Efficacy of a novel topical combination of fipronil, amitraz and (S)-methoprene for treatment and control of induced infestations with four North American tick species (Dermacentor variabilis, Ixodes scapularis, Amblyomma americanum and Amblyomma maculatum) on dogs

Five laboratory studies were conducted to confirm that a single topical dose of the novel combination of fipronil, amitraz and (S)-methoprene, CERTIFECT? (Merial Limited, GA, USA), is efficacious for the rapid control of pre-existing infestations and the prevention of new infestations with Ixodes scapularis, Dermacentor variabilis, Amblyomma americanum and Amblyomma maculatum for at least 28 days on dogs. In each study, 8 male and 8 female purpose-bred, laboratory beagles were randomly assigned to one of two study groups (treated and untreated). Starting on the day before treatment, each dog was infested weekly with about 30 or 50 ticks, depending on the study. Treatment with the novel combination rapidly eliminated pre-existing infestations and controlled weekly re-infestations for at least 28 days. Pre-existing infestations with all four tick species were rapidly and effectively reduced, with post-treatment therapeutic efficacies ranging from 91.7 to 99.5% within 18-48 h post treatment. Amblyomma maculatum numbers were significantly (p<0.05) reduced on treated dogs from the first tick counts as early as 6h post-treatment. All subsequent infestations with each of the 4 tick species were quickly disrupted, with prophylactic efficacies greater than 90% within 18-48 h post-infestation for at least a full month. Because the combination of fipronil, amitraz and (S)-methoprene quickly starts disrupting and killing ixodid ticks within hours of treatment, with similar high levels of efficacy maintained for at least 28 days in these and other studies, the authors conclude that a single topical treatment with CERTIFECT may prevent the transmission of most infectious agents carried by ixodid ticks for at least one month.     

Efficacy of a novel combination of fipronil, amitraz and (S)-methoprene for treatment and control of tick species infesting dogs in Europe

Four studies were conducted to show the effectiveness of a novel combination of fipronil, amitraz and (S)-methoprene in a spot-on formulation (CERTIFECT?, Merial Limited, GA, USA) for the therapeutic and preventive control of Ixodid tick species affecting dogs in Europe: Ixodes ricinus, Dermacentor reticulatus and Rhipicephalus sanguineus. In each, untreated control dogs were compared to others treated with the novel combination. All dogs were infested with 50 adult, unfed ticks prior to treatment and at 7-day intervals after treatment. Ticks on all dogs were counted at 18, 24 and 48 h after treatment (therapeutic efficacy) or infestation (preventive efficacy). Therapeutic efficacy of fipronil, amitraz and (S)-methoprene was excellent as shown by significant (p<0.05) and greater than 97% and up to 100% reductions in the 48 h tick counts and significant (p<0.05) detachment/death of ticks evident at 18-24h after treatment for all three tick species. Preventive efficacy was demonstrated by significant (p<0.05) and greater than 93% and up to 100% reductions in tick counts at 48 h after repeat infestations out to 35 days after treatment for I. ricinus and out to 42 days after treatment for D. reticulatus and R. sanguineus. The time to substantial disruption of establishment of new tick infestations after treatment was less than 18-24h and was maintained for up to 28 days after treatment of I. ricinus and D. reticulatus infestations, and 4h to at most 18 h and maintained up to 35 days after treatment of R. sanguineus. Similar preventive efficacy profiles for each of the Ixodid species tested suggest that CERTIFECT kills all Ixodid species starting 4h after contact as demonstrated for R. sanguineus.     

