Worm count reduced from 950 to 0 in 3 weeks without worming?

[RobinHood]

In the 5yrs I've had my horse his worm counts have always come back as less than 50, no eggs seen, so I was horrified 3 weeks ago when the results came back as 950 (medium count). He react quite badly to vaccinations, wormers etc. so I decided the least risky plan was to use panacur equine guard and then re-test afterwards to check for resistance.

3 weeks went by before I ordered the panacur so I decided to do another worm count, just so I had an accurate result immediately before he was wormed. I took the sample yesterday, received the results this morning and was very surprised to read 'less than 50, no eggs seen in sample'.

Can anyone explain why this might have happened? Just for the record I am awaiting advise from my vet and the lab that tested the samples, but I interested to know if anyone else has ever experienced unexpected results?

 

[soulfull]

Sounds like a mistake with the original count

 

[Gloi]

or the second count.

Maybe the droppings aren't mixed thoroughly enough when sampling.

 

[Scatterbrain]

I too worry about the accuracy of these tests, given it's such a small sample of dung that's tested. If a horse has a burden, will the eggs be present in every small piece of dung I wonder?

 

[amandap]

Accuracy apart, I don't think worms release eggs at a constant rate or do they?

 

[Brightbay]

It's my understanding that worms do not lay eggs all the time. They will often respond to environmental conditions - for example, that's why encysted redworms cause real problems, because they mature en-masse at the same time. If they matured in small batches constantly, the horse would probably cope.

In the same way, worms in the horse's gut do not necessarily lay eggs at a constant rate, like chickens So it is quite possible to see quite a different result from two tests a month or so apart. Early spring is a common time for higher counts, because obviously the worms want eggs deposited on actively growing grass that will be eaten by their host.

That's just my layperson's understanding - best to check with a vet who has a good knowledge of parasitology (they don't all have this!) or a specialist lab who deal with worm counts.

 

[RobinHood]

It's my understanding that worms do not lay eggs all the time. They will often respond to environmental conditions - for example, that's why encysted redworms cause real problems, because they mature en-masse at the same time. If they matured in small batches constantly, the horse would probably cope.

In the same way, worms in the horse's gut do not necessarily lay eggs at a constant rate, like chickens So it is quite possible to see quite a different result from two tests a month or so apart. Early spring is a common time for higher counts, because obviously the worms want eggs deposited on actively growing grass that will be eaten by their host.

That's just my layperson's understanding - best to check with a vet who has a good knowledge of parasitology (they don't all have this!) or a specialist lab who deal with worm counts.

Mmm the lab did say the worms (redworm) might have encysted between taking the last sample and now. Apparently redworm can encyst for anything between 10 days and 2 years and the whens and whys aren't yet fully understood.

I feel more inclined to act upon the first sample, as surely they can't have imagined seeing eggs, whereas they could have been none in the particular bit they looked at under the microscope when doing the second sample. On the other hand this horse is so sensitive I'm really hesitant to worm him and risk laminitis again when it could be unnecessary.

 

[Brightbay]

Apparently giving a wormer can actually cause encysted worms to mature - it seems to be something to do with worms remaining encysted until they somehow detect that there are no adult worms in the gut (so there's room for them!). But since you used the Panacur 5 day, that should have both caused them to mature, and killed them?
I was interested and went off and read some stuff (http://www.midamericaagresearch.net/documents/Equine Parasitology with pictures.pdf) which was fascinating... I was wrong in terms of them shedding eggs at different rates - what actually happens is that the shed eggs don't immediately mature on the pasture, but wait for specific environmental conditions (warm and wet). Then the wee beggars all mature at the same time, aaargh!

I do see your concern - we had wormed correctly up to a few weeks ago when there was exposure to a new horse with pinworms - so we had to give an additional wormer to cover these. One horse has gastric ulcers, so we really would have been much happier being able to stick to our worm counts + Equest Pramox schedule for the sake of his stomach, but the alternative is a horse shedding pinworm eggs everywhere

 

[STRIKER]

agree with Brightbay, but I was always told to take a bit of poo from a few different piles of droppings not just one pile.

 

[SO1]

I know you may not want to do this because of the cost but you could try taking another sample and sending it to a different lab and see what result you get.

 

[happyclappy]

agree with Brightbay, but I was always told to take a bit of poo from a few different piles of droppings not just one pile.

ditto

 

[RobinHood]

Apparently giving a wormer can actually cause encysted worms to mature - it seems to be something to do with worms remaining encysted until they somehow detect that there are no adult worms in the gut (so there's room for them!). But since you used the Panacur 5 day, that should have both caused them to mature, and killed them?

Yes but I haven't given him the panacur yet... I've got it sitting here and trying to decide what to do.

Equest Pramox is definitely a no go for mine, hence the Panacur 5 day followed by Equitape.

 

[claribella]

I read something about this the other day. A vet came on the forum saying that its this time of year that worm counts can come back with inaccurate results so we should leave it until after may. That was his words

 

[RobinHood]

I read something about this the other day. A vet came on the forum saying that its this time of year that worm counts can come back with inaccurate results so we should leave it until after may. That was his words

Oh that is interesting. The trouble is we've just worm counted 40 horses and based our choice of wormers on the results, which is Pramox for those with medium counts and Equitape for those with low counts (and Panacur before Equitape for Mr Sensitive ;-)). Now I've tested mine again and it's come back so different we're a bit stumped about what to do with the whole lot of them.

 

[Hetsmum]

If you send your worm counts away there is new evidence to suggest that eggs can hatch in warm conditions during the post period. So for example if you take sample Sunday morning and post Monday during a warm day you can get a negative reading when it would be positive. My local vets do counts themselves. You pop totally fresh poo to them and they test same day (and it sits in fridge until tested.) Others are correct you should take at least 3 different pieces to sample. Can you not use Equest alone then Equitape later on? Panacur has very large resistance these days in certain parts of the country.