LA Spinal Cord Diseases Flashcards
describe difference in spinal cord exam in large animals
- muscle tone and reflexes are harder to assess! unless recumbent
- no hopping, wheelbarrowing, or hemiwalking (unless small LA)
- gait and proprioception:
try placement tests (could just be a good horse and leave leg where you put it), head elevation, circling, backing, hills, curbs, tail pull
what do LM spinal cord lesions look like in large animals? (5)
- short strided
- trembling
- hypotonic
- atrophy (unless acute)
- weakness progressing to recumbency
what do UMN/GP spinal cord lesions look like in lA?
- long and lopey (floaty)
- stumbling/tripping
- truncal sway
- traveling on two or more tracks
- don’t know where their feet are
-limb placement
-circling
-backing
-hills/cribs - weakness progressing to recumbency
describe equine protozoal myelitis (EPM)
- CNS migration of protozoan parasites: sarcocystis neurona!! and also neospore hughesi
- exposed via ingestion of opposum feces
-horses = aberrant, dead end host; does NOT shed oocytes in poop
-infection is not patent
describe clinical features of EPM
- high seroprevalence but low clinical disease
-in some regions 80-90% of horses have been exposed (seropositive) but less than 1% develop neuro disease - means that environmental and host factors are key but clinical signs vary widely!!! protozoan can go anywhere in CNS that it wants to
- 3 As:
-asymmetry: asymmetric spinal cord deficits most common
-ataxia
-atrophy - could just be poor performance though! can be acute OR slowly progressive
describe EPM diagnosis
- gold standard is finding the parasite in the CNS
-MRI would be helpful bc parasites leave classic regions but most horseys don’t fit so - plan B: consistent clinical signs and prove exposure to organism
-via serology: antibodies against S. neurona in the blood
-LOTS of different tests = none are perfect
–western blot: sucks
–IFAT: sucks a little less
–SAG titers: sucks the least
-these suck because so many horses have been exposed that exposure does not mean disease!! - can look for organism in CSF
-good but you don’t know where the organism is and PCR only works for spinal cord which you can only get on necropsy
-BEST WAY WE HAVE WHEN ALIVE: antibody titers in CSF: document intrathecal Ab production, looking for a combo on surface antigens in serum AND CSF and calculate a ratio
-if serum:CSF ratio <100 suggests EPM!!!!!
-use equine diagnostic solutions lab in kentucky only!!
describe EPM management and prognosis
- anti-protozoal
-3 FDA approved drugs labelled to treat it (you must use them)
-labelled for 4 week treatment, but usually need to treat for 2-9 months - possum management: good luck charlie
prognosis:
1. most improve or stabilize with treatment BUT
2. some progress despite treatment
3. some relapse or are infected when treatment ends
4. some improve but are never neurologically normal: unsafe/unrideable
be pateint!
describe viral myelo(encephal)itis
4 causes:
1. equine herpes virus
2. west nile viru
3. EEE/WEE/VEE
4. rabies
describe equine herpesvirus myeloencephalopathy
- lots of equine herpesviruses (up to 9 so far)
-respiratory signs and abortions are more common than CNS disease - only EHV1 and rarely EHV4 cause EHM
-EHV1 has a neurovirulent form (D752)
-75% of EHM cases are due to D752
-25% are wild type (N752) - epidemiology
-almost all horses infected as foals
-latent in trigeminal ganglia and lymph nodes
-in foals: subclinical infection (enough immunity from mom) and shedding leads to spread
in adults: shedding and clinical disease (usually respiratory) - REPORTABLE
describe EHM pathophysiology
- respiratory epithelial infection!!
-to lymph nodes within 24-48 hors
-shedding for up to 3 weeks - viremia: leukocytes!
-2 weeks - infection of CNS endothelial cells leads to vasculitis that leads to microthrombi and local hemorrhage that causes ischemic CNS necrosis
-does not infect neuron!! - only 10% horses in EHM outbreaks develop neuro signs due to
-virus factors: D752 infection, viremia level
-host factors: age (>5yrs), big breeds, females?
-immunity: recently vaccinated horses tend to be at greater risk!
-environment: season and geography? we don’t rly know
describe clinical signs of EHM (6)
1 variable, onset 6-10 days post exposure
2. fever first but we usually miss it (gone by time of neuro signs)
3. +/- respiratory disease (on farm)
4. ataxia (pelvic more than thoracic commonly) progressing to tetraparesis/recumbency
5. back-end signs are common
-incontinence, loss of tail/anal tone, analgesia
6. other variable CNS signs
describe diagnosis of EHM
- CSF:
-increased protein
-+/- mononuclear pleiocytosis
-not specific for EHM! just mean neuro disease
-xanthochromia (yellow CSF) - acute and convalescent serum titers
-too slow for real world use (books say and NAVLE might ask but don’t do it) - signs + shedding/viremia
-PCR on nasal swabs and/or buffy coat (blood)
-usually positive at least 10-14 days after infection
-can shed intermittently; test more than once! (need to test negative at least twice to actually call negative; give at least 12-24 hours between testing)
describe EHM treatment (4) and prognosis
- SUPPORTIVE CARE
- anti-inflammatories:
-steroids? not for long
-NSAIDS? - anti-virals!: valacyclovir
- anticoagulants (doesn;t attack neuron itself, it causes microthrombi in brain or spinal cord, can slow progression by preventing clotting)
prognosis:
-better if standing and owner has money
-if recumbent, poor
describe EHM prrevention and management
- vaccination:
-killed or MLV
-NEITHER clain to prevent EHM
-but do limit nasal shedding
-DONT vaccinate if think exposed bc can increase risk of neuro form - outbreak management
-early diagnosis: test test test
-teat clinical cases
-prevent spread: isolate and quarantine, +/- vaccinate UNEXPOSED only
describe west nile virus
- flavivirus; not spread horse to horse, spread by mosquitoes
- common in summer/early fall
- clinical severity varies
-subclinical to fatal encephalitis
describe clinical signs of WNV
- fever, depression
- ataxia (symmetric, asymmetric)
- often muscle fasciculations!! (help rule out other viruses)
- +/- other prosencephalon and/or cranial nerve deficits
- any age/sex/breed
- ACUTE ONSET!!
describe diagnostics and management and treatment of WNV
- signs, CBC, CSF; not pathognomonic
- IgM capture ELISA:
-serum or CSF: 100% agreement
-acute infection, even in vaccinated animals - treatment: supportive care
describe prognosis and prevention of WNV
prognosis: 28% mortality (less fatal than herpes, even less if vaccinated); but if recumbency = bad
prevention:
1. vaccinate: several available and effective
2. boost 1st year then annually before mosquitoes
-every six months in warm climates
3. improved prognosis in vaccinated
4. try to control mosquitos but good luck charlie