The prevention of attachment and the detachment effects of a novel combination of fipronil, amitraz and (S)-methoprene for Rhipicephalus sanguineus and Dermacentor variabilis on dogs

A novel combination of fipronil, amitraz and (S)-methoprene (CERTIFECT?, Merial Limited, GA, USA) was evaluated for the prevention of attachment of ticks and its ability to cause detachment of ticks. For the two prevention of attachment studies, 20 purpose-bred beagles were allocated each to two equal groups based on pretreatment tick counts (treated and untreated). Each dog was exposed to 50 adult Rhipicephalus sanguineus and Dermacentor variabilis weekly starting 24h after treatment. In study 1 infestations with R. sanguineus were discontinued after Day 7 but continued to Day 28 for D. variabilis in both studies. Counts of ticks by species were made 2, 4 and 24h after exposure to ticks. Ticks not attaching to dogs were evaluated for viability. For the evaluation of detachment study, 16 purpose-bred beagles were allocated each to two equal groups based on pretreatment tick counts (treated and untreated). Each dog was infested with 50 unfed R. sanguineus and D. variabilis adults on Day -2. Ticks were thumb counted without removal on all dogs on Day -1, and at 4, 12, and 24h after treatment. Ticks were counted and removed at 48 h after treatment. Dogs treated with the novel combination had significantly (p<0.05) lower total numbers of attached R. sanguineus and D. variabilis than untreated controls at 4h through Day 7. For R. sanguineus, percent reduction of attachment at 24h after infestation through Day 29 ranged from 94.5% to 100%. For D. variabilis, the percent reduction of attachment at 24h through Day 22 was above 98.0%. These studies demonstrate that novel combination can disrupt attachment of R. sanguineus and D. variabilis for up to 28 days following treatment. Of those ticks that are exposed to the treatment, even if they do not attach to the dog and remain in the environment, greater than 90% (p<0.05) die within 24h for 2-3 weeks following treatment. Also, for those dogs infested with ticks at the time of treatment, the novel combination causes significant detachment (p<.05) starting at 12h and reaching 98.9% by 48 h after treatment. This product provides an effective means for controlling ticks infesting dogs and limiting the spread of tick transmitted diseases. Additionally, the mortality of ticks exposed to CERTIFECT will reduce infestation of the dog's environment.     

Efficacy of fipronil, amitraz and (S)-methoprene combination spot-on for dogs against adult dog fleas (Ctenocephalides canis, Curtis, 1826)

A novel spot-on formulation combining fipronil, amitraz and (S)-methoprene (CERTIFECT?, Merial Limited, GA, USA) was evaluated in adult Beagle dogs in a study to determine its adulticidal efficacy against the dog flea (Ctenocephalides canis, Curtis, 1826). Sixteen dogs were randomly allocated to treatment groups: 8 dogs served as untreated controls, and 8 dogs were treated once. Treatment consisted of applying a new combination formulation to deliver at least 6.7mg fipronil/kg body weight (bw), 8.0mg amitraz/kg bw, and 6.0mg (S)-methoprene/kg bw. The combination was designed to enhance the efficacy against ticks of the original fipronil/(S)-methoprene combination. Each dog was infested with 100 adult unfed dog fleas within 24h prior to treatment and then at weekly intervals for 8 weeks after treatment. At 24h after treatment or after each subsequent infestation, each dog was combed thoroughly to remove live fleas to be counted. A single treatment with CERTIFECT provided excellent knock-down of fleas within 24h after treatment and controlled re-infestations for up to 7 weeks (efficacy ≥96.5%, p<0.05).     

The effect of water and shampooing on the efficacy of a pyriprole 12.5% topical solution against brown dog tick (Rhipicephalus sanguineus) and cat flea (Ctenocephalides felis) infestations on dogs

The efficacy of a single treatment with a 12.5% pyriprole spot-on formulation against induced infestations with R. sanguineus ticks and cat fleas (C. felis) as well as its persistence after repeated washing and shampooing was investigated in four separate studies. In a first study on R. sanguineus involving 32 beagle dogs, the efficacy at various time-points during the 30 days that followed treatment assessed 48 h after re-infestation ranged from 100% to 99.3%. No engorged ticks, alive or dead, were found in the treated animals. Shampooing 2 days after treatment and weekly washings did not affect the efficacy. In a second study on R. sanguineus involving 32 beagle dogs, the efficacy at various time-points during the 30 days that followed treatment assessed 48 h after re-infestation ranged from 100% to 96.8%. Single washing 8h after treatment and single shampooing 24 h after treatment had no negative impact on the efficacy of the product. In a third study on C. felis involving 28 beagle dogs, the efficacy at various time-points during the 30 days that followed treatment assessed 48 h after re-infestation was always 100% and weekly washings did not diminish the efficacy. In a last study on C. felis involving 24 beagle dogs, the efficacy at various time-points during the 5 weeks that followed treatment assessed 48 h after re-infestation ranged from 100% to 99.8%, and shampooing 24 h after treatment did not reduce the efficacy. The product was well tolerated by the dogs.     

