L4 Flashcards
Eastern equine encephalitis (EEE) type
Togaviridae
Eastern equine encephalitis (EEE) - genome
(+)ssRNA
Eastern equine encephalitis (EEE) virion
enveloped
Venezuelan equine encephalitis (VEE) - type
Togaviridae
Venezuelan equine encephalitis (VEE)
genome
(+)ssRNA
Venezuelan equine encephalitis (VEE)
virion
enveloped
West Nile
type
Flaviviridae*
West Nile
genome
(+)ssRNA
West Nile
virion
enveloped
Rabies type
Rhabdoviridae
Rabies genome
(-)ssRNA
Rabies virion
enveloped
Arthropod Transmission
Selected togaviruses and flaviviruses are transmitted through a vector
Arthropod Transmission (Cont.) common vectors
Mosquitoes: Culiseta, Aedes, Culex
Ticks
Arthropod transmission Reservoirs
Birds
Small Mammals
Arthropod transmission Transmission requires
replication in the vector
Arthropod Transmission (Cont.) Geographic location determined by
vector and reservoir habitat
EEE & VEE Virus - Virus introduced through
the bite of an infected arthropod
EEE & VEE Virus - Infect cells
locally and/or carried by Langerhans cells to LN
EEE & VEE Virus - Replication and release into the
blood stream
EEE & VEE Virus - Infection in other target organs such as the
CNS
Method of crossing blood-brain barrier is unknown
EEE & VEE Virus - Incubation period
4 to 10 days
EEE and VEE virus - Systemic disease
Chills, fever, malaise, arthralgia, myalgia
Lasting 1 to 2 weeks full recovery
EEE and VEE virus - Encephalitic disease
Fever, headache, irritability, restlessness, vomiting, diarrhea, convulsions, and coma
1/3 of encephalitic cases die from the disease 2 to 10 days after onset
Those who recover can have long term sequelae
Seizures, personality disorders, paralysis
EEE & VEE Virus Prevention & Control - A single
A single vaccine is available (TC-83)
Live attenuated TC-83, inactivated C-84
Only provided to at risk military personnel and researchers
Partially effective against inhalation challenge in primates
Veterinary vaccines exist
EEE & VEE Virus Prevention & Control - No
No treatment
Supportive care
Mosquito control strategies
Mosquito repellant
EEE neurovirulence prevalence in the US
Eastern equine encephalitis virus (EEEV) is maintained in a cycle between Culiseta melanura mosquitoes and avian hosts in freshwater hardwood swamps. Cs. melanura is not considered to be an important vector of EEEV to humans because it feeds almost exclusively on birds.
West Nile Virus Disease incubation
2 to 14 days Most persons (80%) have asymptomatic infections
West nile infections
Illness ~20% of infections
Fever, headache, fatigue
Duration of 3 to 6 days
West nile Neuroinvasive disease in
<1%
Aseptic meningitis, encephalitis, flaccid paralysis, altered mental state, tremors
50% of survivors have sequelae 12 mths later
West Nile Virus Prevention & Control - no
approved vaccine No treatment Supportive care Mosquito control strategies Mosquito repellant
Current Topic – Zika Virus
flavivirus - Enveloped, Spherical
RNA genome
Zika hosts
Life long infection inmosquitos (Aedes)
Transient infection in primates, rodents
Zika Disease – Zika Fever
Resemble dengue fever
Lasts several days, fever, red eyes, joint pain, rash
Transmitted by mosquitos, possible via sex, blood transfusions, vertically
Zika Complications
Guillain-Barre syndrome – autoimmune disease attacking the autonomic nervous system Newborn microcephaly (suspected) – birth defect, long term developmental issues
Rabies Virus broad
tropism
Rabies Replication in
cytoplasm only
Rabies Genome order dictates abundance of
transcripts and proteins
Rabies Binding of N to
RNA triggers genome replication
Rabies Frequently produces
defective interfering particles
Rabies Virus Disease - Transmission by bite of infected animal
15% of bites cause disease
60% if on face or head
Rabies Reservoir:
bats, skunks, raccoons, etc.
Common disease of dogs in developing countries
Common source of human rabies deaths
Only a few cases in US every year
Rabies Virus Disease - Incubation period:
1 to 3 months
Longer is possible, though rare
Depends on location of bite
Rabies Spread
Replicates locally until it finds neurons
Moves passively in axoplasm of peripheral nerves to spinal ganglia, spinal cord, and brain
Spreads back to periphery, highly innervated salivary glands & replicates
Symptoms Rabies Virus
Prickling or itching where bitten, fever, headache
Hydrophobia – difficulty swallowing, even saliva, leads to “foaming at the mouth”
Cerebral dysfunction, anxiety, confusion, delirium, hallucinations, and insomnia
Rabies Virus - outcome
Once symptoms appear, disease is nearly always fatal
Only 10 documented survivals, only 2 of those had no history of previous prophylaxis
Rabies Virus Prevention
Vaccine available
Post-exposure prophylaxis
Should be administered immediately for bites that break the skin
4 doses – immediate, 3, 7, and 14 days
Should also receive immunoglobulin (RIG)
Vaccination of dogs and domestic animals essential to control
Some countries attempt to vaccinate wildlife using baits laden with oral vaccines
