equine protozoal myeloencephalitis

Question 1

What are the causative organisms of equine protozoal myelitis?

Answer 1

Sarcocystis neurona
Neospora hughesiWhat

Question 2

What is the definitive host of Sarcocystis neurona?

Answer 2

opossum Didelphis virginiana

Question 3

What life stage of Sarcocystis neurona is passed in opposum feces?

Answer 3

sporozoite containing sporocysts

Question 4

What stage of Sarcocystis neurona is infectious for the intermediate hosts?

Answer 4

sporozoites

Question 5

What are intermediate hosts of S. neurona?

Answer 5

skunks
raccoons
armadillos
cats

Question 6

What is the definitive host for Neospora caninum?

Answer 6

Canids

Question 7

What is the seroprevalence of S. neurona in hroses from teh United states?

Answer 7

15 to 85%, dep on geographic location

Question 8

In what season is S. neurona risk at the greatest?

Answer 8

-3x higher in spring and summer
-6 times higher in the fall

Question 9

What are factors that increase the risk of horses contracting S. neurona?

Answer 9

-presence of opossums (2.5 fold)
-previous diagnosis of EPM (2.5 fold)
-presence of a wooded area (2 fold)
-stressful events, such as heavy exercise, transport, injury, surgery or parturition
-racehorses & show horses

Question 10

Horses with EPM, that were treated with an anticoccidial drug were how many times more likely to improve than untreated horses?

Answer 10

10 times more likely to improve

Question 11

What are presenting clinical signs of EPM?

Answer 11

-focal or multifocal signs of neurologic dz involving brain, brainstem or spinal cord
-C/S stabilize, only relapse days or weeks
-infection of both white & gray matter at multiple sites in CNS

Question 12

What C/S are seen on neurologic examination?

Answer 12

asymmetric ataxia
weakness
spasticity involving on all 4 limbs
areas of hyporeflexia, hypalgesia or complete sensory loss

–>obtudnation, head tilt, facial nerve paralysis & difficulty swallowing

Question 13

For highest accuracy in antemortem diagnosis of EPM, what is recommended?

Answer 13

1. presence of C/S consistent with EPM on neurologic exam
2. other potential causes are ruled out using available tools (ie cervical rads)
3. Immunodaignostic testing of serum & CSF should be conducted to confirm intrathecal antibody production against S. neurona or N. hughesi

Question 14

What is the recommended test for the EPM?

Answer 14

SnSAG2, 4/3 ELISA serum CSF titer ratio & NhSAG1 ELISA serum: CSF titer ratio

Question 15

What are the most consistent/classical clinical signs of EPM?

Answer 15

assymetric gait & focal muscle atrophy

Question 16

What are differentials for neurologic disease to rule out EPM?

Answer 16

-cervical stenotic myelopathy (CVSM)
-trauma
-EHV-1 associated neurologic disease
-equine motor neuron disease (EMND)
others: extradural & spinal cord tumors, epidural abscess, migrating metazoan parasites, rabies, WNV, equine degenerative myeloencephalopathy/nueroaxonal dystrophy, lead poisoning, creeping indigo toxicity, lymes diseas, etc

Question 17

Confirmation of EPM on postmorten examination is based on what?

Answer 17

demonstration of protozoa in CNS lesions

Question 18

What diagnostic tests exist for S. neurona & neospora EPM?

Answer 18

S. neurona:
-Western blot
-indirect flourescent antibody test (IFAT)
-surface antigen (SAG)
-enzyme-linked immunosorbent assays (ELISA)

Neospora:
-ELISA (NhSAG1)
-IFAT

Question 19

What are the current FDA approved drugs?

Answer 19

-Ponazuril
-Diclazuril
-Sulfadiazine/Pyrmethamine

Question 20

What is the mechanism of action of sulfonamides & pyrimethamine

Answer 20

act synergistically by interfering with folic acid metabolism & biosynthesis of purine & pyrimidine nucleotides necessary for parasites survival

Question 21

What are the toxic effects of sulfadiaizne/pyrimethamine (REBALANCE)?

Answer 21

–related to inhibition of folate synthesis & include bone marrow suppression, anorexia, urticaria & self-limiting diarrhea
–progressive mild anemia

Question 22

What will increase the bioavailability of FDA-approved ponazuril?

Answer 22

-concurrent administration of vegetable oil (1/2 cup)

Question 23

What are other supportive medical treatments for EPM?

Answer 23

-NSAIDs- flunixin meglumine: 3-7 days of antiprotozoal treatment to prevent worsening neurologic signs
-corticosteroids: 0.1 mg/kg dex 1-2x daily
-DMSO: 1 g/kg as a 10% solution IV or via NGT
-Vitamin E: 20 IU/kg q24h

Question 24

What is the best prevention of EPM?

Answer 24

-decreasing stress along with reducing exposure to scat from oppossums