DIVISION OF PUBLIC HEALTH SERVICES
DEPARTMENT OF PUBLIC SAFETY
Mosquito and Vector Control
Pay attention to that mosquito buzzing you. It could be carrying West Nile virus. In Hunterdon County, a confirming sign that WNV exists in the community was found recently in two dead crows. "We're keeping a vigilant watch on environmental indicators," reported John Beckley, health officerand director of the Hunterdon County Department of Health. "Crows are the choice marker; when crows test positive for West Nile virus, we know it's here in the county. As standard protocol, our mosquito and vector control staff is conducting surveillance where the dead birds were found and setting up mosquito traps throughout the area."
West Nile virus is transmitted through the bite of an infected mosquito that acquired the virus by feeding on an infected bird. The virus is not directly transmitted from birds to humans or from person to person. However, it can be transmitted through blood transfusions or organ transplants from an infected individual. From 1999 to 2002, 43 people were infected with West Nile virus in New Jersey, 2 of which died.
Statewide, 192 crows have been tested to date by the Department of Health and Senior Services Public Health and Environmental Laboratory. Of the samples, 44 crows found in 15 counties were confirmed positive for the presence of WNV. Of the 3,937 mosquito pools tested, 21 positive pools have been found. Currently, a total of 19 counties have positive WNV cases in either the avian population or in mosquito pools.
"This year, we're definitely seeing a sizable bump up in mosquito activity,"said Tadhgh Rainey, head of the Mosquito and Vector Control program of the Hunterdon County Department of Health. "Field traps that last year at this time caught between 100 to 200 mosquitoes per site per night are now capturing more than 4000 per night." The county health department has traps at 140 locations throughout Hunterdon and in every community. While many of the mosquitoes captured are not a species that feed on mammals, they are integral in spreading the virus.
"Of the mosquitoes we trap, we prepare a batched sample and send them to Trenton for analysis at the state lab," explained Rainey. "Just from our county, the lab is seeing between 500-1000 mosquitoes per week; and with positive results now being experienced, we're at the higher end of that count."
Here in Hunterdon, the health department is using technology to track WNV. "We use our global information system (GIS) to map our trapping sites and the activity experienced at those sites," said Rainey. "This gives us a visual picture of the changing dynamics of the hot spots and newly emerging active zones. This data is then used to plan our program steps."
The county health department also "archives" mosquito samples in refrigeration for testing at later dates. "We have some 50,000 mosquitoes on ice," said Rainey as he described the work done after the height of the season. "Our preserved samples will be tested and compared to other recent samples taken from the same sites to help determine how long the virus might have been in that particular area. This is key to understanding how WNV establishes itself and spreads."
Mosquito control efforts are ongoing. According to Rainey, the only difference in what is done day to day is that during this time of year the intensity of field activities increases. "Our reaction to spot incidents such as finding a dead crow is much more aggressive," Rainey reported. "We'll perform special trappings and testing of mosquitoes from that site to get a sense if the dead bird is an anomaly, did it fly into the area or is it a local sign that there's an established virus. In most cases, if the incident involves more than one bird, the problem is right there in the mosquito population."
From the hundreds of sites the health department monitors, it is clear from the trapped mosquito specimens that the insects are more than likely breeding around private residencies. As Rainey says, "This is where homeowners really can help. They have to be vigilant in getting out there and eliminating any standing water in their yards. Old tires, birdbaths that are not changed frequently, pots collecting rainwater, even clogged rain gutters. All of these are prime breeding grounds for mosquitoes. Residents are protecting their own health when they get rid of these problems."
With the sizable equestrian population in Hunterdon, Rainey pointed out that horse owners should ensure their animals are immunized. "Too many people don't feel this is a high priority," Rainey said. "But the August-September period is the most serious period for WNV transmission. Although it remains unclear how effective the immunization is, we remind horse owners that it is still the main defense available."
The Hunterdon Mosquito and Vector Control team performs larviciding from early March until November during a normal year. However, a bad year such as this one could extend the process through Thanksgiving. "Weather drives much of what can and needs to be done in the field," said Rainey. "This year, the work is non-stop."
Clearly, WNV -- like other growing public health issues -- is making increasing demands on health departments countrywide. As department director, Beckley is working like health officers elsewhere to ensure that their organizations can keep up with WNV and the many other serious health challenges. Undoutedly, there's a certain urgency in Beckley's words: "Public health departments statewide and nationally are dealing with very similar needs: to acquire talented staff, to train that staff for the broad
and growing range of services it must deliver, and to retain the best people. Our goal in Hunterdon is to make certain that the health department team is among the best teams anywhere. Like a business, we're looking continuously and realistically at our resources and at our growing challenges so we are not caught short."