New test results due this week will determine if alterations need to be made to spray schedule.

An unfavorable weather forecast has forced the Richardson Health Department to cancel planned mosquito spraying set for tonight. Weather conditions are also expected to prevent spraying from occurring the rest of the week.


Meanwhile, the Health Department is also waiting for results of this week’s mosquito trap tests. The Richardson Health Department conducts weekly tests of mosquito traps placed throughout the city to help monitor for the presence of West Nile virus in mosquitoes. The City only sprays areas where traps have returned positive findings for mosquitoes carrying the West Nile virus, as well as areas where there are confirmed human cases of the disease. If traps that tested positive last week show negative results this week, then no follow-up spraying operations will be scheduled.

“When we receive positive test results it activates several levels of our overall mosquito abatement plan,” said Richardson Health Department Director Bill Alsup. “We are actively treating for mosquitoes during the day in less visible ways. Specifically, we are adulticiding and larvaciding stagnant bodies of water, and we are fogging storm drains and other locations to knock down mosquito populations. The ground spraying is another component to our overall plan, and is necessary to provide the one-two punch we are hoping will have the highest degree of effectiveness in helping to keep mosquito populations at a minimum. But, it is important for people to know that ground spraying is not the only tool we have at our disposal to help combat the spread of the disease.”

The decision to conduct ground spraying was made after City Health Department workers were notified last week that four traps located in the city returned mosquitoes that tested positive for carrying the West Nile virus.

Richardson began its West Nile virus monitoring program this month, which is the earliest it has ever begun testing for signs of the virus. Typically, the City begins its monitoring program in May, but the Richardson City Council approved increased surveillance this year due to the heightened incidence of West Nile virus cases experienced in the Metroplex in 2012.

The Richardson Health Department conducts ground spraying mosquito abatement operations only if sustained wind speeds are less than 10 miles per hour, if it is not raining, and if temperatures are forecast to be above 50 degrees Fahrenheit.


Richardson is working in conjunction with other cities and health agencies in the Metroplex to mitigate the spread of West Nile virus. Additional measures being taken in Richardson include:

  • - Earlier monitoring of mosquito populations using traps strategically placed in the city;
  • - Residential pool abatement, to reduce areas where mosquitoes can breed;
  • - Surveillance and treatment of storm drain system;
  • - Closer collaboration among departments to reduce areas where water can become stagnant;
  • - Deploying fish that can eat mosquito larvae, and increasing the areas where larvicide is used;
  • - Improving the adulticide response by working with a private contractor that can provide additional ground spraying capacity;
  • - Collaborating more closely with regional partners to provide an improved response.

How Spraying Locations Are Chosen

The Richardson Health Department schedules mosquito spraying based on positive findings of West Nile virus in mosquito traps placed around the city or if a human case is confirmed. Once located, the area around the positive finding is targeted for spraying in an attempt to help limit the spread of the disease. In an effort to decrease the incidents of finding the West Nile virus in people and mosquito traps, targeted neighborhoods are being sprayed twice as part of a comprehensive plan implemented in early 2013 to help deter the spread of the disease. However, spraying is only a measure to help limit exposure, and health workers urge people to maintain vigilance in protecting themselves when going outside.

When Spraying Occurs

Richardson schedules spraying events during overnight hours to limit exposure to people who may wish to avoid contact with the pesticide used to control mosquito populations. Spraying events begin at 9 p.m. and will end by 4 a.m. In order to minimize human exposure, the Health Department typically does not schedule spraying events on Friday or Saturday; however, an increase in findings of West Nile virus may cause the Richardson Health Department to spray on weekends as needed.

Spraying Is One Part Of The Protection Plan

Spraying to control the population of mosquitoes and the spread of the West Nile virus is a last resort, and is part of a comprehensive plan the Richardson Health Department follows to control the mosquito population. Other activities include: continuous monitoring of mosquito test pool results, implementation of a residential pool abatement program to reduce areas where mosquitoes can breed, surveillance and treatment of storm drains, use of larvicide and mosquito eating fish along creeks and other stagnant bodies of water to prevent mosquito eggs from developing into adults, monitoring and notification in neighborhoods where potential mosquito breeding areas are discovered, closer collaboration with regional health departments, and public education efforts through mass communications channels.

How To Protect Yourself

To protect from mosquito bites, people are asked to follow the Four D’s of protection:

  • · DRAIN standing water around the home,
  • · Use insect repellent containing DEET,
  • · Avoid being outdoors at DUSK and DAWN when mosquitoes are most active,
  • · And DRESS to protect yourself with long sleeves and pants to reduce skin exposure.

More On The West Nile Virus

The West Nile virus is transmitted by a bite from an infected mosquito that's already carrying the virus, but not all mosquitoes are capable of carrying or transmitting the disease. In North Texas, the risk of being bitten by an infected mosquito is greatest from July to October. Not everyone who gets bitten by an infected mosquito will get the virus, and it's rare for people to become very sick if they do develop symptoms from the disease.

Symptoms of West Nile virus vary depending upon the person who becomes infected. People who do develop symptoms usually suffer from mild "flu-like" illness. Rarely, symptoms may require medical care or hospitalization. The people who are most susceptible to the disease are the very young, the very old and those with weakened immune systems.

Story courtesy of the City of Richardson

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