A deep, dark, dirty swimming pool was abandoned in the backyard of a home in Merced.
Pieces of cardboard and a decrepit soccer ball floated in its putrid water. But the worst sight was the carpet of tiny black creatures wiggling within it.
“All that stuff you see — that’s mosquito larvae, millions of mosquito larvae,” said Allan Inman, manager and entomologist for the Merced County Mosquito Abatement District.
Pools like this have become a huge problem, especially this year. The rise in foreclosed homes, combined with people letting their own swimming pools fall into disrepair, has brought a large number of urban mosquitoes into Merced County, Inman said.
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These pests carry West Nile virus, a disease that can cause flu-like symptoms or — in about 1 percent of cases — serious symptoms such as a high fever, convulsions and vision loss.
Two types of mosquitoes carry the disease: Culex pipiens, or “house mosquitoes,” that like urban areas; and culex tarsalis, or “encephalitis mosquitoes,” that like fresh water and suburban areas.
House mosquitoes thrive in any basin that holds stagnant water near homes, in drainage systems and dairy lagoons. And they love all the green swimming pools left standing after a family’s home has been foreclosed.
“Any time you are breeding mosquitoes, it’s a health issue,” said Jeff Palsgaard, director of Merced County's environmental health department. “And it has increased over the last couple of years with foreclosures and people not maintaining their pools.”
Numbers of house mosquitoes also increase during dry years like this one because the larvae become more concentrated in smaller bodies of water, Inman said.
Anyone who calls the county health department about a neighbor’s pool gets referred to the abatement district. The same goes for calls to city code enforcement, said city spokesman Mike Conway.
The ongoing dilemma cities face is getting people to take responsibility for pools before they become stagnant. If someone still lives where a swimming pool has become a mosquito haven, the city or abatement district can contact them and tell them to fix the problem.
But if a green pool is at a foreclosed home that has been empty for months — things get more complicated.