A randomized controlled trial of the efficacy of orally administered fluralaner (Bravecto™) against induced Ixodes holocyclus (Australian paralysis tick) infestations on dogs.

Petr Fisara,Maurice Webster

doi:10.1186/s13071-015-0864-8

Abstract

BackgroundIxodes holocyclus ticks are a frequently fatal threat to dogs in eastern Australia. These ticks secrete a neurotoxin that can produce an ascending paralysis after 72 h attachment that can lead to death in affected animals. Fluralaner is a potent systemic acaricide with immediate and persistent efficacy for tick control including evidence of 100% efficacy against Ixodes ricinus ticks within 72 h. This study investigated the potential for oral fluralaner administration to control I. holocyclus infestation and the subsequent risk of host paralysis.MethodsHealthy Foxhound and Foxhound cross dogs immunized against holocyclotoxin were randomly allocated to receive either a single fluralaner (at least 25 mg/kg) dose or no treatment. All dogs were penned individually and infested with 30 adult unfed female I. holocyclus 1 day before treatment and 14, 28, 42, 56, 70, 84, 112 and 140 days following treatment. Ticks were counted and assessed at 24, 48 and 72 h after the initial fluralaner treatment and after each subsequent infestation. Ticks were not removed at the 24 and 48 h assessments, but were removed after the 72 h assessments. On 112 and 140 days post treatment a new group of untreated control dogs was used.ResultsFluralaner treatment efficacy against I. holocyclus was 100% at 72 h post treatment. Following re-infestations the efficacy remained at 100% at the 72 h assessments for 115 days and reached 95.7% at 143 days. The differences between mean live tick counts on treatment and control groups were significant (P < 0.00l) at all assessment time points for 143 days following treatment.ConclusionsOral fluralaner treatment can prevent Australian paralysis tick infestations for at least 115 days.

Highlights

Ixodes holocyclus ticks are a frequently fatal threat to dogs in eastern Australia
An estimated 10,000 domestic dogs are affected by I. holocyclus annually in Australia [2]; a recent study found that toy breeds were most at risk of tick paralysis associated death [3]
A prospective survey conducted at 42 veterinary clinics along the eastern coast of Australia showed that only 14% of all dogs presented at veterinary clinics with tick paralysis were correctly treated with a prophylactic tick control agent

Summary

Methods

Twenty four healthy male and female dogs between 1.0 and 10.8 years old that had not been treated with an ectoparasiticide in the previous 60 days were immunized against holocyclotoxin, the tick paralysis toxin. The 20 dogs found to have the highest tick carrying capacity were randomly assigned to either the treatment or control groups using a randomized block design based on pre-treatment live tick counts. Generalized linear models for Poisson data using the logarithmic link function (loglinear modelling or regression, or Poisson regression) [19] was used to compare mean total live tick counts for dogs in control and treated groups at each post-treatment sampling occasion. This method produces an analysis of deviance, analogous to the analysis of variance for normally distributed data. In the generalized linear models method, the observed counts are analyzed and the mean-variance relation is used to link mean counts to the linear model on the logarithmic scale [20]

Results

Background

Results and discussion

Conclusions