Skip to main content
Download PDF

Evaluation of oral fluralaner (Bravecto®) for efficacy against nymphs of Amblyomma americanum and Rhipicephalus sanguineus (sensu lato)

Parasites & Vectors volume 13, Article number: 315 (2020) Cite this article

Abstract

Background

Amblyomma americanum and Rhipicephalus sanguineus (sensu lato) nymphs commonly feed on and transmit pathogens to dogs (Canis familiaris). Control of immature and adult tick life stages is necessary to fully protect animals. We evaluated efficacy of oral fluralaner (Bravecto®) against induced infestations with A. americanum and R. sanguineus (s.l.) nymphs on dogs in two experiments.

Methods

In each experiment, 10 dogs were administered oral fluralaner chewable tablets one time on Day 0 at a targeted minimum dose of 25 mg/kg body weight and 10 dogs remained non-treated controls. Dogs were infested with two groups of 50 A. americanum nymphs and two groups of 50 R. sanguineus (s.l.) nymphs on Days -1, 6, 28, 56 and 84. At 48 h and 72 h post-infestation, nymphs were collected from dogs, assessed as live or dead, and enumerated into categories defining attachment and engorgement status. Fluralaner efficacy was determined in separate analyses against all live nymphs and against live-fed nymphs, i.e. live nymphs that were attached to dogs at the time of collection and/or were engorged. Fluralaner was considered effective when mean numbers of live ticks were reduced in fluralaner-treated dogs by ≥ 90%.

Results

Fluralaner efficacy against all live and live-fed A. americanum nymphs in the first experiment was > 94% on all collection days. Efficacy against all live R. sanguineus (s.l.) nymphs in the first experiment was  > 96% on all collection days  excluding the 48 h counts for infestations on Days 28 (83.7%), 56 (82.9%) and 84 (86.7%); efficacy against live-fed R. sanguineus (s.l.) nymphs was > 95% on all 48 h/72 h count days. Fluralaner efficacy against all live A. americanum nymphs in the second experiment was > 93% on all collection days for 8 weeks excluding the 48 h count for infestation on Day 56 (87.8%); efficacy against live-fed A. americanum nymphs was > 91% on all count days for 8 weeks. Efficacy against all live R. sanguineus (s.l.) nymphs in the  second experiment was > 91% on all 72 h collection days  except for infestations on Days 28 (76.8%) and 56 (86.3%); efficacy against live-fed R. sanguineus (s.l.) nymphs was 100% on all 72 h count days.

Conclusions

A single administration of oral fluralaner to dogs is effective against A. americanum and R. sanguineus (s.l.) nymphs for up to 12 weeks.

Background

Deleterious effects of tick infestations on animals are numerous. Direct consequences as a result of tick feeding include anemia, dermal irritation, hypersensitivity, and toxicosis. Also, a variety of pathogenic agents are transmitted to animals by ticks during blood-meal acquisition, which may result in illness and death in infested hosts [1,2,3]. Control of immature stages as well as adults is important for complete protection of animals against tick infestations.

A tick species that feeds on a variety of animals and is well-documented on dogs (Canis familiaris) during larval, nymphal, and adult stages is Amblyomma americanum, the lone star tick [4,5,6]. Amblyomma americanum are known to transmit numerous infectious agents as nymphs and adults to dogs and humans including Ehrlichia chaffeensis and Ehrlichia ewingii [5,6,7,8]. Long suspected as a vector of Rickettsia rickettsii, A. americanum was recently experimentally demonstrated to transmit this pathogen to dogs as both nymphal and adult stages [9, 10]. Rhipicephalus sanguineus (sensu lato), commonly called brown dog ticks, are found worldwide and all instars preferentially feed on dogs [11]. Rhipicephalus sanguineus (s.l.) nymphs and adults transmit Anaplasma platys, Babesia spp., Ehrlichia canis, Hepatozoon canis and R. rickettsii [4, 11,12,13,14,15,16]. Infected R. sanguineus (s.l.) nymphs, in particular, were implicated in a R. rickettsii outbreak in Arizona in 2003 involving human fatalities; experimental data confirmed vector competence of immature stages of R. sanguineus (s.l.) [17,18,19].

