Determining the Complete Protection Time of an Insect Repellent With 30% Citriodiol® Against Three Species of Ticks.

This is a single group trial with the participants acting as their own controls. The study is split into two parts; the first to determine a typical consumer dose when applied to repel ticks, and the second to evaluate the longevity of that consumer dose against three tick species.

To determine the typical consumer dose, twenty-five volunteers will be required to apply the repellent product from final consumer ready pump spray bottle to their forearm. Each volunteer will be asked to read the label and apply the repellent according to the instructions to their forearm. They will repeat the application three times. The amount applied by each subject across the three applications will be averaged, and then the average amount applied by each subject will be averaged to arrive at a "typical consumer dose". This typical consumer dose will be used as the application rate for the tick repellent efficacy trial. Three species are required by the EPA to demonstrate the effectiveness of a repellent. The following tick species have been chosen from the list of five species recommended by the EPA.

Ixodes scapularis - Also known as blacklegged ticks or deer ticks, this species is one of the principal vectors of Lyme disease. They are found in eastern and northern Midwest of the United States. The lifecycle takes approximately two years during which the tick develops from egg to larva, to nymph and finally adult. Larvae, nymphs and adults will all blood feed. Larvae usually feed from smaller mammals and birds, whilst nymphs and adults feed on larger mammals such as deer and humans.

Amblyomma americanum - The Lone Star Tick is found in the eastern United States and in Mexico. This species of hard tick can be a vector of human ehrlichiosis, tularaemia, and may trigger an allergy to the carbohydrate alpha gal found in mammalian meat.

Dermacentor variabilis - The American dog tick is usually found in central and eastern areas of the United States. Adults preferentially feed on large mammals such as dogs and humans, however immature stages will also feed on humans if the opportunity arises. They are the most common vector of Rocky Mountain spotted fever, and can also transmit tularaemia.

Rhipicephalus sanguineus - The brown dog tick is distributed worldwide, including across the United States. It is the vector of many pathogens, including Rickettsia rickettsia, the causative agent of Rocky Mountain spotted fever, Coxiella burnetii, causative agent of Q fever, Ehrlichia canis, and Rickettsia conorii. Dogs are the primary host for the brown dog tick in each of its life stages, but the tick may also bite humans or other mammals.

Ticks will be sourced from disease-free colonies at Oklahoma State University and housed at the London School of Hygiene \& Tropical Medicine, United Kingdom, under optimal environmental conditions of 25 ± 3 °C and greater than or equal to 80% Relative Humidity with a 16:8 hour photoperiod.

Single ticks will be exposed to participants' forearms following standardised treatment of one of the participant's forearms with repellent, in a laboratory setting. The treatment will be based on the dose derived from the dosimetry phase of the study, which will be submitted to EPA for review before proceeding to the repellency phase of testing. The treatment will be randomised to either the left or right arm of each participant for each test. There is no blinding employed since the outcome measures are based on tick behaviour. Twenty-five participants will be required for the consumer dose evaluation and to test the repellent against each of the tick species (preferably with a 50:50 ratio of males to females). Participants will test the product at a single dose against at least one of the three species.