EQUINE PROTOZOAL MYELOENCEPHALITIS


Other EPM Therapies

Veterinarians should discuss other drug therapies, in addition to the protozoa killing drugs, to address symptomatic problems that may occur during treatment.  Limiting inflammation of the cerebrospinal column, stimulating the immune system, and anti-oxidants are three things that the owner should be prepared to handle during treatment.  If the veterinarian does not discuss these, ask about them.

Inflammation

Photograph  horse clearing jump
   © EPMhorse.org  Leap of Faith
An active S. neurona infection in the central nervous system (CNS) will produce both temporary inflammation and permanent nerve damage.  The inflammation can get worse when the protozoa start to die during treatment.  This can happen as the treatment drug level builds in the CNS, and is known as a ‘treatment crisis’.  Watch for symptoms to get worse 7 to 14 days after the start of treatment drugs.

 

Inflammation by itself can cause permanent nerve damage, so treating it is important.  Veterinarians report that horses with higher neurologic deficiencies, and possibly higher levels of protozoa, tend to get treatment crises more often that horses with a Mayhew score of 1.  Some veterinarians will place a horse on anti-inflammatory drugs immediately, to prevent additional damage to the CNS. 

Banamine   Many owners already have the non-steroidal anti-inflammatory drug (NSAID) Banamine at the barn.  Even if your horse is a 1 on the Mayhew scale, you may wish to have Banamine on-hand to deal with any worsening of the symptoms.  Banamine can cause gastro-intestinal side effects such as ulcers when given in high doses, or longer than five days.  A January 2009 cost was $35 for 5 doses.

MicroLactin   This supplement is gaining recognition as an overall, mild anti-inflammatory.  This non-prescription supplement is a derivative of cows milk, and is known as Duralactin, or the ingredient ComfortX in Equinyl.  MicroLactin does not have side effects, so it can be used over the entire course of treatment.  It is possible to supplement with Banamine during a treatment crisis.  March 2009 price was $50 per month.

Dexamethazone   (Dex) This steroid suppresses the immune system, so it should not be used as an anti-inflammatory for EPM horses except in an extreme neurological case.  Used longer than 5 days, it can cause Laminitis.

DMSO   Dimethyl sulfoxide given intravenously, can be useful when the horse has extreme neurological symptoms.  The veterinarian should administer this drug, it should only be used for short time periods, and it can interact with other drugs.

Immune System

In many regions of the U.S. more than 50% of the horses have been exposed to EPM.  Researchers do not know why less than 2% of them get an active infection in the CNS.  Studies on blood of EPM horses indicate a change in the immune system response and cells.  Relapse rates for EPM are high, often with the same symptoms.  Some researchers believe that the relapses are latent infections which were never completely killed, and the immune system does not recognize.  Immune system stimulants have been suggested to help the horse fight the infection.

Levasimole   This drug has been used as part of a wormer, and anti-inflammatory.  It is known to increase immune response.  It has not been clinically tested specifically for use with EPM, but is being used for it.

Transfer Factor    This supplement has been around since the 1940’s for human use.  The older studies on humans suggest it increases the cell-mediated immune response.  It has not been clinically tested in horses.  The supplement is suggested to increase the cell-mediated immune response (see research below).  It WILL NOT kill the protozoa; it is only an immune booster.  It is made from cow colostrum, eggs, and mushrooms.  At least two companies produce this for equine use, and while the main ingredients are the same, there are differences.  4 Life Research and Nutrition Horizons USA offer this at March 2009 prices of $150 to $200 per month.

Vitamin E

Vitamin E has been shown to relieve inflammation, promote regeneration of nerve cells, and is an anti-oxidant protecting the CNS.  This vitamin is suggested by many veterinarians for supplementation during and after drug treatment for EPM.  It crosses the blood-brain barrier to work in the CNS.  A deficiency in Vitamin E is thought to impair the blood-brain barrier.  It is suggested at therapeutic rates from 5,000 to 10,000 total IU per day.  Add the total Vitamin E content of all supplements and feed to reach the target rate.  Research has shown that natural source vitamin E (D-alpha tocopherol) is absorbed by the body better than manufactured E (DL-alpha-tocopherol).

Recent Research

A 2006 study published in Veterinary Parasitology indicated: “Our results demonstrated that naturally infected horses had significantly (P < 0.05) higher percentages of CD4 T-lymphocytes and neutrophils (PMN) in separated peripheral blood leukocytes than clinically normal horses.  The product MicroLactin has been shown to limit neutrophil activity thereby reducing the inflammation process in the CNS.  The study goes on to say, “Leukocytes from naturally infected EPM horses had significantly lower proliferation responses, as measured by thymidine incorporation, to a non-antigen specific mitogen than did clinically normal horses (P < 0.05).  Cell-mediated immunity is lowered in EPM positive horses.

An ongoing study by Dr. Bello, Journal of Equine Veterinary Science, vol. 28, issue 8 (2008), uses Marquis, MicroLactin, and transfer factor in a protocol.  The initial study involved 28 horses, and 8 more have been studied.  This study was presented at the AVMA conference in 2007, and was published in 2008. The full text article is available below with permission from Dr. Bello.

Continuing research by others indicates controlling inflammation is a large part of the treatment process, and immune system stimulation is critical to avoiding relapses.

January 2012

References:

Veterinary Parasitology 138 (2006) 200–210

J Appl Res Vet Med 2003;1:272-8.

J Eq Vet Sc, vol. 28, issue 8 (2008) 479-482
An Intensive Approach in the Treatment of Clinical Equine Protozoal Myeloencephalitis Open PDF

Am J Vet Research, June 2008  Vitamin E

J Eq Vet Sc, vol. 25, issue 9 (2005) 380-382

TheHorse.com articles # 12025, 4829