The insecticide resistance bioassay is a critically important component of monitoring programs to detect resistance of mosquito vectors to commonly used insecticide active ingredients. Manuals for conducting insecticide resistance bioassays with mosquito vectors have been produced by the World Health Organization (http://www.who.int/whopes/resistance/en/), and the U.S. Centers for Disease Control and Prevention has produced an online course for evaluating mosquitoes for insecticide resistance (http://www.cdc.gov/ncidod/wbt/resistance/toc.htm). However, we noted that a user–friendly software application to generate dose and time response curves based on data from insecticide resistance bioassays was lacking. We therefore proceeded to develop such an application, called Qcal.

Qcal was developed specifically for calculation of dose and time response curves in insecticide resistance bioassays. The application uses a logistic regression model to generate values for Lethal Dose/Knockdown Dose (LD/KD) or Lethal Time/Knockdown Time (LT/KT) based on data from a bioassay entered into the Qcal user interface. We use the combined language for lethal/knockdown because the same mosquito species may exhibit knockdown for some insecticide active ingredients but be killed by others and the active ingredient is not specified in Qcal.

Standard Qcal outputs include values for LD₅₀/KD₅₀ and LD₉₀/KD₉₀ or LT₅₀/KT₅₀ and LT₉₀/KT₉₀, and Qcal also has an advanced option to obtain values for other custom LD/KD or LT/KT percentages.

The results for the logistic regression model calculations are shown in a graph, and a text box under the graph provides statistical details for the model (Estimate, Standard Error, z–value and p–value) and values for LD₅₀/KD₅₀ and LD₉₀/KD₉₀ or LT₅₀/KT₅₀ and LT₉₀/KT₉₀ (Log value, Back–transformed value from the log value, Lower Limit for 95% confidence interval and Upper Limit for 95% confidence interval).

Regression model outputs can be saved to an xls. spreadsheet by clicking a "Save to Excel" icon.

Qcal is licensed under the GNU General Public License (http://www.gnu.org/licenses/gpl.html), which is a free, copyleft license for software and other kinds of works.

For feedback or questions, please contact Saul Lozano-Fuentes: slozano@colostate.edu

Funding to develop Qcal was provided by the Innovative Vector Control Consortium (http://www.ivcc.com/).