Pathology: infectious and non-infectious diseases of the neural system Flashcards
Septic bacterial emboli are usually seen in young or old animals?
Young
Where in the brain do septic bacterial emboli typically become lodged?
In the cerebrum, at the grey/white matter junction
Causing thrombosis, malacia and abscessation
Histologically will see astrocytic encapsulation
A cow with a septic bacterial embolus is most commonly due to what bacteria?
T. pyogenes
Histophilus somnus
Staph aureus
A lamb with a septic bacterial embolus is most commonly due to what bacteria?
Staph aureus due to tick pyemia
A horse with a septic bacterial embolus is most commonly due to what bacteria?
Strep equi
A dog with a septic bacterial embolus is most commonly due to what bacteria?
Staph aureus
What causes Thromboembolic Mengingoencephalitis (TME) in cattle?
- Histophilus somni (a gram neg coccobacillus)
Causing acute vasculitis which primarily affects the CNS +/- lungs
What bacteria are most commonly associated with abscesses in the brain?
T. pyogenes
Strep spp
Staph spp
Pseudomonas aeruginosa
What are the 2 routes of infection to an abscess in the brain or spinal cord?
- Hematogenous spread
- Direct extension from a penetrating trauma, otogenic or frontal sinus
e. g. migrating grass seed, tail docking in pigs or bulls, or tail biting
An abscess of the pituitary fossa in cattle is usually caused by?
Hematogenous spread of bacteria either from the caudal nasal cavity or frontal sinuses
e.g. nose rings in bulls, or dehorning older cattle
note: patient usually presents with a jaw drop or exopthalmus
At what age is neonatal septicemia most common and why?
Within the first 2 weeks of life
Usually colostrum quantity or quality is lacking, or intrusion through the umbilicus
What are the most commonly found bacteria in neonatal septicemia?
(Calves, foals, small ruminants and swine)
Calves: E.coli, Salmonella, and Pasteurella spp
Foals: Salmonella spp and Actinobacillus equuli
Small ruminaints: Staph. pyogenes
Swine: Hemophilus parasuis
note: these bacteria will release endotoxins and cell wall components, leading to a cytokine secretion, adhesion of neutrophils to the endothelium and subsequent damage and vasculitis
What is the most common bacterial pathogen associated with swine meningitis?
Streptococcus suis
What are the common lesions found in Streptococcal sepsis in piglets?
Lesions are mainly seen in weaned piglets and are associated with lymphadenopathy, meningitis, arthritis, and endocarditis.
Lesions may include fibrinopurulent exudates in the brain, swollen joints, fibrinous serositis, and cardiac valvular vegetation.
Splenomegaly and petechial hemorrhages indicating septicemia are common.
What causes Listeriosis in sheep?
Listeria monocytogenes (gram positive and facultative intracellular bacterium)
recall: this is a zoonotic disease
What are the lesions associated with Listeriosis in sheep?
microabscesses in the brainstem due to retrograde movement up the trigeminal nerve
meningoencephalitis
note: can also cause abortion, septicemia and conjunctivitis
A dog with nonsuppurative meningoencephalitis in the ventral brainstem and periventricular tissue is indicative of what disease?
Ehrlichiosis
agent: Ehrlichia canis
A dog with disseminated suppurative vasculitis is indicative of what disease?
Rocky mountain spotted fever
agent: Rickettsia rickettsii
A dog/ fox with cerebellar meningitis is indicative of what disease?
Salmon poisoning
agent: Neorickettsia helminthoeca
A bovine with polyserositis and disseminated mononuclear-suppurative inflammation with vasculitis is indicative of what disease?
Sporadic bovine encephalitis
agent: Chlamydophila pecorum
A horse with suppurative granulomatous meningoradiculitis is indicative of what disease?
Borrelia burgdorferi (lyme)
What is an important mycotic disease that can cause neurological lesions in cattle?
Aspergillosis
note: often get abortion too and can see mycotic lesions in the aborted fetus brain
What is an important mycotic disease that can cause neurological lesions in dogs and cats?
Cryptococcus neoformans and C.gattii
What is an important mycotic disease that can cause neurological lesions in rabbits? and even dogs
Encephalitozoon cuniculi
What are the routes of invasion for viral infections that affect the brain?
- Hematogenous via BBB
- Replications in vascular endothelium: canine adenovirus-1, ovine herpesvirus-2, equine herpesvirus-1 and Feline coronavirus
- Neural: rabies, borna disease virus and herpesvirus
Neuro Viral infections can be divided into sub-categories depending on the histopathology seen, what are the neurotropic viruses (ones that damage the neurons)?
Rabies: all species
Pseudo-rabies (suid herpes virus 1): pigs, cats and dogs
Bovine herpesvirus-1 and -5: cattle
Teschen/ Talfan Disease: post-weaning pigs
Arthropod-transmitted viruses: Louping-ill (sheep, cattle, horses, dogs and human), West Nile virus (humans, horses, birds, cattle, sheep and small animals), Western & Eastern & Venezuelan equine encephalitis (horses and birds)
What viral infections cause granulomatous inflammation?
