Efficacy testing of several Ixodes ricinus tick repellents: different results with different assays.

In the European Union (EU), tick repellents for humans need to be registered and approved by the authorities in order to be marketed. As there are currently no specific technical guidelines for product evaluation, we compared 3 different test methods: the mechanical moving object bioassay (MOB), and 2 assays involving human volunteers. For the latter, procedures according to the U.S. Environmental Protection Agency (EPA) and the Stiftung Warentest (StiWa), a German consumer care organization, were used. Two repellents, Autan(®) (AU), based on 20% Picaridin [2-(2-hydroxyethyl)-1-piperidinecarboxylic acid-1-methylpropyl ester], and ZeckWeck (ZW), based on 12.5g/100g Citriodiol™ (main compound: p-menthane-3,8-diol) were tested with all 3 assays. Three repellents, Anti Brumm(®) naturelle, based on 20% Citriodiol™ (main compound: p-menthane-3,8-diol), G090141, based on 20% EBAAP (ethyl buthyl acetyl aminopropionate), and G090152, based on 10% decanoic acid (capric acid), which is contained in Zanzarin(®), were tested according to the EPA and the StiWa procedures. The EPA assay indicated a significantly higher repellency of the products AU and G090141 than the StiWa test, but no difference between assays could be detected for the remaining 3 products. Also the corresponding protection times were significantly longer (approximately 4h) when determined according to EPA versus to StiWa for 3 of the products, whilst the difference was insignificant for ZW and G090152. Additionally, significantly lower numbers of ticks initially walked onto the repellent-treated skin when tested according to EPA versus to StiWa in all products except ZW and G090152. Thus, the StiWa protocol appears to pose higher demands on a repellent than the EPA method. Contrary to expectation, the MOB showed the same or even lower product efficacy when compared to the EPA and StiWa tests. Particularly, the percentage of ticks clinging to repellent-treated filter paper was significantly higher than the proportion of ticks walking onto treated skin in the other assays. This could mean that in nature more ticks may probably cling to a human protected by a given repellent than the EPA or the StiWa assay might suggest. Nevertheless, the MOB produced results that are quite similar to the tests involving human volunteers.

Evidence for an increased geographical distribution of Dermacentor reticulatus in Germany and detection of Rickettsia sp. RpA4.

Two studies were performed to elucidate the current distribution of the tick Dermacentor reticulatus in Germany. In the first one in 2003, a total of 365 dogs from 171 sites in the states of Berlin and Brandenburg was screened for ticks, and the corresponding outdoor sites that the dogs usually visited were searched for host-seeking ticks by the flagging method. A total of 1155 ticks was removed from the dogs. The majority were Ixodes ricinus (88.5%), followed by D. reticulatus (9.1%) and I. hexagonus (2.4%). Altogether, 222 dogs carried I. ricinus (60.8%), 41 D. reticulatus (11.2%) and 15 I. hexagonus (4.1%) ticks. Based on scutal index determination, the removed I. ricinus and D. reticulatus had been feeding on the dogs for a mean of 4.0 and 4.5 days, respectively. The dogs infested with D. reticulatus lived at 26 different sites, all previously unknown as Dermacentor sites. Seven of the sites could be confirmed subsequently by flagging the vegetation for ticks. In the second study, a total of 721 deer was shot at 201 different sites from a total of 160 districts all over Germany during the autumn hunting season 2004. A total of 23 deer (3.2%) originating from 14 sites was infested with D. reticulatus. Hereby, significantly more red deer (Cervus elaphus elaphus) than roe deer (Capreolus capreolus) or fallow deer (Dama dama) harboured D. reticulatus ticks. Only two of the sites found had already been known as D. reticulatus areas, whereas all other sites in Brandenburg, Saxony Anhalt, Hesse and Bavaria had been unknown. The results of both studies show that D. reticulatus presently occurs at far more sites than previously known in Germany and thus most likely has expanded its range. Additionally, a total of 135 D. reticulatus removed from deer was screened for Babesia canis and Rickettsia sp. by PCR. A total of 31 D. reticulatus (23%) were positive for Rickettsia. Sequencing revealed in all cases 100% identity with the strain RpA4 that was first isolated from Rhipicephalus ticks in Russia.