Vector Control Program

If you have questions regarding vector control issues please call the Vector Control Specialist, @ the hotline: (972) 721-3755

Mosquito Surveillance and Control

The City of Irving has an active program for assessing the numbers and types of mosquitoes in various neighborhoods.  Each week, a mosquito-control technician sets out approximately 5 traps throughout the city.  The number of mosquitoes trapped at each location is logged, and each trap net's catch (called a "pool" of mosquitoes) is shipped to the state health department's laboratory in Austin for testing.  Mosquitoes are tested for West Nile Virus (WNV), St. Louis encephalitis (SLE) and several other mosquito-borne viruses. Here is some basic information about Irving's mosquito surveillance, public education, and control program:

1. The Public Health Division relies heavily on surveillance and public education to protect Irving's citizens from WNV and SLE.
    
2. Each week, approximately 5 locations are chosen to set out two forms of mosquito traps. They "run" all night, and the mosquito-control tech retrieves these traps on the following morning.
    
3.  Mosquitoes are counted, then shipped by bus to the Department of State Health Services (DSHS) laboratory in Austin.(Dallas County lab services are also available for this testing)
    
4. State lab staff combine all of the mosquitoes from one container (for example, all of the mosquitoes caught in one net from a single family home in Irving), grind the mosquitoes, and perform tests on extracts from this sample.
    
5. A lab report form for each “pool” of mosquitoes Irving sends to Austin is mailed to the Public Health and Environmental Services Department (PHES).
    
6. Mosquito pools which test positive for WNV or SLE are often reported to Irving by phone call or fax machine to speed the information exchange process.
    
7. To minimize Irving citizens’ exposure to airborne insecticide chemicals, PHES relies most heavily on killing mosquitoes in their juvenile form. Wigglers, also known as larvae, are killed in standing water locations using either growth-regulating chemicals or a special bacterium that is toxic only to mosquito larvae. Treating standing water is called “Larviciding.”
    
8. Both the federal Centers for Disease Control (CDC) in Atlanta, GA and the Texas Department of State Health Services in Austin have written guidelines and regulations that relate to municipalities’ and county governments’ use of airborne pesticides (truck-mounted sprayers or aircraft-mounted sprayers). This form of mosquito control is known as “adulticiding” or killing adult mosquitoes. Though most U.S. cities used adulticiding throughout the latter half of the 20th century to reduce “nuisance” mosquitoes (those species that bite humans but normally don’t carry disease), nuisance spraying is heavily discouraged by state and federal health officials. Irving has adopted the recommendations of the CDC when deciding when to send its vector control technician out at night to use the truck-mounted adulticiding unit. These guidelines are as follows:
   
   When a particular trap location has over 100 female mosquitoes in one night of trapping
   
   When a mosquito pool (one trap’s catch of mosquitoes) has tested positive for either WNV or SLE
   
   When the county or state health department reports a suspected human case of WNV or SLE in Irving
   
   When the county or state health department reports a confirmed human case of WNV or SLE in Irving
   
   
9. Irving has carefully studied all available mosquito control chemicals, and has chosen an insecticide formulation that is considered the safest formulation available for people, pets, and wildlife. The active ingredient is a pyrethroid (a man-made derivative of the natural insecticide called pyrethrin). Pyrethroids are very effective at killing flying insects, but have very low toxicities to people, dogs, cats, and wildlife. Fortunately, from an ecological perspective, the pyrethroid Irving uses is destroyed in a matter of hours after the sunrise causes ultraviolet light to contact the droplets (which have landed on grass and other surfaces). On a typical residential lot, Irving’s mosquito spray truck only deposits about two drops of active ingredient (two drops of pyrethroid on a quarter acre lot). This tiny amount of insecticide is not known to kill fish in decorative ponds, or kill bees which are active on flowering plants. CDC studies show that adulticiding does not expose people to harmful levels of insecticides.
    
10. As of August 5, 2006, 1 of the approximately 55 samples of mosquitoes sent to Austin has tested positive for WNV or SLE; however, Dallas County has reported 161 positive pools. As a general rule, mosquito pools begin testing positive for WNV in July, and remain positive until almost Thanksgiving. It is important to remember that WNV and SLE are “bird viruses”. These viruses are naturally-occurring diseases among many species of wild birds. The normal prey for mosquitoes in nature is wild birds and wild mammals. When a female mosquito takes a blood meal from an infected bird, the mosquito (only certain species) can transmit the virus to a person or other warm-blooded creature (like a horse).
     
11. It is very important to realize how rare mosquito-borne diseases really are in Dallas County. There are over 2 million people living in Dallas County. Each year, there are about 20-40 human cases of WNV, making the probability of any one Dallas County citizen developing a symptomatic case of WNV approximately 1 in 100,000. Two facts offset this rarity, however. First, those citizens who contract WNV illness can experience a life-threatening illness, and can have permanent mental and physical disabilities. Second, like all other mosquito-borne diseases, the disease can be prevented by avoiding mosquito bites.
     
12. Another interesting statistic on the relative rarity of WNV and SLE is the percentage of mosquitoes that actually are infected during summer and fall months, and the percentage of people who, after being infected by a positive mosquito, go on to develop symptoms of illness. Studies have shown that, even at the height of the WNV season (late summer and early fall), less than 5% of mosquitoes are infected. In addition, other studies indicate that only about 1% of those persons bitten by an infected mosquito will become ill. In other words, as many as 99% of citizens who are exposed to the WNV virus through a mosquito bite will not get ill.

TIPS- Effective Prevention

Mosquito season in this area is normally from about April through October.  All citizens should do their part to aid in the abatement process and protect themselves by complying with the following guidelines:

First of all, follow the "Four D's".

Dusk and dawn are the time of the day when mosquitoes are most active.  Stay indoors if possible or limit outdoor activity during these periods.

Also,

• Clean and replace pet water containers and bird baths daily.
• Repair any water leaks such as outdoor faucets or sprinkler systems.
• Maintain swimming pools- circulation and filter systems, ph, and chlorine levels.
• Ensure that window screens fit tightly and are in good conditions.
• Report to the Health Department any stagnant swimming pools or other bodies of water in your neighborhood.
• Remove any dead birds found on your property - contact the Health Department if you determine that they are "blue jays" or "blackbirds", or if there is a large number of any kind of dead birds in your neighborhood.

For reporting, contact the Public Health and Environmental Services Department "SKEETERS" hotline at (972) 721-3755.