Equine protozoal myeloencephalitis (S. neurona)

Question 1

Equine protozoal myeloencephalitis is caused by:

Answer 1

sarcocystis neurona

in america

Question 2

Final host of sarcocystis neurona

Answer 2

opossum

Question 3

IH of sarcocystis neurona

Answer 3

Smaller mammals such as raccoon and cat

Question 4

Abberant / causal host of sarcocystis neurona

Answer 4

horse

Question 5

location of sarcocystis neurona

Answer 5

nervous system - CNS

Question 6

life cycle of sarcocystis neurona

Answer 6

1) Final host released sporulated oocysts in the environment after sporogony inside the final host.
2) Horse ingests the oocysts, but the parasite does not form cysts. Horse is a dead-end host and cannot infect other horses.

Question 7

pathogenesis of sarcocystis neurona

Answer 7

Sporocysts penetrate intestinal epithelium, enter blood or lymphatics. It then crosses the blood-brain barrier and multiply as Merozoites in neural tissue. This leads to multifocal inflammation, neuronal necrosis, and demyelination. Lesions are most often found in brainstem, spinal cord and cerebellum. Schizonts and meronts are found in neurons, mononuclear cells and glial cells. After 3 weeks it stays in the CNS.

Question 8

CS of sarcocystis neurona

Answer 8

Incoordination, gait abnormalities, head tilt, facial nerve paralysis, difficulty swallowing, loss of sensation along face, neck and body.

Question 9

Dx of sarcocystis neurona

Answer 9

• Clinical signs and serology
• Post-mortem by histopathology of CNS, immunohistochemistry and PCR

Question 10

Tx of sarcocystis neurona

Answer 10

• Trimethoprim
• Pyrimethamine
• Vitamin B
• Diclazuril
• Toltrazuril
• Ponazuril
• Supportive: NSAIDs, Vitamin B, Vitamin E (antioxidant)

Question 11

control of sarcocystis neurona

Answer 11

Prevent access for opossum fo feed, hay, water
Control opossum populations
Minimize stress in horses
Low dose ponazuril or diclazuril as prophylactic in high-risk areas