Dr, R, Pfleger GmbH, 96045 Bamberg, Germany.
Parasit Vectors. 2008 Apr 8;1(1):8. doi: 10.1186/1756-3305-1-8.
Ticks of the species Ixodes ricinus are the main vectors of Lyme Borreliosis and Tick-borne Encephalitis - two rapidly emerging diseases in Europe. Repellents provide a practical means of protection against tick bites and can therefore minimize the transmission of tick-borne diseases. We developed and tested seven different dodecanoic acid (DDA)-formulations for their efficacy in repelling host-seeking nymphs of I. ricinus by laboratory screening. The ultimately selected formulation was then used for comparative investigations of commercially available tick repellents in humans.
Laboratory screening tests were performed using the Moving-object (MO) bioassay. All test formulations contained 10% of the naturally occurring active substance DDA and differed only in terms of the quantitative and qualitative composition of inactive ingredients and fragrances. The test procedure used in the human bioassays is a modification of an assay described by the U.S. Environmental Protection Agency and recommended for regulatory affairs. Repellency was computed using the equation: R = 100 - NR/N x 100, where NR is the number of non-repelled ticks, and N is the respective number of control ticks. All investigations were conducted in a controlled laboratory environment offering standardized test conditions.
All test formulations strongly repelled nymphs of I. ricinus (100-81% protection) as shown by the MO-bioassay. The majority of ticks dropped off the treated surface of the heated rotating drum that served as the attractant (1 mg/cm2 repellent applied). The 10% DDA-based formulation, that produced the best results in laboratory screening, was as effective as the coconut oil-based reference product. The mean protection time of both preparations was generally similar and averaged 8 hours.Repellency investigations in humans showed that the most effective 10% DDA-based formulation (~1.67 mg/cm2 applied) strongly avoided the attachment of I. ricinus nymphs and adults for at least 6 hours. The test repellent always provided protection (83-63%) against I. ricinus nymphs equivalent to the natural coconut oil based reference product and a better protection (88-75%) against adult ticks than the synthetic Icaridin-containing reference repellent.
We found that the 10% DDA-based formulation (ContraZeck(R)) is an easily applied and very effective natural repellent against I. ricinus ticks. By reducing the human-vector contact the product minimises the risk of transmission of tick-borne diseases in humans.
蓖麻蜱是莱姆病和蜱传脑炎的主要传播媒介，这两种疾病在欧洲迅速出现。驱避剂为防止蜱叮咬提供了一种实用的手段，因此可以最大限度地减少蜱传疾病的传播。我们通过实验室筛选，开发并测试了七种不同的十二烷酸（DDA）制剂对引诱宿主的蓖麻蜱若虫的功效。最终选择的制剂随后用于比较研究市售的驱避剂在人类中的效果。
使用移动目标（MO）生物测定法进行实验室筛选测试。所有测试制剂均含有 10%的天然存在的活性物质 DDA，仅在惰性成分和香料的定量和定性组成上有所不同。在人体生物测定中使用的测试程序是美国环境保护署（U.S. Environmental Protection Agency）描述的一种方法的修改版，该方法推荐用于监管事务。驱避率通过以下公式计算：R = 100-NR/N x 100，其中 NR 是未被驱避的蜱的数量，N 是相应的对照蜱的数量。所有研究均在提供标准化测试条件的受控实验室环境中进行。
MO 生物测定显示，所有测试制剂均能强烈驱避蓖麻蜱若虫（100-81%的保护率）。大多数蜱虫从用作引诱剂的加热旋转鼓的处理表面上掉落（每平方厘米 1 毫克驱虫剂的应用）。在实验室筛选中表现最好的 10% DDA 制剂与基于椰子油的参考产品一样有效。两种制剂的平均保护时间大致相似，平均为 8 小时。人体驱避效果研究表明，最有效的 10% DDA 制剂（应用约 1.67 毫克/平方厘米）能强烈避免蓖麻蜱若虫和成虫的附着，至少持续 6 小时。测试驱避剂始终能提供对蓖麻蜱若虫的保护（83-63%），与天然椰子油基参考产品相当，对成年蜱的保护（88-75%）优于含有合成伊卡瑞丁的参考驱避剂。
我们发现，10% DDA 制剂（ContraZeck（R））是一种易于应用且非常有效的天然驱避剂，可有效防治蓖麻蜱。通过减少人与媒介的接触，该产品最大限度地降低了人类感染蜱传疾病的风险。
