A traditional-style snap trap used
to kill a rat or mouse.
Important guidelines for success

So far this year, a record number of residents have requested rat and mouse inspections  at their homes, exceeding the District's 22-year average.

With cooler weather on the way, that trend isn't likely to change. Weather extremes typically drive rodents indoors. 

Fortunately, residents can be proactive to keep each home and property rat and mice-free. One option stands out above the other.

"As a  public health agency ,  we recommend homeowners consider using snap traps before using bait to reduce the risk of unintended or secondary poisoning to other animals," said District Program Supervisor Jonathan Rehana. 

Here are a few guidelines for both options:

Snap Traps
    1. Read and follow trap instructions.
    2. Remove dead rats and mice from the traps daily.
    3. Traps are easily set and reusable. Be sure to use the proper size for either rats or mice.
    4. Snap traps are best used indoors and out of reach of children or pets.
    5. For outdoor use, place a box with a small hole on each side over the snap trap to reduce the risk of injury to non-target animals
    1. Read and follow product instructions.
    2. Rat poison, which is also referred to as bait, should be secured inside a tamper-resistant bait station to prevent non-targeted animals from exposure.
    3. Bait stations should be placed outdoors.
    4. Check bait stations on a weekly basis and replenish with bait as necessary.
Certain baits that contain rodenticides (poisons designed to kill rodents) can poison non-targeted animals such as birds and mammals when they eat the rodenticides directly or when they eat already poisoned rodents. This is known as secondary poisoning. 

Not all rodenticides cause secondary poisoning, but many can.  Before placing rodenticides, consider the potential impact on non-target animals.

The District's Rats & Mice Program uses products designed to protect public health while minimizing the risk of secondary poisoning. All products are registered with the EPA and are applied by trained and certified vector control technicians.

For more information on rat and mouse prevention and control  or to request a District inspection,  visit our website


Dead bird reports aid in West Nile virus prevention

Contra Costa County residents reported 649 dead birds to the state hotline in 2017 so far, ranking the county third among all counties in California to report dead birds.

Of those reported 43 birds were tested and 19 of them, or 44 percent, tested positive for West Nile virus.

Sacramento County and Los Angeles County ranked #1 and #2, respectively, at 901 birds reported (86 virus-positive or 24%) and 819 (93 virus-positive or 64%). For a complete list of dead bird reports made year-to-date and statewide, click here.

Not all dead birds are candidates for testing. For example, birds that died due to obvious non-illness related causes such as being mauled by an animal or hit by a car, those dead too long to be tested (often depicted by an ant invasion), or species that are less susceptible to the virus in the first place are not picked up for testing.

In any case, all reports, regardless of their candidacy for testing, offer crucial information for our mosquito surveillance and control efforts. Mosquitoes get the virus by biting infected birds and then biting people. In short, the reports help us to pinpoint hot spots of West Nile virus activity so we can control the mosquitoes responsible for disease transmission.

We are thrilled that our residents understand the seriousness of West Nile virus and that they work collaboratively with us to reduce the risk of the disease. 

***THANK YOU for reporting dead birds.***

Although the Dead Bird telephone Hotline is closed for the season at this time, we encourage the public to continue to file reports online throughout the year. 

Community Affairs Representative Andrew Pierce illustrates using a Mosquito Dunk to control mosquitoes at his home's outdoor drain.

Hidden water source just needs a proper dunk to be mosquito free
It's hard enough to control mosquitoes in areas of our home we expect to see them. An even bigger threat are those water sources that breed mosquitoes on the sly--out of view. 

In this In a Minute episode, the District's Community Affairs Representative Andrew Pierce illustrates how the water system in his own yard can produce mosquitoes and the easy remedy to control them.
How To Get Automatic Adult Mosquito Spraying            Notifications & Breaking News

To learn when and where we are fogging for adult mosquitoes, sign up for our spray notifications. You can interact with the map and learn each and every street in our spray zone each time. 

Want breaking news such as when we find West Nile virus or other mosquito-borne diseases? Sign up for our automatic emails delivered right to you.  You choose which publications you wish to receive.
Rats, mice, dead birds---apt subjects for this Halloween month. Vectors can be, well, scary.

But knowledge and action are powerful forces to combat them. Be knowledgeable. Take action. And stay safe.
  • Wear mosquito repellent when trick-or-treating.
  • Bring pumpkins indoors so they don't attract insects and animals.
  • Report dead birds to the state's online hotline.
Be well.


  Deborah Bass
  Public Affairs Manager
  Contra Costa Mosquito & Vector Control


October 27, 2017
Follow us on Twitter
Contra Costa Mosquito & Vector Control