Mosquito-borne Viruses in Vermont

Vermont Department of Health

Mosquito-borne Viruses in Vermont


Mosquito-borne arboviruses inVT

West Nile virus (WNV) Eastern equine encephalitis (EEE)

Arboviruses: Arthropod – Borne- VirusesArthropod definition: invertebrate animals (as insects, arachnids, and crustaceans) that have a segmented body and jointed appendages, and achitinous exoskeleton

Includes mosquitoes and ticks


Eastern Equine Encephalitis Virus Genus Alphavirus Family Togaviridae Outbreaks in horses recorded in 1831 Virus isolated in 1933 First human case confirmed in 1938 in MA Select agent


Culiseta melanura

Aedes, Coquillettidia, Culex species

??


EEE is Rare – Thankfully

Most pathogenic mosquito-borne disease in the US

Human case fatality rate ~35%• Death more common in older people

Among survivors, severe neurologic sequelae in ~50% (esp. children)


Symptoms – Human Incubation period 4 – 10 days Systemic• Chills, fever, malaise, arthralgia, myalgia• Duration 1-2 weeks • Recovery complete as long as no CNS involvement

Encephalitic• Fever, headache, irritability, restlessness,

drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions, coma


Other Species Affected horses and donkeys llamas and alpacas emus and pheasants also puppies, harbor seal, cow, African

penguin, deer Vaccine licensed for horses – may also

be effective in llamas, alpacas and emus


What Did We Know about EEE in VT? Until 2010 no evidence of the virus detected in VT Surveillance • Passive human and veterinary surveillance• Limited mosquito surveillance

Seemed likely to be here…• Found in neighboring states and Quebec• Acidic hardwood swamps and vector species present• Activity increasing in general in northeast??

New foci in ME and NH Increases in human cases in MA


Culiseta Habitat

Acidic swamps (red maple, cedar) Crypts formed by pockets of water surrounding tree roots Brandon, Leicester, Salisbury area Adults emerge in April and May with second emergence

in late June/July

Mosquito Surveillance


Resting Box Passive collecting device Serves as a resting place for blooded

mosquitoes from dawn to noon Attracts blooded, gravid, and host-

seeking Culiseta melanura



Deer Serosurvey for EEE virus 2010 hunting season

• Deer get bitten by a lot of mosquitoes• Develop detectable antibodies• Survive infection although clinical illness has been reported• Limited range – ~1 square mile in summer• Blood readily available

513 blood samples collected from deer and moose at check stations during youth weekend and opening weekend of rifle season

Samples sent to CDC to test for antibodies against EEEV


Deer serosurvey - equipment



Results of 2010 Serosurvey

Deer – 50/489 (10.2%)

Moose – 6/21 (28.6%)

8 positive yearlings


What Did Deer Serosurvey Mean? EEE virus is present in Vermont Need to keep up surveillance – both human

and veterinary More complete mosquito surveillance would

be nice, but expensive Continue to educate Vermonters about

preventing mosquito bites


Deer Serosurvey: 2010 - 2012


EEE in VT emus Sept 21, 2011 – report of ill emus• Southern Rutland County – near large acidic swamp

Several emus in a flock developed hemorrhagic gastroenteritis; ataxia

Earliest onset 9/15 By 9/21, 14 emus had died Last death on 9/24 19/93 died, 2 ill birds recovered• All ages affected




Plans for 2013 Mosquito surveillance in known EEE area• Surveillance data available on-line

Human and veterinary surveillance Education to residents• preventing mosquito bites

On-line availability of a risk-map• Updated throughout the season



WNV & EEE Prevention Promote use of personal protection

• Long sleeves and pants• Insect repellent that contains DEET, Picaridin, or oil of

lemon eucalyptus• Cover baby carriages with mosquito netting• Fix holes in screens• Avoid outdoor activities when mosquitoes are active

Eliminate mosquito breeding habitats• Reduce standing water

Vaccinate horses and other susceptible animals



Thank You

Documents

Mosquito-borne Viruses in Vermont