VECTOR MANAGEMENT PLAN

The purpose of the Vector Management Plan (VMP) is to target specific responses to specific risks and direct our limited resources effectively and efficiently.

Regional Adult Mosquito Surveillance:  The District will continue its surveillance of mosquito vectors based on protocols established by the Massachusetts Department of Public Health (DPH). The District’s Surveillance Program will operate and maintain 31 CO₂ baited New Jersey traps (NJ traps) across the region at fixed locations. NJ traps are placed in the same locations each year and are used to sample the general adult mosquito population. The trap collections allow the District to determine the dominant human biting mosquitoes, potential disease vectors, and population densities of local mosquitoes. Population trends can be compared during the year and between years.  One NJ trap will be placed in each member municipality.  Additional portable traps may be used as necessary, in response to areas with disturbing population trends and/or virus activity.  The District will collect and identify samples from each trap twice a week.

 The District will operate 31 gravid traps. Gravid traps are designed to collect recently blood fed adult female Culex mosquitoes and other container breeding species relevant to WNV transmission.  One gravid trap will be placed in each member municipality in a fixed location and additional portable gravid traps may be used as necessary in response to areas with virus activity. The District will collect and identify samples from each trap twice a week.         

Last year The District operated 180 resting boxes in two tiers.  The first tier in communities of primary concern bordering New Hampshire (NH).  The second tier was deployed in buffer areas or communities bordering communities with previous EEE isolations.  Resting boxes are designed to collecting blood fed female Culiseta melanura mosquitoes, the principle vectors of EEE virus and have demonstrated to be an efficient and effective tool. While there were EEE isolations in mosquitoes and human cases in southern New Hampshire there was no EEE activity detected in our service area last season.  Typically EEE runs in cycles and it is apparent that EEE activity is diminishing. And while we can’t let our guard down as EEE will reappear in the future we are confident that EEE is in a downward trend.

In 2008 we will be operating between 60 and 80 resting boxes in one tier in the primary risk area immediately bordering NH. We will continue to do this for the foreseeable future in order to establish the pattern of EEE cycles in our service area and to serve as a early warning system.  It is important to note that we can redeploy additional resting boxes in short order if necessary.

Six to eight resting boxes will be placed at each fixed location and there will be two locations in each of the municipality bordering NH with the exception of Salisbury, which will have just one location.  The District will collect and identify samples from each box twice a week.

The District will initiate a pilot program of deploying a new type of trap, the BG Sentinel trap.  These traps have shown to be more effective in attracting Aedes albopictus, commonly called the Asian Tiger Mosquito. Last season, District personnel collected specimens believed to be Ae. albopictus but, because of the generally poor condition of the specimens, the identifications could not be confirmed.  Ae. albopictus is a principal vector of Chikungunya, a virus that causes severe headache, chills, nausea, vomiting, and extremely persistent and painful arthritic joints which may persist for weeks to months. 

There is currently a Chikungunya pandemic in countries along the Indian ocean basin, with nearly 2 million people infected. A Chikungunya epidemic broke out in northern Italy this past last summer with over 200 cases. The Italian epidemic is the first known outbreak of this virus outside the tropics.  Six traps will be deployed throughout the District, two in the north, two central and two south, in an effort to confirm the presence and distribution of Ae. albopictus if any.  

Emergent Exotic and Recent Immigrant Mosquito Species:  Through our Surveillance Program, we will also be looking for the appearance of new mosquito species.  Within the past five years, we have seen the appearance and rapid spread of an exotic species, Ochlerotatus japonicus, the Japanese Rock Pool Mosquito, throughout our District.  While this species is a competent disease vector in other areas, there is little to suggest it is currently a disease vector in the Northeast.

Another competent disease vector, the Asian Tiger Mosquito, Ae. albopictus, first found in Houston in 1985, has spread rapidly throughout the temperate regions of the U.S., including southeastern Massachusetts.  Although this species has yet to be collected in our district, its arrival is imminent and its potential as a disease vector should not be underestimated.  Last season District personnel collected specimens believed to be Ae. albopictus and as previously addressed in the surveillance section, a pilot program to confirm the presence and distribution of Ae. albopictus will begin this summer.