Efficacy of selamectin against experimentally induced tick (Rhipicephalus sanguineus and Dermacentor variabilis) infestations on dogs

Seven controlled studies were conducted to investigate the efficacy of selamectin against weekly infestations of dogs with Rhipicephalus sanguineus and Dermacentor variabilis. Treatments (selamectin or vehicle alone) were applied topically at weekly, 2-week, or monthly intervals or in a "Monthly Plus" regimen (monthly treatment with an additional treatment at 14 days after the first treatment). Selamectin was supplied in unit dose tubes designed to deliver a minimum dosage of 6mgkg(-1). The studies ranged in duration from 37 to 90 days. Fifty adult ticks (+/-2) were applied approximately weekly, and tick counts were performed 3, 4, and 5 days after each infestation. The efficacy of selamectin was expressed as the percentage reduction in geometric mean tick counts on selamectin-treated dogs compared with those for dogs treated with the vehicle alone (negative-control). In one study, the engorgement of Dermacentor variabilis was assessed by weighing ticks after removal on the fifth day after each infestation. Weekly and 2-week interval treatments with selamectin provided efficacies against R. sanguineus of >89% across the entire study periods, with 100% efficacy being achieved from 21 days after the first dose and thereafter (study duration, 37 days for the weekly regimen and 44 days for the 2-week interval regimen). D. variabilis also was well controlled by the 2-week interval treatment regimen, with >96% efficacy being achieved from 21 days after the first treatment and thereafter until the end of the study (study duration: 90 days). In five of six studies incorporating three treatments at monthly intervals, the percentage reduction in R. sanguineus and D. variabilis counts 5 days after infestation ranged from 90 to 100% in the second and third months after treatment began. In the sixth study, reductions of > or =95% in D. variabilis counts 5 days after infestation were achieved for 2 weeks after each treatment in the second and third months. For the Monthly Plus regimen, from the second treatment (day 14) onwards, selamectin achieved 83-100% reductions in R. sanguineus and D. variabilis counts 3 days after infestation, and 94-100% reductions 5 days after infestation in three of the four studies. In the fourth study, selamectin demonstrated good efficacy against D. variabilis for 2 weeks after each treatment. In all seven studies, the counts from the selamectin-treated dogs were significantly (P< or =0.018) lower than those from the vehicle-treated dogs on 77 of the 80 assessments made 5 days after infestation. Selamectin also significantly (P< or =0.0105) reduced engorgement of female D. variabilis. These studies demonstrated that selamectin, administered topically to the skin in a single spot at a minimum dosage of 6mgkg(-1) at monthly intervals, was effective in the control of experimentally induced R. sanguineus and D. variabilis infestations on dogs.     

Comparison of an amitraz-impregnated collar with topical administration of fipronil for prevention of experimental and natural infestations by the brown dog tick (Rhipicephalus sanguineus).

