West Nile Virus

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West Nile Virus

• Arboviruses-(arthropod-borne virus) replicate in
  blood-feeding arthropods which in turn transmit
  them to vertebrate hosts. The virus again
  replicates in the infected vertebrate, which
  develops a viremia and serves as a source of
  infectious blood meals for biting arthropods,
  completing the transmission cycle.

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Arboviruses

• The majority of arboviruses infecting wild
  mammals are not known to cause disease in their
  hosts, though these hosts may play a role in
  maintaining the virus in nature.
• Wild mammals are incidental hosts for other
  arboviruses, which use avian maintance hosts or
  in many instances their status as vertebrate
  hosts in the epidemiology of these viruses in
  uncertain.
• Wildlife may play a major role in the over
  wintering of some of the encephalitis viruses

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WEST NILE VIRUSFlavivirus
Electromyography
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West Nile Virus

• The virus is a nonenveneloped single stranded RNA
  virus
• Family-Flaviriridae
• World Wide Distribution

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WEST NILE VIRUSHISTORICAL FACTS

• 1. First detected in the West Nile district of
  Uganda in 1937.
• 2. Currently the virus has been found in Africa,
  Asia, Europe, the Middle East and North America.
• 3. First detected in North America in 1999 in
  the New York area.
• 4. Has preceded southwest since that time.
• 5. First cases in Arizona were in 2004.

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WEST NILE VIRUS

• Zoonotic Disease
• Vector Borne infectionMosquito Transmission
• Wildlife
• Migrating birds, especially crows (ravens) and
  black birds are the reservoir
• Mammals considered an incidental host
• Seasonally endemic in most of North America

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Vocabulary

• Zoonosis-
• Vector-
• Reservoir
• Amplification Host
• Endemic

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Species Infected

• Birds are most susceptible, especially black
  birds (crows, ravens)
• Mammalian Wildlife-Over winter (?) Natural
  disease(?), experimental infection
• Horses are also susceptible Ft Dodge animal
  health reports that 1 of 3 clinically ill horses
  die.
• Humans-Disease in man can also be fatal with many
  people exhibiting milder, flu like symptoms
• Dogs and Cats-Generally not a cause of illness in
  these species.

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SymptomsAvian Species

• Inability to Fly
• Weakness
• Sudden Death
• Black birds, Crows and Magpies are very
  susceptible
• 100,000s of bird died during its southwestward
  migration

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SymptomsEquine

• Fever
• Stumbling, abnormal gait
• Confused, depressed
• Collapsed, unable to stand
• Seizures and death may occur
• Majority of horses which go down die.

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Symptoms Humans

• 80 of exposed people show no symptoms.
• 20 show a fever, headache, body aches and lymph
  node enlargement
• coma, visual loss, paralysis, and even seizures.
  Death can ensue. Recovered patients can have
  permanent neurological problems.

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Avian SpeciesCrow
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Equine Species
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Humans2006 CDC
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Arizona StarOct 12, 2006
TUCSON DAILY STAR OCT. 12, 2006
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West Nile 2006Tucson
TUCSON DAILY STAR SEPT. 20,2006
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West Nile VirusSierra Vista, AZ 2006
SIERRA VISTA HERALD SEPT 19,2006
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WEST NILE VIRUSS CYCLE
Birds amplify The infection
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West Nile CasesArizona

• Stats via Arizona Dept of Health
• 2004 391 human cases, 16 deaths
• 2004 109 equine cases
• 2005 106 human cases 4 deaths
• 2005 43 equine cases
• 2006 150 human cases 10 deaths
• 2006 13 equine cases

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EquineTreatment

• No known antiviral treatments for this disease.
• Treatment is symptomatic and life support.
• A LICENSED VACCINATION
• West Nile-Innovator
• Two dose vaccination
• Fort Dodge Labs
• Excellent reported track record

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Innovator
95 effective, 1 year duration of immunity
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Monitoring Virus

• Mosquito trapping
• Virus isolation
• Poultry
• Sentinel speciesmonitored by the Game and
  Fish department

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West Nile Treatment in Humans

• Symptomatic with life support care in severe
  cases involving the CNS.

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West Nile Virus PreventionHumans

• Disease in considered seasonally endemic now in
  Arizona.
• Mosquito repellants, appropriate clothing
• No vaccination is currently available for humans