Control of immature ticks on dogs as well as adult ticks is important in reducing infestations, decreasing risk of pathogen transmission, and limiting tick populations in the environment. In vivo trials determining acaricidal compound efficacy against immature A. americanum and R. sanguineus (s.l.) are lacking. The isoxazoline fluralaner is a systemic compound that exerts acaricidal and insecticidal activity by blocking gamma-aminobutyric acid (GABA)- and glutamate-gated chloride channels [20]. Oral fluralaner (Bravecto®) is indicated for the treatment and control of tick infestations on dogs, including A. americanum for 8 weeks and R. sanguineus (s.l.) for 12 weeks, as demonstrated using adult ticks in both laboratory experiments and field trials [20, 21]. Here, we present the results of two Good Clinical Practice (GCP) laboratory experiments evaluating the efficacy of oral fluralaner against A. americanum and R. sanguineus (s.l.) nymphs for 12 weeks after administration of the minimum commercial dose (25 mg/kg body weight).

Methods

The efficacy of 13.64% w/w fluralaner chewable tablets (Bravecto®, Merck Animal Health, Madison, New Jersey) against A. americanum and R. sanguineus (s.l.) nymphs was evaluated in two separate randomized, blinded laboratory experiments with parallel-group designs. Each experiment was conducted in compliance with Good Clinical Practice (GCP) guidelines (VICH GL9) [22] and the World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating parasiticide efficacy against flea and tick infestations on cats and dogs [23]. The duplicate experiments were conducted to document fluralaner efficacy against different genetic isolates of nymphal A. americanum and R. sanguineus (s.l.) to demonstrate the compound’s utility in the field against immatures of the species.

Twenty laboratory reared neutered male or intact female beagles, each at ≥ 6 months of age, were used in the two experiments. To reduce the total number of animals used between both experiments, 8 non-treated control dogs from the first experiment were transferred to the second experiment and re-used in control or treated groups along with 12 newly acquired, non-treated dogs. The dogs were initially weighed and physically examined to ensure overall health, and allowed an acclimation period of at least 28 days prior to experiment commencement. Dogs were housed individually or in pairs inside raised kennels with plastic-coated expanded metal floors in designated climate-controlled rooms provided a 12:12 h L:D cycle.

Amblyomma americanum were obtained from colonies maintained by Oklahoma State University (OSU) (Stillwater, Oklahoma) and Texas A&M University (College Station, Texas) and R. sanguineus (s.l.) were from colonies maintained by OSU and El-Labs (Soquel, California) [24]. In both experiments, dogs were infested with 50 R. sanguineus (s.l.) nymphs on Day-28 for treatment group allocation. For all infestations, the hair on the lateral thorax was clipped and nymphs were applied directly to shaved skin beneath bandage pads (Band-Aid®, Johnson & Johnson, New Brunswick, New Jersey, USA). Cotton stockinette (Stockinette, Medline, Mundelein, Illinois, USA) and elastic bandage wrap (Elastikon®, Johnson & Johnson, New Brunswick, New Jersey, USA) was used to further contain nymphs and facilitate later recovery and accurate counting. Elizabethan collars (Well & Good E-Collar, Petco, San Diego, California, USA) were placed on dogs as needed to prevent removal of the tick containment materials. When infested with ticks, dogs were housed individually in kennels. After each counting event, we discarded all ticks.

Rhipicephalus sanguineus (s.l.) nymphs applied on Day-28 were removed after 72 ± 4 h (Day-25) and enumerated into the following 8 categories indicating vitality, attachment, and engorgement status: live, attached and engorged; live, attached and not engorged; live, free and engorged; live, free and not engorged; dead, attached and engorged; dead, attached and not engorged; dead, free and engorged; dead, free and not engorged. On all sampling days, nymphs were collected using fine forceps and examined using a stereomicroscope. Live status of ticks was determined by movement of legs. If no movement was observed, nymphs were gently probed with forceps and stimulated with CO2 (exhaled air) to assess leg movement. Any tick exhibiting leg movement at the time of removal was considered as live. Nymphs were considered attached if mouthparts were partially to completely anchored within the canine dermis at the time of removal. Engorgement status of ticks was determined by inspecting the ventral idiosoma; nymphs that had ingested blood appeared distended and light brown in color while nymphs that had not fed were completely flat and dark in color. Numbers of live and dead nymphs were recorded according to attachment and engorgement status.

