UPDATE: Health Alert: Dallas County is Spraying for West Nile

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City of Dallas West Nile Virus Outbreak and Response

August 21, 2012

All Dallas residents are urged to stay tuned to local news media, call 311, or visit www.dallascityhall.com for up-to-date information on measures to help prevent further human infections of West Nile Virus (WNV).


Humans can contract West Nile virus from a mosquito bite. So far in 2012, Dallas County has 27% of all reported cases of human infections by WNV in the U.S. The virus can cause serious illness or death and, as of August 21, 2012, 11 deaths have been confirmed this year due to WNV in Dallas County.


The Texas Department of State Health Services (DSHS) is working closely with Dallas-area public health and emergency management officials and the Centers for Disease Control and Prevention concerning the record number of human cases of the disease in Dallas County.


Between Thursday, August 16 and Monday, August 21, two citywide applications of pesticide were performed by aerial spraying – a very effective and safe way to kill adult mosquitoes in large, densely populated areas – in Dallas County.  There is no further aerial spraying scheduled at this time.


With aerial spraying completed, Dallas residents are urged to join in fighting mosquitoes and West Nile Virus by seeking out and draining all sources of standing water on their properties.


Ways to Prevent Mosquito Breeding


Where do mosquitoes breed?

A mosquito’s lifecycle has four stages – egg, larva, pupa, and adult. Mosquitoes need water to breed since all mosquitoes spend their larval and pupal stages in water. Therefore, mosquitoes can always be found around water. This is why it is important to prevent stagnant water from standing around your home and apply a larvicide to areas where stagnant water cannot be removed.


How long can water stand in puddles or containers before it poses a problem?

If the water stands for less than a week it will not breed mosquitoes.  Only one species of mosquito (the dark rice-field mosquito) can complete its aquatic life cycle in less than seven days.  It is not a common mosquito, and it would probably not lay eggs in a puddle that would dry up so quickly.  Most mosquito species require standing water for a minimum of 10 to 14 days to complete their development.  Puddles that stand for less than a week are not worthy of concern.


How can mosquitoes be controlled around the home?

Get rid of standing water in which mosquitoes can breed. If there are any places around your home where water collects such as water-holding containers, house cooler drains and ponds, you may be raising mosquitoes.


What specific steps can people take to control mosquitoes outside a home?

Take the following steps to help cut down on the mosquito population:

  • Empty or get rid of cans, buckets, bottles, old tires, empty pots, plant saucers and other containers that hold water.
  • Keep gutters clear of debris and standing water. Remove standing water around structures and from flat roofs.
  • Change water in pet dishes at least once a day. Change water in wading pools and bird baths several times a week.
  • Fill in low areas in the yard and holes in trees that catch water.
  • Maintain your pool or hot tub. Be sure someone takes care of it if you are out of town.
  • Stock ornamental ponds with fish that eat mosquitoes.
  • Cover trash containers so they will not collect water.
  • Water lawns and gardens carefully so water does not stand for several days.
  • Repair any leaking plumbing and outside faucets.
  • Screen rain barrels and openings to water tanks or cisterns.
  • Keep drains and ditches clear of weeds and trash so water will not collect.


How do I report standing water concerns to the City for attention?

If water is standing for more than a week, report the location by dialing 3-1-1. Give the call center representative information on the location and source of the stagnant water, if known. A code inspector will inspect the location within 24 hours and take appropriate action to drain or treat the water.


Do ponds and lakes breed mosquitoes?

If it is a permanent body of water (such as a lake or pond), it is much less likely to be a source of mosquitoes than if it were a temporary body of water such as a puddle.  A puddle three inches deep and three feet in diameter can easily produce 10 to 20 times as many mosquitoes as your average 1-acre farm pond.


Permanent bodies of water develop resident populations of predatory species (aquatic insects, fish, salamanders) that reduce or eliminate the mosquito larvae in that environment.  Most mosquito species would not even lay eggs in a permanent body of water.  Several species of mosquitoes can breed in permanent bodies of water, but most of these have not been implicated in West Nile virus transmission.


Do mosquitoes breed in flowing water?

If the water in a ditch is flowing, it is not likely to produce any mosquitoes. The only species that might be found in a flowing ditch are not species known to transmit West Nile virus.  If the water has no flow (is stagnant) it could be an important source of mosquitoes.


As always, the first line of defense to prevent infection of the WNV is to avoid getting bitten in the first place. We urge citizens to be proactive by employing the 4-Ds of personal prevention:


DEET – use insect repellents that contain DEET, or any other EPA approved insect repellent

DRESS – Wear long, loose and light-colored clothing outside during dusk and dawn hours.

DRAIN – Remove all areas of standing water.  Change water in wading pools, pet dishes and birdbaths several times a week.

DUSK/DAWN – Protect yourself during dusk and dawn hours.


Additional Resources:


Texas Department of State Health Services



AgLIFE EXTENSION, Texas A&M University

Mosquito Proof Your Yard




Effective Non-Toxic Mosquito Control




The Texas Department of State Health Services is working closely with Dallas-area public health and emergency management officials and the Centers for Disease Control and Prevention concerning the extremely high number of human cases of the disease in Dallas County.

“The disease poses an immediate public health threat to Dallas County. We need to use all possible tools, including aerial spraying, to fight this outbreak,” said Dr. David Lakey, DSHS commissioner. “We will support the decisions made by local officials as we work together to confront this situation.”

Aerial spraying is a very effective and safe way to kill adult mosquitoes in large, densely populated areas. For people concerned about exposure during aerial spraying, health officials suggest the following precautions:

Minimize exposure. Avoid being outside, close windows and consider keeping pets inside while spraying occurs.

If skin or clothes are exposed, wash them with soap and water.

Rinse homegrown fruits and vegetables with water as a general precautionary measure.

Cover small ornamental fish ponds and swimming pools.

Because the chemical breaks down quickly in sunlight and water, no special precautions are suggested for outdoor swimming areas.

DSHS contracts with Clarke, a private environmental products and services company, for aerial application of mosquito control products. The product is called Duet, which is labeled and approved by the U.S. Environmental Protection Agency for use in outdoor and residential areas. The active ingredients are in the same chemical family as products currently being used for ground spraying in the Dallas area. The product would be applied at very low dosages – less than an ounce per acre – by small, twin-engine aircrafts flying at approximately 300 feet above ground overnight.

Texas has more than 380 state-confirmed cases of West Nile illness for 2012, including 16 related deaths. Texas is on track to have the most cases of West Nile illness since the disease first emerged in the state in 2002. Humans can contract West Nile virus from a mosquito bite. The virus can cause serious illness or death.

The following Cities have also stated to Dallas County officials that they want their city to also be sprayed via the aerial spraying:
Farmers Branch
Grand Prairie
Highland Park
Univeristy Park

Click Here for all locations that will receive the aerial spraying

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