Intestinal parasites always make for lovely dinner conversation.

When Fudge got to us, he was having some pretty bad diarrhea. After four days of this, we called the vet, who suggested a Power Pak wormer (five days @ 2X dose of fenbendazole). Mind you, this was before we knew about the EPM infection. Wormers stress the horse and the immune system, so giving them should not be taken lightly.

There has been enough anecdotal evidence of ivermectin being linked to worsening of symptoms in EPM horses, that there have been clinical studies on the effects.  The researchers say there is no proof of, and no way to to disprove that ivermectin has any effect on EPM horses.  It is known that ivermectin crosses the blood-brain barrier (BBB), but not how it affects the BBB.  The BBB is what keeps S. neurona from entering the central nervous system.

A fecal test is in order for Fudge, to determine whether he really needs to be wormed, and with which drug.  This will probably be a standard for the first year or more, so that we are not taxing his system with unnecessary wormers.  Just as unnecessary drugs are a drag on the immune system, so is a gut full of worms.

EPM really is a series of two steps forward, and one step back.  You try to prevent worsening of the neurological symptoms any way possible, because they slow the progress of the horse.  Each new neurological deficit may be permanent.  With EPM relapse rates cited from 15% to 40%, you become paranoid at slight missteps, and try hard to prevent unnecessary drug protocols.

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2 Responses to “Wormer”

  1. Cindy D., RVT Says:

    Wormers are not a stress on the horse’s immune system. (This is a common misconception that I have discussed with vets who are involved in EPM research and treatment.) In fact, they provide just the opposite effect by controlling parasite loads so that the horse’s own immune system doesn’t have to work so hard to do so. Each horse’s body will develop a certain amount of resistance to parasites (about 50% of horses will control parasite loads with little chemical control necessary), but when you have more than one stress on the immune system such as fighting GI parasites and fighting protozoal parasites in the central nervous system, the body simply can’t keep up. Thus deworming horses with EPM or any other disease is very important to help reduce the load on the immune system so that it can focus on the disease process that is not as easy to treat as ascarids and strongyles. That being said, there are certain dewormers that should not be used in a horse with EPM without due caution.

    Moxidectin should NOT be given to any horse that is sick or underweight.

    Ivermectin should be given cautiously to horses with neurological disease because the damage to the central nervous system by neurological disease/damage can allow this drug to cross the blood-brain-barrier and lead to further neurological symptoms. Otherwise without the damage to the CNS, ivermectin does not cross the blood-brain-barrier. It’s the damage that is present at the time that ivermectin is given that leads to it’s crossing the BBB and leading to neurotoxicity. ANY damage to the central nervous system—toxicity from plants or other drugs, traumatic injury, encephalytic disease of any cause (EEE, WEE, WNV, EPM, etc). It is not the ivermectin that is the problem, but rather the in-effectiveness of the blood-brain-barrier due to injury/illness.

    And Panacur Power Pacs should be considered carefully before being given to any horse because a study in 2006 showed that they cause serious inflammation of the GI tract and can even cause ulceration. Symptoms of this inflammation occur 2 weeks or more after dosing because of the way that the drug kills the encysted strongyles. This can mean colic and the reduction of absorption of drugs used for treating EPM (or any other disease) due to damage to the walls of the GI tract.

  2. EPMhorse.org Says:

    Editor’s note:
    Cindy is a frequent poster on Yahoo EPM Group, offering good information. The EPM Group is a great place to ask questions about real-life experience with information presented on this site. I am glad that she posted here, to help clarify several items. A discussion from different view points is always helpful to getting information out to equestrians.

    I believe that we agree on two things; that you should perform a fecal exam to find out if and what you should be targeting with wormers, and that it is important to worm so the parasites don’t further degrade the health of the horse. We differ on the wormer affecting the immune system.

    If you look at the Alternative Medicine page, you will find that I subscribe to several methods of medicine for my family. I tend to view the person and the horse as a whole (different from holistic), and not simply treat the symptom. My blog entry did skip several steps in suggesting that wormers inhibit the immune system.

    Please see this Sidney Harris cartoon:

    Beneficial microbes inhabit the digestive tract of both humans and horses. The microbes help to digest food, their fermenting action (in the horse’s cecum) helps to heat the horse, and they attach to receptors in the intestinal wall, preventing pathogens from attaching at those locations. The microbes form a physical barrier to disease causing agents. Changes in diet, stress, or oral drugs can change the balance of microbes in the digestive tract.

    If a sudden die-off of microbes leaves receptors open, pathenogenic (disease causing) microbes can attach to the intestinal walls. This is not how EPM gets started, but is how some other equine diseases start. I would argue that drugs of many types, including ivermectin, suppress the immune system by changing the microbe content in the intestine, as well as requiring the liver to process additional chemicals. This is not innate, or humoral (blood) immunity, or cell-mediated immunity, but I still consider the gut flora the first line of defense in the immune system.

    I have to dust off a collection of studies for further review, but offer these in the mean time. The first is a general listing of how ivermectin affects a range of animals. The second discusses the effect of ivermectin on a specific part of the human immune system.

    The pharmacokinetics and metabolism of ivermectin in domestic animal species
    The Veterinary Journal Volume 179, Issue 1, January 2009, Pages 25-37

    Inhibitory effects of ivermectin on nitric oxide and prostaglandin E2 production in LPS-stimulated RAW 264.7 macrophages
    International Immunopharmacology Volume 9, Issue 3, March 2009, Pages 354-359

    For those of you who would like a little information, but don’t want to read a clinical study: