The Merced County Mosquito Abatement District conducts mosquito surveillance to monitor mosquito populations and detect disease activity early. Our laboratory team plays a critical role in protecting public health by collecting, identifying, and testing mosquitoes across the county.

 

How Our Surveillance Program Works

Our trained laboratory staff set and collect mosquito traps daily throughout Merced County. These traps help us understand what species are present, how populations are changing, and whether disease is circulating.

 

Encephalitis Virus Surveillance (EVS) Traps

EVS traps are used to monitor mosquitoes capable of transmitting West Nile virus.

• Traps are placed in strategic locations throughout the county
• Collected daily by our surveillance team
• Mosquitoes are brought back to the lab for processing

In the laboratory:

• Mosquitoes are sorted by species and sex
• Female mosquitoes of species capable of transmitting disease are separated
• These mosquitoes are grouped into samples
• Samples are sent to the DART Laboratory in Sacramento for testing

The results of this testing allow us to:

• Detect West Nile virus activity early
• Identify specific areas of increased risk
• Focus mosquito control treatments where they are needed most

 

 

Invasive Aedes Mosquito Traps

Invasive Aedes mosquitoes, such as Aedes aegypti, are aggressive day-biters that can spread diseases like dengue.

To monitor these mosquitoes:

• Traps are placed at residential properties with permission
• Traps are collected and checked daily
• Mosquito counts help us determine the extent of an infestation

This data allows us to:

• Identify neighborhoods with invasive mosquito activity
• Track how populations change over time
• Apply targeted treatments to reduce mosquito numbers

In the event of a travel-related dengue case:

• Additional trapping is conducted around the resident’s home
• Mosquitoes may be tested to assess local transmission risk
• Rapid response measures are implemented to prevent spread