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Mosquito invasion coming

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Mosquito invasion coming

Aaron Devencenzi is among the vector control district workers who fights the spread of mosquitoes.

GLENN KAHL/The Bulletin


POSTED February 28, 2010 1:55 a.m.

The series of storms pelting the South County may go a long way toward breaking the three-year drought but they also are creating perfect conditions for mosquitoes and the spread of the deadly West Nile Virus.

Standing water on the ground or in vessels such as flower pots and abandoned tires can help breed millions of mosquitoes in less than 10 days as the weather warms. At the same time abandoned swimming pools of foreclosed homes continue to pose a major threat for the spread of mosquitoes.

Aaron Devencenzi of the San Joaquin County Mosquito and Vector Control District told Manteca Rotarians Thursday noon at Isadore’s Restaurant about the dangers and what they could do to prevent mosquito infestations associated with the fear of the dreaded West Nile Virus

Just one mosquito can produce 1,200 young, Devencenzi said.  A five-gallon bucket of water has the potential to produce enough mosquitoes to invade an entire city block in a residential community. Periods of dusk and dawn are when residents should be most aware of the airborne threat to their health, he noted.

“Up from three to 10 days a mosquito can go through its complete metamorphosis,” he said.  “That’s why as we approach summer time or late fall you will see many, many mosquitoes coming out into their very fast life cycle.”

There are more than 3,000 different species - with some 17 different kinds in San Joaquin County.

“Not every kind of mosquito carries every kind of disease,” he said.  “Two of the mosquitoes we have here – one clean water and one dirty water – both can carry West Nile Virus and they are the ones that we have the most of.”

One mosquito can create up to million relatives in a summer

Normally a mosquito finds you by your breath, heat from your body or chemicals on your body, he said.  One mosquito can lay up to four egg rafts that look like a little boat that floats on the water holding from 150 to 400 eggs at a time.  “One female mosquito in the summer can have upwards to one million relatives,” he noted.

Standing or still water is critical to their lives since any movement in the   the water will cause their eggs to drown.  The eggs go through four in-stars hatching off the water as an adult mosquito.

In the surveillance of disease throughout the county workers run 60 to 70 of these particular traps including encephalitis virus surveillance traps using dry ice emitting CO2 – the attractant for that mosquito – with a small fan blowing them down into a container to check for population and species of the mosquito.

They are logged into a monthly record within 24 hours noting their gender and species in a given area.
Dead bird surveillance and squirrel reports are also used to signal mosquito infestation, he said. Crows, ravens, blue jays, magpies all easily die from West Nile Virus – so you’ll be seeing those around, Devencenzi added.  

“When we first started this, this whole disease was new and we were picking up every dead bird.  What we are asking the public to do is to encourage people to call in any dead bird – it does help us statistically to know where there is a problem,” he said.

He added that squirrels are not too much of a big deal.  A few of them have been reported and they do help in the surveillance program.
 
Last but not least the surveillance through sentinel chickens which has been used for identifying equine encephalitis – endemic to this area.  But with West Nile Virus they are not seen as a great indicator to the disease.  The West Nile Virus shows up in chickens only after birds, squirrels and humans have been stricken.
The county is divided up into 19 different zones by the Mosquito Abatement and Vector Control District in its constant attempt to control the spread of many diseases.
 
“You can only imagine in the abandoned homes – with green pools that look like a swamp – how many mosquitoes come out of them.”

Distributing free mosquito fish
He said current control plans make use of mosquito fish that are provided free to the public, even being delivered to property owners in need of the fish.  Currently there is a low supply as the fish are sedentary just coming out of the ponds.  By the end of March and into April they will be available again for the public to use.  In June there will be a fish distribution day in each city in the county where a district truck with a fish tank will be available for those who can’t get to their office to pick them up.

The fish are used in water troughs, ornamental ponds around the house and dirty swimming pools.

“With our chemical control we generally try to kill the mosquitoes while they are in the water.  The main larvae side we use is ingested by the mosquitoes that stop them from being able to digest food.  When we have mosquitoes with a high amount of virus, and they are older mosquitoes – the ones that are going to be more viremic and their counts are high – that’s when we have to spray the adult mosquitoes to kill them,” he said.

Whether they use a truck or an airplane it is the same product being put out at the same rate.  “When we use airplanes we have to cover larger areas than 5,000 acres – with the truck we can cover 5,000 acres in a night.”

Only two-thirds of an ounce of concentrate is used for treating an acre of land, he added.

 

For more information call 1-800-300-4675 or (209) 982-4675.  On the web it’s www.sjmosquito.org.

Distributing free mosquito fish
He said current control plans make use of mosquito fish that are provided free to the public, even being delivered to property owners in need of the fish.  Currently there is a low supply as the fish are sedentary just coming out of the ponds.  By the end of March and into April they will be available again for the public to use.  In June there will be a fish distribution day in each city in the county where a district truck with a fish tank will be available for those who can’t get to their office to pick them up.

The fish are used in water troughs, ornamental ponds around the house and dirty swimming pools.

“With our chemical control we generally try to kill the mosquitoes while they are in the water.  The main larvae side we use is ingested by the mosquitoes that stop them from being able to digest food.  When we have mosquitoes with a high amount of virus, and they are older mosquitoes – the ones that are going to be more viremic and their counts are high – that’s when we have to spray the adult mosquitoes to kill them,” he said.

Whether they use a truck or an airplane it is the same product being put out at the same rate.  “When we use airplanes we have to cover larger areas than 5,000 acres – with the truck we can cover 5,000 acres in a night.”

Only two-thirds of an ounce of concentrate is used for treating an acre of land, he added.
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