OBJECTIVE: To compare the efficacies of amitraz and fipronil for prevention of experimental and natural infestations of Rhipicephalus sanguineus. DESIGN: Prospective study. ANIMALS: 30 dogs. PROCEDURE: In 3 trials, dogs were allocated to 3 groups of 10 each. In trial 1, dogs were experimentally infested on day--1, and on day 0 were fitted with an amitraz-impregnated collar, treated topically with fipronil, or not treated. Ticks were counted daily until day 7, when viability of ticks and their progeny was determined. In trial 2, dogs were treated on day 0 and experimentally infested on days 7, 8, 10, and 13. Ticks were counted on days 8, 10, 13, and 18, and viability of ticks and their progeny was determined on day 18. In trial 3, dogs were exposed weekly to a tick-infested environment from day--3 to day 70. Dogs were treated on day 0, and ticks were counted and removed weekly from day 3 to day 77. RESULTS: Fipronil and amitraz were acaricidal and inhibited attachment and feeding. Amitraz had a significantly greater effect than fipronil on numbers of live, feeding ticks, egg hatchability, and larval viability, indicating partial ability to interrupt the tick life cycle. In field conditions, amitraz remained effective over the entire observation period. CLINICAL IMPLICATIONS: Amitraz had stronger and more sustained effects against tick infestation than fipronil.     

Confirmation of the efficacy of a novel formulation of metaflumizone plus amitraz for the treatment and control of fleas and ticks on dogs

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated in four laboratory studies to confirm efficacy against fleas and ticks on dogs for 1 month. Three different strains of cat flea (Ctenocephalides felis felis) and four tick species were used. Rhipicephalus sanguineus and Dermacentor variabilis were evaluated concurrently in two studies and Ixodes scapularis and Amblyomma americanum in one study each. In all studies, dogs were randomly allocated to treatment groups and compared with nontreated dogs. One study also included a placebo treatment and a commercial product containing fipronil plus S-methoprene. All treatments were applied to the skin at a single spot between the scapulae on Day 0. Dogs were infested with fleas and/or ticks prior to treatment and then reinfested at weekly intervals for 6 weeks after treatment and evaluated for efficacy at 1 or 2 days after treatment and each reinfestation. These studies confirmed that treatment with ProMeris for Dogs at the proposed commercial dose rate rapidly controlled existing infestations of fleas and ticks on dogs. Treatment provided control of reinfesting fleas for up to 6 weeks and at least 4 weeks control of ticks. Efficacy was confirmed in a variety of dog breeds against three different flea strains and four common species of ticks found on dogs in the United States.     

Antibody and blood leukocyte response in Rhipicephalus sanguineus (Latreille, 1806) tick-infested dogs and guinea pigs

The dog is considered to be the natural host of Rhipicephalus sanguineus and is unable to develop appreciable resistance even after repeated feedings. The guinea pig develops strong resistance after one infestation with adult ticks. Antibody (IgG) titres against tick salivary gland antigens (SGAs) and blood leukocyte numbers in dogs and guinea pigs undergoing experimental R. sanguineus tick infestations were measured to detect a possible correlation with susceptibility or resistance of hosts. Since infested dogs develop an immediate hypersensitivity reaction to R. sanguineus antigens, total and anti-R. sanguineus SGA IgE levels were also measured in this host species. IgG and IgE antibody levels were determined by an enzyme-linked immunosorbent assay (ELISA) along three consecutive infestations of both hosts. Most dogs and guinea pigs displayed low IgG levels against R. sanguineus SGAs, though marked differences in individual response were observed. Although dog's total serum IgE levels increased significantly after infestations, no change in the amount of anti-salivary gland IgE was detected. Total and differential blood cell counts were determined in dogs and guinea pigs during primary and secondary infestation. In dogs, a tertiary infestation and a subsequent higher infestation level were also evaluated. Infested dogs did not display any alteration in blood leukocyte counts throughout the experiment. Guinea pigs, on the other hand, developed a significant basophilia during primary infestation which increased further during secondary infestation. These data reveal similarities and differences in the reactions of resistant and non-resistant hosts to ticks. They contribute for the understanding of such host-parasite relationships and will hopefully aid in the development of immune control of ticks.     

