Making EPM Easier to Understand!

PATHOGENES LIMITED EDITIONSiobhan P. Ellison DVM PhD

Survival Guide forEquine Protozoal Myeloencephalitis

Understanding the Pathogenesis of Disease…

•EPM Syndrome = S. neurona Protozoa + Inflammation• Inflammation in CNS. Not always protozoa in CNS (rarely!) • Identify and treat the right condition

•Treat EPM = Kill S. neurona Protozoa + Treat Inflammation…because 9 of 10 horses with “EPM” can improve, 87% are put back to use!

55% of “suspect EPM” have neuroinflammation (but no antibodies against S. neurona) - (idiopathic encephalitis, IE) and won’t respond to antiprotozoal drugs.

EPM Mimics Other Diseases…

• Neurodegenerative Diseases• *RABIES!• EPM• Lyme• EHV• EEE/WEE/WN• Trauma• Polyneuritis equi• Equine motor neuron disease• Cervical vertebral malformation

SURVIVAL TIP! Rabies should be considered in acute disease! Only considered in 0.63% of our submissions.

…because a common factor is the hosts inflammatory response.

Commonly accepted that S. neurona has 3 Attributes…

• Predilection for the CNS• Difficult to treat because protozoa are in the CNS• Lack of treatment response confirms the diagnosis

A low expectation for treatment success means alternate diagnosis isn’t considered

…these traits make EPM incomprehensible!

Traditional Approach to EPM Diagnosis & Treatment

• Non-specific tests that require CSF analysis• CSF antibodies interpreted as parasites are in the CNS*• Treatment failure is accepted as supporting EPM diagnosis!• Antiprotozoals treat EPM (they don’t treat inflammation!)*statistical calculation based on a few cases. Parasites in CNS are not found using sporocyst challenge model.

60% respond to licensed treatments by a 1 grade change. Many relapse.

Only 25% get better.

Understand the Pathogenesis of Disease…

•EPM Syndrome = Protozoa + Inflammation•Treat EPM by treating protozoa and inflammation•Inflammation in CNS, not protozoa•55% of suspect EPM is not S. neurona•Treat the right condition

…and get the horse back to use!

9 of 10 horses can improve, 87% back to use. Many “suspect EPM” horses have neuroinflammation but no antibodies against S. neurona (idiopathic encephalitis).

SURVIVAL TIP! Understanding the disease process and using available diagnostic tools can change the clinical outcome.

We use tests to identify infection, inflammation due to infection, neuritis due to autoimmune dysfunction, and disease due to a sarcocystis toxin. Response to levamisole HCl may indicate IL6 mediated inflammation.

• Clinical examination

Test What we measure When to use the test How to use the result

SAG 1, 5, 6 Antibody to 3 S. neurona serotypes1) Suspect EPM

2) 8-10 weeks after treatment for a naïve horse and

5 months for an experienced horse

Antibody against S. neurona can suggest the signs are due to S. neurona infection. After treatment the antibodies should drop. The time to seroconvert (turn negative) depends on the immune background of the animal.

CRP C-reactive protein concentration Detect inflammation due to infection

1) Monitor inflammation that is sensitive to levamisole HCl treatment. The inciting cause must be remedied for the value to fall.

2) An elevated value with chronic, relapsing horse should trigger running MPP.

Lyme screen Antibody to Borellia To rule in or out Lyme in the cause of disease

A negative value rules out Lyme. A positive value at 20 does not rule Lyme out, but the cause less likely due to Borellia. A positive value at 40 indicates Lyme should be on the differential. Call for advice on confirmatory testing.

MPP Antibody to myelin protein neuritogenic peptide

Chronic, relapsing and unresponsive cases that show polyneuritis or encephalomyelitis.

Sidewinding older horses.

A positive MPP test indicates there is an autoimmune component to the disease. In a levamisole responsive case it may be prudent to treat the autoimmune reaction and monitor the MPP semiannually. The MPP may indicate longer duration autoimmune disease. There is a relationship between high CRP and MPP. Animals don’t develop tolerance to MPP.

MP2 Antibody to myelin protein

Chronic, relapsing and unresponsive cases that show polyneuritis or encephalomyelitis.

