Dynamics of distribution and efficacy of different spot-on permethrin formulations in dogs artificially infested with Dermacentor reticulatus

After six hours of exposure, a significant acaricidal efficacy (p < 0.001) could be observed in all treated groups over the whole duration of the study, regardless of which product was used. While the arithmetic mean of attached ticks was < 3 on Day 1, numbers increased over the course of the study to a mean of > 9 on Day 28. However, most of these ticks were dead even 28 days after treatment, as the mean of live attached ticks was still < 2. Significant differences could neither be found between the different permethrin spot-on formulations, nor between the two parts of the body (p > 0.05).All products were able to kill ticks within six hours following infestation from Day 1 to Day 28 after treatment. Additionally, no significant difference between the tick numbers on the back and the hind leg could be found at any time, which implies a homogenous distribution of permethrin over the body. The efficacy of all four products was comparable during the whole study period, showing that the different solvents do not significantly affect the dynamics of distribution.There are currently almost 900 known tick species, of which about 10% are parasites that can affect domestic and companion animals making them of focus in acaricidal control [1,2]. The importance of these arthropods arises especially from their role as vectors and parasites. Ticks are known to transmit viruses, bacteria, fungi, protozoa and nematodes, with every genus and species possessing its own specific germ flora. One of the most important ticks in companion animals is Dermacentor reticulatus, a three host tick from the family Ixodidae which is widely distributed across Europe. D. reticulatus has been found from southern France to central Germany [3-5], and from the United Kingdom to as far east as Central Asia [6]. D. reticulatus achieves its main significance from being a vector of Babesia canis, a protozoan piroplasmid that causes babesiosis in dogs [7,8]. Furthermore, D. reticulatus transmits Francisel