Dogs were ranked according to R. sanguineus (s.l.) live-fed nymph counts (i.e. live nymphs categorized as attached and engorged, attached and not engorged, and free and engorged) and animal identification number, then randomly assigned to treatment and control groups. After treatment group allocation, dogs were allowed to co-mingle with the other dogs of the same group. Observations and procedures after animals were randomized, including infestations, tick counts, and tick assessments, were performed by individuals masked to dog treatment status. Sterile gloves, surgical gowns, and shoe-covers were worn when treating and mock-treating dogs, infesting dogs with ticks, and collecting ticks from infested dogs to prevent product cross-contamination between animals. Experiment participants and personnel responsible for husbandry changed protective wear after handling each dog.

Dogs were treated or mock-treated on Day 0 according to assigned group. The number and size of 13.64% w/w fluralaner flavored chewable tablets was determined for each dog by body weight and the targeted minimum dose of 25 mg/kg. Animals were offered a small amount of food (~1/2 cup) and allowed 20 min to eat before treatment. The fluralaner dose was placed in the back of the dog’s oral cavity over the tongue to initiate swallowing. Animals were monitored for 1 h after fluralaner administration for adverse reactions and to ensure that doses were retained.

To evaluate fluralaner efficacy against nymphal A. americanum and R. sanguineus (s.l.), dogs were infested 20 ± 2 h prior to and 1 week (Day 6), 4 weeks (Day 28), 8 weeks (Day 56), and 12 weeks (Day 84) after treatment administration. At infestation, each dog was challenged with two groups of 50 A. americanum nymphs and two groups of 50 R. sanguineus (s.l.) nymphs unless otherwise stated in results. Groups of ticks were applied to separate caudal and cranial locations along the lateral thoraco-abdominal areas of dogs: left side (A. americanum); right side (R. sanguineus (s.l.)). Nymphs were collected from caudal locations 48 h after infestation and from cranial locations 72 h after infestation. At removal, nymphs were morphologically confirmed as A. americanum or R. sanguineus (s.l.) and enumerated into the aforementioned categories delineating vitality, attachment, and engorgement status.

Fluralaner efficacy assessment

SAS version 9.3 was used as the primary software for data analyses [21, 25]. Evaluations of fluralaner efficacy against each tick species were considered valid if the number of all live nymphs (attached and engorged, attached and not engorged, free and engorged, and free and not engorged) removed from individual dogs at each collection time was at least 12 ticks on at least 6 control dogs. The log-counts of all live nymphs from treated dogs were compared to the log-counts of all live nymphs from control dogs at each 48 h and 72 h post-infestation collection time. Additionally, the log-counts of live-fed nymphs (live nymphs that were attached to dogs at the time of collection and/or were engorged) from treated dogs were compared to live-fed nymphs from control dogs at each 48 h and 72 h post-infestation evaluation time. Enumerated live-fed nymphs were categorized as attached and engorged, attached and not engorged, and free and engorged (i.e. free and not engorged counts were excluded from the fluralaner efficacy evaluation). A linear mixed model which included treatment group as a fixed effect and block as a random effect was used for comparisons. In case of any zero count, the logarithm of (count + 1) transformation was applied to all observations prior to analysis [22, 25].

For both tick species, geometric means of all live nymphs and live-fed nymphs from each count day were calculated; t-tests were performed (P < 0.05). Fluralaner control efficacy (%) was calculated against all live and live-fed nymphs at both post-infestation collection times (48 h and 72 h) using Abbott’s formula [23]:

$${\text{Efficacy}}\;(\% ) = {\text{100 X }}({\text{M}}_{{\text{c}}} - {\text{M}}_{{\text{T}}} )/{\text{M}}_{{\text{c}}}$$

where Mc is the mean (geometric) live nymph count from the control group and MT is the mean (geometric) live nymph count from the fluralaner-treated group. Fluralaner efficacy against A. americanum and R. sanguineus (s.l.) nymphs was declared when live counts from treated dogs were reduced by ≥ 90% [23].

