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NEU2 > Ovine neurology > Flashcards

Ovine neurology Flashcards

1
Q

List development neurological diseases of sheep

A
  • Swayback
  • Dandy Walker malformation (hydrocephalus)
  • Daft lamb cerebellar hypoplasia
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2
Q

Give examples of infectious neurological diseases of sheep

A
  • Bacterial: meningitis, abscesses
  • Viral: border disease
  • Parasitic: gid
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3
Q

Give an example of a metabolic/nutritional cause of neurological disease in sheep

A

Cerebrocortical necrosis

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4
Q

Give an example of traumatic cause of neurological disease in sheep

A

Cervical subluxation due to fighting

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5
Q

Give examples (name, diagnosis) of neurological diseases that have an onset that is:

a: immediate
b: in minutes
c: minutes to hours
d: hours
e: hours to days
f: days
g: weeks to months

A

a: cervical injury, group fighting
b: hypomagnaesaemia, response to treatment
c: hypocalcaemia, response to treatment
d: cerebrocortical nercosis/polioencephalomalacia, opisthonus and response to treatment
e: pregnancy toxaemia (urine ketones and blood BHB), louping ill (tick area and time of activity), listeriosis (silage fed, possibly scour)
f: spinal abscess, progressive, increased WBC, crossover from polymorphic to lymphocytes
g: scrapies (>2yo and excessive pruritus), gid (<2yo gradual onset and progressive)

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6
Q

What are your differentials for a young lamb with a neurological condition from birth, that is mentally normal?

A

Swayback, Border disease

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7
Q

What are your differentials for a young lamb that is affected from birth and is mentally abnormal?

A
  • Dystocia injury
  • Border disease
  • Cerebellar hypoplasia
  • Severe swayback
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8
Q

What are your differentials for a young lamb, affected within a few weeks of birth with a neurological conditions, that is mentally normal?

A
  • If ataxic: delayed swayback, spinal abscess

- If stiff: tetanus

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9
Q

What are your differentials for a young lamb, affected within a few weeks of birth with a neurological conditions, that is mentally abnormal?

A
  • Meningitis

- Encephalitis

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10
Q

What are your differentials for a young lamb, affected within a few days of birth with a neurological conditions?

A
  • If pyrexic: meningitis, encephalitis
  • If treated for above and fails to feed: hypothermia, hypoglycaemia
  • If subnormal temp on presentation: hypothermia, hypoglycaemia
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11
Q

What is your most likely differential for a growing lamb, with sudden onset paresis, mentally normal?

A

Cervical injury, especially in rams

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12
Q

What is your most likely differential for a growing lamb with sudden onset coma, opsithotonous, or strabismus?

A

Cerebrocortical necrosis

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13
Q

What is your most likely differential for sudden onset ataxia, coma, paralysis, in a growing lamb in a tick area?

A

Louping ill

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14
Q

What is your most likely differential for sudden onset cerebellar signs in a growing lamb?

A

Space occupying lesioin e.g. gid cyst, abscess

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15
Q

What are your most likely differentials for a growing lamb with gradual onset neurological signs, that is mentally normal?

A
  • Delayed swayback

- Spinal abscess

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16
Q

What are your most likely differentials for a growing lamb with gradual onset cerebral or cerebellar signs?

A

Space occupying lesion e.g. gid cyst, abscess

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17
Q

What is you most likely differential for an adult/number of adults with sudden onset coma, blindness, episthotonus and strabismus?

A

Cerebrocortical necrosis

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18
Q

What are your most likely differentials for a group of ewes late in pregnancy with neurological signs?

A
  • Hypocalcaemia

- Pregnancy toxaemia

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19
Q

What is your most likely differential for a group of lactating ewes showing sudden onset neurological signs?

A

Hypomagnasaemia

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20
Q

What is your most likely differential for a group of sheep with sudden onset neurological signs that are silage fed?

A

Listeriosis

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21
Q

What is your most likely differential for a group of sheep with sudden onset neurological signs that are in a tick area?

A

Louping ill

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22
Q

What is your most likely neurological differential for an adult sheep displaying gradual onset abnormal behaviour, ataxia and pruritus?

A

Scrapie (usually >2yrs)

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23
Q

What are your most likely differentials for a sheep showing gradual onset cerebral or cerebellar signs?

A
  • Gid
  • Abscess
  • Maedi visna
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24
Q

What is the main source of infection with scrapie?

