Pathogenes Inc.

   The definitive diagnosis of EPM can be difficult.  The veterinarian relies on physical exam (neurological exam) as well as excluding or ruling out other causes of CNS disease in the horse. The USDA criteria for disease is by culture of the organism from the CNS as a gold standard.

   The list of neurological diseases in the horse is long. However in the absence of fever and ruling out the other considerations, EPM is suspected.  Fever followed by nasal discharge and ataxia could indicate equine herpes viral infections, fever usually accompanies Arbovirus infections EEE, WEE, VEE and the Flavivirus WNV.  And the other considerations inculde polyneuritis, cervical vertebral myelopathy, equine degenerative myelopathy, parasite migration, trauma, allergic disseminated encephalomyelitis and weakness from another cause.   In a cared for horse that does not have CVM or history of trauma there are useful tests to rule in or rule out S. neurona encephalomyelitis. 

   The inclusion of a test that measures antibodies can be useful.  We have used experimental and confirmed cases of EPM to determine that SAG 1, 5, 6 ELISA's titer detects the organism early after the parasite enters the blood stream.  The disease, EPM, is a sequela of S. neurona infection. An advantage to the SAG ELISA's is the ability to determine therapy choice.  The Peptide ELISA detects antibodies to the 3 antigen types of S. neurona and the test result is reported as a titer.  We found no advantage in using CSF to detect infections (see published data).   

Panel of tests useful in diagnosis and monitoring infection.  In addition to physical exam we offer the following tests: 

IgG titer measured by SAG1, 5, 6 ELISA

IgM titer measured by SAG 1, 5, 6 ELISA

IgG titer against non-pathogenic Sarcocystis sp.

Immunoblot 

PCR

Indirect fluorescent antibody

Isolation of the merozoite from blood

Serum Amyloid A

Lymphocyte proliferation Assay

Pathogenes Multiplex Antibody Test Kit

Determines phenotype

THE TEST IS AVAILABLE FROM :

www.prota-usa.com 

Dr. Kevin Jones (Centaurunivet) @ 913-390-6184

PEPTIDE-ELISA RESULTS EXPLAINED

Click here to understand the test, results, and what they mean.  This is a discussion about the test, antigens, and develping the assay.

What do your PEPTIDE ELISA results mean to you and your horse?

The ELISA test results are reported as a titer for each antigen type.  You will get a titer for SAG 1, SAG 5, and SAG 6.  These three titers indicate reaction to different proteins that identify the three antigenic types of S. neurona causing the infection.  If the animal has antibodies to more than one phenotype the horse has a mixed infection.  More... 

 Our experience with acute and chronic EPM allows us to better interpret antibody levels in the horse. 

    A horse that has any measurable antibodies to SAG1 has ingested oocysts that contained neurovirulent S. neurona.  A low titer (4-16) means that the antigen type SnSAG1 strains are recognized by the horses immune system and an immune response was stimulated.  Some horses mount an effective immune response and the infection is eliminated.  Some strains are more virulent than others and some strains are more resistant to drugs than others.  Successful elimination of the parasite is detected by a fall in titer in 2 to 4 weeks.  Approximately 11% of the equine population has a low titer to S. neurona SAG1 strains, but over 44% of horses with a provisional diagnosis of EPM have these antibodies indicating infection and an immune response.   

   Based on our experience with experimental infections the parasite was present in the animal and the titer rose to a level of 32 or greater during active infection.  Horses with early infections (less than 20 days) can have a low titer.  The titer will increase with time if it is untreated pointing to the value of repeat titers to monitor suspected infections.  A single point-in-time test may have limited diagnostic value in early infections or when other conditions that delay or limit antibody production (drug treatment).  However, an increase in titer, irrespective of its absolute value, coupled with signs of ataxia are strong evidence of active infections.

      Non-specific immune stimulation will not affect the antibody titer measured by our test, however specific immune stimulation (vaccination) will increase the titer.  We have tested the ability of specific immune stimulation to increase titer and have determined the value necessary for a antibody titer that can protect against infection (by homologous challenge) thus reducing or eliminating clinical signs of infection.  Our results are available on our about us page.

      Please contact us for the price of testing or if you have questions about your test results. The tests require specific sample submissions, please read the submission requirements as well as shipping conditions.  We will answer questions at any time.  If the horse is suspected of rabies please mark the sample clearly.  Dog, cat, and marine mammal samples should be marked as such.  Neospora testing is done by request.