The possibility of additional mosquito species becoming established in our area, some more effective at transmitting virus and other disease causing agents can not be dismissed.  Our Surveillance Program will aggressively monitor mosquitoes we collect, not only to measure unusually high populations, but also to detect any new species.

Virus Testing:  Specimens from our trap collections will be sent weekly to DPH to be tested for the presence of encephalitis viruses.  The District has entered into a cooperative agreement with DPH to increase the number of pools tested.

Emergent Virus:  Since its introduction in New York City in 1999, WNV has spread through the country and is now endemic in the Northeast.  Prior to 2004 there was no serious concern about EEEV in Essex County.  This has changed with multiple EEEV isolations in mosquitoes in recent years.  World-wide the threat of mosquito- borne disease is on the rise and the possible introduction of other exotic vector borne diseases must be seriously considered. Through our affiliations and associations with the scientific and mosquito control community world-wide, we will monitor this potential on behalf of our member municipalities. Necessary and appropriate vector/virus intervention measures will continue to be developed and implemented.

The next mosquito bourn virus of potential concern is Chikungunya.   While Chikungunya is rarely fatal it has the potential to infect large numbers of people.  In 2005 and 2006 it sickened almost one third of the 800,000 inhabitants of La Reunion, a French island in the Indian Ocean (Enserink 2006).  Last Summer 200 people in Italy were infected. This is the first known example of Chikungunya transmitted outside the tropics.  According to Dr. Randy Gaugler, Center for Vector Biology, Rutgers University it is likely we will have out breaks of  Chikungunya within the next five years  

 West Nile Virus

Introduction:   While it was previously though that neurological disorders associated with West Nile Virus (WNV) were short-lived and only affected a small percentage of those infected, recent studies suggest that neurological disorders may be more prolonged, serious and effect more victims then original thought.

Culex species are primarily responsible for the amplification of virus in birds and are possible vectors to humans in endemic areas. Cx pipiens breed in highly organic or polluted water that collects in artificial containers such as discarded tires, gutters, bird baths, catch basins and storm water structures, including detention and retention ponds.  The preemptive strategy of treating catch basins has been effective at reducing the population of vector species. 

Surveillance data shows an 80% reduction in Culex species in communities where basins are treated as compared to communities with untreated basins. Contrary to what one would think, drought does not deter breeding of Cx pipiens but instead may enhance it. Wetlands areas dry back and pools become more concentrated with organic debris, providing Culex with additional breeding habitat.  During droughts, catch basins continue to accumulate water from car washing, lawn watering, and concentrated sheet flow from minor rainfall events.  Targeting Culex in basins will reduce adult Culex populations, hence bird-to-bird virus transmission and therefore, reduce risk to humans.

Although Culex salinarus may be present in catch basins, this is probably not its preferred breeding habitat.  If time and circumstance allows the District may evaluate the extent of Cx  salinarus breeding in catch basins.

Catch basin treatment in 2008 will be prioritized as follows:  As previously stated WNV is now endemic to the northeast and it has become clear that the epicenter for our area is the urban coastal communities of Winthrop, Revere, Lynn, Nahant, Saugus, Swampscott, Marblehead and Salem.  Second in order of priority will be Beverly, which had positive birds late in the season last year.

Waste Water Treatment Facilities Inspection:  As a preemptive strategy the District will inspect waste water treatment facilities in an effort to reduce or eliminate Culex breeding or potential breeding in these facilities.  While the District is authorized under the provisions of chapter 252 section 4 of the General Laws of The Commonwealth to enter upon lands for the purpose of inspections, we are not a regulatory agency. Nor is it our intention to cause any imposition to the management of waste water facilities, but rather to be a resource for information and technology to assist waste water facilities managers in preventing and or abating mosquito breeding to the mutual benefit of the facility, the community and mosquito control.

Selective Ground Adulticiding:  As a preemptive measure the District may recommend selective and targeted adulticiding applications to reduce Culex populations when WNV isolations in mosquitoes are discovered.  The District may recommend a target application based on the following criteria: two or more WNV isolations in mosquitoes in close proximity; one or more human cases of WNV.

