If you’ve ever spent time on a farm, the morning routine likely involved feeding the animals and changing their water. My morning routine is quite similar, however, my animal buzzes and bites. The powerful wings, which can beat nearly a thousand times a second, and the sophisticated proboscis, which contains a sheath of six needles, belong to the mosquito. Before they get to the buzzing and biting stages, they progress through four larval stages. Once pupated, I am able to distinguish females from males. I keep the females and boil the males—quite satisfying. After the mosquitoes are sorted, they are fed. The growing larvae devour liver powder. The females slurp-up sugar water and the egg-laying females draw blood from a sedated rodent. But what is this strange and slightly perverse habit for? My name is Lia Beatty and I am a rising sophomore and an intended BBMB major with a passion for global health. This summer I have the privilege to be an undergraduate research assistant for the McDowell Laboratory at the University of Notre Dame in South Bend, Indiana.
For us, mosquitoes are a seasonal annoyance, but for much of the rest of the world, they are the vector for many deadly, infectious diseases. The Aedes aegypti mosquito, the species I am studying, transmits diseases including Chikungunya, Dengue fever, and Zika. Even though mosquito-borne diseases are not common in the states, the Ae. aegypti mosquito can be found here in our backyards. The main mode of action for treating these diseases has been controlling the mosquito-vectors with insecticides. The extensive and indiscriminate use of insecticides, however, has led to resistance in some mosquito populations. Often resistance to one type of insecticide confers resistance to another. Combinations of different insecticides with different modes of action have shown to be effective in overcoming insecticide cross-resistance. My work in the lab involves synergizing one type of insecticide with another. The efficacy of these insecticide combinations is determined with bioassays, which are one way to measure mortality in response to a stimulus. The McDowell Laboratory has synthesized a compound with novel modes of action, and my job is to exploit the synergy of this compound with other insecticides. If this synergy is found to be effective, it could suggest changes in current pest management programs.
After a morning of sorting and feeding, an innocent pot of larvae and a brave cage of mosquitoes make it out of the insectary for experimentation. I test third instar (larval stage) larvae using a contact-based assay. Using serially diluted nanomolar concentrations of compound, I delicately pipette larvae into the 12-well plate. After 24 hours, I record the mortality. The larval contact-assays are meticulous and satisfying, but the painstaking satisfaction of the adult injection-based assays easily out-match the larval assays.
About 5-7 days after the pupae emerge into adult mosquitoes, they are injected with nanoliter amounts of compound. Injections are like performing surgery; it is a timed task that demands assiduous precision. The first step is to transfer about twenty mosquitoes from their cage to the injection station and microscope. With my flashlight-sized vacuum in hand and my gloved-hand in their cage, I sneak up behind the mosquitoes and suck them into the enclosed chamber. From the chamber, I transfer them to the “operating table” which blows out CO2 to temporarily knock out the mosquitoes. From the time they are initially exposed to the CO2 I have five, but no more than six, minutes to perform twenty thoracic injections. If during the injections, they encounter the unfortunate circumstance of mechanical death, they must be omitted from the data. With an unsteady hand, mechanical death is easy to achieve. Although I inject the mosquitoes with a glass needle whose tip can only clearly be seen under at least 32x magnification, injections are invasive. A sharp needle for them would leave a handprint-sized wound on us. A blunt needle is akin to injecting them with a sledgehammer. Injections are a formidable task, but rewarding nonetheless.
My independence and experience has sparked my sense of wonder and encouraged a depth of inquiry, both of which I am excited to continue sharing with–and learning from–others.
Experiences like Lia’s are made possible by the Whitman Internship Grant, which provides funding for students to participate in unpaid internships at both for-profit and non-profit organizations. To learn how you could secure a Whitman Internship Grant or host a Whitman intern at your organization, click here or contact Assistant Director for Internship Programs Victoria Wolff