A

Placenta in lambing environment

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25
Q

Compare typical and atypical scrapie

A

Classical dramatically reduced due to breeding programs, but atypical probably not genetic and may not be infectious

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26
Q

Describe the clinical signs of scrapie in sheep

A
  • Paresis and ataxia, esp. hindlimbs
  • Quadriplegia, recumbency
  • Separation from flock
  • Depression, anxiey or hyperexcitability
  • Head tremor, low head carriage
  • Pruritus
  • WEight loss, bruxism, cud dropping
  • No menace response
  • Usually >2yo
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27
Q

Outline the diagnosis of scrapie in sheep

A
  • Detection of PrPsc in brain on post mortem

- Isolation of PrPsc in biopsy of lymphoid tissue (tonsillar tissue or rectal mucosa)

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28
Q

What is Maedi Visna?

A

2 forms of disease, visna is neurological disease, maedi is respiratory. Visna less common than Maedi in the UK

29
Q

Compare maedi and visna

A
  • Visna commonly accompanied by cachexia and chronic wasting

- Visna commonly younger than maedi (<2yo)

30
Q

Describe the neurological signs of maedi visna

A
  • Ataxia, paresis, drag a leg
  • Hind legs often affected more than front but all 4 can be involved
  • Depression, head tilt, fine tremor of lips
  • Occasionally may appear blind
31
Q

List the differential diagnoses for maedi visna and how is it diagnosed?

A
  • Listeriosis
  • Aberrant larval migration
  • Spinal abscess/mass
  • Scrapie
  • Diagnosis by PM
32
Q

What are the 2 forms of swayback?

A

Congenital and delayed

33
Q

Compare the susceptibility of sheep breeds to swayback

A
  • Only common in hill/upland flock

- UK breeds more susceptible e.g. Scottish Blackface vs continental breeds e.g. Texels

34
Q

Describe congenital swayback (cause, signs, diagnosis)

A
  • Copper deficiency due to little extra feed in mid-late pregnant hill ewes
  • Signs: stillbirth, small weak lambs with fine head tremors, may be bright but weak on HLs, stumbling/swaying gait, fine bones and dull coats
  • Histopath on brain and spinal cord showing cavitation of cerebral white matter and internal hydrocephalus, <6mg copper/kg DM brain or <10mg copper/kg liver
35
Q

Describe delayed swayback (cause and signs)

A
  • Normal at birth but progressive weakness of pelvic limbs at 2-4mo
  • Demyelination and reduced myelin synthesis in spinal cord
36
Q

How can delayed swayback be prevented?

A
  • Injection of chelated copper
  • Glass bolus in mid pregnancy (not for Texel or other continental breeds and primitive breeds, copper toxicity sensitive)
37
Q

What is gid?

A

Infestation with Coenuris cerebralis, the larval stage of taenia multiceps

38
Q

When does acute coenurosis occur in sheep?

A

10 days after turning onto land heavily contaminated with dog faeces

39
Q

Describe the clinical signs of acute coenurosis in sheep

A
  • Pyrexia, listlessness and head aversion

- death 4-5 days after neurological signs

40
Q

Describe the clinical signs of chronic coenurosis in sheep, affecting the cerebral cortex

A
  • Head pressing and depression
  • Loss of menace response
  • Blindness in contralateral eye
  • Contralateral proprioceptive deficits
  • If superficial: wide compulsive circling towards side of cyst
  • If deep: narrow circling away from cyst
41
Q

Describe the clinical signs of chronic coenurosis in sheep, affecting the vestibular system

A

Head tilt towards affected side

42
Q

Describe the clinical signs of chronic coenurosis in sheep, affecting the cerebellum

A
  • Dysmetria, ataxia, wide-based stance
  • Bilateral postural deficits
  • Rapid deterioration
43
Q

Describe the prevalence of coenurosis in different brain regions

A
  • 80% cerebral cortex
  • 10% cerebellar
  • 2% vestibular
  • 8% mutliple locations
44
Q

Describe the development of chronic coenurosis

A
  • More common in growing sheep (6-18mo), very rare >3yo
  • Insidious onset with slowly progressive focal lesion
  • 2-6mo from larval hatching to migration and onset of neurological dysfunction
45
Q

What is the signficance of coenurosis in sheep?

A

Zoonotic, and dog is intermediate host

46
Q

What is Louping ill?

A

Tick transmitted Arbovirus belonging to tick-borne encephalitis complex

47
Q

Describe the clinical signs of Louping ill

A
  • Affects brain
  • Causes varying degrees of incoordination, paralysis, convulsions, death
  • Mortality as high as 100% in naive animals
48
Q

What species can be affected by Louping ill?

A
  • Primarily sheep

- Humans, cattle, goats, pigs, horses, farmed red deer, llamas, dogs and wild red grouse can be affected

49
Q

Describe the diagnosis of Louping ill

A
  • Serology for antibody to virus
  • Most commonly diagnosed in lambs and yearlings in areas where Louping ill is endemic
  • Most common when susceptible sheep first moved to Louping ill area
50
Q

Describe the treatment and prevention of Louping ill in sheep

A
  • No treatment
  • Prevent by vaccination
  • Dipping in OPs reduces risk but does not induce immunity
51
Q

What are the most common poisonings leading to neurological in sheep?