Results

All dogs accepted fluralaner readily and retained treatments in both experiments. Based on body weight at treatment, each dog received a single dose of 26–36 mg/kg fluralaner. No adverse events associated with treatment were observed. Two non-treated dogs in the first experiment developed localized inflammatory reactions associated with A. americanum attachment on Day 28; lesions on one dog resolved rapidly, but one dog had persistent dermal inflammation and was not infested with A. americanum on Days 56 and 84. In the second experiment, one dog developed a localized, inflammatory lesion associated with R. sanguineus (s.l.) attachment on Day-28 (prior to fluralaner administration). This dog was not infested with R. sanguineus (s.l.) at the caudal location (for 48 h count) on Days -1 and 7, but was infested at this location on subsequent dates.

Adequacy of infestation with A. americanum nymphs (at least 12 live ticks on at least 6 non-treated dogs) was achieved in both experiments for all 48 h and 72 h counts. Adequacy of infestation with R. sanguineus (s.l.) nymphs was achieved in the first experiment for all 48 h and 72 h counts and for all 72 h counts in the second experiment. Due in part to a bandage breach on some dogs, 48 h R. sanguineus (s.l.) nymph infestations were not adequate in the second experiment and these data were not included or interpreted. When live-fed nymphs were assessed, adequacy of infestation was not achieved for R. sanguineus (s.l.) in the first experiment at the 48 h count on infestation Day 56, and in the second experiment at 72 h counts on infestation Days 28, 56 and 84. Because infestation adequacy was achieved for all live R. sanguineus (s.l.) nymphs on these specific count days however, the corresponding live-fed nymph efficacy data are also reported.

Geometric means of A. americanum and R. sanguineus (s.l.) all live (L) nymph counts and live-fed (LF) nymph counts, statistical results, and calculated fluralaner efficacies (%) are presented in Tables 1, 2, 3, 4.

Table 1 Percent efficacy of fluralaner based on all live and live-fed Amblyomma americanum nymphs from control and treated dogs (Experiment 1). Each group had 10 dogs unless otherwise noted
Full size table
Table 2 Percent efficacy of fluralaner based on all live and live-fed Rhipicephalus sanguineus (sensu lato) nymphs from control and treated dogs (Experiment 1). Each group had 10 dogs
Full size table
Table 3 Percent efficacy of fluralaner based on all live and live-fed Amblyomma americanum nymphs from control and treated dogs (Experiment 2). Each group had 10 dogs
Full size table
Table 4 Percent efficacy of fluralaner based on all live and live-fed Rhipicephalus sanguineus (sensu lato) nymphs from control and treated dogs (Experiment 2). Each group had 10 dogs
Full size table

Experiment 1

All live and live-fed A. americanum nymph counts from fluralaner-treated dogs at 48 h and 72 h post-infestation were significantly lower (P < 0.001) than counts from control dogs for all tick challenge days. Fluralaner efficacy against all live and live-fed A. americanum nymphs was > 94% at 48 h and 72 h for all time points evaluated through infestation Day 84 (Table 1).

All live and live-fed R. sanguineus (s.l.) nymph counts from fluralaner-treated dogs at 48 h and 72 h post-infestation were significantly lower (P < 0.001) than counts from control dogs for all tick challenge days. Fluralaner efficacy against all live R. sanguineus (s.l.) nymphs at 48 h was variable and ranged from 82.9% to 97.7%, but was > 96% for all 72 h counts; fluralaner efficacy against live-fed R. sanguineus (s.l.) nymphs was > 95% at 48 h and 72 h counts for all tick challenge days through infestation Day 84 (Table 2).

