Lecture 4: Diseases of Nervous System: infectious Flashcards
What is the primary reservoir for viral encephalitides
bird species
what transfers viral encephalitides to horses and humans
mosquitoes
what is the pathophysiology of viral encephalitis
- Virus enters CNS by crossing BBB through endothelial cell penetration
- Affects cerebral cortices, thalamus, hypothalamus, and sometimes spinal cord (less affected)
- Neurophagia and gliosis progressing to malacia and necrosis
which viral encephalitis has the greatest affect on the spinal cord
WNV
what are some clinical signs of viral encephalitis 1-3 days with infection
fever, depression, anorexia, fire is
what are some clinical signs of viral encephalitis 1-3 days following fever
hyper excitability progressing to somnolence, depression, recumbency, cortical blindness, propulsive walking, head pressing, ataxia
what is the mortality to eastern equine encephalitis
75-99%
T or F: horses are dead end hosts for EEE
true, don’t transmit
what is the morality rate for western equine encephalitis
20-50%
T or F: horses are dead end hosts for WEE
true, don’t transmit
what is the mortality rate of Venezuelan equine encephalitis
20-80%
T or F: horses are dead end hosts for VEE
false, horses can become viremic and primary reservoirs- infect you and other horses
what is the mortality rare for West Nile virus
2%
what is the best way to diagnose viral encephalitides
Serology- IgM capture ELISA can distinguish between vaccinated >30-60 days and natural infection
Rapid and reliable
what are some CSF findings for WNV
mononuclear pleocytosis, variable protein
what are some CSF findings for EEE
high protein, neutrophilic marked pleocytosis
what are some CSF findings for WEE
lymphocytic pleocytosis
how can you dx viral encephalitides post mortem
viral isolation on brain tissue
what is the tx for viral encephalitides
- Supportive care (ineffective for EEE)
- Corticosteroids-reduce brain edema
- Mannitol- reduce brain edema
- NSAIDS (best in WNV)
how do you prevent viral encephalitides
- Yearly vaccination prior to mosquito season
- Mosquito control
what does EHV-1 cause
respiratory disease, neurological disease, abortion storms/ weak foals, chorioretinopathy
what does EHV-2 cause
respiratory disease and keratoconjunctivitis
what does EHV-3 cause
coital exanthema
what does EHV-4 cause
respiratory disease, rarely associated with abortion and neurological disease
what does EHV-5 cause
equine multinodular pulmonary fibrosis
what is the pathophysiology of EHV 1 and 4
- Virus enters respiratory system and transported to LN
- Virus enters peripheral WBCs and circulates blood
- Results in vasculitis and thrombosis
what genetic variant in EHV-1 is commonly associated with neurological disease
mutation of aspartic acid (D) instead of asparagine (N) at position 752 in DNA polymerase gene
T or F: avoid testing healthy horses for herpes because they all have it
true
what is the test of choice for herpesvirus
real time PCR of nasal swab or fresh whole blood
what are the clinical sides of EHV neurotrophic form
fever, dog sitting, upper motor neuron bladder (turgid, unable to void, spastic)
what areas of the spinal cord are most commonly affected with EHV
caudal spinal cord and sacral cord
what are the CSF findings of EHV
- Increased total protein
- Xanthochromia (yellow color)
how can you prevent neurological signs in horses exposed to EHV
- Valcyclovir/ valganciclovir decreased viral replication and signs
- LMW heparin to prevent thrombosis
- Banamine
what is treatment for EHV
- NSAIDS
- Corticosteroids
- Monitor urination- catheterization and antimicrobials to prevent septic cystitis
- Anticoagulant therapy- LMW heparin
- Antiviral drugs to decrease shedding
- Quarantine for 3 weeks past last fever
how do you prevent EHV
- Minimize stress
- Vaccinate q3 months
- High virus neutralizing antibody vaccines
what horses should be vaccinated against EHV/when to vaccinate
afebrile and asymptomatic
what vaccines for eHV have greatest ability to limit nasal shedding and viremia
- Antiabortion vaccines- pneumabort-K and prodigy
- MLV vaccines: rhino use and calvenza
how long do horses exposed to eHV have immunity
3-6 months
what is prognosis for EHV
- Good for non recumbent horses
- Poor for recumbent horses
what causes EPM
sarcocystis neurons or neospora hugheshi
what is the definitive host for EPM
opossums
what are some clinical signs of EPM
Ataxia, weakness, dysphagia, head tilt, obtundation, facial nerve paralysis, muscle atrophy, switching leg lameness
how can you dx EPM
- Rule out other differentials
- Serum IFAT
- Serum to CSF ration- best one
- Necropsy- demonstrate protozoans in CNS lesions- gold standard
which diagnostic test for EPM has a high negative predicative value and what does that mean
western blot- a negative result means strong likelihood you dont have EPM, a + result is not helpful
what is tx for EPM
- Thiazide coccidiostats- Marquis ponazuril, portability-diclazuril
- Folate inhibitor combination-sulfadiazine/pyrimethamine
what is prognosis for EPM
- 60% of horses will improve 1 grade
- 10-20% will relapse
T or F: good idea to vaccinate against EPM
false, doesn’t work well and complicates diagnosis
how do you manage a grade 5 neurological horse
- Inform owner 1 in 10 horses ever stand again
- Refer- heavily sedate in trailer
- Wrap legs and head in trailer for protection
- Isolate, quiet and dark, deep bedding and padded stalls
- Monitor ability to eat and drink, IV fluids
- Turn recumbent horses every 2-4hrs
