (In my mind, it’s the resistance issue compounded by the fact that it’s putting what is essentially poison (dewormer) into your horse every day instead of 2-3x a year… although I do know that they are using it temporarily on horses who are rescues, not forever)
Pyrantel tartrate is in the tetrahydropyramidine drug class which has extremely widespread and well-documented resistance issues in cyathostomins. The overuse of daily Strongid is likely a contributing factor to resistance against this drug class. You’re essentially exposing the worms to a continuous low dose of the drug and rapidly selecting for resistance.
I would assume that their goal is to kill as few worms at a time as possible because they’re concerned about an impaction in the rescues, but really the drug is so ineffective that they’re likely not even reducing the burden (if it’s even high in the first place) enough to make a difference when they finally do treat with something else. I’m not a DVM though so they should definitely follow their vet’s advice. Rescues are just generally so tight on money, I’d hate to see them tossing money to the wind with a product that doesn’t do much of anything.
They may have issues with ascarids in rescues, particularly if they’re young or immunocompromised, so maybe that’s why they’re going with a pyrantel product. The issue is that there are already limited cases of loss of pyrantel efficacy against Parascaris, and we really do not want to speed up that process, which is in all likelihood what a daily product will do. But again, they should go with whatever their vet prescribes.
I’ll copy your input on the subject and show to them, thanks!
Yeah no problem! It’s funny timing because my PhD advisor just commented on a FB post on a veterinary page the other day about please don’t use daily deworming products. 
My vet said to use Equimax and not use Quest plus at all. She said Quest plus should be used as a last resort due to the development of resistance.
As a side note, neither of those seems to work on pinworms. I had to use fenbendazole for those. Equimax used to be a little cheaper. Not sure it still is?
Most horses don’t have severe worm infestations so identifying the high shedders is important.
At the end of the day they’re both in the same drug class with the same mechanism of action so resistance to one will likely confer resistance to the other. We’ve seen huge reductions in egg reappearance period for both drugs over the past few years; both are down around 5-6 weeks now. The big advantage of moxidectin was that it took significantly longer for eggs to reappear and it had some efficacy (0-37% for early 3rd stage and 50-89% for late 3rd and mucosal 4th stage larvae; still roughly similar) against encysted stages.
Martin Nielsen just wrote a great review on the status of resistance: http://dx.doi.org/10.1016/j.ijpddr.2022.10.005
There’s already resistance to ivermectin and moxidectin in some form. Both have a reduced egg reappearance period in some areas. Ascarids (rarely a concern for adults) are resistant to ivermectin and pinworms are as well.
Even though they’re in the same class of drugs, you’re going to speed up resistance to whichever one you use most on a given farm. If you speed up survival resistance to ivermectin by only using that, you’re leaving yourself with only 1 effective broad-spectrum drug, and then you’ll speed up resistance by only using that.
Alternating 1 each a year will slow down the rate of resistance to both.
When I finally got around to having a fecal done, I had a high shedder. JB got me educated although I did need a few reminders:
Spring is QuestPlus
Autumn is Equimax.
I tested and it was effective.
By submitting your email, you agree to our Terms of Service and Privacy Policy. You may also receive promotional emails from The Chronicle of the Horse. You can opt out at any time.
For Customers
Company
Terms of Use
