Horse Health and Disease: Lesson 8
Terms
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- What is the vertebral formula for the horse?
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C7 T18 L6 S5 C15-21
* Think 7 before 6 before 5. Sum them and you get 18. - Where does the spinal cord end?
- S2
- What are the segments of the spine starting from head to tail?
- cervical (c), thoracic (t), lumbar (l), sacral (s), caudal (cd)
- What are the meninges?
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-pia mater
-dura mater
-arachnoid - How are spinal nerves made up?
- Dorsal and ventral roots that exit at intervertebral spaces.
- What is the difference between afferent and efferent neurons (roots in this case)?
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efferent: away from spine to body parts
afferent: towards the spine from sensory neurons of body (like fingers for example) - What type of neurons are motor neurons? Sensory neurons?
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motor=efferent (signals must go out of spine to area that needs to move)
sensory=afferent (signals come towards spine to translate from fingers/sensory receptors). - Which neurons are the dorsal and ventral roots?
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dorsal= sensory/afferent
ventral= motor/efferent - Where is the diameter greatest in the vertebral canal and why? Where does is begin to lessen?
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At the atlas to allow for head movement without spinal constriction.
It lessens at the axis. -
Where does the spine widen again?
Where is it smallest? -
-Two spots: cervical intumescence and lumbar intumescence.
-Smallest at mid-thoracic region - What are the 6 major neurological diseases we studied in class?
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1) Equine protozoal myeloencephalitis (EPM)
2) West Nile Virus (WNV)
3) Cervical vertebral stenotic myelopathy (wobbles)
4) Equine herpesvirus 1 myeloencephalopathy (rhinopneumonitis)
5) Equine degenerative myeloencephalopathy
6) Equine motor neuron disease - What is the most commonly diagnosed neurological disease?
- EPM (equine protozoal myeloencephalitis)
- What is the number one way to determine EPM? WNV? Wobbles? Rhinopneumonitis? EDM? Motor neuron disease?
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EPM: CSF
WNV: blood test
Wobbles: myelogram
Rhino: serology/nasopharyngeal swabs
EDM: Vit. E levels
Motor: No loss of coordination! - What causes EPM?
- Ingestion of sarcocystis neurona.
- What are the natural carriers of sarcocystis neurona?
- Birds and oppossum.
- Describe EPM's effect on horses?
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-Infects brain and spinal cord
-Horse is dead-end host
-obscure lameness
-progressive, asymmetric ataxia
-facial paralysis/muscle atrophy
-head tilt/trouble swallowing
-wide range of severity - How can you test for EPM?
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-use clinical signs
-blood test (30% of time= false positive)
-CSF (cerbrospinal fluid) tap - Where are CSF taps done?
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Between atlanto-occipital space
or lumbo-sacral space - What is the treatment of EPM?
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-anti-protozoal medication such as Marquis
-treat for 8-12 weeks
+/- 60% success rates - What is the natural resevoir for WNV?
- Birds
- How is WNV transmitted?
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Through insect bites (horses and humans are dead end hosts)
*Found in all states - List clinical signs of WNV from most common to least common
- ataxia/incoordination, depression/apprehension, weakness, stumbling/falling down, death, fever, anorexia, hyperesthesia, hypermetria, excessive sweating, disorientation, teeth grinding/bruxism, weight loss.
- What is the incubation period of WNV and what does this cause?
- +/- 2 weeks causing encephalitis
- How do you diagnose WNV?
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-clinical signs
-serology
-CSF tap
-post mortem - How can you treat and prevent WNV?
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Treat: none specific, supportive
Prevent: Vax, mosquito control - What causes "wobbles"?
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-malformation of cervical vertebrae
-narrowing of the vertebral canal
-compression and damage to spinal cord
-DOD - How do you diagnose wobbles?
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-use clinical signs and signalment
-radiography (myelogram) - How do you treat wobbles?
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-conservative
-surgical using vertebral fusion/stabilization - What does stenotic mean?
- Constriction
- What are clinical signs of rhinopneumonitis?
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-may follow upper respiratory outbreak by 7-14 days
-acute onset of ataxia, weakness, swelling
-may be bladder paralysis
-signs usually occur acutely, progress for 1-3 days and then stabilize
-most recover fully - How can you diagnose rhinopneumonitis?
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-use clinical signs and history
-virus isolation (nasopharyngeal swabs)
-serology (acute and convalescent samples
-CSF tap (look for xanthoghromia and elevated protein) - How do you treat rhinopneumonitis?
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Isolation
supportive - What causes equine degenerative myeloencephalopathy (EDM)?
- Not sure yet.
- How can EDM be treated?
- Give vit. E if levels are low.
- EDM targets what in the body?
- Diffuse degeneration of brain and spinal cord.
- What are the signs of EDM?
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-possible familial predisposition
-may be related to Vit. E deficiency
-must consider other nutritional or toxic causes
-horses less than 3 years
-symmetric ataxia, hypermetria, weakness
-may progress to recumbency - How do you diagnose EDM?
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-History and signs
-Vit. E levels
-necropsy - What is the pathology of equine motor neuron disease?
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-degeneration and death of motor neurons in brain and spinal cord
-similar to human ALS (Lou Gehrig's disease)
-cause unknown - What are the clinical signs of equine motor neuron disease?
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-any age, breed, or sex
-weight loss and muscle atrophy
-weakness
-muscle tremors (fasciculations)
-drooping head due to muscle weakness
-short strided, tentative gait
-sweating - How can you diagnose equine motor neuron disease?
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-history and clinical signs
-muscle biopsy
-electromyography (look at nerve muscle conduction)
-possible low Vit E - What are some other conditions with neurologic signs?
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-atlanto-occipito-axial malformations
-rabies
-encephalitis
-trauma
-cervical vertebral osteomyelitis