Research: DEET and Repel protect against Zika carrier

Media release Wednesday 29 June 2016

Research confirms DEET and Repel insect repellents provide 100% protection against carrier of Zika

New Zealanders heading to the tropics for a mid-winter getaway can be assured of 100% protection against the carrier of the Zika virus, according to the results of independent research carried out into Repel Ultra, Repel Tropical-Strength and Repel Oil of Lemon Eucalyptus (OLE!) insect repellents.

The primary carrier of Zika, Dengue and Yellow Fever viruses, the Aedes aegypti mosquito, is an urban-based mosquito that is found in a growing number of countries commonly visited by kiwis including Fiji, Samoa, Tonga, Rarotonga and the Cook Islands.

Commissioned by the New Zealand-based manufacturer of the tested products, Skin Shield Products, the independent field trial was carried out by Professor Scott Ritchie and Dr Brian Johnson from The Edward Koch Foundation in Australia, to specifically test the effectiveness of the Repel products against the mosquito.

The trial confirmed that Repel Ultra, Repel Tropical-Strength and Repel OLE! insect repellents provide 100% protection against the Aedes aegypti mosquito.

General Manager of Skin Shield Products, Vanessa Bradley said the company wanted to put the products through the field-trial to reassure New Zealand travelers they would be protected against the Zika-virus carrying mosquito if they use Repel and follow the recommended application of the repellents.

“There has been a great deal of publicity around the Zika virus of late, much of it centering on infection transmitted via the Aedes aegypti mosquito. While our own research confirmed that people would be protected by applying our products, we felt it was important to commission independent research to provide complete confidence to kiwis travelling to higher-risk countries.”

The four-day field trial was conducted in Cairns in April this year by Professor Scott Ritchie and Dr Brian Johnson, in an environment mimicking the habitat of Aedes aegypti mosquitoes. Human testers were exposed to hundreds of Aedes aegypti mosquitoes resulting in three times the normal biting intensity experienced in the mosquitoes' natural habitat.

Before applying any insect repellent, the human testers recorded the number of mosquitoes landing on exposed skin over two minutes. On average they recorded between 19.4 and 55.9 successful mosquito landings.

Bradley said the testers subsequently applied Repel pump spray and gel stick products following the recommended application guidelines and recorded the number of mosquito landings over the next eight hours.

The field trial results concluded that the Repel Tropical Strength products (30% DEET, stick and spray applicator) matched their respective labelled effective times (up to eight hours protection), while the Repel Ultra (40% DEET, spray applicator) matched expectations (up to 10 hours protection).

Bradley said the trial also tested the 100% natural non-DEET insect repellent, Repel OLE!, which contains Oil of Lemon Eucalyptus.

“The report also found that Repel OLE! provided long-term repellency and would be a good alternative for DEET-sensitive individuals, providing 100% protection for almost seven hours - which is beyond expectation for a botanical product. This is the only natural insect repellent recognised as offering effective protection by the World Health Organisation (WHO) and the US Centre for Disease Control (CDC) [1].

“Participants who did not wear Repel protection would have been bitten between 238-318 times throughout the trial. For those wearing Repel the figure was zero,” she said.

Bradley says it is important that repellent is applied to all exposed skin.

“A thin layer should be applied all over the skin. A couple of swipes around your ankles is not going to do the job! Product should be applied to the skin and then rubbed in to ensure complete coverage,” she says.

“As mozzies can and do bite through clothing (including denim) it is important when travelling to an area where diseases can be contracted to treat your clothing as well as your skin. Permethrin is the best treatment for fabric. Long sleeves and long pants will increase your protection [2].

“Mozzies like dark colours – which makes it easier to hide, so wearing light colours also helps keep them away.”

ENDS

Evaluations of Repel DEET and Oil of Lemon Eucalyptus products against Aedes aegypti mosquitoes – the primary vector for Dengue, Yellow Fever and Zika viruses.

A report prepared for the Edward Koch Foundation, April 2016 by Professor Scott Richie PhD, and Dr Brian Johnson MSc, PhD.

The trial was conducted with human testers over four days in April 2016 in Cairns, Australia. A purpose-built environment mimicking the habitat favoured by Ae. Aegypti mosquitoes was used, with an average temperature of 30.1c and humidity of 66.7% during the trial period.

200 female mosquitoes were initially released into the test area, plus an additional 50 added at the start of each day to maintain a high biting intensity. The biting intensity was approximately three times the ‘natural’ biting intensity level for Ae. aegypti in their normal habitat.

Before applying any repellent to exposed skin, the human testers recorded an overall mean LR (Landing Rate*) of between 19.4 and 55.9 mosquito landings every 2 minutes.

The testers then applied Repel Pump Spray and Gel Stick products in accordance with the product’s recommended application guidelines and recorded the LR over the next 8 hours.

Results

Repel’s DEET products had zero landings, and were 100% effective and provided 100% protection for 8 hours. All DEET products provided exceptional repellency with no successful landings being recorded during the duration of the study.

Repel’s OLE product provided a CPT (Complete Protection Time) of 6.9 +/- 0.5 hours with 1 participant recording 100% protection after eight hours. The mean repellency of OLE! was 97.9% +/- 1/5% demonstrating an exceptionally high degree of repellency.

If the human testers had not worn Repel protection, they would have recorded between 238 and 318 successful landings of Ae. aegypti (possibly carrying Dengue, Yellow Fever and / or Zika viruses) in the eight hour time period. With Repel DEET-based products they had zero landings.

*LR (Landing Rate) = a mosquito lands on the skin of a tester for more than 3 seconds.

The conclusion of the report states:

“The results of the semi-field trials indicate that all of the Repel DEET-based repellents provided exceptional repellency against Ae. aegypti mosquitoes under high biting intensity. The Repel OLE! oil of lemon eucalyptus product also provided long-term repellency and would be a good alternative to DEET-sensitive individuals.

Overall, the repellency of all products tested was highly effective under extreme biting intensity (>30 attempts/2 min) for a mosquito species that often averages <10 mosquitoes/house (Codeço et al. 2015, Rodrigues et al. 2015).

The Repel Tropical Strength products (30% DEET, stick and spray applicator) matched their respective labelled effective times (up to 8 hrs protection), while the Repel Ultra (40% DEET, spray applicator) matched expectations (up to 10 hrs protection).

Although the Repel OLE! product was the only repellent to experience failure (3 mosquitoes landing), it performed above expectations for a botanical-based repellent and its CPT time matched its labelled protection time (up to 6 hrs protection). Based on these results, all four products tested would provide exceptional protection against Ae. aegypti mosquitoes.

[1]1 http://www.cdc.gov/chikungunya/pdfs/fs_mosquito_bite_prevention_travelers.pdf

[2] The Repel Permethrin Fabric Treatment Kit contains everything that is needed to treat clothing to provide complete protection against mosquito borne disease.

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