Neurological Viruses

Question 1

Eastern Equine Encephalitis (EEE) and Venezualan Equine Encephalitis (VEE)

Answer 1

Family: Togaviridae
Genome: (+)ssRNA (wrapped in an icosahedral nucleocapsid)
Enveloped
Enters cell through cell mediated endocytosis and exit through budding
Transmission: birds and mosquitos

Question 2

West Nile Virus

Answer 2

Family: Flaviviridae
Genome: (+)ssRNA
enveloped
Transmission: birds and mosquitos

Question 3

Rabies Virus

Answer 3

Family: Rhabdoviridae
Genome: (-)ssRNA
enveloped

Question 4

Describe EEE and VEE

Answer 4

Proteins: E1 and E2 are involved with cell attachment and entry.
Causes and acute infection
Carried by Langerhans cells
Incubation period 4-10 days
Symptoms: chills, fever, arthraligia, malaise
~ 5% of cases there is CNS involvement and this is where encephalitis comes in. With encephalitis, you get fever, headache, irritability, restlessness, vomiting, diarrhea, convulsions, and coma (1/3 of cases die 2-10 days later)
- those who recover have long term sequelae: seizures, personality disorders, or paralysis
Prevention: There is a live attenuated vaccine TC-83 and inactivated vaccine C-84 (only provided to at risk military and researchers because it is really rough recovery from it)
Recovery: No treatment but full recover usually occurs 2 weeks after infection
- best prevention is mosquito control strategies

Question 5

Describe West Nile Virus

Answer 5

Incubation period: 2-14 days
Most people are asymptomatic (80%) but 20% have illness such as fever, headache, and fatigue.
- in rare cases(<1%) there is neuroinvasive disease with aseptic meningitis, aseptic encephalitis, flaccid paralysis, altered state of mind, tremors. 50% of neuroinvasive survivors have sequelae for 12 months after.
Prevention: mosquito control

Question 6

Describe the Rabies Virus

Answer 6

Proteins involved include: Nucleoprotein, phosphoprotein, matrix, glycoprotein (attachment and entry), polymerase
Rabies has a broad tropism (receptors can facilitate entry into many types of cells). Replication occurs in the cytoplasm.
- binding of N-protein triggers the RNA into genome replication
Transmission: bite of infected animal. 15% of bites lead to disease, but that number jumps to 60% if bit on the head or neck
Incubations: 1-3 months (depending on where bitten)
Spread: replicated locally until it finds neurons. Once this occurs it moves passively in axoplasm of the peripheral nerves to the spinal ganglia, spinal cord, and brain -> once in brain it travels back to highly innervated salivary glands where it replicates quickly.
- induces people not to swallow the saliva so virus is in area of bite
Symptoms: prickling or itching at site of bite, fever, headache, hydrophobia, difficulty swallowing, foaming of saliva.
- It causes cerebral disfunction, anxiety, confusion, delirium, hallucinations, and insomnia
- once symptoms appear disease is almost always fatal
Prevention: vaccine is available, but is only used as a post exposure prophylaxis in the US because rabies virus is not common. Should be administered immediately after bite. Vaccine is 4 doses (immediate, 3 days, 7 days, 14 days) and is accompanied by RIG (immuglobulin). We also vaccinate dogs and domestic animals

Question 7

Neurological viruses summary

Answer 7

• Commonly have arthropod transmission (Vectors: mosquitos, ticks,)
• Reservoirs for these are birds and mammals
• Transmission requires replication in the vector