2020 Mosquito and Vector Control Association of California Annual Meeting

On January 26-29, the Mosquito and Vector Control Association of California (MVCAC) held their annual meeting in San Diego. District laboratory staff presented on some of the projects they conducted during the previous year.

The SMCMVCD Laboratory presented three scientific posters at MVCAC:

“Field Evaluation of Mosquito Gravid Trap Bait Solutions” Mosquitoes that are ready to lay eggs (gravid) are the most likely to be infected with West Nile virus. Throughout the United States, gravid traps are used to collect these mosquitoes but every agency seems to use a different bait formula (a “gravid broth”) to attract them. District vector ecologists Tina Sebay and Theresa Shelton obtained recipes for many different “broths,” and evaluated them in the field to see if any of them worked better. They found that location and time of year were much more important in collecting gravid mosquitoes and that no single bait formula clearly outperformed the others.


“Diversity and Distribution of Borreliae across San Mateo County, 2018-2019” While many people are aware of Lyme disease, few people know that the bacteria that causes Lyme is actually part of a complex of many different bacteria strains – not all of which can cause disease. The test used by most vector control agencies to detect bacteria in ticks cannot tell the difference between all of these strains. Laboratory intern Arielle Crews tested San Mateo County’s tick bacteria samples using a specific PCR assay in order to see how many were Lyme-causing and how many were other strains. She found that, while the Lyme complex is found in less than 2% of ticks in San Mateo County, only 34% of those positive ticks are carrying Lyme disease-causing bacteria.  This confirms that Lyme-causing bacteria are carried by a very small overall percentage of ticks in San Mateo County.


“The Identification of Mysteri-eggs Using Conventional PCR with Extraction Protocol Recommendations.” With the looming threat of Aedes aegypti invading San Mateo County, vector ecologist Tara Roth and laboratory intern Arielle Crews developed a PCR-based assay technique that will allow the laboratory to identify suspicious mosquito eggs or damaged mosquito specimens in just days. This means that, should Ae. aegypti return to our county, we will have the best possible chance to identify it early and eliminate it before it has a chance to spread.

An additional talk was presented by San Francisco State University graduate student Kacie Ring, “Determination of LC-50 of permethrin acaricide in the western blacklegged tick.”  Kacie worked in collaboration with the District to experimentally expose nymphal ticks to a range of concentrations of permethrin in a laboratory setting.  Permethrin is often used to protect people from tick exposure by applying it to clothing.  Ticks exposed to permethrin treated clothes are killed before they can attach to the person and transmit disease.  Her work was made possible by a grant from the Pacific Southwest Center of Excellence in Vector-Borne Diseases.