Comparative Study Of Exotic Tick Species For Human Repellent Registration

There are detailed requirements for the registration of anti-tick products in Europe, e.g. when tested on humans, the tick must leave the treated skin within ≤ 1 minute or move a distance < 3 cm within a 3-minute test period. However, there are large differences between the species and, in particular, adult ticks are not repelled as effectively as the nymphs. If a product is claimed for use in tropical areas, Hyalomma marginatum (vector of e.g. Crimean-Congo haemorrhagic fever virus) or Amblyomma variegatum should also be tested according to EU guidelines (A. americanum for registration in North America). Against these two tick species, we tested the repellency of three active ingredients (A.I.) (DEET, Icaridin and Eukalyptus citriodora oil) commonly used in repellents against arthropod vectors worldwide. 20% ethanolic solutions of the A.I. were tested on either a temperature-controlled surface (in vitro) or on human forearms (in vivo). The results show that a walking distance of 3 cm is not sufficient as a repellent criterion. Adult ticks can cover distances of over 10 cm of the treated surface in a short time, before dropping off.