NSERC Chair for

Women in Science & Engineering

Prairie Region

ICAN-WISE 2017 Feature

Sachi Villanueva

Sachi worked with her mentor Dr. Bernadette Ardelli from Brandon University on the molecular biology of the drug ivermectin in insect disease vectors. What effect does ivermectin have on the insect’s gene regulatory pathways, and how does this influence its capacity for infection?

Weeks 1-2

In my first two weeks, I have been reading literature about the mechanism of action of ivermectin. Understanding what receptors in an invertebrate are targeted by the drug will help in determining how the Colorado potato beetles, as pests, will be affected after their exposure to ivermectin. The goal of this project is to ultimately repurpose ivermectin as an effective insecticide.

Weeks 3-4

During this time, I have studied about the life stages of the beetle, as well as how to properly rear them. The picture above shows beetle larvae feeding on potato leaves enclosed in a small tent located in a controlled greenhouse. Once these larvae emerge as adults, adult beetles are fed with potato leaves treated with ivermectin. In the past two weeks, I have been using varied drug concentrations and observing the beetles after their first and repeated exposures to the drug to examine their relative conditions.

Weeks 5-6

I have designed a better protocol for the project based on my observations from the previous trials that used different ivermectin concentrations. The picture above shows preparation for the dilution of new ivermectin solutions for the next set of trials. The treatments range from low to high dosage of the drug in order to determine the rate of mortality of the beetles for each of the solutions.

Weeks 7-8

In the photo, I am putting tubes containing beetles into the freezer to store them at -80℃. Beetles are collected to be frozen at certain time points after their exposure to ivermectin for later analysis. One of the goals of my research project is to understand how the Colorado potato beetles respond at the molecular level to the drug at different concentrations.

Weeks 9-10

The photo shows a beetle that has fed on ivermectin treated leaf. My research project involves observing the behavior of beetles during the duration of the survivability assay. The observation helps in determining the appropriate time points for collecting the beetles. Each chosen time point will represent a snapshot of the beetle’s response to ivermectin at the molecular level.

Weeks 11-12

Here is a photo of myself holding a beaker containing starved beetles. In the process of repeating my experimental trials, I starved some beetles overnight to ensure they would feed on the ivermectin treated leaves the next day. Interestingly, the starved beetles responded differently than the non-starved beetles to the same concentration of ivermectin in terms of mortality rates. My research project is aiming to understand the different mechanisms of the molecular incidents that ivermectin induces in the Colorado potato beetles.

Weeks 13-14

In order to avoid inconsistency in the survivability assay results, I have found a new way of preparing my ivermectin dilutions. The photo above shows some potato leaves treated with ivermectin as the active ingredient, plus other chemicals that fully dissolve the drug in solution. With this approach, I am hoping to get consistent results to continue on with the gene expression profiling of the Colorado potato beetles’ response to ivermectin.

Weeks 15-16

The picture shows a tube containing beetles that received the “control” treatment before freezing them in liquid nitrogen and then stored in -80℃ freezer. This is the last step of the survivability assay. For the gene expression profiling, RNA sequencing will examine genome-wide expression changes to examine the gene regulatory pathways induced in the insect vector by ivermectin.

The difference in the changes in gene expression between the beetles that were not exposed to the drug or were exposed to the drug will account for the effect of ivermectin, in different concentrations, to the vector at the molecular level. My goal is met when I discovered that the “wonder drug” affects not only the pathogen or the host but also the insect vector, as most scientific studies on ivermectin are on its effects to the pathogen or the host.

This project is designed to explore the feasibility of the drug as an insecticide, specifically for the Colorado potato beetles since they have extraordinary detoxifying abilities that make them quite insensitive to insecticides. Additionally, most insecticides are harmful to humans, whereas ivermectin is safe and is used to treat parasitic infections in humans.