Lecture 3: Neuropathology- Inflammatory and Infectious Flashcards
What is myelitis
Inflammation of spinal cord
What is meningoencephalomyelitis
Inflammation of meninges, cerebrum and spinal cord
What is polioencephalitis
Inflammation affecting the gray matter
What is leukoencephalitis
Inflammation affecting the white matter
What is ganglionitis
Inflammation of ganglia
What would cause suppurative inflammation
Bacteria
What would cause non-suppurative, mixture of lymphocytes, plasma cells and macrophage inflammation
Virus or immune mediated
Dog euthanized for extreme mentation changes, hypersalivation and neurological symptoms. Suspected rabies histo of brain showed the following. What does histo show
Intracytoplasmic inclusions- negri bodies
What could cause granulomtous or pyogranulomatous inflammation
- Certain bacteria- mycobacterium
- Fungal organisms
- Certain virus- FIP
What would cause eosinophilic inflammation
Parasites
What is the most common route of neurological infection
Hematogenous
How do infections travel up nerves to CNS and what are some examples
Travel retrograde up peripheral nerves to brain
1. Herpesviruses
2. Lyssavirus (rabies)
3. L. Monocytogenes
What are the 3 “gatekeepers” to CNS infection
- Subarchanoid barrier
- Blood brain barrier
- CSF barriers
What forms the subarachnoid barrier
Skull and meninges
What forms the blood brain barrier
Intercellular junctions between endothelial cells of blood vessels and astrocytes
What forms CSF barrier
Epithelial cells of choroid plexus and endothelial cells of vessels
How does the olfactory portal serve as passageway to brain
Olfactory system bypasses physical and cellular barriers through the cribiform plate where olfactory nerves travel to olfactory bulb in brain
L. Monocytogenes causes a bacterial infection of CNS in who
Ruminants, typically small ruminants
What is the pathogens is of L. Monocytogenes
- Previous oral trauma
- Ingestion of food/silage that is contaminated with L. Monocytogenes
- Bacteria gain access to peripheral nerves via wound in oral cavity and extend to brainstem/cerebellum
- Causing a neuritis/ suppurative meningoencephalitis
Where are the lesions located in brain for L. Monocytogenes
Brainstem
What is likely cause of this lesion and histo. What does histo show
L. Monocytogenes
Histo shows small clusters of neutrophils (microabscesses) that disrupt neuroparenchyma
How do ruminants present with L. Monocytogenes
Fever, depression, ataxia, head pressing
Aka circling disease
What cranial nerves are affected with L. Monocytogenes and what symptoms are seen
CN V, VII, and VII
Symptoms: unilateral facial paresis/ paralysis, head tilt, ear droop, loss of sensation, depression, recumbency
What causes thromboembolic meningoencephalitis
Histophilus somni
What are the gross lesions associated with thromboembolic meningoencephalitis caused by H. Somni
Multifocal random, embolic hemorrhagic infarcts in brain +/- spinal cord
What could have caused this in cattle
H. Somni
What are the histological findings with H. Somni TEME
Necrotizing vascular is and thrombosis
Vessels in meninges contain septic fibrin thrombi
What do you see and what could have caused this
Vessel with septic fibrin thrombi, vascular necrosis and vascular is
Cause: H. Somni leading to TEME
How do viruses injury the brain
- Direct ability to kill CNS cells (cytotoxicity)
- Induce immune response and inflammation
What are some common histological features of viral encephalitides
- Inflammation- lymphocytes, plasma cells, macrophages
- Viral inclusions
- Neuronal necrosis- dead, red neurons
- Increase number of glial cells
What would cause these histological features: bacteria, virus, or fungi
virus
What wrong here and what would cause this, bacteria, virus or fungi
Neuronal necrosis- dead, red neurons
Cause: viral
What domestic species are most commonly affected by rabies
Cats, cattle and dogs
What are important wildlife reservoirs for rabies
Raccoons, skunk, foxes, bats
What is the incubation period for rabies
30-60 days
What is pathogensis for rabies
- Virus enters muscles tissue via bite wound- saliva
- Enters PNS via NMJ
- Travels from PNS to spinal cord and brain
- Virus Undergoes extensive replication leading to neuronal dysfunction
- Virus replicates in salivary glands and is excreted in saliva
- Enters peripheral nerves of the skin and Purkinje cells
- Spreads from brain to infect many tissues and organs
Once symptomatic rabies is fatal in ___days
7-10
What is the furious type of rabies
Encephalitic form- infection in limbic system
What is the paralytic form of rabies
Dumb form- early muscle weakness, with progression to coma and death
What microscopic lesions are associated with rabies
- Polioencephalomyelitis and craniospinal ganglionitis
