West Nile Flashcards
Is West nile virus a positive or negative RNA virus?
Positive
What genus is west nile?
flavivirus
What species is west nile virus?
west nile virus
How many lineages does it have?
2
How many clades does lineage 1 have?
3: 1a, 1b, and 1c
How many proteins does it encode for total? how many are structural and how many are non-structural?
10: total
3: structural
7: NS
What is protein E?
a glyco protein: structural
what is the function of glycoprotein E?
receptor binding, viral attachment, and entry into the cell through membrane fusion
What is protein M
membrane protein matrix protein: structural
Where does the virus get the membrane?
host
What molecules does the flavivirus mebrane contain?
cholesterol and phosphatidylserine,
What are the C proteins, and what do they do?
which are 105 amino-acid residues long, to form the nucleocapsid.
The capsid proteins are one of the first proteins created in an infected cell
Structural protein
What are the three structural proteins ?
E, M and C
The capsid has been found to prevent apoptosis by affecting what pathway?
Akt pathway
What are the non structural protien s and what do they do?
NS1 NS1 is a cofactor for viral replication, specifically for regulation of the replication complex.[17]
NS2A NS2A has a variety of functions: it is involved in viral replication, virion assembly, and inducing host cell death.[18]
NS2B A cofactor for NS3 and together forms the NS2B-NS3 protease complex.[14] Contains transmembrane domains which bind the protease to intracellular membranes.
NS3 A serine protease that is responsible for cleaving the polyprotein to produce mature proteins; it also acts as a helicase.[12]
NS4A NS4A is a cofactor for viral replication, specifically regulates the activity of the NS3 helicase.[19]
NS4B Inhibits interferon signaling.[20]
NS5 The largest and most conserved protein of WNV, NS5 acts as a methyltransferase and a RNA polymerase, though it lacks proofreading properties.
How many copies of the E protein are there?
180
How many sets does the 180 copies of the E protein form?
60
What shape does the 60 copies of 3 E proteins create?
icosahedron
How many of the E proteins within a set does a human receptor recognise?
2 of the 3
During the budding process the amino particle that is on the end of the ______ protein is released by a proteolytic cleavage process which produces a mature _____ protein, necessary for an infectious West Nile particle. The genomic progeny is assembled into an enveloped, icosahedral nucleocapsid.
pre-M
M
What is the secondary bninding factor that the E proteins bind s in the host
glycosaminoglycans
What is the primary receptor in the host?
DC-SIGN, DC-SIGN-R, and the integrin αvβ3
Where is West Nile found?
Middle east
Africa
SW Asia
What are the statistics of the 1999 New york infections?
62 cases and 7 deaths lineage 1aNY99 2.6% of the population infected 20% of those mild symptoms 0.7% meningoencephalitis
What animals were infected in the 1999 new york outbreak initially?
zoo birds, corvids, and horses
since being introduced to america what percentage has the crown population been decreased by?
45%
How many cases were reported to the CDC in the USA between 1999-2021?
54649
How many cases were reported to the CDC in 2009, but how many were there estimated to be?
720 cases reported to the CDC, but number of infected estimated at 54,000. Due to under reporting.
How many deaths took place between 1999-2021
2,376 deaths in the USA
As a result of _________ cases dropped until 2003. but there was a peak in _____ because the safety precaustions of people began to fall.
herd immunity
2012
What time of the year are their peaks in the USA?
August and September
What countries had an outbreak in 1998?
- Serbia
- Italy
- Greece
- Hungary
- Romania
How many cases were there in Europe in 2020? and how many deaths?
66 cases
6 deaths
Explain all the steps for the virus entering the cells
• Attaching receptor:
o Binding factors:
Glycosaminoglycans
Primary receptors:
• DC-SIGN
• DC-SIGN-R
• integrin αvβ3
o antibody recognizes only two of the E proteins in each set of three
o This kind of asymmetry, where you have two proteins binding and one not binding, has not been seen before.”
o The researchers theorize that, although chemically identical, these E proteins exist in different environments relative to each other and might, therefore, have slightly different structures
• Catherin-mediated endocytosis:
o Enters within an endosome: The acidity of the endosome catalyzes the fusion of the endosomal and viral membranes releasing the viral genome into the cytoplasm
• Translation: Translation of the positive-sense single-stranded RNA occurs at the endoplasmic reticulum
o RNA is translated into a polyprotein which is then cleaved by both host and viral proteases NS2B-NS3 to produce mature proteins
• Replication:
o In order to replicate its genome, NS5, a RNA polymerase, forms a replication complex with other nonstructural proteins to produce an intermediary negative-sense single-stranded RNA
o The negative-sense strand serves as a template for synthesis of the final positive-sense RNA
• Virion building:
o Once the positive-sense RNA has been synthesized, the capsid protein, C, encloses the RNA strands into immature virions.
o The rest of the virus is assembled along the endoplasmic reticulum and through the Golgi apparatus, and results in non-infectious immature virions.
o mature viruses are then secreted out of the cell.
• Budding:
o During the budding process the amino particle that is on the end of the pre-M protein is released by a proteolytic cleavage process which produces a mature M protein, necessary for an infectious West Nile particle. The genomic progeny is assembled into an enveloped, icosahedral nucleocapsid.