Experiment 2

All live and live-fed A. americanum nymph counts from fluralaner treated dogs at 48 h and 72 h post-infestation were significantly lower (P ≤ 0.018) than counts from control dogs for all tick challenge days. Fluralaner efficacy against all live A. americanum nymphs was > 94% at 48 h and 72 h counts through infestation Day 28, was 87.8% (48 h) and 93.5% (72 h) on infestation Day 56, and was 68.3% (48 h) and 78.0% (72 h) on infestation Day 84; fluralaner efficacy against live-fed A. americanum nymphs was > 91% for all 48 h and 72 h counts through infestation Day 56, and was 70.6% (48 h) and 78.0% (72 h) on infestation Day 84 (Table 3).

All live and live-fed R. sanguineus (s.l.) nymph counts from fluralaner treated dogs at 72 h post-infestation were significantly lower (P ≤ 0.002) than counts from control dogs for all tick challenge days. Efficacy against all live R. sanguineus (s.l.) nymphs at 72 h post-infestation was 100% on Day -1, 94% on Day 6, 76.8% on Day 28, 86.3% on Day 56, and 91.9% on Day 84; fluralaner efficacy against live-fed R. sanguineus (s.l.) nymphs was 100% at all 72 h post-infestation counts for 12 weeks (Table 4).

Discussion

Although several compounds have been evaluated in vitro for efficacy against larval or nymphal stages of ticks [20, 26,27,28,29,30], reports of in vivo trials in dogs to determine efficacy against immature stages of ticks are sparse [25]. However, limited field trial data from dogs indicate efficacy [30]; data gleaned from in vivo experiments in other animals with other acaricides also indicate efficacy [25, 27]. Oral fluralaner (Bravecto®) is labeled for the treatment and control of A. americanum for 8 weeks and R. sanguineus (s.l.) for 12 weeks based on experiments using adult ticks [20, 21]. Although logical to deduce its efficacy against immature tick stages in the field, acaricidal activity of the systemic compound against nymphal A. americanum and R. sanguineus (s.l.) has not been experimentally demonstrated in vivo until now. Here, we document efficacy of oral fluralaner in dogs against nymphal A. americanum and R. sanguineus (s.l.) in two separate laboratory controlled experiments. Taken together, efficacy data against all live and live-fed ticks in both experiments demonstrated a single administration of oral fluralaner to dogs at the minimum approved dose was effective against A. americanum and R. sanguineus (s.l.) nymphs for as long as 12 weeks.

Lower than expected (< 90%) fluralaner efficacy against all live nymphs on some tick challenge days in both experiments could be due to several reasons, or combinations thereof. First, the live unengorged nymphs that were not attached to dogs but entrapped in bandage adhesive were enumerated as live, free and not engorged, and were included in counts of all live nymphs used for efficacy calculations. However, these nymphs apparently had not attached to dogs and thus had not ingested the fluralaner. Feeding is necessary for exposure of ticks to isoxazoline acaricides [20]. This is demonstrated by the fact that, with the exception of Day 86 counts for A. americanum in the second experiment, fluralaner efficacy was restored to ≥ 90% for both species on all count days when geometric means of live-fed nymphs were analyzed. Additionally, the 12-week efficacy maintained against live-fed A. americanum nymphs in the first trial suggests that immature A. americanum may be more susceptible to fluralaner than adults, as has been demonstrated for other tick species in in vitro experiments [20, 28].

Another explanation for the occasional decrease in fluralaner efficacy against all live counts on some sampling days in both experiments, as well as Day 86 live-fed A. americanum counts in the second experiment, is that cohorts of nymphs used for successive infestations may have taken longer to attach and feed. Thus, these nymphs would have ingested less fluralaner before collection at 48 h and 72 h, and the fluralaner would have had less time to exert its acaricidal effects on nymphs prior to their evaluation. Also, in Experiment 2, the 8 dogs transferred from the first experiment may have developed some level of immunity to infestation, which may have decreased efficiency of tick feeding [31] and potential fluralaner ingestion. Still, despite challenges leading to occasional reductions in fluralaner efficacy, overall data indicated that the compound was highly efficacious against A. americanum and R. sanguineus (s.l.) nymphs.

