Health officials in Chicago, Illinois, USA, have started a vigorous mosquito eradication campaign following recent rains that brought a surge in the mosquito population, and signs that West Nile Virus (WNV) carrying species are also on the rise, reports the Chicago Tribune.
Trucks spraying mosquito killing insecticide are now making their way around the city’s most likely mosquito infested areas.
WNV is a potentially life threatening disease. So far this year the city of Chicago has seen three cases of people infected by WNV, one of whom has died.
Normally not a worry for the city’s health department, but a nuisance to city dwellers, mosquitoes are a common feature this time of year. Once rain pools warm up and stagnate they form ideal breeding sites for mosquitoes and the species that most commonly bites Chicago’s suburban and city dwellers is the annoying but mostly harmless species known as Aedes vexans.
However, it appears that Culex pipiens, the mosquito that carries the West Nile Virus (WNV), has joined its harmless cousin in many parts of the city. Over 100 mosquito trapping sites across Chicago are monitored several times a week, and until recently only one or two have trapped WNV carrying mosquitoes, but this number went up to 13 two weeks ago and 32 last week.
Chicago Health Commissioner Terry Mason told the newspaper that the WNV mosquito now poses a threat to public health and the situation calls for “quick and decisive action”.
Health officials have started spraying insecticide in the affected parts of the city. It will take two days to cover all the locations where the WNV carrying mosquito has been found, and if the weather stays dry the job should be completed by tonight, Wednesday, they told the Tribune.
In the whole state of Illinois last year there were 215 cases of human infection, some 40 cases fewer than the year before. This year so far there have only been 4 documented cases, compared to 15 the same time last year.
Health officials say this does not necessarily signify a downward trend since the long season of wet weather could just mean that the emergence of cases has been displaced to later in the season.
If you add the two weeks or so it takes for symptoms to emerge, plus the few days it takes the eggs to hatch and the grubs to become adults, the effect of the rise in mosquitoes last week may not show until end of August or early September. The worst is yet to come, an entomologist at the state health department told the newspaper.
80 per cent of people who are bitten by a WNV carrying mosquito have no symptoms, and the rest, about 1 in 5, will have mild to moderate symptoms. These arrive between 3 and 14 days after being bitten.
But 1 in 150 persons who are bitten by a WNV mosquito gets very ill with severe symptoms ranging from headache, stiff neck, fever, apathy, tremors, convulsions, weak muscles, feeling disoriented, dizzy, numb, and more rarely to paralysis, coma and death.
There is a slight risk of brain and nervous system damage and people over 50 are at higher risk than others.
WNV carrying mosquitoes like to move around at dawn and dusk, so the best way to avoid being bitten is to stay indoors at these times, or if you have to go out wear long sleeves and pants and cover any exposed skin with a recommended repellent, for instance containing DEET, Picaridin or oil of lemon. Also make sure window and door screens have no holes and tears and are well fastened.
To reduce breeding sites, check your garden and back yard for standing water: drain ponds, tip out paddling pools and empty flower pots of water.
Click here to read the full story in the Chicago Tribune.
Click here for more information about West Nile Virus from the Illinois Department of Public Health.
Written by: Catharine Paddock