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Flashcards in Farm animal neurology Deck (85):
1

2 main types of cortical disease

- cerebrocortical necrosis (CCN)
- viral (MV, CAE, BDV, BVD)

2

Most important brainstem and CN disease

listeriosis

3

Name 3 metabolic diseases with neuro effects

- nervous ketosis
- hypoclacaemia
- hypomagnasaemia

4

List spinal cord and peripheral nn disorders

- spastic paresis (Elso heel)
- enzootic neonatal ataxia (swayback)
- fractures, luxations, spinal abscesses

5

Name 2 neuromuscular disease

- tetanus
- botulism

6

Which parasites can cause neuro disease?

- louping ill
- coenurosis / gid
- sarcocystis
- nervous coccidiosis

7

Another name for cerebrocortical necrosis (CCN)

polioencephalomalacia (PCN)

8

aetiology - CCN

- multiple, all lead to necrosis of grey matter:
- THIAMINE metabolsim
- SULPHUR metabolism

9

Species - CCN

all ruminants and pseudo-ruminants

10

Occurence of CCN

worldwide, common

11

Pathogenesis - CCN - altered thiamine metabolism

- thiamine is co-factor for transketolase in pentose phosphate pathway (--> glucose for brain), loss --> increased lactate, pyruvate and oxoglutarate --> intraneuronal swelling (decreased ATP Na/H2O transport) --> increased ICP adn neuronal necrosis --> oedema and cortical necrosis

12

Outline ruminant thiamine storage

poor - daily requirement only marginally less than production in rumen

13

Cause - altered thiamine metabolism which leads to CCN

any condition that inactivates thiamine in rumen OR its synthesis --> rapidly causes thiamine deficiency:
- exessive grain intake or sudden feed change (promotes thiaminase producing bacteria)
- deficient pastures, unsupplemented
- thiaminase producing plant spp (bracken)

14

Explain how altered sulphur metabolism --> CCN

- sulphur found in beef cattle fed as sulphur, sulphates, gypsum, cruciferous vegetables, molassess
- sulphate reduced to SULPHIDES and ultimately incoorporated into CP and energy is released. Sulphide are NEUROTOIXC (inhibit cytochrome C oxidase thus preventing ATP production) --> neuronal swelling --> increased ICP (as for altered thiamine metabolism)

15

CCN - CS

- sudden death or found recumbent, comatose, convulsions, hypertonic between seizuers (GRAVE prognosis)
- or can develop over hours to days: cortical blindness, opisthotonus, hypermetric gait, hyperaesthetic progresses to depreession, miosis, strabismus, head tilt

16

Tx - CCN

- THIAMINE - IM or SQ, NOT multivit (--> toxicity), Iv --> anapphylaxis
- DEXAMETHASONE ? to reduce CE
- DIAZEPAM - control seziures
* usually respond within 24 hours, can be dramatic

17

Dx - CCN

- response to tx, hx and CS
- Erythrocyte transketolase activity (sensitive, specific, expensive, hard to find lab which runs it)
- CSF (mild pleiocytosis and increased [protein])
- PME: cortical swelling, softening, flattening of gyri, necrotic areas of cerebral cortex autofluoresce under UV, severe cases can herniate the cerebellum (indicated by constant seizuring)

18

Name viral diseases which affect neuro system

- Maedi visna (MV(
- CAprine arthritis encephalitis (CAE)
- Border disease
- BVDV

19

CS - MV

- DIFFUSE ENCEPHALITIS: ataxia, proprioceptive deficits, circling, blindness, coma, convulsions.
- Can show just emaciation
- Time from onset - death: 1-2 years
- immunosuppression

20

Pathology - MV

diffuse non-suppurative inflammation

21

Spread - MV

* aerosol*
- colostrum, milk, transplacental

22

Is there an accreditation testing scheme for MV?

