Terry Settje

Evaluation of the efficacy of emodepside plus praziquantel topical solution against ascarid infections (Toxocara cati or Toxascaris leonina) in cats

Eleven controlled studies were conducted in the United States and Europe to evaluate the efficacy of a topical solution of emodepside (3 mg/kg)+praziquantel (12 mg/kg) (Profender®, Bayer AG, Leverkusen, Germany) against infection with various stages of the ascarid nematodes Toxocara cati and Toxascaris leonina. Infections were induced by administration of larvated ascarid eggs, and stage–specific efficacy was evaluated by treating cats at scheduled intervals post–inoculation. All studies featured random allocation to treatment groups, placebo–treated control animals and assessment of outcome measures by masked personnel. The product (emodepside+praziquantel topical solution) was 100% effective against mature adults and immature adult T. cati. In addition, it was 96.8% effective against third stage larvae and at least 99.4% effective against fourth stage larvae of T. cati, respectively. Efficacy against mature, immature adult and L4 stages of T. leonina exceeded 93.4%, but regulatory “adequacy of infection” criteria were not met in sorne studies. No adverse reactions to treatment were noted in cats treated with the emodepside+praziquantel topical solution.

Safety of imidacloprid plus moxidectin topical solution applied to cats heavily infected with adult heartworms (Dirofilaria immitis)

A topically applied formulation containing 10% imidacloprid+1% moxidectin (Advocate®/Advantage multi®) has been developed for monthly application to cats for the prevention of feline heartworm (HW) disease caused by Dirofilaria immitis; and for the treatment and control of flea infestations, ear mite infestations, and intestinal nematode infections. A study model was designed to evaluate the safety of this product in cats harboring adult D. immitis infections. Eighty adult cats (40 males/40 females) were each inoculated with 60 third–stage D. immitis larvae on test day (TD) 1. On TD 243–245 echocardiographic imaging was performed on each cat to confirm and estimate the number of adult D. immitis residing in the cardiovascular system. A total of 35 cats were subsequently eligible for safety evaluation based on inclusion criteria. Four treatment groups were established and randomly selected for treatment: imidacloprid+moxidectin solution at the label dose (n=9) (group 1), imidacloprid+moxidectin solution at 5x the Iabel dose (n=9) (group 2), 6% selamectin topical solution (Revolution®) at the label dose (positive control, n=8) (group 3), and topical treatment with placebo (negative control, n=9) (group 4). All cats were treated on TD 250. Treatments for groups 1, 3, and 4 were repeated on TDs 278 and 306. Group 2 cats were euthanized and examined for adult D. immitis on TD 288. All other cats were euthanized and examined for adult D. immitis on TD 334. No adverse events attributable to treatment with the test articles were observed during the study. The geometric mean numbers of adult D. immitis recovered at necropsy from treatment groups 1–4 were 2.9, 3.2., 4.0, and 2.7, respectively. There were no statistically significant differences in the comparison of adult D. immitis recovered at necropsy (ANOVA overall group effect P–value of 0.5356). The results of this study demonstrate that imidacloprid+moxidectin topical solution can be used safely in cats heavily infected with adult D. immitis.

Echocardiographic quantification of Dirofilaria immitis in experimentally infected cats

The safety of heartworm preventives in heartworm-positive cats has traditionally been evaluated using adult Dirofilaria immitis removed from infected dogs and surgically implanted into the cats. An alternate study model uses infective larvae to establish adult infections in cats. Unfortunately, the number of adult worms resulting from the latter method varies widely from none to more than 30, both unacceptable for studies of natural heartworm infection and for studies evaluating product safety in heartworm-infected cats. We sought to determine infection severity in experimental infections via echocardiography to reduce the chances of enrolling uninfected and heavily infected cats into a study. Eighty adult cats were each inoculated with 60 infective D. immitis larvae and maintained for 8 months to allow for the development of adult worms. Antigen and antibody testing, as well as echocardiographic imaging, were performed to confirm and estimate adult worm burdens. Approximately 8 and 12 months post-infection, echocardiographic examination was performed to confirm and enumerate adult D. immitis populations in the cardiovascular system. Worm burdens were stratified as 0, 1-3, 4-11, and > 11 adults, with 0 being considered uninfected and more than 11 considered too heavily infected to be relevant for anthelmintic studies. Cats with clinically relevant infections (1-10 adults) subsequently received multiple treatments with the investigational drug, and worm burdens were confirmed by necropsy 30 days following the final treatment. Worm burden estimated with echocardiography correlated well, but not precisely, with post-mortem counts (p < 0.001, r2 = 0.67). Echocardiography under-, over-, and exactly estimated heartworm burden 53%, 27%, and 22% of the time, respectively. Although the correct category (0-4) was determined by echocardiography in only 54% of cats, positive cats were distinguished from negative cats 88% of the time and the heaviest infections (> 11) were correctly categorized 95% of the time. Both false negative and false positive results were observed. We conclude that echocardiography is useful for detecting mature experimental heartworm infections, identifying cats that have rejected mature infection, and detecting very heavy heartworm burdens, but it is only moderately accurate in classifying lesser burdens. While echocardiography cannot be relied upon to consistently determine the exact heartworm burden in experimentally infected cats, it is useful in stratifying worm burdens for anthelmintic safety studies.