The ability of a topical novel combination of fipronil, amitraz and (S)-methoprene to protect dogs from Borrelia burgdorferi and Anaplasma phagocytophilum infections transmitted by Ixodes scapularis

Healthy, purpose-bred laboratory beagle dogs that had not been exposed to ticks and were seronegative for Borrelia burgdorferi and Anaplasma phagocytophilum were randomly assigned to four groups of eight dogs each. Control group 1 was not treated. Groups 2, 3 and 4 were treated with a single topical application of a new formulation of fipronil, amitraz and (S)-methoprene (CERTIFECT?, Merial Limited, GA, USA) at 28, 21 or 14 days prior to tick infestation, respectively. Each dog was infested with 25 female and 25 male field-collected adult Ixodes scapularis ticks that had infection rates of 66% for B. burgdorferi sensu stricto and 23% for A. phagocytophilum, as determined by polymerase chain reaction. Two and five days after tick infestation, control dogs had an average of 9.5 and 13.9 attached adult female ticks, respectively, whilst the 24 treated dogs remained tick-free aside from a single tick on the 2nd day after infestation. Serial serological tests demonstrated that the ticks successfully infected 8/8 control dogs with B. burgdorferi and co-infected 6/8 with A. phagocytophilum. B. burgdorferi infection also was confirmed in most control dogs by culture (6/8) and PCR (7/8) of skin biopsies. In contrast, CERTIFECT protected all 24 treated dogs against infection by both B. burgdorferi and A. phagocytophilum, as demonstrated by their negative serological tests throughout the study and the absence of any positive skin biopsy culture or PCR in these dogs.     

Efficacy of two 65 % permethrin spot-on formulations against canine infestations of Ctenocephalides felis and Rhipicephalus sanguineus

The efficacy of two formulations of a topically applied 65% permethrin spot-on for dogs (Defend EXspot Treatment for Dogs, Schering-Plough Animal Health Corp.) was evaluated against experimental infestations of the cat flea, Ctenocephalides felis, and the brown dog tick, Rhipicephalus sanguineus. Thirty dogs were randomly allocated to treatment with 65 % permethrin in diethylene glycol monomethyl ether (original formulation), 65 % permethrin in propylene glycol monomethyl ether (test formulation), or to an untreated control group. Dogs assigned to treatment with a permethrin formulation received either 1 or 2 ml of the formulation in accordance with label directions on Day 0. One hundred unfed, adult cat fleas and 50 unfed, adult ticks were placed on each dog on Days -1, 5, 12, 19, 26, 33, and 40. Live fleas and ticks were counted on each dog on Days 2, 7, 14, 21, 28, 35, and 42. Treatment of dogs with either formulation of 65 % permethrin significantly (P <.05) reduced the number of live fleas and ticks from Days 2 through 42. No statistical differences were noted between the formulations regarding efficacy against C. felis or R. sanguineus.     

Amitraz: a tick and flea repellent and tick detachment drug

A topical formulation of amitraz (Mitaban Liquid Concentrate, The Upjohn Company, Kalamazoo, Michigan, U.S.A.) was evaluated as a tick repellent and detachment agent, and flea repellent. The diluted liquid concentrate (250 p.p.m. active drug) was topically applied as a single treatment to dogs; the concentration was identical to the rate recommended for treatment of demodicosis and scabies. Brown dog tick (Rhipicephalus sanguineus) and American dog tick (Dermacentor variabilis) populations were eliminated and repelled. Repellent activity (92-95%) was observed against R. sanguineus for 2 weeks post-treatment; the treatment was moderately active (63%) during the third week, and at 4 weeks post-treatment the drug was inactive. Established R. sanguineus populations were also treated, and the diluted liquid concentrate had 100% tick-detachment efficacy. Repellent activity (99%) was also detected against D. variabilis; the activity was monitored for only 7 days. The ectoparasiticide had low to moderate flea (Ctenocephalides felis) repellent activity (42%) for 4 days post-treatment; thereafter the treatment was ineffective. Side-effects were not observed in any of the dogs treated with amitraz, or the placebo.     

