Sheep_neurological disease 2021-2.pdf

Neurological Disease In Sheep Approach To Neurological Cases • History – signs observed by farmer – age group • Learn your differential diagnosis by age group – – – – • • • • number affected speed of onset/progression time of year feeding/ diet change full clinical examination Neurological exa...

Neurological Disease In Sheep Approach To Neurological Cases • History – signs observed by farmer – age group • Learn your differential diagnosis by age group – – – – • • • • number affected speed of onset/progression time of year feeding/ diet change full clinical examination Neurological exam (see Chapter 8 diseases Sheep) Ancillary test CSF tap response (or not!) to treatment Neurological Examination • Some diseases affect specific areas of brain and show different clinical signs • Really helpful diagnosis – Cerebrum – Cerebellum – Vestibular system – Brain stem – Spinal cord The brain is conveniently divided into six areas, each with a recognised neurological "syndrome” but only four; cerebral, cerebellar, ponto-medullary (brainstem), and vestibular syndromes are common. Cerebrum Cerebellum Brainstem Cerebrum • • • • Common Diffuse Local Severity of signs stage of disease A.C WINTER A.C WINTER Cerebrum • Diffuse • Altered mental state – Depressed – Hyperexcitable – Disorientated • Blindness • Seizures • Opisthotonus – Recumbant – Extended front legs flexed hind legs • Examples of Cerebral Diseases – Bacterial meningitis – Cerebrocortical necrosis – Pregnancy toxaemia Cerebrum Local • • • • Contralateral blindness Circling Proprioceptive deficits Examples – GID cysts (coenuris cerebralis, Taenia multiceps) – Brain abscess – Trauma Cerebellum • Altered head carriage • Balance – Ataxia not weakness – wide-based stance • Dysmetria – High stepping • Congenital – Cerebellar hypoplasia • Border disease Hairy Shaker A.C WINTER – Cerebellar hypoplasia • Poss abscess (rare) • intention tremor (inc. nystagmus) A.C WINTER Vestibular System • Head tilt to affected side key feature • loss of balance • circling • falling or rolling to one side • spontaneous nystagmus • Examples – Middle ear infection • Unilateral facial nerve paralysis runs close to middle ear A.C WINTER Brainstem (Pontomedullary) • Depression – because of Ascending Reticular activation system • Cranial nerve deficits brainstem nuclei – especially V, VII, VIII, – Facial and trigemminal sometimes IX, X, XII • Ipselateral hemiparesis (motor tracts passing through) • Example condition: listeriosis A.C WINTER Spinal Cord • • • • • • • • • • • no signs of central disease Depends on site of spinal cord Tetraparesis/ paraparesis Proprioception Skin sensation Pain Pedal and other spinal reflexes Spinal abscess- joint ill, tick pyaemia Wobblers syndrome-texels Trauma Congenital abnormality Young Lambs Birth to 3 months • Common problems in young lambs • Were they mentally normal or abnormal at birth? • IE CONGENITAL OR ACQUIRED Common problems in young lambs at birth- 3 months old • Border Disease (tremors, hairy shakers-congenital)CEREBELLAR • Congenital Swayback (ataxia) copper deficiency – delayed swayback (older lambs) SPINAL • Drunken Lamb Disease and Lamb nephrosis (ataxia, depression)- see lamb lecture CEREBRAL • Bacterial meningitis (depression collapsed)CEREBRAL • Tetanus- Neutotoxin • Trauma Accident- ANYWHERE A.C WINTER Common Problems birth to 3 months • spinal abscess (joint ill ) – Treat 1mg/kg dexamethasone – Penicillin-5 days at least • Listeriosis- rare in young animals – circling – facial nerve paralysis – Pontomedullary • Louping ill – cerebral Louping ill (flavivirus) • tick borne • most infections are slight and give immunity • clinical disease in all ages depending on immunity – colostral antibody – think of exposure periods • Often young animals, bought in stock, immunologicaly naive • can get outbreaks of disease • important in Grouse (80% mortality) • variable signs – – – – – head pressing trembling & tremors nystagmus lip twitching etc “louping gait” • Vaccine available Common problems 3 months to adult • • • • • CCN listeriosis Trauma accident Gid cysts louping ill (tick area) Cerebro-cortical necrosis (CCN) • Vitamin B1 deficiency (thiamin) • acute onset in growing lambs (2 – 6 months) • sporadic but can get outbreaks • history of diet change or worming – thiaminase production in rumen • Clinical signs vary depending on progression of disease – – – – – – – dull Disorientated Blind Tremors Recumbancy Opisthotonus convulsions CCN • Treatment – Vitamin B1 iv – Vit B1 i/m every 12 hours – For 3 days – PME – brain – House quietly – Vision should return 57days • Prevention ? – diet changes Listeriosis • Common • Listeria moncytogenes • Associated with feeding poorly preserved silage soil contaminated (mouldy) • 18-24 months old common, but not exclusive changing molar teeth allowing infection of buccal