A group of 14 persons who live in an area of Australia endemic for the Australian paralysis tick, Ixodes holocyclus, and who were involved in regularly collecting and handling these ticks, was examined for antibodies to tick-transmitted bacterial pathogens. Five (36%) had antibodies to Coxiella burnetii, the causative agent of Q fever and three (21%) had antibodies to spotted fever group (SFG) rickettsiae (Rickettsia spp). None had antibodies to Ehrlichia, Anaplasma, Orientia, or Borrelia (Lymedisease) suggesting that they had not been exposed to these bacteria. A total of 149 I. holocyclus ticks were examined for the citrate synthase (gltA) gene of the SFG rickettsiae and the com1 gene of C. burnetii; 23 (15.4%) ticks were positive for Rickettsia spp. and 8 (5.6%) positive for Coxiella spp. Sequencing of fragments of the gltA gene and the 17 kDa antigen gene from a selection of the ticks showed 99% and 100% homology, respectively, to Rickettsia australis, the bacterium causing Queenslandtick typhus. Thus, it appears that persons bitten by I. holocyclus in NE NSW, Australia have an approximate one in six risk of being infected with R. australis. Risks of Q fever were also high in this region but this may have been due to exposure by aerosol from the environment rather than by tick bite. A subset of 74 I. holocyclus ticks were further examined for DNA from Borrelia spp., Anaplasma spp. and Ehrlichia spp. but none was positive. Some of these recognised human bacterial pathogens associated with ticks may not be present in this Australian tick species from northeastern New South Wales.

Repellency is a highly desirable attribute for an acaricide that protects dogs against the Australian paralysis tick (Ixodes holocyclus). A bite from a single tick of this species can be fatal and carries the risk of transmission of vector-borne diseases. A randomised, controlled study was conducted to confirm the repellency sensu stricto and sensu lato (expellency) of a 10 % imidacloprid/4.5 % flumethrin collar (Seresto ® , Bayer) on dogs, against artificial infestations of I. holocyclus. Based on a novel protocol, dogs treated with Seresto ® , or a placebo collar, were sedated and placed in infestation chambers for 1 h at varying time points up to 6 months after treatment. Ticks were released alongside the dogs, and allowed to approach and/or attach. Treating dogs with a Seresto ® collar resulted in significantly (p < 0.001) more residual ticks being found in the infestation chambers (repellency sensu stricto) compared to the placebo treated dogs for the 168-day duration of the study (range 67.5% to 90.2 %). Repellency sensu lato (expellency) was reflected in significantly (p <0.002) fewer ticks being found attached to treated dogs throughout the study. Comparative decrease in ticks attached exceeded 95 % for 84 days, when assessed after 6 h. When assessed after 24 h, there was a > 95 % comparative decrease in ticks attached until Day 84, > 90 % on Days 112 and 140 then > 95 % to Day 168. Efficacy (killing effect) of the Seresto ® collar based on total live tick counts was > 95 % 6 h after tick challenge throughout the 6 month study period. This study demonstrated the excellent repellency effect of the Seresto ® collar against I. holocyclus in dogs. S146Ectopar asitEs

Background: The Australian paralysis tick, Ixodes holocyclus, causes tick paralysis in dogs and cats in the eastern coastal regions of Australia. Prevention is the best option to protect dogs against this potentially fatal disease and sarolaner provides rapid and sustained efficacy against I. holocyclus. In this laboratory study, the efficacy of two combination endectocides containing sarolaner + moxidectin + pyrantel (Simparica Trio ™) and afoxolaner + milbemycin (NexGard Spectra ®) was evaluated against an artificial infestation of I. holocyclus. Methods: Twenty-four (n =24) foxhounds were randomly allocated to three treatment groups and artificially infested with 30 adult female viable ticks on Days − 1, 7, 14, 21, 28 and 35. On Day 0, dogs in each treatment group were treated with either Drontal ® (control group), Simparica Trio ™ at the label dose to provide minimum doses of sarolaner (1.2 mg/kg), moxidectin (24 µg/kg) and pyrantel (5 mg/kg) or NexGard Spectra ® to provide minimum doses of afoxolaner (2.5 mg/kg) and milbemycin (0.5 mg/kg). Live tick counts were performed at 48 and 72 hours after treatment and after each re-infestation on Days 7, 14, 21, 28 and 35. Efficacy was determined at each time point relative to counts for control dogs based on geometric means. Results: Against an existing infestation, efficacy of both Simparica Trio ™ and NexGard Spectra ® was 99.6% and 100% at 48 and 72 h time points, respectively (P = 1.000). Against subsequent weekly infestations, treatment with Simparica Trio ™ and NexGard Spectra ® resulted in efficacy of ≥ 97.7% and ≥ 95.5% (P ≥ 0.0911), respectively at the 48 h time point and at the 72 h time point, Simparica Trio ™ and NexGard Spectra ® resulted in efficacy of ≥ 99.0% and ≥ 98.4% (P ≥ 0.0511), respectively. There were no treatment-related adverse events in the study. Conclusions: Single doses of Simparica Trio ™ and NexGard Spectra ® were highly efficacious and provided comparable efficacy against the Australian paralysis tick, I. holocyclus for up to 35 days.

Objective The objective of this study was to determine the repellency and efficacy of a 10% imidacloprid/4.5% flumethrin (Seresto ® , Elanco) collar over an 8-month period against the eastern paralysis tick (Ixodes holocyclus) on cats.Methods Two non-blinded, open gender, randomised, placebocontrolled pen studies were conducted, with 26 cats enrolled in each study. Prior to inclusion, cats were immunised with I. holocyclus holocyclotoxin. Cats were treated on Day 0 with either an imidacloprid/flumethrin or placebo collar. Tick infestations with 20 unfed adult female eastern paralysis ticks commenced on Day 7, and were repeated monthly for 8 months. Repellency was determined by comparing the mean number of attached ticks on imidacloprid/flumethrin treated cats, to placebo collar treated cats at 6 and 24 h post infestation. Efficacy was determined by comparing the mean number of live ticks on imidacloprid/flumethrin collar treated cats to placebo collar treated cats at 72 h post infestation. ResultsEfficacy was 100% (P < 0.001) at 72 h, and repellency was greater than 96% (P < 0.001) at 24 h for every tick challenge in each of the two studies, from Day 7 to the final infestation at 8 months for imidacloprid/flumethrin collar treated cats.Conclusions In two pen studies, an imidacloprid/flumethrin collar controlled and repelled the eastern paralysis tick (I. holocyclus) on cats for 8-months. The marked repellency effect in addition to controlling tick paralysis would be beneficial in preventing tick bites and their sequelae.