Conference noted::equitation

    I just talked to our vet about this too. He said that the risk is so small
    that he's not suggesting that his clients stop using ivermectin. He
    feels that the millions of doses that have been used without incident
    is overwhelming compared to what he feels is a "casual" connection
    between ivermectin and any neurological problems.
    
    He also said that he is keeping on top of the research reports in case
    there is more than a "casual" connection. I asked him what he meant by
    a casual connection and he said that ivermectin is so widely used that it 
    is bound to come up as a common link between any horses that had any 
    problem from stone bruises to neurological disorders.
    
    I can tell you from personal experience that ivermectin is safer to use than
    the old dichlorvos and other "nerve" gas related dewormers we were
    using 10 years ago. When we used them at HALF the recommended dose our
    horses went into shock from the drug!

    RE .0
    I used to use Dr Purdy when I still had Jasper. He's expensive but
    good. Go with your gut feelings. There are other wormers out there, so see
    what Dr. Purdy recommends. 
    		Cindy
    

    Do you have any updates on the nerve disorder issue related to
    Ivermectrin use?  My vet asked me for the name, date, and source so he
    could look into it.  He felt that based on his knowledge and experience
    that there was such a small risk associated with Ivermectrin that we
    should continue using it.
    

    As Karen said, there has been no definite connection made between the
    nerve disorder and the Ivermectrin, but the are checking it out as a
    possibility.  I believe Dr. Purdy is taking a better safe than sorry
    approach.
    
    I believe Dr. Purdy saw several cases of nerve disorders that resembled
    Lou Gehrigs (spelling?) disease in humans.  He got Cornell involved,
    they started checking and found that there all of a sudden does seem to
    be this "new" nerve disorder that they haven't seen before.   I would
    suspect they are looking for common links between all the horses
    affected (and those that have died).  
    
    I know first hand that Ivermectrin, in excessive overdose, causes nerve
    disorders.  I know someone who foolishly gave some to her cat, which
    had to be put down as a result.  I'm not saying I believe it is what's
    causing the nerve disorders, but I can see why they're checking it out.
    
    Kathy  

    
    1) I have written to Cornell's Animal Health Newsletter and asked for
    whatever information they could provide. I'll post their response here
    when I get it.
    
    2) I don't know that ivermectin has ever been approved for use in cats.
    The fact that it may be toxic to cats does NOT mean that it's toxic to
    horses. In fact, aspirin and Tylenol are toxic to cats and are widely
    used in horses with safety. BTW, knowing somebody who had a problem
    is SECOND HAND experience not first hand.

    I agree - I don't believe ivermectin is approved for 
    cats.  However it did cause nerve problems in a cat.  I would think,
    tho I'm guessing, that if it causes nerve problems in cats, it could
    possibly do the same at some megadose rate in horses.
    
    I said first hand because I saw the person give it to the cat and I
    also saw the reaction of the cat.  When we brought the cat to the vets
    the vet looked up overdose of ivermectin in cats and it said nerve
    damage.

    One of the wormers that I gave to my cat from the vet had Ivermectin
    in it as I was joking with him on the cost...I could do two horses
    for what it cost for the cat.
    
    The dose was VERY small....will get the name of it.
    
    Kathie
    

    I wouldn't want to go off on a tangent with this cat issue, but I
    believe that it illustrates a very good point about people
    administering their own medication.  In this case Ivermectin in the
    paste form comes in a handy dispenser that is marked off in increments
    of a horses weight.  Usually, a full tube is for a 1200 lb horse with
    the average light horse weighing in at about 1000 lbs.  If you were to
    assume that a cat's metabolism is the same as that of a horse you could
    measure out a suitable amount.  Assuming an average cat weight of 6
    lbs, this would give you .005 or .5% of the full tube.  This is very
    little of the paste in a tube (note that one tube would worm 200 cats). 
    Remember that I assumed that a cat's metabolism is the same as a
    horses, not a very safe assumption.  
        Getting back to horses, there are many horses who are much lighter
    than 1200 lbs, and there is little control on how owners administer the
    medication.  Given this combination, it could be easy to assume that
    there is a problem with the drug when in fact it really is a problem of
    overdosing.  I'm not saying that this is what is happening, only that
    it is a possible explaination of how a drug can be tested in a
    controlled environment and turn out to be a problem.
    	This is even more evident when looking at the history of the drug
    in its injectable form.  There was a big flap after it was introduced
    on the market because it was said to cause many problems at the
    injection site (edema, infection, etc).  Turns out that several farms
    who reported the problem where usinging the same needle and syringe on
    a number of horses to save money.  This is bad news regardless of the
    drug used and only happened because it was a non-clinical environment. 
    
    
    The bottom line is "USE ONLY AS DIRECTED"!
    
    Bob
    

    I mentioned the Invermectin question to a friend living near Southern
    Pines, NC who in turn asked her vet.  The answer she got was that there
    possibly four recently imported Warmbloods that were wormed with
    Ivermectin and later died.  It was later determined that the horses died
    from blockages (possibly in arteries and/or linings of organs, I'm not 
    sure) from worms.  The Ivermectin did what it was supposed to do,
    unfortunately the Europeans have a huge resource of great horses but
    are not known for their progressive worming programs.
    