Barrier Treatment:  The District uses a system called Ultra Low Volume (ULV) for ground adulticiding applications.  ULV is designed to dispense very small amounts of pesticides over a large area.  While this is a cost effective means of reducing mosquito populations on a large scale, it only affects those mosquitoes present at the time of the application and repeated applications are sometimes necessary to sustain the initial reduction in the mosquito population in some areas.  To reduce the need for repeated applications and provide more sustained relief from mosquitoes in high public use areas, the District may recommend a barrier spray treatment to public use areas such as schools (applications to schools must be incompliance with MGL ch85), playgrounds, athletic fields, etc. A barrier spray may reduce mosquitoes for two or more weeks. The District strongly recommends member municipalities take advantage of this service.

   Eastern Equine Encephalitis Virus

Introduction:  From what we have learned over the past three years it is apparent that EEEV radiates from the Southern New Hampshire area, in particular Exeter, Kingston and Newton.  There has been EEEV activity in these towns from the beginning of the current cycle in 2004 to the present.  It appears that EEEV migrates south from this focus area to the Northeast Massachusetts area.

While there were EEEV isolations in mosquitoes and human cases in NH in 2007, there was no EEEV activity in our service area. We did recommend and conduct adulticiding application in Amesbury, Merrimac and Haverhill as a preemptive measure due to spikes in vector mosquito  populations.  We do not anticipate EEEV activity in our service area in 2008 but are prepared for any contingency.

Habitat Surveillance:  Through the winter months the District will continue to locate, identify and enter into our data base potential Culiseta melanura habitat in communities bordering New Hampshire, specifically Amesbury, Merrimac Methuen and Haverhill, as well as in the communities of Boxford and Hamilton.

Selective Ground Adulticiding: As a preemptive measure the District may recommend selective and targeted adulticiding applications to reduce Culiseta melanura populations in an effort to break the virus cycle in bird-to-bird transmission phase.  Often by the time EEE appears in horses and humans other mosquito species, the so called “bridge vectors” are targeted for adulticiding; but it is late in the season when intervention efforts are made and are limited at best and often nonexistent.  The District will recommend a targeted adulticide application based on the following criteria:  above average Culista melanura populations in a year of anticipated EEE activity; one or more EEE virus isolations in mosquitoes; one or more EEE virus isolations in horses; one or more human EEE cases.

Barrier Treatment:  The District uses a system called Ultra Low Volume (ULV) for ground adulticiding applications.  ULV is designed to dispense very small amounts of pesticides over a large area.  While this is a cost effective means of reducing mosquito populations on a large scale, it only affects those mosquitoes present at the time of the application and repeated applications are sometimes necessary to sustain the initial reduction in the mosquito population in some areas.  To reduce the need for repeated applications and provide more sustained relief from mosquitoes in high public use areas, the District may recommend a barrier spray treatment to public use areas such as schools (applications to schools must be incompliance with MGL ch85), playgrounds, athletic fields, etc. A barrier spray may reduce mosquitoes for two or more weeks. The District strongly recommends member municipalities take advantage of this service.

Emergency Response Aerial Adulticiding Plan (ERAAP):  In the event that the risk level escalates to a point were it is deemed that ground adulticiding is insufficient to reduce that risk an emergency aerial adulticiding application may be warranted.  This would require a consensus of the District, the State Reclamation and Mosquito Control Board, the Massachusetts Department of Health, an independent advisory board and a declaration of a Public Health Emergency from the Governor.

Typically, once the decision is made to do an aerial application the need is immediate and window of opportunity is short.  The ERAAP provides the guidance and logistics of executing an aerial application. The ERAAP consists of a continually revised Global Positioning Satellite (GPS) mapping program, which can be downloaded to aircraft navigation systems to direct the pilot(s) where to spray.  Memorandums of Understandings with designated airports have been formalized to insure operational staging areas and ground support facilities are available and ready.  Contracts with aerial applicators and insecticide suppliers are in place for rapid delivery and deployment.  With these factors addressed and accounted for, aerial applications can commence soon after the Public Health Emergency is declared. 

 

References

 

CDC, Guidelines for surveillance, prevention, and control of West Nile Virus infection - United States, Morbidity and Mortality Weekly Report 2000;49:25-28.