Sidewinding older horses.

A positive MP2 test indicates there is an autoimmune component to the disease. The MP2 can indicate earlier disease than the MPP test. Animals develop tolerance to MP2.

S. fayeri toxin Antibody to Sarcocystis toxin Rule in or out toxin associated with sarcocyst stages that can cause ataxia and gut inflammation

A positive test indicates the horse has S. fayeri sarcocysts. Use this test when CRP remains high, with or without clinical signs, after treatment. The toxin affects the gut and treatment includes protocidal drugs (for cysts) and ulcer therapy.

IFAT: S. neurona Antibody to SarcocystisAntibody to Sarcocystis. IFAT tests are not specific for S. neurona.

This is a study specific test and is used to enroll all horses into our FDA studies. We suggest for clinical use the serotype specific tests are more useful. IFAT detects S. fayeri.

WHAT WE MEASURE WHEN TO USE THE TEST HOW TO USE THE TEST RESULTS

Treatments

• First generation pyrimethamine/sulfadiazine• Treatment fail due to inability to maintain drug concentrations• Short elimination half-life in the horse• Need to treat for years “until CSF is negative for antibody”• Safety data for 30 days, not long term

• Second generation triazine antiprotozoals• 60% improve 1 grade with 10% relapse rate• Only 25% become useful after EPM- Rob MacKay• Metabolizes to fat!• Current dogma use 4x loading doses, extended treatment… $$

• Third generation treatment includes treating inflammation

S. neurona treatments!

EPM treatment!

EPM Syndrome = Protozoa + Inflammation

• Orogin is a combination drug• Treat protozoa with protocidal decoquinate• Treat inflammation with levamisole HCl

• Other neurodegenerative diseases respond to levamisole HCl• Serum testing help can define disease processes and possibly etiology

• Rule in or out other causes of disease: Lyme, EHV, EW-WN, RABIES, trauma• Monitor inflammatory responses to infection with C-reactive protein• Monitor autoimmune disease with MPP and MP2• Monitor sarcocyst toxins with S. fayeri toxin ELISA

SURVIVAL TIP! RESPONSE TO LEVAMISOLE HCL CAN INDICATE THE INFLAMMATORY PATHWAY IN DISEASE.

Stage 1. Acute diseaseEPM in Horses is a Biphasic Disease

Horses ingest S. neurona in contaminated feed. Parasites are disseminated to viscera via leukocytes.

Parasite dependent suppression of PMA/ionomycin stimulated leukocytes is evident by 72 hours post infection. At this stage, SAG 1, 3, 5, microneme and enolase parasite proteins may mimic species specific IL6 pathway proteins to down regulate protective (IFNγ) responses and that favors infection.

Innate immune responses to infection increases IL6. IL6 is both pro and anti-inflammatory. IL6 stimulates liver production of acute phase proteins, particularly CRP. CRP enzymatically cleaves IL6 and its receptor into the plasma. The complex, IL6-IL6r, at the blood-brain (choroid plexus) barrier can result in neuroinflammation. Toxins may be associated with gut inflammation.

Decoquinate targets the parasite in the gut and viscera. Levamisole HCl targets IL6 mediated inflammation.

Board certified neurologists determined disease in a blinded, placebo controlled study involving 13 horses. Ten horses were challenged with a SnSAG1 strain using the Trojan horse model. Three horses were unchallenged controls. Horses were evaluated before (0 DPC) and after infection q 30 days (thru 120 DPC). We show thru 17 DPC here. Parasite dependent suppression of PMA/ionomycin stimulated leukocytes was detected at 3 DPC*. Serum antibody detected by SAG1 ELISA correlated with onset of clinical signs of disease*. CSF antibodies were detected by day 30 but often were no longer detected at day 60*.

0

50

100

150

0 DPC

3 DPC

4 DPC 5 DPC

Days Post Infection

12 DPC

17 DPC

Tite

r

3

4

5

6

9

10

11

12

13

14

PMA/I suppression

ACUTE CHRONIC

*Published data.