Control of immature ticks is necessary for complete protection of animals from tick infestations. Amblyomma americanum are aggressive and feed on a variety of animals during all instars [5]. Because of this generalist feeding behavior, A. americanum are exposed to a wide variety of pathogens during all instars and can successfully vector numerous infectious agents to dogs and humans [4, 5, 9]. Rhipicephalus sanguineus (s.l.), although less diverse in feeding behavior, are well known to establish thriving infestations surrounding and within kennels and homes; infestations with R. sanguineus (s.l.) instars can be difficult to mitigate once established [4]. If R. sanguineus (s.l.) are feeding on dogs that are infected with pathogenic agents, this creates a dangerous circumstance for other dogs and humans near or within infested environments [17, 19]. The experimental demonstration of long term in vivo acaricidal activity of oral fluralaner against nymphal A. americanum and R. sanguineus (s.l.) indicates the isoxazoline is an appropriate treatment for dogs infested with immature and adult stages of these tick species in the field.

Conclusions

Empirical evidence from two separate GCP-governed laboratory experiments presented here demonstrates that oral fluralaner (Bravecto®) is effective in controlling infestations on dogs with A. americanum and R. sanguineus (s.l.) nymphs for as long as 12 weeks, indicating the compound would be efficacious in the treatment of dogs naturally infested with immature stages of these tick species. Eliminating feeding nymphs and adults on dogs will lead to fewer tick instars developing in the environment that will subsequently go on to feed on new hosts, and thus would be expected to reduce the risk of pathogen transmission.

Availability of data and materials

The datasets generated and/or analyzed during the present experiments are not publicly available but are available from the corresponding author on reasonable request (upon permission from experiment sponsor).

References

  1. Boulanger N, Boyer P, Talagrand-Reboul E, Hansmann Y. Ticks and tick-borne diseases. Med Malar Infect. 2019;49:87–97.

    Article  CAS  Google Scholar 

  2. Sonenshine DE. Range of expansion of tick disease vectors in North America: implications for spread of tick-borne diseases. Int J Environ Res Public Health. 2018;15:478.

    Article  Google Scholar 

  3. Jongejan F, Uilenberg G. The global importance of ticks. Parasitology. 2004;129:S3–14.

    Article  Google Scholar 

  4. Dryden MW, Payne PA. Biology and control of ticks infesting dogs and cats in North America. Vet Ther. 2004;5:139–54.

    PubMed  Google Scholar 

  5. Childs JE, Paddock CD. The ascendancy of Amblyomma americanum as a vector of pathogens affecting humans in the United States. Annu Rev Entomol. 2003;48:307–37.

    Article  CAS  Google Scholar 

  6. Koch HG. Seasonal incidence and attachment of ticks (Acari: Ixodidae) on domestic dogs in southeastern Oklahoma and northwestern Arkansas, USA. J Med Entomol. 1892;19:293–8.

    Article  Google Scholar 

  7. Ewing SA, Dawson JE, Kocan AA, Barker RW, Warner CK, Panciera RJ, et al. Experimental transmission of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae). J Med Entomol. 1995;32:368–74.

    Article  CAS  Google Scholar 

  8. Anziani OS, Ewing SA, Barker RW. Experimental transmission of a granulocytic form of the tribe Ehrlichiaea by Dermacentor variabilis and Amblyomma americanum to dogs. Am J Vet Res. 1990;51:929–31.

    CAS  PubMed  Google Scholar 

  9. Levin ML, Zemtsova GE, Killmaster LF, Snellgrove A, Schumacher LBM. Vector competence of Amblyomma americanum (Acari: Ixodidae) for Rickettsia rickettsii. Ticks Tick Borne Dis. 2017;8:615–22.

    Article  Google Scholar 

  10. Parker RR, Kohls GM, Steinhous. Rocky Mountain spotted fever: spontaneous infection in the tick Amblyomma americanum. Public Health Rep. 1943;58:721–9.

    Article  Google Scholar 

  11. Dantas-Torres F. Biology and ecology of the brown dog tick Rhipicephalus sanguineus. Parasit Vectors. 2010;3:26.

    Article  Google Scholar 

  12. Ipek NDS, Özübek S, Akatas M. Molecular evidence for transstadial transmission of Ehrlichia canis by Rhipicephalus sanguineus. J Med Entomol. 2018;55:440–4.

