Evaluation of the Ovicidal Activity of Lufenuron and Spinosad on Fleas’ Eggs from Treated Dogs Michael W. Drydena Patricia A. Paynea Smith Vickia Ritchie L. Debraa Allen Lynnb aDepartment of Diagnostic Medicine /Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS. 66503. bNovartis Animal Health US Inc., 3200 Northline Ave. Suite 300, Greensboro NC. 27408 Corresponding author: Michael W. Dryden phone: Department of Diagnostic Medicine /Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS. 66503. (785) 532-4613; FAX: (785) 532-4851; e-mail address: [email protected] KEY WORDS: Ctenocephalides felis, fleas, into rearing media to determine adult flea KS1, dog, flea egg, lufenuron, spinosad, emergence. The percent adult flea emer- milbemycin oxime gence from eggs collected from untreated ABSTRACT control dogs ranged from 19.3% to 69.4% throughout the study. Eggs collected from This study was conducted to compare the dogs treated with spinosad had percent adult production and viability of flea eggs on emergence of 49.2%, 20.3%, and 37.9% on dogs treated with either the combination of collection days 30, 60, and 90, respectively. milbemycin oxime-lufenuron or spinosad. Even though eggs were collected on days Fifteen dogs were randomly distributed into 51, 72, and 79, those eggs were not viable. three treatment groups and housed individu- No adult fleas developed from eggs collect- ally. Dogs in group 1 served as untreated ed from dogs treated with lufenuron-milbe- controls, dogs in group 2 were treated with mycin oxime over the entire 90-day study. milbemycin oxime-lufenuron, and dogs in group 3 were treated with spinosad. Prod- INTRODUCTION ucts were administered orally according to The elimination of fleas on dogs and cats label directions on days 0, 30, and 60. All and in the surrounding environment can be dogs were infested with 250 cat fleas,Cteno - achieved by killing adult fleas on the host cephalides felis, KS1 strain, on days 14, 28, and eliminating environmental life stages. 42, 49, 58, 70, 77, and 88. Forty-eight hours Several residual insecticides such as dinote- after each infestation, dogs were placed furan, fipronil, imidacloprid, selamectin, and into egg collection cages for 3 hours. Flea spinosad do an excellent job of killing exist- eggs were collected, counted, and placed ing adult fleas on the pet.1-8 However, after 198 Vol. 10, No. 3, 2012 • Intern J Appl Res Vet Med. treatment, the pet still lives in an infested conducted in Alabama, North Carolina, and home environment with flea eggs, larvae, Ireland, using dogs 14 to 16 weeks of age, pupae, and emerging fleas. These remain- was given.15 The combined efficacy of the ing life stages provide an ongoing source of three trials on day 29 was remarkably only adult fleas that will continually reinfest pets 2% .15 It is unknown if this poor residual treated only with adulticidal compounds.9 efficacy was due to variability in flea strain Historically, repeated application of insec- or the age of the dogs. ticides and insect growth regulators formu- Then, in 2011, two studies were pub- lated as environmental sprays were used in lished using the KS1 flea strain.7 This pub- an attempt to eliminate the premises flea lication detailed two studies where the ef- life stages.9,10 However, client compliance ficacy of spinosad against the KS1 flea strain with environmental treatment protocols was in dogs was 22.1% and 32.5%, respectively, disappointing and often resulted in recurrent on day 29 post-treatment.7 In each of the infestations and client dis-satisfaction.. above reported studies, adulticidal efficacy New insecticides and insect growth began to wane at approximately day 15 post- regulators in convenient dosage forms treatment. Additionally, in a 2011 study (spot-ons, tablets, oral suspensions, and conducted in France, the residual efficacy of injectables),applied directly to the pet, pro- spinosad and fipronil against fleas infest- vide prolonged residual activity and have ing dogs at 24 and 48 hours, the efficacy of dramatically improved pet owner compli- spinosad was 85.0% and 89.0%, respectively ance, helped to eliminate recurrent infesta- on day 28 post-infestation was evaluated.16 tions, and improved client satisfaction.11-12 Because the adulticidal efficacy of Although residual flea adulticides spinosad has been shown to wane in several such as dinotefuran, fipronil, imidacloprid, of the aforementioned studies, we conducted selamectin, and spinosad provide prolonged this study to determine if fleas survived long adulticidal activity, efficacy may decrease enough on spinosad-treated dogs to feed, throughout the month following administra- mate, and produce viable eggs. Therefore, tion. 2,7,13-17 As the residual efficacy decreas- this study was conducted to compare the es, adult female fleas may live longer than production and viability of flea eggs on dogs 24 hours and start producing eggs.13,14,16,18 treated with either the combination of milbe- The production of viable eggs may extend mycin oxime/lufenuron or spinosad and the infestation within the home. infested with the KS1 flea strain. We used Providing ovicidal (lufenuron, me- lufenuron as a positive reference control for thoprene, pyriproxyfen, or selamectin) egg viability. activity as part of a flea treatment protocol MATERIALS AND METHODS is extremely beneficial because any eggs Fleas produced by adults surviving adulticide treatment will be rendered nonviable. 