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Gathering Data on EPM and PNE (polyneuritis equi)

Updated: Jan 4, 2023

Here is a photograph of some of our research yearlings. This herd was vaccinated with recombinant SAG 1 vaccine and challenged with a SAG 1 strain of S. neurona. We were pleased the vaccine was effective. As you can see they did well and were ready to go to their final homes. We completed a lot of paperwork on this herd, the first form was our Submission Form.

The submission form is more than a record of the sample you submitted. Here’s some insight on what we do with the information.

Please notice the Equine Submission and Consultation from is a carefully laid out document. We intend to get important information up front, like what do you want us to test? The check boxes indicate the Test(s) requested: Sometimes you give us carte blanche and leave it blank. Thank you! The lack of an entry may trigger a call from us. Unless, of course, you unwaveringly select the same tests for each submission. A tip off to us is the form comes as a pre-filled, xerox copy. Then we will surely call you, because each case is different!

The Veterinary Information section documents who submitted the sample and some sort of communication path so we can get results to you. Believe it or not, we sometimes have to resort to the return address on the package to find out who sent the sample! And if you paid cash at a UPS drop station, good luck to us. But we are crafty. We often successfully sleuth the name on the tube and cross-referenced with the town of orogin of the package. We will get hold of you even if we have to use Google to do it!

The next section is important, the Animal Information questions. Age and weight are critical to our evaluation of the data. We like the name on the form to match the name on the tube. It is not always the case, and mismatched identification of the sample will trigger a phone call from us to clarify. We make the appropriate entry on the form and have the FDA approved operating procedure to say we changed the form. And while we are on the topic, it really helps to use the same name for the same horse for all submissions. Using the registered name and then in another sample, using the barn name loses continuity and the animals history in our records. We are crafty and when we suspect this happened, we seek clarification. We are sharp enough to sort out when you put 10 for breed and Quarter horse for age!

The largest section on the page is titled Animal Evaluation. There is a check box that will give us a heads up on signs of polyneuritis equi. It is a tiny check box and it is often missed. We’d like to change that question to “are signs of PNE observed” instead of listing the most commonly observed PNE signs.

The next set of gait assessments, scored 0-5, relate to a specific FDA study. It is hard to compare evaluations between examiners and our program is instructed to sort data by using the criteria GAS 0 or GAS >0. It can also be useful to use GAS 0 and GAS >1. For the FDA study the more complete form parses the entry. The FDA form asks how many steps it takes to regain control after the tail pull when examining an ataxic horse. Just email us if you would like to see that form.

There are some more neurological signs to check off because they are signs that are commonly reported, they are behavior, seizure, stringhalt, muscle atrophy, and cranial nerve signs. Most veterinarians suspect EPM so we want to know how long the signs have been observed. We track how long the horse has been sick and how long it’s been since a last submission. The FDA influence is there, in concurred studies that require CSF we’d like to record how often CSF samples are available. Does the veterinarian suspect Lyme, and it’s important to know if the animal is being treated or was treated. The “was treated” is big historical question for us, this information helps us with relapses and our PNE work. We want to know what you treated with and how much drug you gave.

In cGLP studies it is inappropriate to write on the back of the form, in fact, any “spurious” mark must be documented. The forms are immortalized into a PDF for retrieval when needed.

We process the sample and get the results. The data is entered into our data base specific tables. Here it has to pass the Quality Analysis (QA) officer evaluation and then we subject the data to 35 individual queries. A query is a request for data (or information) from a database table or a combination of tables. The queries are algorithms and in less that an instant, the algorithm provides an answer to what we asked. Querying the data is very useful. Once a week a second QA officer makes sure that there are no entry errors. Our data must be accurate.

Every day we run a query that tells us data is missing. We run “missing data query”` and link the report to an email that asks for the missing information we consider important. Next, we analyze the daily testing results and combined with the recent history, we get a clinical picture of your case. It tells us if you should consider one of our studies, like the NfL analysis or the Hope Initiative. We do more!

For example, we might want to know the age range that horses first test positive for myelin protein antibodies and how that relates to outcome. We may related the weight of the horse to previous treatment and look for associations. We may want to know, over time, the progress of myelin-based disease and its relation to treatment. We may want to calculate the incidence or prevalence of sarcocystosis (by serotype) in an area of the country. We can relate that data to the predictive value of a test result, predictive values are often used by veterinarians to understand how meaningful a test result is to the case.

Horses we tested in Idaho don’t have antibodies against S. neurona, the veterinarians there diagnose polyneuritis. Isn’t that interesting? Are there opossums in Idaho? Do people not buy hay from opossum-populated states omitting that source of infections? And when a veterinarian questioned how many horses were seropositive to SAG 6 in Missouri…I typed in the query while he was on the phone…758 horses in Missouri had titers that indicated infection with the S. neurona SAG 6 strain. One might want to know what the incidence, by serotype, is of S. neurona in the United States. The questions are endless and we can look for the answers in our database of nearly 40,000 submissions. Mostly, our laboratory looks for patterns.

We recognized a pattern in the data that suggested S. fayeri was an issue in S. neurona seronegative horses. That goes against what is taught in veterinary school. We developed a test to investigate what was going on. The first hint something was amiss was that 55% of samples submitted by veterinarians from clinically ill horses didn’t have antibodies to S. neurona, yet veterinarians thought EPM was on the differential diagnosis list because neurodegenerative disease was present. The horses often had seropositive results to common S. neurona antigens (SAG’s 2, 3,4). The most common presentation was muscle wasting. The answer was that these horses most often had S. fayeri antitoxin antibodies, when we finalized that assay, the data made sense. We could correlate the clinical signs most often associated with S. fayeri-toxin seropositive horses and let our research proceed from there. Without a large database the conundrum would continue to this day! Hopefully these observations will make it to the veterinary school curriculum.

A common question at EPM society meetings is does S. neurona linger in the tissues as an invisible, single cell sarcocyst and this is why horses “relapse”? We used our skills and algorithms to select horses to answer this question. We already had an idea there were a significant number of polyneuritis horses that were misdiagnosed as “relapsing EPM”. With the S. neurona serotyping, S. fayeri anti-toxin assay and the anti-myelin protein assay we solved the riddle to our satisfaction. You can read the result in our peer reviewed paper “Three diseases that look like EPM”.

If you have global association-type questions, go ahead and email them to us and we will create an algorithm, and ask the database. There are more answers to find, we just have to ask the questions.

If you have global association type questions, go ahead and email them to us and we will create an algorithm, and ask the database. There are more answers to find, we just have to ask the questions.


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