slide1
Download
Skip this Video
Download Presentation
WEST NILE VIRUS

Loading in 2 Seconds...

play fullscreen
1 / 41

WEST NILE VIRUS - PowerPoint PPT Presentation


  • 108 Views
  • Uploaded on

WEST NILE VIRUS. West Nile Virus: Background. First isolated 1937 Flavivirus Africa, West Asia, Europe and the Middle East 1999 US isolate similar to a goose isolate from Israel. Mosquito vector. Incidental infections. Incidental infections. Bird reservoir hosts.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' WEST NILE VIRUS' - allistair-guthrie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
west nile virus background
West Nile Virus: Background
  • First isolated 1937
  • Flavivirus
  • Africa, West Asia, Europe and the Middle East
  • 1999 US isolate similar to a goose isolate from Israel
slide3

Mosquito vector

Incidental infections

Incidental infections

Bird

reservoir hosts

Incubation period -- 3 to 15 days

slide4

Vectors and Hosts

  • Isolated from over 43 mosquito species
    • Mostly Culex species:
      • Cx. univittatus, Cx. perixiguus, Cx. pipiens, Cx. modestus, Cx. quinquefasciatus, Cx. tritaeniorhynchus, and Cx. vishnui
    • Other mosquito species:
      • Aedes, Aedeomyia, Anopheles,
      • Coquillettidia, Mansonia, Mimomyia
culex tarsalis
Culex tarsalis

Majorvector potential WNV vector in Western US

epidemiology
Epidemiology
  • Mosquitoes feed on infected birds
  • Pass the virus to warm-blooded animals.
  • Horses cannot spread WNV to other horses, people or pets.

Dead-end Host

mammals
Mammals
  • Infected with WN virus
    • Mortality: bats, rabbit, chipmunk, gray squirrel, horse, cat, alpaca, dog
    • Seropositive: dog, bears, sheep, goats, wolf
clinical signs
Clinical Signs
  • Ataxia 86%
  • Depression 51%
  • Hindlimb weakness 49%
  • Difficulty or inability to rise 46%
  • Muscle tremors 41%
  • Fever only 24%
  • Death in 25-33% of affected horses
clinical signs colorado
Clinical Signs: Colorado
  • Clinical signs:
    • Ataxia – 73%
    • Weakness – 69%
    • Lethargy, depression – 61%
    • Muscle fasciculations – 60%
    • Unable to rise on their own – 38%***
    • Fever – 35%
    • Altered mentation – 31%
    • Hypersesthesia – 30%
    • Cranial nerve deficits – 27%
subclinical infection
Subclinical Infection
  • Symptomatic:asymptomatic ratio is approximately 1:9
epidemiology colorado
Epidemiology: Colorado
  • 9 years (3 mos – 35 yrs)
  • No breed, gender predilection
  • 71.4% (344/482) survived
  • Horses that died were older
  • Unvax: 36.6% mortality
  • At least one vax: 20.3% mortality
recumbent horses
Recumbent Horses
  • Average duration: 2.3 days
  • Range: 1-7 days
  • Onset to recumbency: 2.1 days (range = 0-14 days)
  • Recumbency as first sign: 4 horses
  • Nonvax 2.4 times more likely to be unable to rise
diagnosis
Diagnosis
  • Clinical signs
  • CSF: mononuclear pleocytosis, normal to increased protein
  • IgM antigen-capture ELISA
  • Plaque reduction neutralization assay
  • PCR, IHC
diagnosis1
Diagnosis
  • Serum and CSF results similar
  • Horses do not develop an IgM response to vaccine
treatment
Treatment
  • Symptomatic
  • IV fluids
  • Anti-inflammatory medication
    • Flunixin meglumine
    • DMSO
    • Corticosteroids
treatment of wnv
Treatment of WNV
  • Alpha interferon
  • Hyperimmune plasma
prognosis colorado
Prognosis: Colorado
  • 82% considered fully recovered
  • Some residual signs in 21% (decreased stamina, weight loss)
  • Estimated 2 unreported cases for every 3 laboratory confirmed cases
increased likelihood of survival if
Increased likelihood of survival if:
  • Steroid treatment (p=0.10)
  • Hospitalization (p<0.0001)
  • Vaccination (p=0.0005)
  • Not recumbent
  • Affected late in epidemic
aged horses 18 yrs
Aged Horses (>18 yrs)
  • Survivors avg. age = 8.9 yrs
  • Nonsurvivors avg. age = 10.8 yrs
  • Aged were 2.6 times as likely to die
  • Older horses not more likely to be recumbent
  • Older horses not less likely to be vaccinated
treatment of wnv1
Treatment of WNV
  • Anti-inflammatory medication
    • Flunixin meglumine
    • DMSO
    • Corticosteroids?
residual effects
Residual Effects
  • Florida: 15%
  • Minnesota: 40%
    • Average followup time 6 months
    • 59.2% had no neurologic or behavioral abnormalities
    • Average duration of signs: 35 days (1-180)
residual effects1
Residual Effects
  • Behavioral change
  • Loss of muscle mass
  • More frequent stumbling
  • Diminished energy
  • Weak hind limbs
  • “Abnormal” gait
  • Vision loss
  • Dysphagia
  • Relapses (2 wk to 5 mo)
prevention of wnv
Prevention of WNV
  • Eliminate mosquito breeding sites
  • Control mosquito larvae
  • Reduce exposure to adult mosquitoes
  • Vaccinate
slide30

Mosquito Breeding Sites

1. Storm drains

2. Clogged roof gutters

3. Window wells

4. Uncovered containers

5. Leaky faucets and standing water

6. Garden ponds

7. Swimming pools

8. Tires and wheelbarrows

9. Birdbaths and children’s toys

control mosquito larvae
Control Mosquito Larvae
  • Stock water tanks with fish that consume mosquito larvae
  • Use mosquito “dunks” in water tanks
  • Clean water tanks weekly
reduce exposure to adult mosquitoes
Reduce Exposure to Adult Mosquitoes
  • Stable horses during active mosquito feeding times
  • Screen the stables
  • Fans, barrier cloth, flysheets
  • Repellants applied frequently
wnv vaccine whole virus
WNV Vaccine-whole virus
  • 1cc dose, booster 3-6 weeks
  • Induces antibody response
  • Conditional license
does the vaccine work

Infect Horse Experimentally

Vaccinate Horse

See if horse gets disease

Does the Vaccine Work?

The BEST way to test a vaccine: Experimental Challenge Model

Most horses do not get sick after experimental infection!

vaccine efficacy
Vaccine Efficacy

Experimental Challenge

  • One year after vaccination
  • Controls
    • 9 of 11 infected--82%
  • Vaccinates
    • 1 of 19 infected--5% (95% Protective)
infection mortality vs vaccine status colorado
Infection & Mortality vs. Vaccine Status:Colorado

372 Total

230 = No Vax

97 = 1 Vax

45 = 2 Vax

post approval reaction rates fort dodge
Post-Approval Reaction Rates:Fort Dodge
  • <0.025% adverse effects reported
  • lumps and bumps
  • fever
  • lack of efficacy ?
merial vaccine
Merial Vaccine
  • Canarypox vector
  • Mosquito challenge model
  • Similar results for safety, efficacy
web site resources
Web site resources

For more information about humans and WNV: www.cdc.gov

For more information about WNV, USDA Website: www.aphis.usda.gov/oa/wnv

For more information about WNV in horses:

http://prevmed.vet.ohio-state.edu/

ad