Caprine Arthritis Encephalitis virus: goats
Equine Infectious Anemia: horses
Feline Infectious Peritonitis: cats
What viral infections cause vasculitis?
Classical Swine Fever: swine
Equine Herpesvirus-1: horses
Malignant Catarrhal Fever (ovine and caprine herpes virus-2): cattle, sheep and goats
Canine adenovirus: canids
What viral infections cause leukoencephalitis (inflammation of the white matter)?
Canine distemper: dogs
Maedi-visna: sheep
FIV/ FeLv: cats
What is the most common macroscopic change to the neural tissue in a viral infection?
Most common: NO CHANGE!
sometimes haemorrhage and edema but not often
note: so an animal with neurological issues with no macroscopic changes to the neural tissue is suggestive of a viral infection
What is the most common lesion found in the neural tissue during a protozoal parasitic infection?
Non-suppurative inflammation +/- abundant eosinophils
What is the definitive and intermediate host of Toxoplasmosis?
Definitive: cat
Intermediate: sheep, rarely dogs, humans
What does Toxoplasmosis cause in sheep?
abortion + multifocal encephalitis in the fetus (lamb)
What is the definitive and intermediate host of Neosporum caninum?
Definitive: Dogs
Intermediate: Cattle
What does Neosporosis cause in dogs and cattle?
Dogs: Myositis/ meningoencephalomyelitis + hindlimb paralysis
Cattle: abortion at 5-6 months gestation with multifocal encephalitis in the fetus
What is the definitive and intermediate host to Sarcocystis neurona?
Definitive: possum
Intermediate: horse (rarely dogs)
What kind of lesions are found in the neural tissue of the horse infected with Sarcocystis neurona?
Lesions in the spinal cord- necrotizing inflammation of the grey and white matter, perivascular mononuclear cuffs and infiltration of the parenchyma with neutrophils, eosinopphils and sometimes giant cells
What is the most common lesion found in the neural tissue during a helminth parasitic infection?
Suppurative with necrosis, haemorrhage with variable numbers of eosinophils, + granulomatous in chronic lesions
What is a common tape worm infection in sheep that can cause neurological signs?
Coenuris cerebralis (‘Gid’), which is the encysted larvae of Taenia multiceps
Dog excretes in the feces, sheep ingests it and it will migrate to the CNS
What is the difference between acute and chronic forms of Gid in Sheep? (Coenuris cerebralis)
Acute: occurs 3-4 weeks after ingestion, malacia is caused by the migratory tracts of many migrating larvae
Chronic: occurs 6 months after ingestion, larve with encyst themselves in the cerebrum causing compression, edema, hydrocephalus and bone softening
What is the most common lesion found in the neural tissue during a non-infectious and/or immune-mediated inflammatory disorder?
Non-suppurative with various degrees of granulomatous inflammation
Can affect the meninges, blood vessels, brain, spinal cord or peripheral nerves
What is Granulomatous meningoencephalomyelitis (GME) in dogs?
GME is an acute, progressive inflammatory disease of the central nervous system (CNS) of dogs. GME is a common differential for dogs that are affected by focal or diffuse neurological diseases
What age and breed is Granulomatous meningoencephalomyelitis (GME) most commonly seen in?
- Young to middle aged dogs
- Small breeds: terrier and toy breeds
What are the clinical signs associated with Granulomatous meningoencephalomyelitis (GME) in dogs?
- Depends on the location of the inflammation as it can occur anywhere in the neural system
Spinal lesions: ataxia, paresis or paralysis
Brainstem: vestibular dysfunction
Cerebrum: changes in behaviour, forced movement and circling, depression and convulsions
What is Necrotizing meningoencephalitis (NME) in dogs?
Necrotizing meningoencephalitis (NME) is an idiopathic, breed specific, unique inflammation disorder of brain in small breed dogs diagnosed more frequently in young to adult animals, from six months to seven years of age
What lesions are commonly associated with Necrotizing meningoencephalitis (NME) in dogs?
What lesions are commonly associated with Necrotizing Encephalitis (NE) in dogs?
NME:
- Lesions in Cerebral cortex
- Mainly grey matter, asymmetrical multifocal bilateral cerebal necrosis
- Commonly affected: Pugs, Maltese, ShihTzu
NE:
- Lesions in midbrain, brainstem and cerebellum
- Necrotizing lesions confined to white matter
- Commonly affected: Yorkies, french bulldogs and Pomeranian
What are the 3 neurological immune-mediated inflammatory lesions in dogs?
1) Steroid responsive meningitis-arteritis: german shepherds and boxers
2) Idiopathic eosinophilic meningoencephalitis: golden retrievers and rottweilers
3) Greyhound meningoencephalitis: young greyhounds in ireland
What is Cauda Equina Neuritis?
A chronic, progressive, rare and sporadic disease in horses
- Etiology unknown: possibly autoimmune or post-infectious following EHV-1 or allergy
- Clinical signs include: tail paralysis, urinary incontinence, fecal retention, weakness, atrophy of the coccygeal muscles and atrophy of the hindlimb muscles
- Histologically: Lesions consisted of nonsuppurative inflammation of the nerve trunks and proliferation of the perineurium of the cauda equina with marked swelling