6,13,19-21 The KS-1 strain of Ctenocephalides felis was used in the study. The KS1 cat flea An orally administered residual adul- strain of Ctenocephalides felis has been ticide flea product containing spinosad has maintained as a closed colony at Kansas been approved for use in the U.S. market. In State University since 1990. The colony 2010 and 2011, studies indicated that under was originally established by removing certain conditions or with some flea strains, fleas from dogs and cats at a local animal the residual efficacy of spinosad decreases shelter in Riley county Kansas. In-vitro and markedly towards the end of the month.7,15 in-vivo evaluations have indicated that the In a presentation on spinosad residual ef- KS1 strain has some level of resistance or ficacy given at the 55th Annual Meeting reduced susceptibility to carbaryl, chlorpy- of the American Association of Veterinary riphos, fenthion, fipronil, imidacloprid, per- Parasitologists, results from three studies methrin, pyrethrins, and spinosad. 2,7,13,18, 22-26 Intern J Appl Res Vet Med • Vol. 10, No. 3, 2012. 199 Due to the hardiness of this flea strain, it has 14, 28, 42, 49, 58, 70, 77, and 88. This cor- been used extensively as an indicator of flea responds to 14 and 28 days following the product performance. In fact, almost every first treatment; 12, 19, and 28 days follow- major flea product has been tested against ing the second treatment; and 10, 17 and 28, this flea strain either before or shortly after days following the third dosing. introduction to the US market. Forty-eight hours after each flea infes- Animals and Housing tation, the dogs were removed from their This study used 15 purpose bred mongrel individual kennels and placed into stainless dogs between 6 and 12 months of age steel metabolic cages with expanded metal housed in individual kennels. The line of floors over stainless steel solid surface col- dogs is one approved by the FDA for pivotal lection pans for flea egg collections. Dogs studies; the age range is standard and usual were housed in the metabolic cages for 3 for conducting investigations. Dogs must be hours. After 3 hours, the dogs were brushed housed in individual kennels for individual to dislodge any remaining eggs. The dogs observation and to obtain accurate data. were then removed from the metabolic During the 14-day preconditioning phase, no cages, given one dose of Capstar® (niten- medications or pesticides were administered pyram) (minimum dose 1.0 mg/kg) orally, or used, and none of the dogs were bathed or and returned to their original kennels. shampooed. All animal care and procedures All flea eggs collected in the stainless conformed to the established guidelines of steel pans were counted. Up to 100 eggs the Kansas State University Institutional from each dog were placed in glass Petri Animal Care and Use Committee and those dishes containing growth media (sand, of Novartis Animal Health. ground dog chow, brewer’s yeast, and Animal Selection and Randomization dried blood), and held in a growth rearing On day 1, the dogs were weighed and chamber (I-30B, Percival Manufacturing randomly distributed into three groups, five Co, Boone, IA; 27-28° C, 70-80% relative dogs in each group. humidity, 24 hours dark). At 10 – 12 days after egg collection, pupae (and any larvae Treatments and Infestation that had not completed cocoon formation) Dogs allocated to group1 served as untreated were sifted from the media and placed into controls. Dogs in group 2 were treated with plastic vials with lids. Adult emergence was ® ® Sentinel Flavor Tabs (Novartis Animal determined by counting emerged adult fleas Health) milbemycin oxime - lufenuron at about 28 days after egg collection. Per- (minimum dosage 0.5mg/kg milbemycin ox- sonnel conducting egg counts, egg collec- ime, 10mg/kg lufenuron) per label directions tions, and viability assessments were blinded immediately after a meal. Dogs in group 3 to treatment group allocation. were treated with the appropriate size Com- Statistics fortis® (Elanco) spinosad tablet (minimum dosage 30 mg/kg) per label directions, with An analysis of variance (ANOVA, SAS a meal. PROC MIXED) was used to compare the percent of adult fleas that developed Dogs were observed to ensure they had from eggs recovered from each dog in the consumed a meal before treatment and ob- milbemycin oxime - lufenuron and spinosad served for 1 hour after tablet administration treatment groups.