Evaluation of an imidacloprid (8.8% w/w)--permethrin (44.0% w/w) topical spot-on and a fipronil (9.8% w/w)--(S)-methoprene (8.8% w/w) topical spot-on to repel, prevent attachment, and kill adult Rhipicephalus sanguineus and Dermacentor variabilis ticks on dogs

This study evaluated the effectiveness of two topical spot-on formulations, imidacloprid (8.8% w/w)--permethrin (44.0% w/w) and fipronil (9.8% w/w)--(S)-methoprene (8.8% w/w), to repel, prevent the attachment of, and kill adult Rhipicephalus sanguineus and Dermacentor variabilis on dogs. Twelve purpose-bred beagles were distributed into three groups of four dogs each; one group served as untreated controls and each of the other two groups received one of the test products. Dogs were exposed to 25 adult ticks of each species for 10 minutes on posttreatment days 3, 7, 14, 21, and 28. Nonattached or repelled ticks were collected and evaluated for viability, and on-dog tick counts were conducted at 3, 24, and 48 hours after tick exposure. The imidacloprid-permethrin formulation provided significant repellency of R. sanguineus and D. variabilis for up to 3 and 4 weeks after treatment, respectively; and provided good overall control for R. sanguineus and D. variabilis during the study period. The fipronil--(S)-methoprene formulation provided good overall tick control during the study period.     

Movement of Rhipicephalus sanguineus adults between co-housed dogs during active feeding

Adult male ticks have been shown capable of experimental acquisition and transmission of tick-borne pathogens without requiring a molt. To determine the ecological relevance of this intrastadial transmission route, we evaluated the extent to which actively feeding male Rhipicephalus sanguineus move naturally between co-housed infested dogs. Dogs (n=4) were infested with single color-coded ticks, individually housed in tick-confinement cages for 48 h while infestations established, and then each dog examined and the ticks present counted. Dogs were then co-housed in a large, group pen for an additional 7 (study 1) or 5 (study 2) days. In the first study, sex ratios were adjusted to encourage migration, with two dogs receiving predominantly female ticks and two dogs receiving all male ticks. In the second study, each dog received a ratio of ticks that parallels that found in natural infestations (4:1 male to female). Results showed that ticks readily migrated between infested, co-housed dogs. Rates of immigration, defined as the percentage of ticks previously attached to one dog that moved onto another dog, ranged from 0 to 46% (mean=31.1% study 1; 9.4% study 2). Emigration rates, defined as the number of ticks initially infesting one dog that moved to another dog, averaged 35.2% in study 1 and 10.8% in study 2 (3.6-67.6%). Movement of adult ticks between dogs represents a naturally occurring form of interrupted feeding, a strategy which has been shown to shorten the feeding time necessary to allow transmission of pathogens. In ticks that readily detach from one host and reattach to a second host to resume feeding, replication of any pathogens present has already been initiated and therefore the same delay in transmission seen in ticks attached to a host for the first time may not occur.     

Evaluation of the efficacy of fipronil formulations in the treatment and control of biting lice,Trichodectes canis (De Geer, 1778) on dogs

The efficacy of FRONTLINE SPRAY (0.25% (w/v) fipronil), FRONTLINE SPOT-ON FOR DOGS (10% (w/v) fipronil) and FRONTLINE PLUS FOR DOGS (10% (w/v) fipronil and 9% (S)-methoprene) against the biting louse Trichodectes canis on dogs was confirmed under laboratory conditions. A field study evaluated the efficacy of a single topical application of FRONTLINE SPRAY and FRONTLINE SPOT-ON against the parasite on dogs. A total of 48 dogs of mixed breeds, both sexes, aged 2 months-7 years and weighing 1.8-37.0kg were used. The animals were either experimentally (laboratory study) or naturally (field study) infested with lice. Dogs were housed individually in order to prevent contact between animals. In the laboratory study, animals were allocated based on pre-treatment louse counts from 38 hair coat-partings per animal. Dogs were randomly assigned to the four treatment groups: (1) untreated control; (2) FRONTLINE SPRAY, at 6ml/kg; (3) FRONTLINE SPOT-ON as per label and (4) FRONTLINE PLUS as per label. Dogs in treatment groups 2-4 were treated twice topically on Days 0 and 28. The number of live lice in the 38 hair coat-partings per animal were counted on Days 2, 7 and weekly to Day 63. In addition, a whole body comb count was performed on Day 63. No live T. canis were found on dogs treated with FRONTLINE formulations at any post-treatment examination. The difference from controls was significant (P<0.01) for each product at each examination. Based on the whole body comb count at Day 63, the efficacy of each product was determined to be 100%. In the field study, dogs were allocated in strict order of presentation. Dogs were randomly allocated to one of the three treatment groups: (1) BOLFO collar (propoxur); (2) FRONTLINE SPRAY, at 6ml/kg and (3) FRONTLINE SPOT-ON as per label. Dogs were treated once topically on Day 0. The number of live lice was determined by whole body searches on Days 0 (pre-treatment), 2, 28 and 42. Louse counts of dogs treated with either FRONTLINE SPRAY, or FRONTLINE SPOT-ON were not different than those of dogs receiving the propoxur collar. The efficacy was determined to be >98% on Day 2 and, 100% on Days 28 and 42 in all treatment groups. The results of these studies demonstrate that fipronil in topical formulations is effective for treatment and control of biting lice (T. canis) infestations on dogs.     

