Field trial investigating the efficacy of a long-acting imidacloprid 10%/flumethrin 4.5% polymer matrix collar (Seresto®, Elanco) compared to monthly topical fipronil for the chemoprevention of canine tick-borne pathogens in Cambodia

Abstract

The tropical brown dog tick, Rhipicephalus linnaei, commonly infests canines in the tropics and is an important vector for disease-causing and sometimes lethal pathogens including Babesia spp., Ehrlichia canis, Hepatozoon canis and Anaplasma platys. In tropical climates ticks and their pathogens exert an extremely high infection pressure on unprotected dogs. To protect canines in such regions, effective acaricidal products possessing a speed of kill that blocks pathogen transmission is paramount. We conducted a 12-month community trial to compare the chemoprophylactic efficacy of two topical commercial acaricidal formulations: an imidacloprid 10% and flumethrin 4.5%, 8-month acting collar (Seresto®) against a monthly spot-on containing 12% w/v fipronil (Detick, Thailand). In a separate analysis, we used baseline data collected at the start of the trial to quantify tick-borne pathogen (TBP) infection status in dogs with a prior history of being administered a systemically-acting (isoxazoline) versus a topically-acting ectoparasiticide. We found that both topical products in the community trial demonstrated high efficacy at protecting dogs from ticks and TBP, with Seresto® demonstrating a moderate increase in protection at 3 (95% confidence interval (CI): 1-5) TBP-positive dogs per 100 dog-years at risk compared to 11 (95% CI: 4-26) TBP-positive dogs per 100 dog-years at risk for those on fipronil. Additionally, at baseline dogs treated with commercial systemic isoxazoline acaricides prior to the trial's commencement were 2.7 (95% CI: 0.5-15.0) times more likely to be TBP-positive compared to dogs that had been topically treated, highlighting such isoxazoline products as being less efficacious than topical products at preventing canine TBP acquisition in a tropical setting.

Keywords: Canine health; Chemoprevention; Fipronil; Seresto; Tick-borne pathogens; Topical ectoparasiticide.

Graphical abstract

Fig. 1

Experimental design for (i) baseline assessment where metadata collected were used to compare rate of tick-borne pathogen (TBP) positivity in canines treated with systemic, topical and no ectoparasiticides prior to the study’s commencement and (ii) prospective community trial comparing two topical ectoparasiticides (Seresto® and Detick) for prevention of TBP contraction.

Fig. 2

Error barplot showing crude (unadjusted) tick-borne pathogen (TBP) apparent prevalence estimates as assessed by qPCR for dogs treated with systemic, topical and no ectoparasiticide products, conditioned by environment (urban, rural). TBP prevalence is expressed as the number of TBP positive dogs per 100 dogs at risk. The error bars show the lower and upper bounds of the 95% confidence interval (CI) for the TBP prevalence estimates.

Fig. 3

Error barplot showing crude (unadjusted) apparent vector-borne pathogen (TBP) exposure prevalence estimates as assessed by serology for dogs treated with systemic, topical and no ectoparasiticide products, conditioned by environment (urban, rural). TBP prevalence is expressed as the number of TBP exposed dogs per 100 dogs at risk. The error bars show the lower and upper bounds of the 95% confidence interval (CI) for the TBP prevalence estimates.

Fig. 4

Error barplot showing the crude (unadjusted) tick-borne pathogen (TBP) incidence rate estimates, as assessed by qPCR, for dogs treated with CP (fipronil) and IVP (Seresto® collars), conditioned by environment (urban, rural). TBP incidence rate is expressed as the number of TBP positive dogs per 100 dog-years at risk. The error bars show the lower and upper bounds of the 95% confidence interval (CI) for the TBP incidence rate estimates.