48. Equine encephalomyelitis caused by togaviruses (Zoon.). Flashcards
Equine Encephalomyelitis: Family & Genera
- Family: Togavitidae
- Genera:
- Alphavirus
- Rubivirus
Equine Encephalomyelitis: Notable Alphavirus species
- Eastern equine encephalitis virus
- Western equine encephalitis virus
- Venezuelan equine encephalitis virus
- Getah virus
Equine Encephalomyelitis: Notable Rubivirus genus
Rubella virus
Eastern, Western & Venezuelan Equine Encephalomyelitis: Occurrence
- Eastern: Canada; USA (east coast); Central America
- Western: Canada; USA (west coast); Mexico; S. America
- Venezuelan: USA (southern); Central & South America
Equine Encephalomyelitis: Alphavirus summary
NOTIFIABLE & ZOONOTIC DISEASAE
- Enveloped; ssRNA
- Weak resistance in the environment
- Arbovirus - Mosquito transmission
Equine Encephalomyelitis: Alphavirus - Affected species
Euryxen virus
- Horse*
- Human*
- Donkey
- Mule
- Rodents
- Birds
*Dead-end hosts
Equine Encephalomyelitis: Alphavirus - Epizootiology
- Eastern Equine Encephalomyelitis virus
- Bird-Mosquito cycle
- Long-distance transmission - Bird migration
- Seasonal epidemics; Weather-related
Equine Encephalomyelitis: Alphavirus - Epizootiology
- Western Equine Encephalomyelitis virus
- Bird-Mosquito-Rodent cycle
- Dependent on host preference of mosquitos
Equine Encephalomyelitis: Alphavirus - Epizootiology
- Venezuelan Equine Encephalomyelitis virus
- Horse/rodent-Mosquito-Horse/rodent cycle
- Summer/rainy season
- Enzoonotic in rodent
- Epizootic in Eq - CSx & Death
Equine Encephalomyelitis: Alphavirus - Pathogenesis
Mosquito bite → Regional LN → 1st Viraemia → Viscera → 2nd Viraemia
Equine Encephalomyelitis: Alphavirus - Pathogenesis (Transplacental infection)
Embryo developmental problems: Hypoplasia; Hydrocephaly
Equine Encephalomyelitis: Alphavirus Pathogenesis - The course is dependent on…
Age & Dose
Equine Encephalomyelitis: Virulence
- Eastern
- Western
- Venezuelan
- Eastern: 75-100%
- Western: 10-50%
- Venezuelan: 32-86%
Equine Encephalomyelitis: Convalescence
- Life-long immunity
- Partial cross-protection
Equine Encephalomyelitis: Incubation time
1-3 Weeks
Equine Encephalomyelitis: Forms of CSx
- Peracute
- Acute/Subacute
- Chronic
Equine Encephalomyelitis: CSx (Peracute form)
- Fever
- Shock
- Death
within 12 hrs
Equine Encephalomyelitis: CSx (Acute/subacute form)
- Biphasic fever
- Initially: Excitement & increased sensitivity
- Later: Apathy; ↓ Appetite; Icterus
- Encephalitis; Myelitis
- Death
Venezuelan: Colic & Diarrhoea too
Equine Encephalomyelitis: What is significant to recovery?
There will be permanent damage to the body
Equine Encephalomyelitis: Pathology
Ø Macroscopic
- Histopathology:
- Encephalitis & Myelitis
- Blood vessel endothelial damage; Thrombosis
Equine Encephalomyelitis: Dx
CSx; Seasonality; Geographic origin
- Blood sample (PBMC) peripheral blood mononuclear cell; Brain
- Isolation: Suckling mouse brain; Embryonated egg; Cell culture
- Direct: RT-PCR; IHC
- Indirect: Serology: HAI; VN; CF (Complement fixation)
Equine Encephalomyelitis: DDx (Infectious)
- Rabies
- Rhinopneumonitis
- West Nile Virus; Borna; Getah
- Botulism
Equine Encephalomyelitis: DDx (Non-infectious)
- Heavy-metal poisoning
- Plant poisoning
Equine Encephalomyelitis: Tx
- Supportive therapy
- Mosquito control
-
Vaccine
- Inactivated; Trivalent
- Venezuelan: TC38 Strain = Attenuated
Equine Encephalomyelitis: Public health
ZOONOTIC DISEASE
- Pregnancy: Abortion; Newborn cerebral necrosis
- Children: More sensitive; CNS signs
- Fever; Headache; Nausea; Vomiting
- Head & Leg Oedema; Cyanosis
- Convulsions; Paralysis - High mortality
Human vaccine available