What vectors pass west nile virus?
mosquitto
ticks
How can west nile be spread? Humans
labratory, pregnancy, breast feeding, blood transfussion, organ transplant.
How can birds spread west nile? how do they cause outbreaks
direct contact, shown to cuase outbreaks along migratory paths
How many species of mosquito are there in America that can spread west nile?
59 species
What is the main genus of mosquitto that spreads west nile?
culex genus
What is the incubation period of west nile virus?
2-14 days
what percentage of cases are aymptomatic?
80%
What are the two forms of the disease?
- West Nile Fever
- West Nile Neuroinvasive Disease
Out of the people who get West Nile, how many get West Nile fever? ?/?
1/5
What are the common symptoms with west nile fever, and what is the one rare symptom?
- Most common form
- Flu-like symptoms
- Resolves in 2-6 days
- Persistent fatigue can occur
Some patients: Erythematous (red) rash – arms, legs, torso.
What percentage of people get the West Nile neuroinvasive disease? ?/?
1 in 150
What are the symptoms of west nile neuroinvasive disease?
- Encephalitis o Disorientation o Ataxia o Changes in consciousness o Parkinsons-like Rigidity in muscles Slow movements - Meningitis o Stiff neck o Photophobia o fever - Acute flaccid paralysis o Can affect all muscles Persistent neurological dysfunction can occur
How many species of bird hve been shown to get infected? what are their symptoms?
300 species
leg paralysis and tremours
What happened to the birds in Utah in 2013?
20,000 lake water birds died
29 bald eagles died
What symptoms do cats and dogs getr?
often asymptomatic: or fever depression, muscle spasms, paralysis and mycarditis
What physical symptoms do horses get, what behavioural changes happen in horses?
Physical: anorexia, ataxia, weakness, difficulty swollowing, facial oedema, urinary disfuntion
Behavioural: teeth grinding, circling, Tremours and convulsion
What ruminants does it affect: what are there symptoms, and how long after infection do they die?
Neurological symptoms
Sheep, alpacas, reindeer, and white tailed deer
Death 1-2 days
What animals can catch it?
- Bats
- Horses, Goats, sheep, cattle, Llama, alpaca, deer
- Rabbit, chipmunk, skunk, squirrels
- Wolf, black bear
- Alligator, crocodile
cat and dogs
How can West Nile virus be diagnosed in humans and horses?
Diagnosis – Humans - Serology (most common) for IgM IgM can persist for a year… so not definitive o Serum or Cerebral-spinal fluid o IgM capture ELISA But Cross reactions with dengue, yellow fever etc. o Plaque neutralisation test - Detection of virus, antigen, or nucleic acids o RT-PCR (particularly blood donations) o Immunohistochemistry Horse – Diagnosis - Live horses: o Serology -4 fold increase in WNV-abs - Necropsy o Brain & spinal cord RT-PCR Immunohistochemistry
What treatment is there for humans?
No specific treatment – just supportive care (fluids etc.) Clinical trials: - Interferon - Antisense nucleotides - Intravenous immunoglobulin - Antiviral drugs
What treatment is there for animals?
Treatment – animals
- Several commercial vaccines available for horses
- Usually 2 doses: 3 - 6 weeks apart
- Annual revaccination
- Vaccines sometimes used off-label to protect birds
What mosquitto managment is there?
- Surveillance
- Source reduction
- Personal protection
- Biological control
- Larvicide
- Adulticide
How can surveillence reduce transmission?
- Dead bird testing
- Sentinel chicken flocks
- Mosquito collection
o Test for pathogens
o Account for species?? - Larval & adult mosquitoes
o Map habitats
o Record keeping
What water source reduction can you do?
- Elimination of larval habitats: o Tyres o dis-used swimming pools o bird baths o rain-filled containers o guttering o water troughs - Making habitats unsuitable for larval development - Public education - Marsh water management o Facilitate drainage - allows fish access o Gated – minimally flood during summer
What PPE can be used?
- Limit time outdoors at peak biting times
- Cover limbs - Long trousers & sleeves
- Use mosquito repellent
o 50% DEET
o Do not use DEET on animals - Keep window screens intact
- Replace outdoor light bulbs with yellow bulbs
- Empty water from all outdoor containers
What biological controls are there?
Use of natural & introduced predator species to eat larvae and/or pupae
- Mosquito fish
o Gambusia affinis, G. holbrooki
o Fundulus spp., Rivulus spp., killifish
- Other agents used but limited availability
o Fungus, protozoa, nematodes
o Copepods
How can larvacides be used?
- Used when source reduction & biological control not feasible
- More effective & target-specific
- Less controversial than adulticides
- Applied to smaller geographic areas
o Larvae concentrated in specific locations
How are adulticides used?
- Used when other control measures are unsuccessful
- Low efficiency
- Timing of application & correct type of control increases efficacy
o Ultra-Low Volume foggers
o 1 ounce per acre
o Small droplets contact and kill adults
What precautions to take in a lab?
- Mosquito avoidance precautions
o Insect spray, long sleeves, etc. - Wear gloves or double plastic bags to collect dead birds
- Wash hands after handling specimens in field
- Manipulate carcasses for necropsy in biosafety cabinet when possible
