Objectives for NS 3: You should be able to define, describe pathogenesis,

list lesions and know how to diagnose the following

conditions:

•Meningitis

•ITEME

•Listeriosis

•TSE

•Rabies

•Distemper

•West Nile Viral encephalitis

•Equine protozoal encephalomyelitis

Infectious diseases of CNS

BloodNervesParacranial and paravertebral infections(sinuses, ear, bones et cet)

Portal of entry

Meningitis

• Et: E. coli, Streptococcus, Haemophilus

Cryptococcus, FIP virus etc. • Most common in young animals (Bo, Po)• Often as part of polyserositis• Lesions: inflammatory exudate• Diagnosis:

Gross (impression smear) and histology

Bacterial/fungal culture

Encephalomyelitis

• Viral• Bacterial• Mycotic• Protozoal• Parasitic (nematodes)• Prion

There are many infectious agents

Infectious thrombotic (thromboembolic) meningoencephalitis

• Et: Haemophilus somnus • Pneumonia, arthritis, heart abscess….in Bo• Pathogenesis:

H. somnus invades circulationDamages endothelium of CNS venulesSubendothelial collagen exposedThrombosis, infarction, & vasculitisCNS hemorrhage, necrosis and inflammation

Bacterial infections - H. somnus

Diagnosis

• Gross and histologic lesions

• Bacterial culture

Bacterial infections - H. somnus

Listeriosis

• Et: Listeria monocytogenes

• Abortion, septicemia, CNS in Bo, Ov, (Ho)

• Pathogenesis:

•Invasion of oral mucosa•Cetnripetal intraaxonal migration •Infection of Trigeminal gang. and brainsteam•Multifocal suppurative meningoencephalitis

Bacterial infections - Listeriosis

Diagnosis

• Histologic lesions (with Gr + bacteria)

• Bacterial culture

Bacterial infections - Listeriosis

Transmissible spongiform encephalopathy

•Unique and very unusual dz!!!???• Scrapie in sheep and goats

• Bovine Spongiform Encephalopathy in cattle

• Chronic Wasting Disease in elk, white-tailed

deer, black-tailed deer and mule deer

• Transmissible Mink Encephalopathy

• Several forms in humans

• Recent reports in other species

TSE

Pathogenesis

• Normal prion protein PrPc is present in neurons and it has helix conformation• Abnormal prion protein PrPres or PrPsc has

sheet conformation• PrPres can induce conformational change in

PrPc to become PrPres

• Accumulation of PrPres in neurons causes dz.• Interspecies transmission depends on in each

PrPc species

TSE

PrPcPrPc

PrPc

PrPres PrPc

PrPres PrPresConformational

change

PrPres

InoculationTransmissionMutationInheritance

TSE

Diagnosis

• Histology• IHC

TSE

What to do if …? • Submit the animal to a diagnostic lab and

indicate that it is “TSE suspect”• If diagnostic lab is far away:

Wear double gloves, mask and eye protectionDecapitate the animal and send the head

Rabies

• Rabies virus can infect all mammals

• Maintained in nature in reservoir host(skunks (prairies); foxes (ON), raccoons, bats)

• Pathogenesis: •Transmitted by bite•Centripetal intraaxonal migration to CNS•Infects many neurons incl. Lymbic system•Centrifugal migration to salivary gl.•Death is due to progressive paralysis

Viral infections - Rabies

Lesions • Clin. phases: prodromal, excitatory

(furious or dumb form), & paralytic• Non suppurative encephalitis

and ganglioneuritis • Intracytoplasmatic inclusion bodies

Diagnosis

• Fluorescence antibody test• Mouse or tissue culture inoculation• Histology & IHC

Viral infections - Rabies

What to do if…?

• Label: “RABIES SUSPECT” and submit to diagnostic lab

• If you are doing necropsy yourself:

•Should be vaccinated against rabies•Use double gloves, mask and eye protection•Never use power tools for brain removal•Avoid, contact with saliva, brain and CSF•Submit half brain (frozen) to CFIA •Other half in formalin

Viral infections - Rabies

Distemper

• Distemper virus, morbillivirus, Paramyxov.

• Dogs, fox, wolf, hyena, ferret, raccoons, etc

• Rarely seen in dogs due to vaccination

• Multisystemic dz (lung, skin, CNS, urinary,

lymphoid tissue immunosuppression)

Viral infections - Distemper

Infection (inhalation)Replication in tonsils/lungsOther lymphoid tissues >> immunosuppressionCNS & Epithelia (~ 8-9 days after infection)

Death due toSevere viral infection +/- 2o bacterial infect.

Recovery

CNS infection1o demyelination due to direct viral damage 2o demyelination due to inflammatory reaction

PathogenesisViral infections - Distemper

Diagnosis

• Histology• IHC

Lesions in CNS:Demyelination (primary and secondary)

Non suppurative encephalitis with I/N and I/C inclusion bodies

Viral infections - Distemper

Viral infections - WNV

West Nile Virus

• Arthropod-borne flavivirus in birds, Eq, Ho

• Usually no clinical signs in birds

• However, fatal CNS dz. WAS PRESENT in

various birds in the recent US outbreak.

• Lesions: non suppurative encephalitis

• Diagnosis: IHC, PCR,

Serology in live

Viral infections - in utero

In utero viral infections

• Cerebellar hypoplasia Feline panleukopniavirus

• Cerebellar hypoplasia, hydranencephaly and/or hypomyelination

Bovine viral diarrhea virusHog cholera virusBlue tongue virusBorder disease virus

Protozoal infections

• Equine protozoal encephalomyelitis

Sarcocysis neurona (defin. host - opasum)

Lesions: necrosis/malacia, inflammation

most frequently in the spinal cord

Diagnosis: Histological lesions

IHC

Neoplasia

Neoplasia

• Meningioma• Astorcytoma• Oligodendroglioma• Ependymoma

Diagnosis

Histology