The effectiveness of deet and phytochemical repellents in the prevention of head lice (Pediculus capitis) transmission

Canyon, Deon (2003) The effectiveness of deet and phytochemical repellents in the prevention of head lice (Pediculus capitis) transmission. In: Papers from Annual Queensland Health and Medical Scientific Meeting. pp. 1-20. From: Annual Queensland Health and Medical Scientific Meeting "Making It Better: Encouraging health research and innovation", 25 - 26 November 2003, Brisbane, QLD, Australia.

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Purpose of Study: With increasing global prevalence and awareness of pediculosis, the number of head lice repellents and preventatives has increased dramatically without quality assurance or control. Synthetic chemicals require scrutiny before they reach the market, however, phytochemicals are not covered by USEPA legislation and require no testing. This study compares the efficacy of several phytochemicals against DEET and lubricant controls to determine their efficacy in preventing head lice infestations.

Methods: The efficacy of 10 repellents was assessed in 3 experiments. Experiment 1 investigated the likelihood that a louse would transfer from an untreated hair onto a passing hair (26 reps). Experiment 2 investigated irritancy in terms of tropotaxis, klinokinesis and orthokinesis (20 reps). This involved placing lice on the center of a hair that was coated in repellent on both ends. Experiment 3 investigated repellent and antifeedant properties of repellents applied to human skin. Adult lice (610) recently harvested from school children and maintained on blood were used.

Results & Discussion: Chi-square exact tests showed overall models in all experiments were significant (p<0.01). In Experiment 1, application of repellent to hair inhibited lice transfer by 35-65% with lubrication responsible for 40%. In Experiment 2, tropotaxis in response to repellent treated hair was minimal except to coconut oil. Orthokinesis and klinokinesis were similar for most repellents with coconut, neem and scalp oil performing well. In Experiment 3, most repellents applied on skin did not inhibit louse movement with most lice remaining on treated skin and bloodfeeding. Tea tree oil was the most effective repelling 55%. Less effective repellents were Lavender, Scalp Oil, Coconut, DEET Peppermint (10-35%).

Side-effect - dispersal Lice are thought to use activity-related human hosts as “rooms in their house” rather than to prefer a particular host (Speare and Canyon, unpublished). Repellents can shorten the residency period and increase dispersal within the “room” or between “rooms”.

Antifeedant Efficacy: Will lice bloodfeed in the presence of a repellent? Most repellents were not effective with most lice bloodfeeding. Some inhibition of feeding was caused by lavender (35%) tea tree (25%) and neem/citronella (5%)

All the so-called repellents tested failed to act as repellents in any significant degree.

Several phytochemical oils outperformed DEET in every experiment indicating some promise.

Future research will focus on discovery of novel phytochemical repellents.

Item ID: 9373
Item Type: Conference Item (Presentation)
Date Deposited: 19 Aug 2010 03:14
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111705 Environmental and Occupational Health and Safety @ 100%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920405 Environmental Health @ 100%
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