A
  • Lead
  • Plant e.g. Bracken
  • Oxalate
52
Q

What is Bracken poisoning in sheep?

A

Ptaquiloside toxicity, causes “Bright Blindess”

53
Q

Describe the clinical signs of Bracken poisoning in sheep

A
  • Tapetal hyperreflectivity
  • Permanent blindness and characteristic alert attitude
  • Poor response of pupils to light
  • Ophthalmic exam in advanced cases shows narrowing of arteries and veins, pale taeptum nigrum with fine cracks and spots of grey
  • Bone marrow suppression
  • Haemorrhage
  • Immunosuppression
  • Urinary tract neoplasia
54
Q

Describe the histological apperance of the retina in sheep affected by Bracken poisoning

A

Severe atrophy of retinal rods, cones and outer nuclear layer that is most pronounced at the tapetal portion of the retina

55
Q

How does oxalate poisoning occur in sheep?

A
  • Contained in feed crop

- All beet crops concentrate oxalate in the leaves so feeding of tops as well as bulb can be dangerous

56
Q

Describe the clinical signs of oxalate poisoning and the treatment and prevention

A
  • Symptoms and treatment same as for hypocalcaemia
  • Prevention by limiting % of diet that is the leaf of beet plants by strip grazing or lifting crop to just feed the bulb
57
Q

Describe the clinical signs of cerebellar syndromes in sheep and give generalised and localised diseases that may cause this

A
  • Ataxia, hypermetria, head tremor, high head carriage, jerky movement, intention tremors, usually bilateral proprioceptive defects or ipsilateral and circle towards
  • Generalised: cerebellar hypoplasia, border disease, scrapie
  • Localised: gid, abscess
58
Q

Describe the clinical signs of cerebral syndromes in sheep and give generalised and localised diseases that may cause this

A
  • Mental state/behaviour change, stupor, depression, hyperaesthesia, opisthotonus, head pressing, head deviation, contralateral proprioceptive defects, contralateral blindness (but normal PLR), circling towards superficial and away from deep lesions
  • Generalised: CCN/PEM, bacterial meningitis, pregnancy toxaemia, scrapie
  • Localised: gid, abscess
59
Q

Describe the clinical signs of vestibular syndromes in sheep and give diseases that may cause this

A
  • Head tilt with falling, rolling or circling, nystagmus

- Middle or inner ear infection (often also facial nerve paralysis and Horners syndrome)

60
Q

Describe the clinical signs of pontomedullary syndromes in sheep and give diseases that may cause this

A
  • Depression, cranial nerve deficits, ipsilateral hemiparesis, circling (VIII), facial paralysis, cheek muscle paralysis and decreased sensation, abnormal resp patterns (resp centre in medulla)
  • Listeriosis
61
Q

Describe the clinical signs of midbrain syndromes in sheep and give diseases that may cause this

A
  • Depression, coma, limb rigidity, opisthotonus, normal vision with strabismus and mydriatic pupil
  • Disease: hepatic encephalopathy, cranial trauma (uncommon in sheep)
62
Q

Describe the clinical signs of hypothalamic syndromes in sheep and give diseases that may cause this

A
  • Altered behaviour/mental state, hyperaesthesia, aggression, disorientation, impaired vision, dilated, poorly responsive pupils, appetite and thermoregulation affected
  • Diseases: pituitary gland tumours and abscesses (not common in sheep)
63
Q

What would facial nerve damage look like in a sheep?

A
  • Drooped ear, eyelid and lips

- Food packing in cheek

64
Q

Compare the strabismus that occurs with oculomotor, trochlear and abducens nerve damage

A
  • III: lateral strabismus
  • IV: dorso-medial strabismus
  • VI: medial strabisumus
65
Q

What would damage to the trigeminal nerve look like in a sheep?

A
  • Decreased facial sensation
  • Dropped jaw
  • Saliva pooling
  • Food packing in cheek
66
Q

What is a common outcome of damage to the glossopharyngeal, vagus and accessory nerve in sheep?

A

Dysphagia

67
Q

What nerve, when damaged, would lead to tongue paralysis?

A

Hypoglossal

68
Q

Outline a prevention and treatment plan for gid in sheep

A
  • Worm dogs every 6 weeks and remove carcasses from yard
  • Surgery possible
  • In cerebrum: trephine 1-2cm lateral to midline and rostral to coronal suture line
  • Cerebellum: trephine midline between nuchal line and suture between occipital and parietal bones
  • Incise the dura mater and tissue filled hole, drain and remove cyst wall and protoscolices with forceps
  • Provide post-op analgesia and antibiotics
  • Corticosteroids to reduce post surgical brain oedema
  • Euthanasia is the most rational option in 99% cases

NEU2 (23 decks)

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