Sarcocystis neurona (1)

Question 1

What is the definitive host?

Answer 1

Opossum

Question 2

What are the intermediate hosts?

Answer 2

Cats

Striped skunks

Nine banded armadillo

Fishers

Sea otters

Raccoons

Question 3

What are the accidental (aberrant) hosts?

Answer 3

Horses

Question 4

How do you identify?

Answer 4

Same as Sarcocystis

Impossible to make a diagnosis as to species based on finding Oocysts/Sporocysts in opossum feces

Question 5

Explain the life cycle

Answer 5

IH ingest Sporocysts

Develop to schizont -> sarcocyst
- Schizogony in IH -> Bradyzoites in muscle cells

Opossum ingests sarcocyst
- Sarcocyst -> Micro/Macrogamont -> Unsporulated oocyst ->
Sporulated oocyst -> Sporocysts
- Gametogony in final host

Sporocysts ingested by IH

 - Aberrant IH: Horse
        - Ingests Sporocysts -> schizont -> Merozoites in neuron 
        - No development of muscle cysts
        - Schizonts with Merozoites located in neuron in CNS

Question 6

What are the sites of infection?

Answer 6

FH - intestines

IH - Bradyzoites in muscles

Horses - Schizonts develop in neurons
- Cause disease EPM

Question 7

Describe the Pathogenesis

Answer 7

A progressively debilitating disease affecting the CNS, brain, brain stem, and spinal cord

Unusual or atypical lameness or seizures

Difficulty with standing, walking, or swallowing

May progress very rapidly

Infection in FH - Non-pathogenic

IH - pathogenic effect attributable to 2nd stage of Schizogony in
vascular endothelium

Accidental Host (Equid) - pathogenic effect occurs when nervous tissue
rather than muscle tissue is infected because
of 3rd stage Schizogony

Question 8

What are the clinical signs in equids?

Answer 8

Neurological disease

 - Stumbling
 - Paresis (slight paralysis)
 - Lameness
 - Ataxia (failure of muscular coordination)
 - Recumbency (lying down)
 - Constipation
 - Urinary incontinence (unable to control excretory functions) 
 - Muscle atrophy

Question 9

How do you diagnose?

Answer 9

Positive diagnosis based on Histopathological demonstration of S. neurona organisms in association with lesions in CNS

Western blot test on CSF

Antemortem

  - Clinical signs
  - Western blotting, 14, 13, and 3 kDa
  - PCR-CSF

Postmortem
- Histopathological demonstration of S. neurona in CNS
- Brain - multi focal areas of perivascular cuffs, focal vasculitis,
Hemorrhages
- Spinal cord - heavy parasitized neuron

Question 10

How do you treat and prevent?

Answer 10

Antiprotozoals

CNS damage may remain

Opossum control critical

Prevent feed contamination by opossum feces

Applied as quick as possible once diagnosed
- Sulfadiazine: 20 mg/kg per os, > or = 12 weeks
- Pyrimethamine: 1.0 mg/kg per os, > or = 12 days
- Nitazoxanide: 11.36 mg/kg 5 days followed by 23 days of double
doses

A successful recovery in 70-75% horses

Question 11

What is the common name?

Answer 11

Equine Protozoal Myeloencephalitis (EPM)