Yes - Premium Sheep and Goat Health Scheme

23

Dx - MV

Ab ELISA

24

Define CAE

Caprine Arthritis Encephalitis virus

25

CS - CAE

- LEUKOENCEPHALOMYELITIS: ataxia, paresis, head tilt, nystagmus, opisthotonus, reduced PLR, parallysis
- symmetric or asymmetric
- usually young goats (neuro form)
- (adults: enlarged joints, shifting lameness, weight losss, mastitis, ill thrift)

26

Spread - CAE

aerosol and colostrum, milk, transplacental

27

IS there a CAE accreditation testing scheme?

Yes - Premium Sheep and Goat Health Scheme

28

Dx - CAE

Ab ELISA

29

Tx - CAE

Test and cull OR make 2 herds (dirty and clean, keep at least 6m b/w the two)

30

Outline Border disease virus infection

- infects naive ewes in pregnancy
- abortion, infertility, deformities
- lambs infected in utero in first half of gesttation become immunotolerant and remain viraemic --> PI
- adult sheep develop short, inapparent viraemia, develop immunity to reinfection
- similar to BVDV
- vertical and horizontal

31

What happens if a lamb is infected in utero before 60 dyas?

- foetal survival - hairy shakeer
- weak or normal lambs which are PI with virus
- no Ab detectable

32

When does a lamb foetus gain immunological competence?

between 60 and 85 days gestation

33

CS - border disease virus

- lambs infected

34

Dx - border disease virus

- AB testing young sheep for flock status
- Virus/Ag testing to find PIs

35

BVDV - CS

- weak
- head tremors
- proprioceptive deficits
- ataxia
- blindness
- stabismus/ nystagmus
- often die shortly after birth

36

Brain abnormalities

- hydrocephalus
- cerebellar hypoplasia

37

What is another name for ovine encephalomyelitis?

Louping ill in sheep

38

Transmission - ovine encephalomyelitis

Tick - Ixodes ricinus

39

What are the 2 commonest parasitic diseases in farm animals that cause CNS problems?

- ovine encephalomyelitis / louping ill
- coenurosis

40

What is coenurosis?

= Coenurus cerebralis
- intermediate stage of Taenia multiceps (tapeworm)
- causes cranium SOL: ataxia, unilateral vision loss, head tilt, circling hypermetria, coma
- adult worms shed in dog/cat faeces, infested on pasture, eggs hatch in SI and migrate to CNS via blood

41

Tx - coenurosis

PRAZIQUANTEL - to worm dog/cat.
- prevent dog/cat access.

42

What are nervous coccidiosis and sarcocystis?

other parasites which can cause neuro signs

43

What causes TSEs?

accumulation of abnormal prion proteins (PrPsc) in CNS, deposited as amyloid plaque within lymphoreticular and nervous tissue. PrPc post-translational modification to abnormal PrPsc which has a different protein structure, resistant to degradation

44

Which species does Scrapie affect?

sheep and goats

45

Is scrapie notifiable?

yes - like all TSEs

46

Age of animals with scrapie

1-5 years

47

CS - scrapie

- BEHAVIOURAL: separate from flock, restlessnes, nervous
- WEIGHT LOSS
- PRURITUS: wool loss, dermatitis, excoriation, nibble reflex (lip smacking)

48

What is the TSE testing programme?

all fallen stock (sheep, goats) > 18 mo need testing for scrapie

49

Transmission - scrapie

spread by colostrum, milk, dam to offspring, placenta, faeces/urine
* can survive in soil

50

Can you breed for genetic resistance to scrapie?

Yes - there a 3 codons on chromosome 13 to control susceptibility

51

Dx - scrapie

IHC and western immunoblot

52

BSE - age

4-6 years

53

CS - BSE

- BEHAVIOUR: separate from herd, fear, panic or excited
- Hyperaesthesisa, aggression, ataxia, tremors

54

What does BSE cause in humans?

nvCJD

55

Is there a genetic component to BSE?

No - unlike sheep scrapie

56

How can BSE risk be prevented in food chain?

