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| | [[Central Nervous System Infectious Inflammation]] | | [[Central Nervous System Infectious Inflammation]] |
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| − | ==Routes of Entry==
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| − | * CNS inflammation is usually the result of infection.
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| − | ** This may be caused by:
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| − | *** Bacteria
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| − | *** Fungi
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| − | *** Protozoa
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| − | *** Viruses
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| − | * Organisms must first enter the CNS in order to establish infection.
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| − | ** There are several routes of entry that allow this:
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| − | **# '''Haematogenous entry'''
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| − | **#* This is the most common route.
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| − | **# '''Entry via the peripheral nerves'''
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| − | **#* Organisms track within the axoplasm of axons.
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| − | **#* For example, ''Listeria monocytogenes''.
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| − | **# '''Penetrating trauma'''
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| − | **#* For example, dehorning wounds, skull fracture or tail docking.
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| − | **# '''Direct spread of infection'''
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| − | **#* From the nasal cavity, middle ear or paranasal sinuses.
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| − | ==Localisation of Infectious Organisms==
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| − | * After entry, organisms may establish in one or more of four main areas:
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| − | *# '''Epidural space'''
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| − | *#* Infection tends to manifest as abscess formation.
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| − | *# '''Subdural space'''
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| − | *#* Manifests as abscess formation.
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| − | *#* Fairly uncommon.
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| − | *# '''Leptomeninges'''
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| − | *#* Causes leptomeningitis, which may be:
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| − | *#*# Suppurative
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| − | *#*#* The most common form.
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| − | *#*#* Neutrophils are the predominant cell type.
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| − | *#*#* Caused by bacteria
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| − | *#*#** E.g. ''E. coli'' and ''Streptococcus''
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| − | *#*#* There are often no gross lesions, but the brain may appear swollen and the meninges opaque.
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| − | *#*#* Usually results in death.
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| − | *#*# Eosinophilic meningoencephalitis
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| − | *#*#* The classic example of this is porcine salt poisoning, when water has been restricted and the suddenly replenished.
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| − | *#*#* Perivascular eosinophilic cuffing is seen in the cerebrum and meninges.
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| − | *#*# Lymphocytic
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| − | *#*#* Usually of viral origin.
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| − | *#*# Granulomatous
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| − | *#*#* Caused by fungal diseases and Mycobacteriosis.
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| − | *# '''CNS parenchyma'''
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| − | ==Bacterial Infections==
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| − | [[Image:pneumococcalmeningitis.jpg|thumb|right|150px|Pneumococcal meningitis. Image courtesy of BioMed Archive]]
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| − | * Bacterial infections typically result in abscesses.
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| − | ** These may be single or multiple depending on the route of entry, and vary in size.
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| − | ** They contain a central, liquefied cavity.
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| − | * There are differences between cerebral abscesses and those occuring elsewhere.
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| − | ** Encapsulation is slow.
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| − | *** This is due to a lack of fibroblasts.
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| − | *** There is therefore less collagen in the capsule.
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| − | ** Astrocytic glial fibers are not as strong as collagen
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| − | * Other organisms may cause similar infections:
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| − | ** Rickettsial organisms
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| − | *** E.g. ''Ehrlichia''
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| − | ** Spirochates
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| − | *** E.g. Leptospirosis
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| − | ==Viral Infections==
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| − | * Viral infections tend to reach the CNS by haematogenous spread and via peripheral nerves.
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| − | * There are three hallmark lesions of CNS viral infections:
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| − | *# Neuronal necrosis
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| − | *# Gliosis
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| − | *# Vascular changes
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| − | * Several types of virus may cause inflammation in the CNS. [[Image:negribodies.jpg|thumb|right|150px|Negri bodies, as seen in rabies. Image courtesy of BioMed Archive]]
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| − | ** '''Neurotropic''', e.g.
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| − | *** Rabies (rhabdovirus)
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| − | *** Aujesky’s disease (herpesvirus)
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| − | *** Visna (ovine lentivirus)
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| − | ** '''Endotheliotropic''', e.g.
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| − | *** Infectious canine hepatitis (canine adenovirus)
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| − | *** Classical swine fever (pestivirus)
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| − | *** Equine herpesvirus type 1 (herpes)
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| − | ** '''Pantropic'''
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| − | *** Infectious canine distemper (morbillivirus)
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| − | *** Infectious bovine rhinotracheitis (bovine herpesvirus type 1)
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| − | * Other examples of viruses affecting the CNS:
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| − | ** Distemper
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| − | ** Parvovirus
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| − | ** Parainfluenza
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| − | ** Herpes
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| − | ** FIP
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| − | ** FIV
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| − | ** FeLV
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| − | ** Pseudorabies
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| − | ** Rabies
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| − | ==[[Prion Disease]]==
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| − | [[Category:Central Nervous System - Inflammatory Pathology]]
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