2 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 exoskeletonIncludes mosquitoes and ticksMosquitoes and ticks are the important arthropod vectors in VT.
3 Eastern Equine Encephalitis Virus Genus AlphavirusFamily TogaviridaeOutbreaks in horses recorded in 1831Virus isolated in 1933First human case confirmed in 1938 in MASelect agentNot new to the US. Probable horse cases back in the 1830sVirus is mostly present east of the Mississippi River – mostly along the coastal areas but also some inland swampsPresent in Central and S. America – but different lineage of the virusSelect agent- considered a potential BT agent
4 ? Culiseta melanura Aedes, Coquillettidia, Culex species Amplifying hosts: Passerines – contain more than half of all bird species – perching songbirds,Small to medium body sizeCuliseta melanura is the enzootic vector – the species of mosquito that keeps the virus circulating among birdsThis species primarily bites birds but will occasionally bite mammalsBridge vectors – ones that bite birds and mammals – thought to be responsible for transmitting the virus from birds to mammalsThese 3 species may play a role but more recently it’s been proposed that Cs melanura is responsible for mammalian infections – may be why human illness is uncommon – this species bites humans and other mammals infrequentlyAs for WNV – humans and other mammals are dead-end hostsAedes, Coquillettidia, Culex species
5 EEE is Rare – Thankfully Most pathogenic mosquito-borne disease in the USHuman case fatality rate ~35%Death more common in older peopleAmong survivors, severe neurologic sequelae in ~50% (esp. children)
6 Symptoms – Human Incubation period 4 – 10 days Systemic Encephalitic Chills, fever, malaise, arthralgia, myalgiaDuration 1-2 weeksRecovery complete as long as no CNS involvementEncephaliticFever, headache, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions, comaTwo presentations –Systemic and Encephalitic
7 Other Species Affected horses and donkeysllamas and alpacasemus and pheasantsalso puppies, harbor seal, cow, African penguin, deerVaccine licensed for horses – may also be effective in llamas, alpacas and emus
8 What Did We Know about EEE in VT? Until 2010 no evidence of the virus detected in VTSurveillancePassive human and veterinary surveillanceLimited mosquito surveillanceSeemed likely to be here…Found in neighboring states and QuebecAcidic hardwood swamps and vector species presentActivity increasing in general in northeast??New foci in ME and NHIncreases in human cases in MAAlthough we hadn’t documented EEE in VT until recently, it seemed likely to be here. First of all, it had been found in our neighboring states and Quebec. Secondly, we have the enzootic vector, Culiseta melanura, here. And we have some acidic hardwood swamps – the preferred breeding habitat for that mosquito.Finally, there seems to be increased activity in New England in general.
9 Mosquito Surveillance Culiseta HabitatTo look for EEE you want to look for habitat where the enzootic vector lives.This is the preferred habitat for Cs melanura.They overwinter as larvae deep in in crypts under tree roots – this makes it difficult to reduce their numbers with larvicides because it’s hard to get the chemicals into the crypts.Brandon, Leicester, Salisbury swamp area is our largest acidic hardwood swampThe first emergence in April and May are not infected with EEE. You can’t isolate the virus form mosquitoes until the second emergence. We don’t know exactly why that is.Acidic swamps (red maple, cedar)Crypts formed by pockets of water surrounding tree rootsBrandon, Leicester, Salisbury areaAdults emerge in April and May with second emergence in late June/July
10 Resting Box Passive collecting device Serves as a resting place for blooded mosquitoes from dawn to noonAttracts blooded, gravid, and host-seeking Culiseta melanuraThe best method for collecting this species.
11 This shows were potential bridge vectors and the enzootic vectors have been found in VT.
12 Deer Serosurvey for EEE virus 2010 hunting seasonDeer get bitten by a lot of mosquitoesDevelop detectable antibodiesSurvive infection although clinical illness has been reportedLimited range – ~1 square mile in summerBlood readily available513 blood samples collected from deer and moose at check stations during youth weekend and opening weekend of rifle seasonSamples sent to CDC to test for antibodies against EEEVWe started doing deer serosurveys in CDC partners with us on this project. They test the samples for us.Convenient samples – easy to obtain
13 Deer serosurvey - equipment Very simple equipment and little training needed to get samples.Samples collected by volunteers.
15 Results of 2010 Serosurvey Deer – 50/489 (10.2%) Moose – 6/21 (28.6%) 8 positive yearlingsThis showed a surprisingly widespread distribution of virus. Surprising because most EEE virus had previously been found in close proximity to the acidic hardwood swamps. This study did not show any clustering of positive deer near known good Culiseta habitat.
16 What Did Deer Serosurvey Mean? EEE virus is present in VermontNeed to keep up surveillance – both human and veterinaryMore complete mosquito surveillance would be nice, but expensiveContinue to educate Vermonters about preventing mosquito bitesThe virus is clearly here and is widespread. But since we hadn’t recognized any domestic animal or human cases in most of the state (until recently), the risk for transmission to people appears to be low.
17 Deer Serosurvey:This map shows 3 years of data. Still shows evidence of widespread exposure in deer.
18 EEE in VT emus Sept 21, 2011 – report of ill emus Southern Rutland County – near large acidic swampSeveral emus in a flock developed hemorrhagic gastroenteritis; ataxiaEarliest onset 9/15By 9/21, 14 emus had diedLast death on 9/2419/93 died, 2 ill birds recoveredAll ages affectedFirst evidence of EEE causing illness in a domesticated animal in VT.Emus are very susceptible to this virus. Unlike mammals, they tend to get a viscerotropic form – it affects the GI tract and internal organs. In addition to developing neurologic signs they typically get a bloody diarrhea. The bloody secretions are infectious to other emu and potentially to people. Unlike horses, illness tends to go through the flock, often killing up to 30% of the animals.People must use caution when taking care of sick emus.Pheasants also can have a similar presentation.
19 2012 – Mosquito surveillance focused on EEE. Because of limited resources, mosquito surveillance limited to this area.This are was chosen because is has the only active mosquito control districts ANDIt is an area of high mosquito activity ANDIt has the largest hardwood swamp in VTThis paid off, as the very first detections of EEE in mosquitoes in VT occurred in 2012 in this area. Most isolations were from one trap site and occurred for several weeks in a row starting in late July.
20 Unfortunately, mosquitoes weren’t the only ones infected Unfortunately, mosquitoes weren’t the only ones infected. About the same time we were learning about the virus being present in the mosquitoes, we learned about two possible human cases. Both of these people ended up being infected with the virus and dying from their illnesses.
21 Plans for 2013 Mosquito surveillance in known EEE area Surveillance data available on-lineHuman and veterinary surveillanceEducation to residentspreventing mosquito bitesOn-line availability of a risk-mapUpdated throughout the season
23 WNV & EEE Prevention Promote use of personal protection Long sleeves and pantsInsect repellent that contains DEET, Picaridin, or oil of lemon eucalyptusCover baby carriages with mosquito nettingFix holes in screensAvoid outdoor activities when mosquitoes are activeEliminate mosquito breeding habitatsReduce standing waterVaccinate horses and other susceptible animals