Investigative study into whether an insect repellent has virucidal activity against SARS-CoV-2

Abstract

A small-scale study with Mosi-guard Natural spray, an insect repellent containing Citriodiol, was performed to determine if it has virucidal activity against SARS-CoV-2. A liquid test examined the activity of the insect repellent and the individual components for virucidal activity. A surface contact test looked at the activity of the insect repellent when impregnated on a latex surface as a synthetic skin for potential topical prophylactic application. Both Mosi-guard Natural spray and Citriodiol, as well as other components of the repellent, had virucidal activity in the liquid contact test. On a latex surface used to simulate treated skin, the titre of SARS-CoV-2 was less over time on the Mosi-guard Natural-treated surface but virus was still recovered.

Keywords: Citriodiol; SARS-CoV-2; anti-viral activity; insect repellent; skin.

Fig. 1.

Virucidal activity of Mosi-guard Natural spray and its components. (a) In a standard measure of virucidal activity, SARS-CoV-2 was mixed 1 : 1 with Mosi-guard Natural spray, Citriodiol, ethanol, isopropanol or a combination of ethanol and isopropanol to give final concentrations as indicated on the x-axis. Viral titres of SARS-CoV-2 recovered after 1 min contact time are shown. (b) To measure Mosi-guard Natural spray at close to neat, concentrated SARS-CoV-2 was mixed 1 : 10 with Mosi-guard Natural spray to give a final concentration of 90 % (v/v). For both (a, b) each replicate is shown with a solid line at the geometric mean and error bars representing +/-sem. The dotted line at 10 TCID₅₀ ml⁻¹ is the limit of quantification of the assay. The number above each set of data points is the log₁₀ reduction in viral titre observed.

Fig. 2.

Change in viral titre over time on Mosi-guard Natural-treated or untreated surfaces. Latex synthetic skin discs (a, circles) or a polystyrene 24-well plate (b, squares) were treated with Mosi-guard Natural (filled shapes, solid lines) or left untreated (open shapes, dashed line). SARS-CoV-2 was added and recovered at various time-points. TCID₅₀ counts were log₁₀-transformed and linear regression performed. For both (a) and (b) each point represents the geometric mean of three replicate samples each assayed in duplicate with error bars representing +/-sem. The dotted line at 1 log₁₀ TCID₅₀ is the limit of quantification of the assay.