^^ THIS. Over-dosing of de-wormer does not cause resistance, under-dosing does.
That is a not true.
Worms are building up resistance for the same reason bacteria are building up resistance to antibiotics.....OVERUSE!!!!!!!!!
You might want to do some reading on this topic so you can be better informed.
In January 2010 the British vetinary association issued new guidelines which called for "the immediate cessation of blanket worming in all grazing animals, including horses. This is because of increasing drug resistance of the worms caused by overuse of wormer chemicals. Each time a wormer is used it increases the chance of the worms developing resistance against the wormer. There are no new wormers being made, we need to change to "targeted worming"
80% of the worm burden is usually found in 20% of the horses. This means the 80% are being wormed unecessarly, ingesting strong chemicals,wasting money and increasing the chance of resistance to wormers. Worming - cobswallop How bad is parasite resistance in horses today?
- Entire classes of equine dewormers no longer work well against small strongyles.1,2,4,5
- Small strongyles — the major target of parasite control in mature horses — have demonstrated widespread resistance to two of the three major dewormer classes (benzimidazole and pyrantel products).1,2,4,5
- While products in the third class (macrocyclic lactones) still control small strongyles,2,3,6 resistance could develop from overuse.7,8,9,10
Parasite resistance to equine dewormers Drug resistance occurs by overexposing a pathogen to a medication. This overexposure gives the pathogen more opportunities to find a way to avoid the effects of the medication. Evidence has been presenting itself around the world that resistance of equine parasites to current medications is already occurring. Parasite resistance to equine dewormers - Equiworld -Horse and Pony Informationon the internet- Text Only
My point to all of this is that double dosing should be done ONLY on a vet's reccomendation, not done by people just because their horse is losing weight, itchy tail, becaue its 6 weeks are up or has a "grass belly", etc.
Let me be plain spoken: what I see on this thread is some posters advocating and engaging in (per their statements} gross MISUSE and OVERDOSING of wormers. While this may be a medical necessity in some rare vet endorsed cases, that is not what I am seeing here. I am seeing a bunch of worm phobic people going way above the reccomended dosage thinking that they are helping their horse, when all they are doing is breeding worm resistance that may some day come back on ALL horse owners, including themselves.
FYI, our vet recommends worming be done ONLY after a fecal test is done and worms found. She DOES NOT ENDORSE the routine six week worming.... nor do alot of boarding facilities around here.
And when people like Indy horse and AB say things like above....it's downright scary how uninformed horse owners are to this threat.
I encourage BOTH of you and all horse owners to do some research on this topic. UNDERUSE is not the cause of worm resistance. INFORM yourself...do some googling.....