    Article  CAS  Google Scholar 

  13. Jongejan F, Su BL, Yang HJ, Berger L, Bevers J, Liu PC, et al. Molecular evidence for the transovarial passage of Babesia gibsoni in Haemaphysalis hystricis (Acari: Ixodidae) ticks from Taiwan: a novel vector for canine babesiosis. Parasit Vectors. 2018;11:134.

    Article  Google Scholar 

  14. Giannelli A, Ramos RA, Di Paola G, Mencke N, Dantas-Torres F, Baneth G, et al. Transstadial transmission of Hepatozoon canis from larvae to nymphs of Rhipicephalus sanguineus. Vet Parasitol. 2013;196:1–5.

    Article  Google Scholar 

  15. Bremer WG, Schaefer JJ, Wagner ER, Ewing SA, Rikihisa Y, Needham GR, et al. Transstadial and intrastadial experimental transmission of Ehrlichia canis by male Rhipicephalus sanguineus. Vet Parasitol. 2005;131:95–105.

    Article  Google Scholar 

  16. Groves MG, Dennis GL, Amyx HL, Huxsoll DL. Transmission of Ehrlichia canis to dogs by ticks (Rhipicephalus sanguineus). Am J Vet Res. 1975;36:937–40.

    CAS  PubMed  Google Scholar 

  17. McQuiston JH, Guerra MA, Watts MR, Lawaczeck E, Levy C, Nicholson WL, et al. Evidence of exposure to spotted fever group rickettsiae among Arizona dogs outside a previously documented outbreak area. Zoonoses Public Health. 2011;58:85–92.

    Article  CAS  Google Scholar 

  18. Piranda EM, Faccini JL, Pinter A, Pacheco RC, Cançado PH, Labruna MB. Experimental infection of Rhipicephalus sanguineus ticks with the bacterium Rickettsia rickettsii using experimentally infected dogs. Vector Borne Zoonotic Dis. 2011;11:29–36.

    Article  Google Scholar 

  19. Nicholson WL, Paddock CD, Demma L, Traeger M, Johnson B, Dickson J, et al. Rocky Mountain spotted fever in Arizona: documentation of heavy environmental infestations of Rhipicephalus sanguineus at an endemic site. Ann N Y Acad Sci. 2006;1078:338–41.

    Article  Google Scholar 

  20. Williams H, Zoller H, Roepke RK, Zschiesche E, Heckeroth AR. Fluralaner activity against life stages of ticks using Rhipicephalus sanguineus and Ornithodoros moubata in in vitro contact and feeding assays. Parasit Vectors. 2015;8:90.

    Article  Google Scholar 

  21. Rohdich N, Roepke RK, Zschiesche E. A randomized, blinded, controlled and mulita-centered field experiment comparing the efficacy and safety of BravectoTM (fluralaner) against FrontlineTM (fipronil) in flea- and tick-infested dogs. Parasit Vectors. 2014;7:83.

    Article  Google Scholar 

  22. International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products (VICH), 2000, VICH Guideline 9: Good Clinical Practice (GCP). https://www.fda.gov/regulatory-information.

  23. Marchiondo AA, Holdsworth PA, Fourie LJ, Rugg D, Hellmann K, Snyder DE, et al. World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) second edition: Guidelines for evaluating the efficacy of parasiticides for the treatment, prevention and control of flea and tick infestations on dogs and cats. Vet Parasitol. 2013;194:84–97.

    Article  CAS  Google Scholar 

  24. Jones EO, Gruntmeir JM, Hamer SA, Little SE. Temperate and tropical lineages of brown dog ticks in North America. Vet Parasitol Reg Stud Reports. 2017;7:58–61.

    PubMed  Google Scholar 

  25. Lasmar PVF, Murphy M, Nanchen S, Drake J, Coumendouros K, Borges DA, et al. Laboratory evaluation of the efficacy of lotilaner (Credelio™) against Amblyomma cajennense (sensu lato) infestations of dogs. Parasit Vectors. 2018;11:537.

    Article  Google Scholar 

  26. Arafa WM, Mohammed AN, Abo El-Ela FI. Acaricidal efficacy of deltamthrin-zinc oxide nanocomposite on Rhipicephalus (Boophilus) annulatus ticks. Vet Parasitol. 2109;268:36–45.