tissues • Ascending infection to brain stem Listeriosis • Brainstem lesion – Anorexia, depression – Unilateral hemiparesis • Cranial nerves affected – Trigemminal nerve paralysis • Salivation, food impacted in cheek – Facial nerve paralysis drooped ear, lowered eyelid, deviated muzzle, loss of blink Listeria • Diagnosis – Clinical signs – CSF tap – PM • Treatment – Good if caught early – Gold standard treatment for a 75kg ewe –Off licence 28 day meat withhold – 6g benzylpenicillin (Crystapen x 2 vials) i.v – 20ml procaine peniciliin i.m (divided sites) one dose on day of examination – 1mg/kg dexamethasone i.v – 5ml procaine penicillin daily for 5 days • Treatment – Supportive care • Remove silage Gid • Taenia multiceps – Eggs picked up by sheep, cysts develop in brain cerebral, cerebellar (Coenoris cerebralis) – Primary host dog • Gradual onset – circling – unilateral blindness • opposite side to lesion – head tilt – skull softening • Treatment – Surgical Precise – signs depend on site of lesion – cerebral – good prognosis – cerebellar – poor • Control – worm dogs every 6 weeks praziquantel – keep away from sheep caracsses Vestibular disease • Commonly misdiagnosed at listeriosis • Associated with otitis media and ascending infection from respiratory /pharanx of Eustachian tube • Pasturella spp. Streptococcus, Truperalla pyogenes • Clinical signs – Los of balance – Head tilt towards affected side – Horizontal nystagmus – Aural discharge – Can get facial nerve paralysis too • Treatment – At least 5 days penicillin Common problems in adults • Cervical sub-luxation (paresis, rams fighting) • Gid cyst • Listeriosis • Brain abscess • Louping Ill (tick areas, abnormal gait) • Trauma Accident • Metabolic disease (pregnancy) – Pregnancy toxaemia• blind, dull – Hypocalcaemia • Collapsed, bloated, flaccid paralysis – Hypomagnesaemia • staggers, hyperaesthesia • Wobbler Texels • Scrapie (rare) Nervous disease at lambing time (collapsed recumbent ewe) • Pregnancy toxaemia – diagnosis –BOHB levels blood, – treatment – – propylene glycol etc • Hypocalcaemia – before lambing – stress factors – treat with 20 – 40 ml 20 % Ca Borogluconate I/V – instant and complete response ( 80 ml s/c slower response) • Septicaemic listeriosis – poor prognosis Hypomagnesaemia • seen after lambing (usually growing twins) – milk drain (no magnesium stores) – stress • sudden death usually • recumbent, convulsive • Treatment – i/v Ca & Mg (slowly) or Mg s/c – prevention – high magnesium cake Scrapie • Classical Scrapie – Infectious neurological disease of sheep – Fatal chronic progressive, brain disease of sheep • TSE – BSE – CJD – Atypical Scrapie (very rare only picked up by fallen stock sampling) • Non infectious sporadic • Prion disease – very resistant to heat, disinfectants U.V light – causes abnormal protein to accumulate especially in brain causing neurological dysfunction – Spread mother to offspring (vertical transmission) prenatally and colostrum and milk – Horizontally birth fluids, placenta • Considerable Genetic Variation in Suspecibility to Infection Very low level in U.K due to severe control measures in 1980-2000s to control BSE and scrapie Scrapie • Clinical Signs • Progressive Fatal Neurological disease • Long incubation period • 2-5 years old • Single animal • Neurological – Altered mental state excitable nervous depressed, aggressive – Trembling – High step ataxia – recumbancy • Skin prurititus, rubbing scratching, wool loss • Weight loss • Death • Although its rare – Think of it single itchy sheep no scab – Progressive neurological signs and weight loss Scrapie • • • • If suspect Scrapie Notifiable Report to DEFRA/AHPA Test animal If positive – Complusory Scrapie Flocks Scheme – Movement Restriction, Genotyping, Testing and Culling – http://www.defra.gov.uk/ahvla-en/diseasecontrol/notifiable/scrapie/csfs/ Statutory Scrapie Control • Testing Scheme • The UK is required to test annually for TSE usually at fallen stock centres • TSE Feed Controls • The feed controls are the key animal health control for BSE. It is illegal to feed animal protein to ruminants • SRM Controls at abattoirs – Specified Risk Material Removed from Sheep over 6 months old and Incinerated – (brain, spinal cord and spleen) Private Scrapie Controls • SRUC • Pedigree breeding stock, export • Scrapie Monitoring Scheme – Annual flock inspection – Sampling and testing fallen stock scrapie • Scrapie Genotyping Scheme – Breeding stock – Check for susceptibility to disease • http://www.sruc.ac.uk/info/120113/premium_sh eep_and_goat_health_schemes/511/diseases/5 Finally • The list of neurological problems is not endless! • Think of the common ones first! • Use the logic of history, systematic examination and localisation to help you come to a possible/probable diagnosis, References • Sheep Medicine PR Scott Chapter 8 on Neurological Diseases • Cases 3,4,13,14,29