    As for using horse medications on cats, I don't.  Cats have a very 
    sensitive metabolism than other animals and due to their livers many 
    chemicals cause fatal results.  The chemicals in some people shampoos
    can harm a cat, so it would stand to reason not to use horse products 
    either.  I wouldn't change my horse wormer because of a reaction when
    used on a cat.  I wouldn't bother to mention cats in a horse notesfile,
    except that 99% of barns have at least one cat.

    HUH??????????
    
    I thought that one of the advantages of ivermectin was that it killed the
    worms over a period of time which helped PREVENT blockages. Most de-wormers 
    kill the worms all at once(more or less) which would make them even
    more prone to producing blockages if used on a horse that had been 
    dewormed irregularly.
    
    So what's left to use on such a horse? What strategy did your friend's
    vet recommend for such a horse?

    re .-1
    
    I never heard anything about Ivermectin killing worms over a period of
    time.  In fact, shortly after it came out, I asked a vet why they
    weren't using it for heartworm in dogs, since the real benefit of
    Ivermectin is that it kills *all* parasites in the body, not just those
    it encounters in the digestive tract.  Well, she said that since it was
    so effective, the worms in the dog's heart would be killed all at once,
    causing blockages.  I think there is now a heartworm treatment that
    does use Ivermecetin, possibly in small doses?

    Ivermectin is used as a heartworm preventative in dogs. ONCE a month in
    very low doses. It does kill the worms throughout the bloodstream as well 
    as in the gut. That's what makes it effective for 2 months versus
    Strongid T's or Strongid P's 1 month efficacy.
    
    However, I believe that the way it kills the adult forms of worms in
    the gut causes the worms to die over a period of 1-3 days as opposed to
    instantly through a few hours. As I recall its action, ivermectin
    paralyzes the adult forms and they die off gradually. Perhaps, I'm
    mistaken but that's the way I remember reading about it.
    
    I'll check some back issues of Animal Health Newsletter and other
    places I may have read about ivermectin and see if I can substantiate
    (or disprove)my recollection.

    Maybe the horses that died had very bad infestations of worms, so that
    even if they died gradually there were enough to cause blockages?
    
    Mary

    The vet in NC only mentioned that the blockages were of dead worms in
    the meninges.  I do not know how soon after worming these horses got
    into trouble.  Apparently the infestations were quite bad.  This did
    not surprise me as I have read elsewhere that worming programs are
    frequently poor among Warmblood breeders overseas.  What I was 
    wondering is if the blockages were in the mininges of the spinal column.
    If so, perhaps these horses showed neurological disorders and where the
    same that were mentioned earlier in this Note. 

    This is beginning to make sense! The meninges(plural of meninx) refers
    to any of the membranes that enclose the brain and spinal cord.
    
    There are some parasites that can migrate into the nervous system.
    If ivermectin kills them while they're in the nervous system(?????),
    I can see where a horse with a heavy infestation of parasites IN ITS
    NERVOUS SYSTEM could get into serious trouble.
    
    That's all speculation on my part so let's wait for some research
    results and see what reality is. I haven't got around to looking for
    that other info on ivermectin's action so when I do I'll include
    looking for info on:
    
    1) parasites that can migrate into the nervous system and
    2) ivermectin's effect on them while there in the nervous system
    (But don't hold your breath. I'm swamped!)

    I no longer use Ivermectrin as a wormer for my horses. I owned a
    10 year-old Quarter Horse Gelding that suddenly contracted the nervous
    disorder that was described by the base noter. I will not use anything
    that is even being considered a factor in this disease.
    
    I found Big Red one evening laying in his still and when he stood up
    he had the shakes. He was standing with his legs under, his head
    hanging to the groung and was having a hard time moving around. My vet 
    Stephen R. Purdy was called right away. He made four trips to see my 
    horse in one week, but the horse didn't show any improvement. Steve 
    thought Big Reg was suffering from some kind of stomach disorder or colic. 
    He advised us to take him to an animal hospital where more tests could be 
    done.
    
    We took the Big Reg to Tufts University in Grafton, Ma. After the
    vets examined him they rule out stomach problems and said there was
    something wrong in the nerves and muscles. We brought Big Red home
    no better than he had been the previous week. Tufts gave us medication
    to give to him for muscles. We also put Big Red on Vitamin E
    supplement. Steve Purdy called and conferred with many vets at this
    time. This disease was very new and rare and the vets couldn't give
    ideas of any other treatments.
    
    About a month when by and there wasn't much improvement in Red's
    condition, he still spent most of his time laying down in his stall
    or his pasture. My husband called on of the vets at Tufts and asked him
    about steriods, because it helps body builders get bigger muscles. 
    The vet said it was worth a try and he conferred with Steve Purdy and
    Red was put on steriods for awhile. After taking the steriods for a
    few weeks Red was standing more and not shaking much at all. He still
    stood with his rear legs under and had very little coordination.
    
