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Gathering Information on Autoimmune Polyneuritis

sidewinder3 (2)Horses with neuromuscular disease that are unresponsive to the usual treatments can be frustrating for veterinarians and horse owners. This post encourages you to get in touch with us if you have a horse with "EPM" and is not responding to treatment. ELISA Submission Form


We are following 38 horses that have clinical signs consistent with polyneuritis equi or cauda equina neuritis, an often overlooked syndrome associated with EPM. Our goal is to develop a treatment protocol for veterinarians dealing with these cases. Sometimes these horses are weak on one side, they have hemiparesis, and that prevents them from tracking normally.  The weak rear end falls to the weak side.  A commonly used descriptive term is "sidewinder". Ellison 2015 MPP MP2 Assay

There are other clinical signs of this disease.  Dragging limbs, tripping, or even drooling and dropping feed (cranial nerve dysfunction) are observed. The tongue can be atonic.  Another sign in these horses can be dripping urine or an inability to empty the bladder.  The most common comment in the history is multiple EPM treatments. We developed tests that can lead to a diagnosis of polyneuritis equi. Pathogenes Testing Options

Historically, the distinction between polyneuritis equi and cauda equina neuritis was the presence of cranial nerve involvement.  Discerning the disease by cranial nerve signs may not be accurate because horses with cauda equina may also have cranial nerve deficits.  In terminal cauda equina, horses are unable to urinate and often colic.  We don’t distinguish the two diseases by cranial nerve function because the owners and veterinarians involved with the horses we track often report difficulties with chewing, droopy lips, or facial muscle atrophy. These signs are often responsive to specific treatment.

Two serum tests, MPP and MP2,  measure anti-myelin protein antibodies.  Horses with polyneuritis equi often have circulating antibodies that are reactive against myelin protein and/or a reactive site on myelin.  The presence of antibodies are evidence that an autoimmune reaction is involved in the disease process.  A positive test can assist in diagnosis and potentially life-saving treatment.  2015 EPM and MPP

Eventually we think we will be able to stage to degree of damage using these tests. The C-reactive protein assay (CRP) may be the most useful test for case monitoring after a diagnosis is made.  The CRP assay is useful because response to treatment precedes a reduction in the pathologic inflammatory cycle. It may be that polyneuritis is the early stages of disease that ends in cauda equina syndrome.  That is to say, chronic idiopathic polyneuritis left untreated will eventually develop into clinical cauda equina.

If we understand the disease process correctly, it may be possible to prevent the progression of disease.  We are following the clinical course of 38 horses, their therapy, and the outcome of treatment.  We are assembling the data for a statistical analysis of the diagnostic and treatment options.  This data-based approach will be very useful to veterinarians trying to manage these horses.  The long game is devising a standard treatment protocol for afflicted horses to keep them healthy,  but we are not there yet.

Recently Dr. H. wrote a quick email asking if it was concerning that the CRP (C-reactive protein) level remained elevated in his patient, a 7 year old mare with a 3-year history of relapsing disease.  The good news is that she is currently clinically great while receiving treatment.  He wanted to know what is next.  What can be expected?  Unfortunately for Dr. H.,  we don’t have all the answers.  We sent back all the variables, the possibilities, and the literature he could review to make his clinical decisions.

Dr. Laura Benedetti is busy contacting veterinarians, asking for gait scores to update our records and requesting blood samples on the horses we’ve identified that could have this condition.  She answers emails about polyneuritis equi.  What is missing from the process is a forum for owners to discuss their horses with other owners similarly diagnosed horses.  While there are numerous forums and posts about individual horses with suspected EPM, these sites aren’t that useful for those facing a polyneuritis equi diagnosis for their horse.

We were pleased with the support offered to Taylor Lin (Blaze was posted on January 22 at Pathogenes Inc. Facebook), who initially felt alone before finding others who had been there before and kindly posted comments.

Horses with polyneuritis equi and cauda equina should receive a potential diagnosis and an individualized treatment protocol based on data that includes clinical examination by a veterinarian and laboratory testing.  Sub-clinical disease is an important aspect of chronic idiopathic polyneuritis. Dr. H’s mare  looks great and is performing well.  However, serum testing indicates she still has disease that needs to be treated.  Often the CRP can be used determine an endpoint to treatment.

We welcome you to post your questions and observations on Pathogenes Inc. Facebook page.  The information will be useful for others facing this disease in their horse.  Pictures and short videos are also welcome.  Individual treatment options are discussed privately with veterinarians because these need to be tailored to the specific cases.