New method using quantitative PCR to follow the tick blood meal and to assess the anti-feeding effect of topical acaricide against Rhipicephalus sanguineus on dogs

A 28-day study was conducted to assess the dynamic of blood feeding by Rhipicephalus sanguineus ticks on dogs treated or not with a novel topical combination of fipronil, amitraz and (S)-methoprene. Dogs were infested weekly through exposure to ticks in crates for 4 h. Ticks were then counted in the crates at 2 h and 4 h post dog exposure. Ticks were also counted and removed from the dogs at 2 h, 4 h, 6 h, 12 h and 24 h post tick exposure. The inhibition of blood feeding was assessed by both tick quantification and designing and performing a quantitative PCR (qPCR) to detect the canine hydroxymethylbilane synthase (HMBS) gene in ticks. The percentage of repellency sensu lato based on the ticks collected in crates at 2 h varied from 4.7% at day 28 to 48.3% at day 7. The immediate mortality rate of the ticks expelled at 2 h varied from 1.5% at day 21 to 31.7% at day 7. The efficacy calculation showed that the acaricidal combination started to kill ticks in as little as 2 h. The average efficacy reached 90.0% at 12 h post crate challenges and 100% at 24 h post exposure in crates. The inclusion of an internal amplification control was used to ensure that no significant template-derived PCR inhibition (≤6.2%) affected the overall results. The reduction of blood feeding was significant at 4 h (>80.0%) and >99.0% at 24 h post tick exposure in the crate. The high repellency rate and the lethal efficacy of CERTIFECT^® resulted in significantly fewer live attached ticks, consequently reducing blood intake and fluid exchanges.     

Efficacy of an adulticide used alone or in combination with an insect growth regulator for flea infestations of dogs housed in simulated home environments.

OBJECTIVE: To determine the effect of an adulticide on flea populations of dogs and to evaluate efficacy of combined use of the adulticide and an insect growth regulator (IGR) in dogs with experimentally induced flea infestations. ANIMALS: 40 adult Beagles. PROCEDURE: Each group of 5 dogs was housed in a separate room. Each dog was infested 3 times with 50 fleas, and fleas were counted beginning on day -21. Groups of dogs and treatments (initiated on day 0) were as follows: 1, adulticide once; 2, adulticide on days 0 and 7; 3, adulticide on days 0, 3, and 7; 4, sham treatment; 5, IGR monthly; 6, IGR monthly plus adulticide once weekly for 6 weeks; 7, IGR monthly plus adulticide twice weekly for 6 weeks; 8, sham treatment. Flea counts were compared between treated and control dogs. RESULTS: By 24 hours after initial treatment, all adult fleas but 1 were dead in treated dogs. In groups 1 and 3, populations increased to 15 to 20 fleas/dog 2 months after treatment, compared with 48 fleas/dog in group 4. After treatment, mean flea counts were significantly lower for groups 1, 2, and 3, relative to group 4. Efficacy of treatment for group 5, relative to group 8, was > 94% after day 84. Efficacy of treatment for groups 6 and 7 was 99% after day 28. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with adulticide alone or in combination with an IGR had better efficacy, compared with sham treatment or IGR alone. Administration of adulticide twice weekly was not more efficacious than treatment once weekly.     