Stage 2. Chronic diseaseEPM in Horses is a Biphasic Disease

Serum antibodies are detected by day 17. Production of CSF antibodies are variable and can be detected by day 30 and decrease by day 60. Clinical signs coincide with the production of serum antibodies. Parasite proteins SAG 1 and 5 and antibodies against SAG 1, 5 and 6 may trigger gp 130 (IL6 signaling pathway) by trans- signaling that results in a pro-inflammatory response in the CNS. SAG 6, 1, IL6, and parasite toxins may increase neuroinflammation. Chronic inflammation disrupts myelin. Anti-myelin protein antibodies set up an autoimmune response resulting in polyneuritis and/or neuroinflammation. Immune responses to S. neurona, unintended consequences of anti-protozoal drug exposure, or natural degeneration, may disrupt S. fayeri cysts releasing toxins that are pro-inflammatory.

Levamisole decreases IL6 production, may target the IL6 trans-signaling pathway (probably at the blood/CSF barrier (choroid plexus)) by down regulating IL6 transcription. Decoquinate can reduce the production of S. fayeri cysts and is protocidal to S. neurona.

CLINICAL PRESENTATION OF S. NEURONA INFECTIONS

Blue Jazzy Chicago Red James

2 years with clinical signs. Multiple visits to Purdue. CSF tap SN negative, radiographs small changes consistent with hock issues, Grade 4, would fall.

Unknown onset. Drags rear feet. Grade 2. Unsafe to ride.

Chronic, relapsing EPM. Grade 3. Multiple Marquis treatments. CSF tested. Unsafe to ride.

Acutely recumbent. Grade 5. No vaccination history.

Weak older horse with decreased body condition and/or muscle atrophy. Sidewinder.

By the way…

Dogs and cats can have antibodies to S. neurona SAG 1, 5, and 6.

Cats are intermediate hosts. Opossums that eat infected cats can spread disease on the farm. Cats don’t spread disease to horses.

There is published literature on the treatment of dogs for sarcocystis. Generally dogs are screened and under treatment for Toxo. We evaluate serum antibodies pre and post treatment.

Leo

Acute onset, Toxo negative, SN positive. Mild response to decoquinate.

Refer to Dr. Young.

Dogs get S. neurona infections!

Grade 5: Acute

Down animals can respond to treatment. Those that do respond, generally need an extended duration of levamisole HCl (10 days in Orogin followed by 14 days levamisole HCl). DMSO IV is useful. Sometimes dysphasic, NeuroQuel absorbs through mucous membranes, response in 3-5 days. Not up within a day or so has a grim prognosis. Rule out rabies, herpes, trauma.

Tests: SAG 1, 5, 6, CRP…Lyme?....

Experience with 55 cases with Grade 5. Thirteen died within days. 15 had antibodies against S. neurona and 27 did not. S. neurona was detected in the CNS (PCR negative) of 1 that went to pathology. Other postmortem diagnosis included wobbler, CNS trauma, tumor, EMD, and unknown.

AcuteHorse is unable to rise, will eat, not febrilePrognosis: Poor to grave

Grade 5 0.5%

Grade 1-4: Most Recognized

Usually disease is over 17 days because they have antibodies to SN. Some behavior or weakness issues are early EPM and the early cases may not have serum antibodies.

Treatment response by day 5 on Orogin. Most resolve clinical signs by day 10. Those that responded to treatment, but not back to normal need to continue NeuroQuel 14 days. Generally don’t re-present with “EPM”.

Ruled out other causes of lameness and ataxia. Antibodies to S. neurona and ataxia are considered EPM. Response to treatment supports the diagnosis. May need NeuroQuel after treatment if disease is chronic, history may not be supportive of actual onset of disease.

Tests: SAG 1, 5, 6, CRP, Lyme. A naive horse will have low titers and an experienced horse will have higher titers. Titer relates to duration of infection not severity of disease. Horses experience with infection will dictate how long serum antibodies are detected and when to retest after treatment. Antibodies may last 5 months in experienced horse

Orogin, follow with NeuroQuel treatment if necessary. Can repeat NeuroQuel, use every other day second time. Monitor CRP. If CRP remains elevated need to resolve primary cause of inflammation.

Grade 1-4 83%

Grade 2-5: Chronic

11.5%Chronic, relapsing disease. Historically may be treated multiple times with anti-protozoal and health declines; over time signs exacerbate.

