Stupid question about deworming protocol

[shadesofbay3]

Hi all,

I have a (I think) really dumb question about deworming, and would like opinions before I have to bother my vet, as he is obviously busy.

I have my senior horse and then 2 months ago I bought a new mare.

My senior has a lot of health issues and has been a high shedder most years.

This is my vet’s deworming protocol for high and low shedders:

Horse 1 - (My new mare) Pulled a fecal once I bought her and she was a high shedder. I dewormed her and per my vet’s recommendations, pulled another fecal in 30 days for a recheck. That recheck was just last week and she came back at 0 egg count with a recommendation for nothing further needed to be done. HOWEVER, since the very first fecal in March had her as a high shedder, I was planning on deworming on June 1 per the chart above. So I’m confused on what to do - nothing else per the recheck or deworm again since she was a high shedder the first time in March? I know deworming too much is obviously not good.

Horse 2 - (My senior) Similiar to the situation above, I pulled her fecal in March, and she came back as a high shedder. I wormed her per vet recommendation and vet recommended returning in 30 days with another fecal. I had her fecal rechecked last week and she came back still high so I need to do a powerpac deworming (5 days in a row). Similar to my questions above, after that deworming is done, I’m assuming that satisfies my June 1 deworming of her as a high shedder?

Again, I know these are probably really stupid questions, but I would rather ask this community than bother my busy vet. I think I know the answers but would rather double check and be safe. Thanks

[JB]

There are several issues here:

Low shedder is < 200
Moderate is 200-500
High is > 500

Low shedders get dewormed Spring and Fall, not 3x a year, and certainly not with what’s likely to be an ineffective drug (pyrantel pamoate)

Moderate shedders (200-500) get a 3rd deworming. Whether that’s mid-Summer or mid-Winter depends on where you are and the management. If Summers are hot (prolonged above 85*) and dry, re-infection after Spring deworming is low, and if Winters are mild (lots of temps above 45*) and the horse is on pasture, reinfection rates can be high for the hose who can’t control things himself very well. But even then, whether you can use pyrantel depends on whether you’ve proven on your farm, through a high enough FEC and a reduction rate of at least 90%, that it’s effective. If you haven’t, or it proved ineffective, you shouldn’t use it (same with fenbendazole)

30 days for a recheck isn’t a suitable timeframe. 10-14 days is when you check to make sure the drug was effective. Or, you wait about 4 weeks past the typical ERP - egg reappearance period - for that drug. For ivermectin, it’s 8 weeks, but in some areas it’s been reduced to 4, so you might wait 6 weeks after dosing. Add 4 weeks for moxidectin, and remove 4 weeks for pyrantel and fenbendazole for the ERP

Horse 1

@shadesofbay3

since the very first fecal in March had her as a high shedder, I was planning on deworming on June 1 per the chart above.

A single FEC as a high shedder doesn’t mean that’s what they are. You need repeated FECs to show they’re a regular high shedder. Since you did a FEC only 4 weeks after dosing ,you don’t know what her status is, so see above. Do another FEC then, THEN decide if she needs to be dewormed agian

Because she’s new to your farm, so isn’t carrying farm-specific eggs, a reduction test isn’t worthwhile. So use a drug known to be effective (moxidectin, ivermectin) and deworm if her actual count is > 200

Horse 2

@shadesofbay3

I pulled her fecal in March, and she came back as a high shedder. I wormed her per vet recommendation and vet recommended returning in 30 days with another fecal. I had her fecal rechecked last week and she came back still high so I need to do a powerpac deworming (5 days in a row).

a PP is not a suitable choice. It may do a decent job targeting encysted strongyles, may not, but that’s not what’s showing on the FEC anyway, it’s adults. And it’s very likely to be very ineffective against adults.

You need to know the actual counts, not just high or low, and not just < 400 or < 500. You need that in order to do reduction testing (FECRT) to determine what is, and isn’t effective.

Reduction testing IS useful with this horse who is carrying farm-specific parasites.

Here’s all the latest and greatest on drugs, resistances, when to deworm and why, etc
Internal-Parasite-Guidelines_Updated.pdf

[HPFarmette]

JB, thanks for this great information.
Shadesofbay3, I am sad when someone feels that they are asking a "stupid " question. Look how complex this whole thing is!

[JB]

Oh for sure, this was NOT a stupid question! Nobody knows anything until they do. And if you don’t ask…

On this topic, there’s still sooooo much wrong and outdated information out on the web, so even with that, you have to be careful and vet the source, which is tricky since some of the sources are vets/vet hospitals