    Article  Google Scholar 

  27. Mehlhorn H, Schumacher B, Jatzlau A, Abdel-Ghaffar F, Al-Rasheid KA, Bhushan C. The effects of flumethrin (Bayticol® pour-on) on European ticks exposed to treated hairs of cattle and sheep. Parasitol Res. 2012;110:2181–6.

    Article  Google Scholar 

  28. Freitas EP, Zapata MRA, Fernades FF. Monitoring of resistance of susceptibility of adults and larvae of Amblyomma cajennense (Acari: Ixodidae) to synthetic acaricides in Goias, Brazil. Exp Appl Acarol. 2011;53:189–202.

    Article  CAS  Google Scholar 

  29. Barré N, Li AY, Miller RJ, Gaïa H, Delathière JM, Davey RB, et al. In vitro and in vivo evaluation of deltamethrin and amitraz mixtures for the control of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in New Caledonia. Vet Parasitol. 2008;155:110–9.

    Article  Google Scholar 

  30. Fernandes Fde F, Freitas Ede P. Analysis of the use of fenthion via epicutaneous in dogs for Rhipicephalus sanguineus control. Rev Soc Bras Med Trop. 2001;34:339–42.

    Article  Google Scholar 

  31. Wikel SK. Tick modulation of host immunity: an important factor in pathogen transmission. Int J Parasitol. 1999;29:851–9.

    Article  CAS  Google Scholar 

Download references

Acknowledgements

The authors would like to thank all personnel who assisted with these experiments. Additionally, we thank Laboratory Animal Resources personnel at the Oklahoma State University College of Veterinary Medicine (OSU-CVM) for assistance with dog husbandry.

Funding

The experiments reported herein were funded by Merck Animal Health.

Author information

Authors and Affiliations

  1. Department of Veterinary Pathobiology, Oklahoma State University, College of Veterinary Medicine, Stillwater, Oklahoma, 74078, USA

    Kelly Allen & Susan Little

  2. Merck Animal Health, De Soto, Kansas, 66018, USA

    Melissa Petersen

  3. Department of Comparative Diagnostics and Population Medicine, University of Florida, College of Veterinary Medicine, Gainesville, Florida, 32611, USA

    Jeff Gruntmeir

  4. Merck Animal Health, Madison, New Jersey, 07940, USA

    Anne Barrett, Fangshi Sun & Frank Guerino

  5. Diagnostic Medicine/Pathobiology, Kansas State University, College of Veterinary Medicine, Manhattan, Kansas, 66506, USA

    Brian Herrin

  6. Department of Pathobiology, Auburn University, College of Veterinary Medicine, Auburn, Alabama, 36849, USA

    Lindsay Starkey

Authors
  1. Kelly Allen
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Susan Little
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Melissa Petersen
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Jeff Gruntmeir
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Anne Barrett
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Brian Herrin
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Lindsay Starkey
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Fangshi Sun
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Frank Guerino
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

KA, SL, MP and FG conceived of and designed the experiment. FS consulted on experiment design and performed statistical analyses. JG, AB, BH and LS were instrumental in developing techniques and conducting the experiments. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Kelly Allen.

Ethics declarations

Ethics approval and consent to participate

The experiments reported (tick infestations of dogs) were conducted in accordance with the Oklahoma State University Institutional Animal Care and Use Committee (IACUC).

Consent for publication

Not applicable.

Competing interests

Logistic and laboratory support was provided by OSU-CVM personnel. KA and SL are employees of OSU-CVM. MP, AB and FG are employees of Merck Animal Health. JG, BH, LS and FS declare that they have no competing interests.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Allen, K., Little, S., Petersen, M. et al. Evaluation of oral fluralaner (Bravecto®) for efficacy against nymphs of Amblyomma americanum and Rhipicephalus sanguineus (sensu lato). Parasites Vectors 13, 315 (2020). https://doi.org/10.1186/s13071-020-04179-y

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s13071-020-04179-y

Keywords

Parasites & Vectors

ISSN: 1756-3305

Contact us