Flashcards in Farm animal neurology Deck (85):
2 main types of cortical disease
- cerebrocortical necrosis (CCN)
- viral (MV, CAE, BDV, BVD)
Most important brainstem and CN disease
Name 3 metabolic diseases with neuro effects
- nervous ketosis
List spinal cord and peripheral nn disorders
- spastic paresis (Elso heel)
- enzootic neonatal ataxia (swayback)
- fractures, luxations, spinal abscesses
Name 2 neuromuscular disease
Which parasites can cause neuro disease?
- louping ill
- coenurosis / gid
- nervous coccidiosis
Another name for cerebrocortical necrosis (CCN)
aetiology - CCN
- multiple, all lead to necrosis of grey matter:
- THIAMINE metabolsim
- SULPHUR metabolism
Species - CCN
all ruminants and pseudo-ruminants
Occurence of CCN
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
Outline ruminant thiamine storage
poor - daily requirement only marginally less than production in rumen
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)
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)
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
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
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)
Name viral diseases which affect neuro system
- Maedi visna (MV(
- CAprine arthritis encephalitis (CAE)
- Border disease
CS - MV
- DIFFUSE ENCEPHALITIS: ataxia, proprioceptive deficits, circling, blindness, coma, convulsions.
- Can show just emaciation
- Time from onset - death: 1-2 years
Pathology - MV
diffuse non-suppurative inflammation
Spread - MV
- colostrum, milk, transplacental
Is there an accreditation testing scheme for MV?
Yes - Premium Sheep and Goat Health Scheme
Dx - MV
Caprine Arthritis Encephalitis virus
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)
Spread - CAE
aerosol and colostrum, milk, transplacental
IS there a CAE accreditation testing scheme?
Yes - Premium Sheep and Goat Health Scheme
Dx - CAE
Tx - CAE
Test and cull OR make 2 herds (dirty and clean, keep at least 6m b/w the two)
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
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
When does a lamb foetus gain immunological competence?
between 60 and 85 days gestation
CS - border disease virus
- lambs infected
Dx - border disease virus
- AB testing young sheep for flock status
- Virus/Ag testing to find PIs
BVDV - CS
- head tremors
- proprioceptive deficits
- stabismus/ nystagmus
- often die shortly after birth
- cerebellar hypoplasia
What is another name for ovine encephalomyelitis?
Louping ill in sheep
Transmission - ovine encephalomyelitis
Tick - Ixodes ricinus
What are the 2 commonest parasitic diseases in farm animals that cause CNS problems?
- ovine encephalomyelitis / louping ill
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
Tx - coenurosis
PRAZIQUANTEL - to worm dog/cat.
- prevent dog/cat access.
What are nervous coccidiosis and sarcocystis?
other parasites which can cause neuro signs
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
Which species does Scrapie affect?
sheep and goats
Is scrapie notifiable?
yes - like all TSEs
Age of animals with scrapie
CS - scrapie
- BEHAVIOURAL: separate from flock, restlessnes, nervous
- WEIGHT LOSS
- PRURITUS: wool loss, dermatitis, excoriation, nibble reflex (lip smacking)
What is the TSE testing programme?
all fallen stock (sheep, goats) > 18 mo need testing for scrapie
Transmission - scrapie
spread by colostrum, milk, dam to offspring, placenta, faeces/urine
* can survive in soil
Can you breed for genetic resistance to scrapie?
Yes - there a 3 codons on chromosome 13 to control susceptibility
Dx - scrapie
IHC and western immunoblot
BSE - age
CS - BSE
- BEHAVIOUR: separate from herd, fear, panic or excited
- Hyperaesthesisa, aggression, ataxia, tremors
What does BSE cause in humans?
Is there a genetic component to BSE?
No - unlike sheep scrapie
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
What is Listeria monocytogenes?
gram positive anaerobic bacteria
How does listeriosis affect brain?
acute meningoencephalitis and multifocal brain abscesses in brain tissue
How many animals does listeriosis affect?
usually individuals, may be more
How does fatality rate of listeriosis vary between sheep/goats and cows?
Sheep/goats - more acute disease so higher fatality than cattle
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.
How does environment affect L monocytogenes?
survives long periods in environment, multiplies in low temps
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.
CS - listeriosis
- FEVER (early in disease): anorexia, depression, proprioceptive deficits, head pressing, compulsive circling
- CN 5-12 dysfunctional- progresses to unconsciousness, coma and seizures
How does listeria affect CN 5 (trigeminal)?
dropped, asymmetric jaw, facial analgesia
How does listeria affect CN 6(abducens)?
medial strabismus on lesion side
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
How does listeria affect CN 8 (vestibulocochlear)?
nystagmus, head tilt toward lesion, circle to lesion side
How does listeria affect CN 9, 10 , 12 (glossopharyngeal, vagus, hypoglossal)?
stertor, dysphagia, paresis of tongue, tongue may protrude from ipsilateral side
Dx - listeriosis
- clinical suspiciion
- CSF tap: increased protein and WBCs
Tx - listeriosis
- high doses of penicillin (above label limit), BIM if IM or QID if IV
- (oxytetracycline is alternative but penicillin better)
How is listeria a public health concern?
contamination of milk products (raw milk and cheese)
Name 3 spinal cord and peripheral nn disorders
- spastic paresis
- peripheral nn disorders (e.g. sciatic, obturator nn paralysis)
- enzootic ataxia (swayback)
Another name for spastic paresis
= Elso heel
Which animals are affected by spastic paresis?
Cattle - genetic basis (Holstein, Angus, Charolais, Shorthorn, Herefords)
Age of animals affected by spastic paresis
young animals (3wks - 1 year)
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
Ddx - spastic paresis/ Elso heel
- patella luxation
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)
What is another name for swayback?
enzootic neonatal ataxia
What does swayback affect?
lambs and kids
What cuasees enzootic neonatal ataxia/ swaybakc?
What does enzootic neonatal ataxia cause?
progressive incoordination and recumbency, starting in HLs and progressing to TLs
CS - swayback
- progressive incoordination and recumbency, starting in HLs and progressing to TLs
- coat changes