Survey of cases of tick-paralysis and the presence of the eastern paralysis tick, Ixodes holocyclus, and the southern paralysis tick, Ixodes cornuatus, in the Greater Melbourne Area

Year-round efficacy of a single treatment of fluralaner injectable suspension (Bravecto QuantumTM) against repeated infestations with Ixodes holocyclus in dogs

BACKGROUND

The longer the duration of protection of an acaricide against canine infestation with Ixodes holocyclus, the lower the risk of gaps in tick control programs that will place dogs at risk of potentially fatal tick-induced paralysis. Two studies investigated the duration of efficacy provided by a novel injectable suspension of fluralaner (Bravecto QuantumTM) against this tick species.

METHODS

In both studies, 20 clinically healthy dogs were randomized to an untreated control group or to a group treated once, on Day 0, with the injectable fluralaner suspension (15 mg/kg). Dogs were infested with up to 25 unfed adult female I. holocyclus ticks on Day -1, during Weeks 1 and 2, and then at intervals no greater than approximately 3 months for the 13 months following treatment. Ticks were assessed in situ at 24 and 48 h and assessed and removed at 72 h following treatment and each subsequent infestation. Efficacy was determined by comparing arithmetic mean live tick (attached or free) counts in the treated group with the control group.

RESULTS

The untreated control dogs maintained adequate infestations for efficacy evaluations at all assessment weeks, with mean tick counts ranging from 16.2 to 21.6 in Study 1 and 14.0 to 23.5 in Study 2. The efficacy of fluralaner injectable suspension against existing infestations, determined 72 h following treatment administration, was 64.1% in Study 1 and 42.7% in Study 2. Efficacy against post-treatment infestations in Study 1 ranged from 95.7 to 100% from Week 1 through Week 57; in Study 2 efficacy was 100% at every assessment from Week 1 through Week 57. No treatment-related adverse events were recorded in either study.

CONCLUSION

The injectable fluralaner suspension was highly effective against I. holocyclus infestations of dogs from one week through 13 months following a single treatment. By placing treatment with the veterinarian, killing ticks within 72 h of attachment, and providing a full year of protection, fluralaner injectable suspension can help facilitate owner compliance with tick control treatment recommendations, thus reducing the risk of canine tick paralysis.

Perception of Ticks and Tick-Borne Diseases Worldwide

In this comprehensive review study, we addressed the challenge posed by ticks and tick-borne diseases (TBDs) with growing incidence affecting human and animal health worldwide. Data and perspectives were collected from different countries and regions worldwide, including America, Europe, Africa, Asia, and Oceania. The results updated the current situation with ticks and TBD and how it is perceived by society with information bias and gaps. The study reinforces the importance of multidisciplinary and international collaborations to advance in the surveillance, communication and proposed future directions to address these challenges.

Two seasons of tick paralysis in Victoria yet one season in Queensland and New South Wales, Australia

We studied 22,840 cases of tick paralysis in dogs and cats that were attributable to infestation with the eastern paralysis tick, Ixodes holocyclus. We report that the mortality rates from the holocyclotoxins of the tick or from euthanasia due to complications arising from tick paralysis in dogs and cats were 10% and 8%, respectively. The distribution of cases of tick paralysis among the 52 weeks of 22 years (1999 to 2020, inclusive) in four regions along the eastern coast of Australia revealed much about how the life-cycle of this tick varied among regions. The four regions in our study were: (i) Cairns, Innisfail, and surrounding postcodes in Far North Queensland; (ii) South East Queensland; (iii) Northern Beaches of Sydney in New South Wales; and (iv) the Shire of East Gippsland in Victoria. We found that the season of tick paralysis started earlier in more northerly latitudes than in more southerly latitudes. We also found that Victoria has two seasons of tick paralysis, one from approximately the third week of February to the first week of May, and another from approximately the third week of September to the third week of December, whereas all of the other regions we studied in eastern Australia only had one season of tick paralysis. When we studied the two seasons of tick paralysis in Victoria, we found a statistically significant negative correlation between the number of cases of tick paralysis between the two seasons: the more cases in one season, the fewer the cases in the next season. One possible explanation for the negative correlation may be immunity to I. holocyclus acquired by dogs and cats in the first season.

Eight-month repellency and efficacy of an imidacloprid/flumethrin (Seresto® ) collar against the eastern paralysis tick (Ixodes holocyclus) on cats

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, placebo-controlled 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.

RESULTS

Efficacy 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.

Immunomic Investigation of Holocyclotoxins to Produce the First Protective Anti-Venom Vaccine Against the Australian Paralysis Tick, Ixodes holocyclus

Venom producing animals are ubiquitously disseminated among vertebrates and invertebrates such as fish, snakes, scorpions, spiders, and ticks. Of the ~890 tick species worldwide, 27 have been confirmed to cause paralysis in mammalian hosts. The Australian paralysis tick (Ixodes holocyclus) is the most potent paralyzing tick species known. It is an indigenous three host tick species that secretes potent neurotoxins known as holocyclotoxins (HTs). Holocyclotoxins cause a severe and harmful toxicosis leading to a rapid flaccid paralysis which can result in death of susceptible hosts such as dogs. Antivenins are generally polyclonal antibody treatments developed in sheep, horses or camels to administer following bites from venomous creatures. Currently, the methods to prevent or treat tick paralysis relies upon chemical acaricide preventative treatments or prompt removal of all ticks attached to the host followed by the administration of a commercial tick-antiserum (TAS) respectively. However, these methods have several drawbacks such as poor efficacies, non-standardized dosages, adverse effects and are expensive to administer. Recently the I. holocyclus tick transcriptome from salivary glands and viscera reported a large family of 19 holocyclotoxins at 38-99% peptide sequence identities. A pilot trial demonstrated that correct folding of holocyclotoxins is needed to induce protection from paralysis. The immunogenicity of the holocyclotoxins were measured using commercial tick antiserum selecting HT2, HT4, HT8 and HT11 for inclusion into the novel cocktail vaccine. A further 4 HTs (HT1, HT12, HT14 and HT17) were added to the cocktail vaccine to ensure that the sequence variation among the HT protein family was encompassed in the formulation. A second trial comparing the cocktail of 8 HTs to a placebo group demonstrated complete protection from tick challenge. Here we report the first successful anti-venom vaccine protecting dogs from tick paralysis.

Tick paralysis in Australian birds caused by Ixodes holocyclus

Tick paralysis is an uncommon cause of neuromuscular paralysis affecting 0.12% of wild birds presented to Currumbin Wildlife Sanctuary, Queensland, with a strong seasonal predilection towards spring and summer. Clinical signs and progression of paralysis showed similarities to companion animals and were consistent across 20 species. Tick location, number of engorged ticks and number of clinical signs did not affect the outcome; however, all mortalities occurred within 4 days of admission. Treatment with canine-derived tick antiserum resulted in clinical improvement within 24 h and a recovery rate of 73%. Average time to resolution of clinical signs was 4.3 days, with juvenile birds recovering more quickly than adults. The treatment and release of wild birds affected by tick paralysis are both achievable and rewarding, further research is required to establish treatment guidelines in birds.

Efficacy of combination products containing sarolaner, moxidectin and pyrantel (Simparica Trio™) or afoxolaner and milbemycin (NexGard Spectra®) against induced infestations of Ixodes holocyclus in dogs

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.