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California takes a Proactive Approach to Managing Resistance Issues

Insecticide resistance is among the most challenging issues facing public health professionals, not only in California but around the world. As disease pressure increases, so does the number of interventions that government, businesses, and homeowners need to keep vectors at bay. For conventional adulticides such as pyrethroids and organophosphates, increased applications can result in mosquito populations that are resistant to the pesticides. This is especially true when applications and resistance are not being closely monitored.

It was only six years ago that indigenous species of Culex and West Nile virus (WNV) were the focus of California mosquito control programs. Since then, multiple invasive Aedes species have been discovered in counties all across the state, increasing the risk of diseases such as dengue, chikungunya, and now Zika virus.

While WNV remains the primary concern, these changing dynamics mean a more significant burden on California mosquito abatement districts (MADs) and the taxpayers who fund them. For most, adulticides are typically a last line of defense while an aggressive Larval Source Management strategy forms the foundation of the program. Homeowners and businesses (ag businesses and structural control pest operators, in particular) may still rely heavily on adulticides, however. And when adulticiding does become necessary, MADs can’t afford to use solutions that might not be effective.

Enter the California Surveillance Gateway, a program being coordinated by the California Department of Public Health. Grounded in epidemiological needs, the Gateway program provides centralized storage for virus detection and surveillance data along with rapid reporting. And with help from the University of California-Davis Arbovirus Research Program, the Mosquito and Vector Control Association of California (MVCAC), and some key districts, that Big Data approach will soon extend into the realm of resistance management.

“The state has recognized the significance of the resistance issue,” says Gary Goodman, Director of the Sacramento-Yolo Mosquito and Vector Control District. “With the help of the University system and coordination through others at MVCAC, we’re hopeful of bringing a new database online that will help track pesticide applications, monitor resistance, and help us make decisions based on the best data available.”

The innovative new database is called “Pesticide Application and Resistance Testing,” or PART. Using PART in tandem with Gateway will allow vector control officials to leverage localized transmission risk and product resistance status information and select optimal control options. Several districts are already conducting regular resistance monitoring and sharing results via an MVCAC survey. The same districts with experience in resistance monitoring are hosting workshops to train other districts’ personnel to do the same—extending the reach of the dataset.

Placer County Mosquito and Vector Control District Manager and MVCAC Integrated Vector Management Committee Chair and board member Joel Buettner says the effort is a key component of a new “Statewide Resistance Guidance Document” being developed by MVCAC. The document is due to be voted on at the board’s next meeting. “Right now we’re working on standardizing the data structure to work with PART while we continue to gather data,” Buettner says. “At the same time, we want to get districts used to gathering resistance information and sharing what we have. It’s already been a useful tool, even in its raw form.”