Orogin treatment response by day 5. Clinical signs resolve by day 10 but needed further NeuroQuel treatment.

Ruled out other causes of ataxia. Most of these cases have been extensively worked with a diagnosis of EPM without resolution of disease. Disease is due to chronic inflammation.

Tests: SAG 1, 5, 6, CRP, Lyme. A naive horse will have low titers, and experienced horse will have higher titers. May be negative for S. neurona antibodies after antiprotozoal therapy.

Signs can recur after NeuroQuel discontinued. These cases usually respond to longer duration of NeuroQuel. Can repeat NeuroQuel, use every other day and move to every 3rd day. Monitor CRP. Consistently elevated CRP: treat for ulcers and test for S. fayeri. Consider prevention along with multiple exams and monitor serum antibodies. Can get re-exposure from environment, monitor SAG 1, 5, 6. May need prevention therapy with decoquinate.

Grade 2-5

Grade 2-5: Chronic (Autoimmune)

3%Chronic, relapsing disease over several years. Any age. No diagnosis despite extensive work up. Signs progress over time signs. Can have muscle atrophy. Loss of top line.

Orogin treatment response by day 5. Clinical signs resolve by day 10 but needed further NeuroQuel treatment. Require longer duration of NeuroQuel, 2 to 3 treatments.

Three percent (3%) present just after vaccination. Use NeuroQuel before vaccination to prevent signs and continue NeuroQuel.

Test for neuritogenic peptide, MPP. Monitor CRP.

When MPP is elevated consider using alternate day dexamethasone at a low dose (0.25 to 0.1 mg/kg EOD 14 days) in addition to NeuroQuel. Horses with elevated MPP will respond for several years to NeuroQuel as disease continues need to treat for extended duration. At some time (4 years) they don’t respond completely or to steroids. Consider using steroids sooner and use CRP/MPP to monitor course of disease.

Grade 2-5Autoimmune

Hemi-paresis: Sidewinder

1.5%Older horse. Chronic disease. Thin, weak with loss of muscle mass. Responds to Orogin with weight gain and improved strength. Responds to longer duration NeuroQuel. CRP elevated, likely MPP positive.

Older horse. Thin, chronically weak with loss of muscle mass. Muscle atrophy apparent. Responds to Orogin with weight gain and strength. No response to follow-up NeuroQuel, responds to longer duration decoquinate. CRP elevated, can be S. fayeri positive.

Sidewinder

0.5%Weak.

Can’t pick up hind legs. Muscles tremble.

Treatable Presentations Diagnosed as EPM

Acute, first presentation. Grade 1-4 OR chronic Sidewinder

Test: SAG’s, CRP, +/-Lyme. Tx Orogin and NeuroQuel (if signs persist). Retest SAG’s, CRP.

Relapsed, responds to NeuroQuel relapses when NeuroQuel discontinued

Test: CRP, MPP. NeuroQuel EOD, low dose dexamethasone EOD if MPP+. Determine source of chronic inflammation.

Relapse, responded to Orogin but no change on NeuroQuel

Test: CRP, S. fayeri. GastroGuard. SF + long term decoquinate

Ongoing Research…

Effect of levamisole HCl on S. neurona

• Sarcocystis have levamisole receptors. The effect of the drug on protozoa are increased motility.

• Levamisole HCl affects the parasite and host. We are developing a parasite recovery model-parasites are recovered after challenge. This allows us to recover and study drug resistance in S. neurona.

It is important to kill parasites with an anti-protozoal drug during EPM treatment!

Triazine drugs (blinded, placebo controlled, horse challenge, evaluated by board certified DVM’s, n=26) show parasitemia 10 days after challenge.

Conclusion

Important factors in understanding EPM are the clinical history, current presentation, interpreting test values and the change in values with time. Most important, evaluating a treatment response!

Understanding the pathogenesis of protozoal disease is necessary for a good outcome. The effects of drugs on both the parasite and on the horse are important. The immune reactions to infection and treatment make repeat testing important.

EPM Survival Guide

Contact us at www.pathogenes.com to get your copy of the 50 page EPM Survival Guide.