    My husband, Big Red and I tried to fight this disease for a year. After
    a year my husband and I had to make a decision, because we could she
    that Red wasn't going to get any better. We decided to donate him to
    Cornell Univesity for research. We had three options and this one
    seemed to be the best. Red was put into experienced hands to be
    oberserved for as long as he lived. I just found out that Cornell
    had to put Red to sleep this spring, because he was going downhill
    again and they promised us that they wouldn't let him suffer.
    
    Big Red lived for about 2 years with this disease that there is no
    cure for and there is really no know cause. Red looked like a skelton
    a few weeks after he became sick and with the medications he was able
    to put some weight back on but not all of it. He was a big muscular
    16 h Quarter horse and all of his muscules deteriorated and he looked
    very thin. 
    
    This was our first horse and it hurt us badly to have to give him up. I
    am just glad that he is no longer suffering. I know this disease is
    very rare, but we still worry about our other horses coming down with
    it. I know it isn't contagious, because there were at least 20 horses
    at the stable where I board and none of the other horses got sick.

    re: .16  Do you know if Red was ever wormed with Ivermectin prior to
    this treatment.  All this sounds like someone (Tufts, etc) should be
    researching the effects of late-useage of Ivermectin and developing a
    method to test for possible problems (ie: infestation).  
    
    Above all, I wouldn't stop using Ivermectin.  It's safe and effective. 
    But, if I bought a new horse and I knew that this horse may not have
    been on a regular worming program, I'd call the vet and plan a careful
    deworming strategy - knowing that something may go wrong like
    blockages... 

    My Husband and I owned Red for two years before he became sick. I am
    not sure what kind of wormer the prior owners used. We had used
    Ivermectin a few times. This was the wormer that was used just before
    Red became sick. I know that Cornell University is doing alot of
    research into the nervous disorder that Red had. The problem that they
    are having is that alot of horses that contract this disease either die
    or are put to sleep before their cases can be researched. I cost us
    thousands of dollars to try to save Red. 
    
    Cornell isn't sure was causes this disease and Ivermectin is only one
    of the possible causes that they are looking. The other suspected cause
    that I am aware of is something the horse picks up from the
    environment.

    Yesterday, I got a response to the letter I sent to Cornell in April 
    about ivermectin in horses. My letter read: 

    "Several people have recently told me that their veterinarians 
    recommended that they stop using ivermectin dewormers on their horses.
    The recommendation is said to be based on reports that ivermectin may 
    have caused nervous system disorders.  Can you provide more information 
    on this situation and related  research? What problem ivermectin is 
    suspected of causing? How widespread have the occurrences been? How 
    great is  the risk?

    Frankly, I don't see how the risk could be greater than with the old 
    dichlorvos, trichlorfon and related organophosphate drugs."

    The response was from Dr John F Cummings, DVM, PhD. He agreed that the 
    risk of the old dewormers is great: "As you note, the organophosphate
    anthelmintics because of their known acute and delayed toxicity posed a 
    problem" but did not comment directly on ivermectin. Dr Cummings 
    included copies of several research articles and left me to read them 
    and draw my own conclusions. I'll just summarize what I learned by 
    reading those papers:

    1. Ivermectin paste has had sales of tens of millions of doses. Only
       0.0003% have produced REPORTS of any type of adverse reactions.
       NONE of the reported reactions have been confirmed as being caused
       by ivermectin. 

    2. Field reports of horses developing central nervous system problems 
       some time after treatment with ivermectin are not new! Such reports 
       first surfaced 9 years ago when the drug was still approved in the 
       injectable form. However, such reports are anecdotal and have not
       been reproduced in studies UNLESS THE HORSES WERE GIVEN AT LEAST
       10 TIMES THE NORMAL DOSE and/or given repeated overdoses!

    3. Five of 11 horses treated with 10 times the normal dosage for two 
       consecutive days showed transient impaired vision, ataxia(loss of 
       coordination) and depression. Two more showed signs of dehydration 
       for 5 days after this treatment.

    4. After single treatments at  60 times the standard dosage, horses 
       showed ataxia, tremors, paresis(slight or parital paralysis). Some 
       had to be euthanized.

    5. Dr Stephen M Reed(at Ohio State U) speculated in 1983 that horses 
       having certain blood-tissue barrier abnormalities may accumulate 
       higher concentrations and be more subject to toxicity. He also 
       reports giving ivermectin to horses which were showing severe
       ataxia without increasing their symptoms.

    6. Ivermectin works by paralyzing the worms which causes them to die
       and pass out of the horse's system. It works the same way as the old
       dewormer, piperazine. Piperazine has an excellent reputation for 
       safety and was used in foals and young horses until ivermectin was 
       developed.

    7. Ivermectin is not believed to penetrate the central nervous system 
       readily. However, it has been found in the brain and spinal cord
       of rats and dogs that had been given higher dosgae rates than is 
       standard for horses. 
    
    
    Pay your money and take your choice!