Thad Allen Post 1

I recently began graduate school with the Saarman lab at USU. Working with SLCMAD this summer has provided me with invaluable background knowledge in mosquito biology and mosquito control methods. I've done a woeful job taking pictures of the day-to-day operational activities I've participated in, so first I'll describe the research project I'm working on this summer. 

L. sphaericus bacteria produce a toxin that is highly effective against Culex genus mosquitoes, the main vector of West Nile Virus in North America, with very little impact on non-target species. However, SLCMAD has had to stop using this product because the local C. pipiens population developed resistance several years ago.

I am attempting to collect Culex pipiens larvae that are resistant to a bacterial larvicide, Lysinibacillus sphaericus, for future genomic analysis. I am setting out pans of "stinky water" to lure female C. pipiens to lay eggs. Then, I hatch these eggs in the lab and expose the larvae to L. sphaericus once they. Individual larvae are considered "resistant" if they survive the exposure assay, and I consider an egg raft to have resistance if it contained 1 or more "resistant" larvae. This process, from placing the bin to performing the exposure assay, takes about a week. So far I've collected and reared 53 egg rafts and found resistance in 6 of them. I have another 13 egg rafts cooking in the lab as we speak. 

Interestingly, I've only observed resistance in the southwest corner of SLC. While we expected resistance in this area, I was surprised to find 0 resistant larvae anywhere else in the city. My study has been designed primarily to generate resistant samples for genomic analysis, not to canvas the city evenly for resistance, so this finding should be taken with a grain of salt. While it is alarming to see such high rates of resistance in certain locations (3/8 egg rafts from one location), it is reassuring that the resistance appears to be localized right now. In the past, resistance was much more geographically widespread. Another interesting pattern is that only a few larvae in a given "resistant" raft typically survive the assay. Eight or less individuals out of an entire egg raft (100+ larvae) survived the assay in 5 of the 6 resistant egg rafts.