Efficacy of a novel formulation of metaflumizone for the control of fleas (Ctenocephalides felis) on cats

A novel spot-on formulation containing metaflumizone (ProMeris for Cats, Fort Dodge Animal Health, Overland Park, KS) was evaluated in five laboratory studies to determine the duration of residual efficacy in cats against fleas after a single spot treatment. In each study, eight domestic shorthair cats were randomly allocated to each treatment group and individually housed. One group in each study remained non-treated. In one study, an additional group of eight cats was treated with a placebo formulation. Cats were treated topically with metaflumizone formulation to provide a dose of at least 40mg metaflumizone/kg. Cats were infested with 100 cat fleas (Ctenocephalides felis felis) once per week for approximately 8 weeks. Cats were comb counted 48h after treatment and each infestation to determine the number of viable fleas present. There were no significant differences in flea counts between the non-treated control and the placebo-treated control (P>0.05) other than a 26% reduction at week 1, demonstrating that the formulation excipients had no activity. Metaflumizone treatment resulted in significantly lower flea numbers relative to non-treated controls on all post-treatment count days (P<0.05). Metaflumizone provided >90% control of flea infestations up to 7 weeks following a single treatment.     

Rhipicephalus sanguineus (Ixodida, Ixodidae) as intermediate host of a canine neglected filarial species with dermal microfilariae

The life cycles of filarioids of dogs presenting dermal microfilariae have been little studied. Following the recent retrieval of dermal microfilariae identified as Cercopithifilaria sp. in a dog from Sicily (Italy), this study was designed to assess the role of the brown dog tick Rhipicephalus sanguineus as an intermediate host of this filarial species. An experimental tick infestation was performed on an infected dog using 300 nymphs of R. sanguineus. Engorged nymphs were collected and examined by both microscopic dissection and molecular analysis at five time points (i.e., the same day of tick detachment and 10, 20, 30 and 50 days post-detachment) to detect the presence and developmental stage of filariae in the ticks. A total of 270 engorged nymphs were collected from the dog and developing filarioid larvae detected in 10 (5%) out of 200 ticks dissected. Infective third-stage larvae were observed in 4 (2%) of the all dissected ticks, 30 days post-detachment. Twelve (6.6%) out of 181 samples molecularly tested were positive for Cercopithifilaria sp. This study demonstrates that nymphs of R. sanguineus feeding on a dog naturally infected by Cercopithifilaria sp. can ingest microfilariae, which develop up to the third infective stage thus suggesting that this tick species might act as an intermediate host of this little known canine filarioid.     

Acaricidal activity of hydroethanolic formulations of thymol against Rhipicephalus sanguineus (Acari: Ixodidae) and Dermacentor nitens (Acari: Ixodidae) larvae

The aim of this study was to assess the acaricidal activity of hydroethanolic formulations of thymol at varying concentrations on Rhipicephalus sanguineus and Dermacentor nitens larvae. The larval packet test was used and the thymol concentrations tested were 2.5, 5.0, 10.0, 15.0 and 20.0 mg/ml. The control group was exposed only to water and ethanol (50/50%) and there were 10 repetitions for each treatment. The mortality was evaluated after 24 h. For the R. sanguineus larvae, the mortality rates were 47.5, 50.2, 96.7, 95.9 and 98.1%, while for D. nitens the rates were 14.1, 75.0, 90.2, 90.3 and 99.5%, at respective thymol concentrations of 2.5, 5.0, 10.0, 15.0 and 20.0 mg/ml. The results indicate that the hydroethanolic formulations of thymol tested have acaricidal activity on R. sanguineus and D. nitens larvae exposed topically, causing mortality greater than 90% 24 h post-treatment starting at the concentration of 10 mg/ml.