- Inclusion bodies- Negri bodies
Lesions for rabies are located in ___
Brainstem
In ruminants where are negri bodies found
Cerebellar Purkinje cells
In carnivores where are negri bodies found
Hippocampal neurons
In horses where are negri bodies found
Brainstem and cervical spinal cord
Based on the location of this negri body, what species is likely affected
In Purkinje cells- cattle
How do you diagnose rabies
- Requires head and brain removal
- Fluorescent antibody testing
What is the disease course for canine distemper
Acutely fatal or chronic and relapsing
How is canine distemper virus transmitted
Respiratory
What are the microscopic findings with canine distemper virus
- Necrotizing meningioencephalitis
- Large areas of demyelination
- Intranuclear/ intracytoplasmic inclusion bodies
Dog presents with respiratory signs that progressed and were eventually fatal. Brain histology shows this. What do you see and what is likely cause
Left: demyelination
Right; intranuclear inclusions
Cause: canine distemper virus
What is the pathogenesis for FIP (especially related to brain)
- Ingested FIP
- Enters and replicates in enterocytes and Peter’s patches
- Replicates and mutates in monocytes a and macrophages
- Infected monocytes or macrophages have high affinity for meninges
- Pyogranulomatous vasculitis
What is the unique microscopic lesion for FIP
Pyogranulomatous vasculitis
Dry or wet form of FIP:
1. decreased cell mediated response
2. Delayed Type IV hypersensivity- pyogranulomatous inflammation and phlebitis
3. More prolonged clinical course
Dry form
Dry or wet form of FIP
1. Anti-viral antibody produced
2. Accumulation of antigen-antibody complexes- type III hypersensitivity that deposit in blood vessels—> pyogranulomatous inflammation
3. Rapid clinical course
Wet form
What form of FIP typically affects CNS
Dry form
Describe what you are seeing and potential cause
brain: proteinacious exudate in lateral ventricles
Histo: pyogranulomatous inflammation in ependymal cells surrounding cerebral vasculature
Cause: FIP
The ___subfamily of herpes have predilection for infection of nervous system resulting in ___
Alpha, resulting in necrosis- neuronal, glial and endothelial, hemorrhage
What virus can cause myeloencephalitis in horses
Equine herpes virus 1
Who is affected by EHV-1
Adult horses
What is a typical history of EHV-1
Respiratory disease and late term abortion
How do horses with EHV-1 present
Ataxic, weakness, dog sitting, recumbent, paralysis
Called out to farm due to horse unable to use hind limbs. Owner informs you there has been some recent respiratory diseases and late term abortions what is top differential
EHV-1
What is the gross appearance of EHV-1
Hemorrhage and malacia in the spinal cord—> brain
What is the microscopic appearance of EHV-1
CNS vasculitis and thrombosis
How do you dx EHV-1
PCR from blood, nasal swabs or fresh spinal cord
Horse spinal cord- what are you two top differentials
- EHV-1
- Equine protozoan myeloencephalitis
What is the definitive host for toxoplasma gondii
Cats
What is the definitive host for neospora spp
Canids
What is definitive host for S. Neurona
Opossums
What two parasitic infections can cause equine Protozoa myeloencephalitis
- Sarcocystis neurona
- Neospora Hughesi (less common)
Where does equine protocols myeloencephalitis affect
Spinal cord—> brain stem—> rest of brain
What is the most common species affected with cryptococcus
Cats
What is the primary site of infection for cryptococcus
Nasal cavity
What is the microscopic appearance for cryptococcus
Pyogranulomatous inflammation with intralesional yeast
What caused these brain lesions and histo presentation
cryptococcus
What is a prion
Proteinacious infectious particle
What causes transmissible spongiform encephalopathies
Prions
What do prions cause in sheep, cattle, and deer
Sheep: scrapie
Cows: bovine spongiform encephalopathy
Deer: chronic wasting disease
What is pathogensis for transmissible spongiform encephalopathy
- External prion protein PrPsc ingested
- Converts normal alpha helical structure of host protein to misfolded B pleated sheet with unknown protein co-factors
- First found in lymphoid tissue and GI
- Travel retrograde up nerves to spinal cord and brain
What are the microscopic findings for transmissible spongiform encephalopathies
Spongiform (vacuolation)/ degeneration of neurons and grey matter neuropil
Histo from necropsy of sheep brain, what could have caused this
Transmissible spongiform encephalopathy- scrapie
What do most diagnostic labs require for diagnosis transmissible spongiform encephalopathy
OBEX fixed in formalin and fresh
Besides OBEX what else can be submitted for transmissible spongiform diagnosis
Retropharyngeal LN or tonsils