Cape May County’s Department of Mosquito Control has been tracking the growth of mosquito larvae since April and killing them where they find them, using a bacteria not harmful to humans.
The goal is to kill them in the larval stage with the bacteria Bti (Bacillus thuringiensis israelensis), but once mosquitoes make it to the adult stage, more controversial methods are used that involve insecticides.
Complicating the job this year are the after-effects of Hurricane Sandy. Mosquito control officials are normally concerned with rainfall and lunar tide cycles, but Sandy has created another worry: Debris clogging the salt marshes and storm drains along the coast could help those mosquitoes linked to diseases
“I’ve seen aerial surveys and there’s a lot of debris like hot tubs, kitchen sinks, boats and such.” said Administrator Robert Kent of the New Jersey Office of Mosquito Control. The debris provides good breeding grounds for the mosquitoes and shields them from aerial spraying, Kent said.
And while computer modeling can predict mosquito numbers based on weather conditions, there is no way to predict impacts from increased mosquito breeding habitat due to storm debris.
Kent said there are 63 mosquito species in New Jersey but only a few cause disease problems. Of special concern are the salt marsh mosquito, Aedes sollicitans, which can transmit Eastern equine encephalitis, and the rain barrel mosquito, Culex pipiens, which transmits West Nile virus.
Kent said the debris could boost both populations. Anything that collects rainwater, or prevents it from draining properly, increases populations of the rain barrel mosquito, while damp debris on the edges of the salt marshes could increase production of salt marsh mosquitoes.
“They’re the two we should be concerned about. Our focus statewide is on West Nile and in the southern part of the state Eastern equine encephalitis,” Kent said.
More mosquitoes can mean more disease, though that is not a given. Birds also play a big role in the chain that gets the mosquito-borne diseases to humans.
West Nile cases were at their highest level ever in New Jersey last year. In 2010 there were three cases and no deaths. In 2011 there were seven cases and no deaths. Last year, Kent said, there were 48 cases and six confirmed deaths in New Jersey, Kent said.
It was also the worst year for West Nile nationally since 2003 with 5,674 cases and 286 deaths, according to the Centers for Disease Control and Prevention. Kent believes that may be a conservative number.
While West Nile virus is fatal less than 15 percent of the time. Eastern equine encephalitis has a 50 percent fatality rate and often leaves survivors with permanent disabilities. When it does appear it is mostly a problem at the shore. In 1959 an outbreak killed 21 people and ended the summer season early from Cape May to Asbury Park. A smaller outbreak occurred in New Jersey in 1968, with 12 cases and six deaths. There have only been a few fatalities since then.
Eastern equine encephalitis is more of a problem in the south because it also requires the cedar swamp mosquito, Culiseta melanura, to transmit the virus between birds. The virus gets transferred from the cedar swamp mosquito to the salt marsh mosquito by birds that roost at night in the cedar swamps but feed on the salt marshes during the day. The salt marsh mosquito is the vector to humans.
A third mosquito-borne disease, Saint Louis encephalitis, caused 10 deaths in New Jersey in 1964 and three in 1975, the last time it was recorded here. It is fatal less than 10 percent of the time and is transmitted by the rain barrel mosquito, also known as the northern house mosquito.
Kent pointed out that computer models do not take into account actions taken to control mosquitoes, and all 21 counties in the state have mosquito control programs.
South Jersey’s mosquito control departments have been busy since April.
Rich Candeletti, who handles mosquito control for Ocean County, said his department has been applying Bti and practicing water-control methods to reduce breeding habitat. Ocean County is also concerned about hurricane debris, and Candeletti said they are trying to get rid of it or at least spray it.
Atlantic County, which has had mosquito control since 1912, has been sampling waters and so far has only found larvae, said Office of Mosquito Control Superintendent Doug Abdill.
“We may do an aerial larvacide (Bti) in the next week or two,” Abdill said.
One concern he has is the full moon and new moon tides are forecast to be higher this year than the past several years.
Samples are constantly being taken to check disease levels in the blood-sucking pests. Last year about 10 percent of these tests statewide were positive for West Nile, a record number for the state followed by a record number of cases and deaths. Abdill said they would use pesticides if needed to kill adult mosquitoes.
“If it comes down to a public health hazard, we take the view of the greater good is not getting people sick from West Nile virus or Eastern equine encephalitis,” said Abdill.
There are numerous other control methods, such as stocking waterways with mosquito-eating fish to increasing tidal flow in saltwater wetlands. Peter J. Bosak, superintendent of the Cape May County Department of Mosquito Control, uses them all.
Bosak said Sandy wasn’t all bad when it comes to mosquito control, flushing out some historically clogged waterways.
Mosquito control officials say a number of myths persist about mosquitoes and what kind of season awaits them.
People think a cold winter kills them, but most over-winter in the egg stage and the cold has no impact.
“The egg survives freezing and thawing,” Abdill said.
Another myth is rain helps all mosquito species. Abdill said some species produce eggs that have to “dry down” to hatch. Too much water can be a bad thing for them.
Still another myth is a rainy spring leads to a banner mosquito year. Bosak said mosquitoes react more quickly to nature than people think. It could be a dry spring but if it rains a lot in June it will be a bad summer for mosquitoes.
Another myth is rising ocean levels will breed more salt marsh mosquitoes. Bosak said higher waters are decreasing salt marsh mosquito habitat because larger areas are under water all the time.
“With mosquitoes, it’s really a matter of inches with elevation,” Bosak said.
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