- Specific RIsk Material COntrol (brain, eyes, SC, distal ileum, tonsils don't enter food chain)
- cattle> 30 months not sold for food unless tested and born after 1996
- no mechanically recovered meat

57

What is Listeria monocytogenes?

gram positive anaerobic bacteria

58

How does listeriosis affect brain?

acute meningoencephalitis and multifocal brain abscesses in brain tissue

59

How many animals does listeriosis affect?

usually individuals, may be more

60

How does fatality rate of listeriosis vary between sheep/goats and cows?

Sheep/goats - more acute disease so higher fatality than cattle

61

Source - listeria

COntaminated forage (e.g. spoiled silage) but occasionally seen on animals not on silage. Faeces carrier animals (end pregnancy and lambing time). rotting veg.

62

How does environment affect L monocytogenes?

survives long periods in environment, multiplies in low temps

63

How does listeria infect brain?

infects brain by haematogenous spread or by ascent from CN (trigeminal) rootlets. later exposed in younger animals when permanent teeth erupt or break in mucosa.

64

CS - listeriosis

- FEVER (early in disease): anorexia, depression, proprioceptive deficits, head pressing, compulsive circling
- CN 5-12 dysfunctional- progresses to unconsciousness, coma and seizures

65

How does listeria affect CN 5 (trigeminal)?

dropped, asymmetric jaw, facial analgesia

66

How does listeria affect CN 6(abducens)?

medial strabismus on lesion side

67

How does listeria affect CN 7 (facial)?

ptosis, loss of menace response, absent palpebral reflex, drooped ear, deviated philtrum (loss of tone), drooling saliva from ipsilateral side, exposure keratitis

68

How does listeria affect CN 8 (vestibulocochlear)?

nystagmus, head tilt toward lesion, circle to lesion side

69

How does listeria affect CN 9, 10 , 12 (glossopharyngeal, vagus, hypoglossal)?

stertor, dysphagia, paresis of tongue, tongue may protrude from ipsilateral side

70

Dx - listeriosis

- clinical suspiciion
- CSF tap: increased protein and WBCs

71

Tx - listeriosis

- high doses of penicillin (above label limit), BIM if IM or QID if IV
- (oxytetracycline is alternative but penicillin better)
- NSAIDs
- fluids

72

How is listeria a public health concern?

contamination of milk products (raw milk and cheese)

73

Name 3 spinal cord and peripheral nn disorders

- spastic paresis
- peripheral nn disorders (e.g. sciatic, obturator nn paralysis)
- enzootic ataxia (swayback)

74

Another name for spastic paresis

= Elso heel

75

Which animals are affected by spastic paresis?

Cattle - genetic basis (Holstein, Angus, Charolais, Shorthorn, Herefords)

76

Age of animals affected by spastic paresis

young animals (3wks - 1 year)

77

What does spastic paresis cause?

progressive hyperextension of HL
- excessive extensor tone when standing (gastrocnemius and superficial extensor mm)
- progressive contraction of gastroc mm --> non-weight bearing of affected limb
- unable to flex hock during HL protraction
- overstimulation of gamma motorneurons of spinal cord

78

Ddx - spastic paresis/ Elso heel

- patella luxation
- fractures

79

Tx - spastic paresis

- SURGICAL: tibial neurectomy (if in early stages) OR partial tenectomy of medial and lateral heads of gastrocnemius tendon (later stages)
- these are salvage procedures to enable continued growth and comfort before culling
- don't keep in herd (genetic basis)

80

What is another name for swayback?

enzootic neonatal ataxia

81

What does swayback affect?

lambs and kids

82

What cuasees enzootic neonatal ataxia/ swaybakc?

copper deficiency

83

What does enzootic neonatal ataxia cause?

progressive incoordination and recumbency, starting in HLs and progressing to TLs

84

CS - swayback

- progressive incoordination and recumbency, starting in HLs and progressing to TLs
-weight loss
- diarrhoea
- coat changes

85

Tx - swayback

- usually cull animals affected with CS
- Cu supplements at level needed--> toxicity,
- tx aim = prevent is rest of herd