Efficacy of a Single Topical Application of Advantage Multi® (= Advocate®) Topical Solution (10% Imidocloprid + 2.5% Moxidectin) in the Treatment of Dogs Experimentally Infected with Crenosoma vulpis

Crenosoma vulpis is a metastrongylid lungworm of canids causing chronic respiratory disease in dogs in parts of North America and Europe. The objective of this study was to determine the efficacy of imidacloprid 10% + moxidectin 2.5% (Advantage Multi®/Advocate® Topical Solution) against C. vulpis infection in experimentally infected dogs. Eighteen beagles (9 M, 9 F) were each given 100 infective third-stage larvae of C. vulpis. The 16 dogs (8 M, 8 F) with the highest faecal larval counts were stratified by gender and larval counts and randomly assigned to a treatment group. Group 1 received placebo only; group 2 was given a single topical treatment of Advantage Multi®/Advocate® (10 mg/kg imidacloprid/2.5 mg/kg moxidectin) at 4 weeks PI. Dogs were euthanised at 8 weeks PI and the lungs were removed and examined for the presence of adult worms by lung flush. The mean (geometric) number for adult C. vulpis recovered in untreated dogs was 70.0 (range 58 to 87) compared with 0.0 in animals treated with Advantage Multi®/Advocate®. The resulting efficacy against C. vulpis was 100%. The number of C. vulpis was significantly lower for treated dogs than the burden shown in the untreated group (p = 0.003).

Evaluation of the efficacy of emodepside+praziquantel topical solution against cestode (Dipylidium caninum, Taenia taeniaeformis, and Echinococcus multilocularis) infections in cats.

Emodepside+praziquantel topical solution was developed to provide broad–spectrum anthelmintic activity against gastrointestinal parasites in cats. Eight controlled studies were conducted to evaluate the efficacy of a topical solution of emodepside (3 mg/kg) and praziquantel (12 mg/kg) (Profender®, BayerAG, Leverkusen, Germany) against feline infections with three species of cestodes. Studies featured naturally acquired infections of Dipylidium caninum or Taenia taeniaeformis, or experimental infections with Echinococcus multilocularis that were placebo–controlled, randomized and blinded. Cats were euthanatized and necropsied between 2 and 11 days after treatment, depending on the target parasite. The efficacy of emodepside+praziquantel topical solution was 100% against D. caninum and T. taeniaeformis, and 98.5– 100% against E. multilocularis. No significant systemic or local adverse reactions to treatment were noted in cats that received the combination. Topical treatment of cats with emodepside+praziquantel topical solution was safe and highly effective against cestode infections.

Comparative Efficacy of an Imidacloprid/Flumethrin Collar (Seresto®) and an Oral Afoxolaner Chewable (NexGard®) against Tick (Dermacentor variabilis and Amblyomma americanum) Infestations on Dogs: a Randomised Controlled Trial

This randomised controlled laboratory study demonstrated the residual speed of efficacy of an imidacloprid/flumethrin collar (Seresto®, Bayer) for the control of ticks (Dermacentor variabilis, Amblyomma americanum) at 6 and 12 hours postinfestation on dogs when compared to oral afoxolaner (NexGard®, Merial). Dogs were randomised by pre-treatment tick counts: Group 1) imidacloprid 10 % (w/w) / flumethrin 4.5 % (w/w) collar, 2) afoxolaner chewable (dosage 3.1 – 6.2 mg/kg), and 3) non-treated controls. Ticks (50/species/dog) were infested on days 3, 14, 21, and 28; live (attached and non-attached) and dead attached ticks were counted 6 and 12 hours later. Efficacy against live D. variabilis at 6 hours for Group 1 was 95 – 100 % and for Group 2 was 38 – 48 %; efficacy at 12 hours for Group 1 was 97 – 100 % and for Group 2 was 27 – 59 %. Efficacy against A. americanum at 6 hours for Group 1 was 94 – 100 % and for Group 2 was < 0 – 38 %; efficacy at 12 hours for Group 1 was 98 – 100 % and for Group 2 was 1 – 40 %. Live and total (total live and dead attached) tick counts in Group 1 against both tick species were significantly lower (p ≤ 0.05) than Group 2 and 3 at all time points. The number of live or total ticks on Group 2 dogs was never significantly lower when compared to the respective number of ticks on Group 3 (controls). This study demonstrated that an imidacloprid/flumethrin collar was highly efficacious (94 – 100 %) at repelling and killing ticks on dogs at 6 and 12 hours post-infestation and was more efficacious than afoxolaner on all challenge days.

Design and Testing of a Natural Dirofilaria immitis Infection Model to Evaluate the Safety of an Imidacloprid plus Moxidectin Combination in Cats

The safety of heartworm-preventative products in heartworm-positive cats has traditionally been evaluated with a study design where adult D. immitis are removed from infected dogs and surgically implanted into cats. An alternate study model was developed to establish adult infections in cats for subsequent product safety testing. Eighty adult cats were each inoculated with 60 D. immitis L3 on test day (TD) 1. The cats then were maintained for eight months to allow for the development of adult worms. Antigen/antibody testing, as well as echocardiographic imaging, were performed to confirm and estimate adult worm burdens. Thirty-five cats determined to have clinically relevant D. immitis infections were blocked by infection intensity score and randomised to one of four treatment groups: 1) 0x (nine cats); 2) 1x dose imidacloprid + moxidectin (nine cats); 3) 5x dose of imidacloprid +moxidectin (nine cats); and 4) selamectin 1x dose (eight cats). Treatments were topically administered on TD 250. Cats in groups 1, 2 and 4 received additional treatments on TD 278 and 306. On TD 288, group 3 cats were euthanised for recovery of adult heartworms. All other cats were euthanised on TD 334. No adverse events attributable to treatment with the test articles were observed during the study. The geometric mean numbers of adult D. immitis recovered from groups 1–4 were 2.73, 2.86, 3.24 and 3.97, respectively. There were no statistically significant differences in the adult D. immitis recovery between groups (p = 0.5356). The results of the study indicate that cats currently infected with D. immitis can be safely treated with 10% imidacloprid + 1% moxidectin, even at dosages five-fold higher than recommended for clinical use.