ridecamp@endurance.net: Re: Parasites in horses

Re: Parasites in horses

gerhardt (gerhardt@theriver.com)
Sun, 13 Apr 1997 12:49:39 -0700


Good points.

I have read those studies, too, and wondered about the effect on horses.
The studies you are referring to seem to point to a lack of allergic and
auto immune problems such as are so rampant in Western society, in
non-industrial parts of the world in which the human populations tend to be
heavily infested with parasites. The work in this area is very
controversial and the conclusions that have been drawn are far from
accepted in mainstream science at this time. The opponents to those
conclusions argue in part that the authors of those studies are mistaking
cause and effect, that is, they find that the populations are heavily
infested with parasites, and are relatively free of autoimmune and allergic
disorders and conclude that the first causes the second, when in fact there
has been no showing of anything other than a correlation which is very
different than a cause. The opponents argue that the auto immune and
allergic reactions that are found in more industrialized societies are
actually caused by the widespread exposure of those populations to
substances that are the by product of civilization, both what we normally
think of as pollution as well as substances that we do not think of as
pollution, but which can cause allergic reactions in individuals, like
perfumes. The mainstream of study in this area rejects the conclusion that
lack of parasite infestation in a population is a cause of allergic and
auto immune disorders, although there is a correlation of those phenomena.

One point in that regard is that the horses on the daily wormer have never
been shown to have a higher incidence of asthma, allergic reactions or
autoimmune disorders. So, it would seem that the theory that being parasite
free is a "cause" of such maladies has not been proved as to equines that
are kept worm free, or as close to it as possible within the limits of

As to the concerns you voice about breeding super worms, this has been
concern of horse owners since both ivermectin and the strongid products
were introduced. There has never been any showing of worms developing
resistance to either product in years of testing and use by horse owners.
However, because of that nagging doubt that I have, too, I should have
mentioned in my post that I take my horses off the daily wormer while the
flies are not active, on the theory that if it is too cold for flies then
it is too cold for worms. This is from the hard frost that gets rid of the
flies until about now. I saw a few flies recently, so I will worm with
ivermectin soon, and all here will go back on the daily wormer until next
fall. I will also worm with ivermectin again in the fall, when the foals
are weaned. Those two wormings are to clean up any worms that might become
resistant to the daily wormer, and also bots, which are not affected by the
daily wormer. I am told that the vets in the Phoenix area do not feel that
the daily wormer is as necessary there as it is where it does not get so
hot and dry, because the worms do not thrive as readily in such an

Thanks for your thoughts. As I said, good points, that I have also thought

> From: MBlanchrd@aol.com
> To: ridecamp@endurance.net
> Subject: Parasites in horses
> Date: Sunday, April 13, 1997 3:01 PM
> Annette, you mention that your horses, by being parasite free, have an
> system that isn't so depressed from constantly fighting off infections.
> I am not a veterinarian, but I do read a great deal. This is going to
> sound really bassackwards, but recent studies done on humans show that
> parasite free isn't always the very best thing, if you are an immune
> In humans, at least, studies have indicated that, sometimes, if the
> system has nothing to fight it will INVENT something to fight..from which
> get such seemingly irrational auto- immune diseases, the most common one
> found in this case being asthma.
> I have no idea if it's the same in horses. I would be surprised if it
> WASN'T. Does this mean we need to ADD parasites? No, no!!! The idea is to
> keep them under control so that the immune system can keep them within
> tolerable limits. Foals go through a period when the immunity granted by
> mother's colustrum wears off and their system is just gearing up. An
> system needs to "learn" how to handle the assaults visited on it, just as
> army needs to train to fight the enemies. Keeping a foal totally parasite
> free is probably impossible, but if it's immunity system doesn't "learn"
> to fight and how, the system may, as in humans, just go and find SOMEONE
> fight, by golly, and if it fools itself into thinking something in it's
> body is the enemy,then the foal is going to have problems.
> I have to believe that daily wormers are serving to build up the
> immunities to the poisons we attack them with. In most cases of -cides
> any sort, be they pesticides, herbicides, the 'cide of choice is not
going to
> have a 100% kill rate. I believe the highest one can hope for is 90%.
> means 10% of the population of worms you are seeking to kill are going to
> survive, and pass on that survival benefit to the next generation of
> worms..which will sneer at the same stuff, day after day after day. In my
> humble opinion, using daily wormers is just a way of breeding for
> super-resistant worms.
> Michelle

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