Field study to investigate the effectiveness and safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio® Plus) against natural flea and tick infestations on dogs presented as veterinary patients in Europe

BACKGROUND

A pivotal randomised, blinded, positive-controlled, multicentre, European field study was conducted to evaluate the effectiveness and safety of a novel combination tablet of lotilaner and milbemycin oxime (Credelio® Plus) administered orally to client-owned dogs naturally infested with fleas and/or ticks.

METHODS

In this field study, households with flea- or tick-infested dog(s) were enrolled on Day 0 into the study to provide data for either the tick or flea infestation cohorts. Households were randomised in a 2:1 ratio to receive either the combination investigational product (IP, Credelio Plus® tablets) or the control product (CP: Nexgard Spectra® tablets). Dogs were administered IP (flea cohort n = 135; tick cohort: n = 147) or CP (flea cohort: n = 67; tick cohort: n = 74) once every 4 weeks for a total of three times at a dose rate of 20.0-41.5 mg/kg bodyweight lotilaner and 0.75-1.53 mg/kg bodyweight milbemycin oxime (IP) or as recommended (CP). Percentage reduction was calculated by comparing individual dog flea and tick counts at each assessed post-treatment time point to their respective baseline (pre-treatment) infestation. Resolution of the clinical signs of flea allergy dermatitis (FAD) was assessed in flea-allergic dogs on the days that flea counts were performed.

RESULTS

Flea effectiveness of Credelio Plus® after 3 consecutive monthly treatments was 100% against Ctenocephalides felis, C. canis and Pulex irritans. Tick effectiveness of Credelio Plus® over the same time frame was 99.3% for Ixodes ricinus and 100% against Rhipicephalus sanguineus (s.l.). Flea effectiveness of the CP after three consecutive monthly treatments was 100% against C. felis, C. canis and P. irritans. Tick effectiveness of the CP over the same time frame was 99.8% for I. ricinus and 100% against R. sanguineus. Credelio Plus® was well tolerated based on the safety assessments in all treated dogs in this field study. Within both treatment groups there was a reduction in total FAD scores from baseline.

CONCLUSIONS

This pivotal European field study demonstrated the excellent effectiveness and safety of a combination of lotilaner and milbemycin oxime (Credelio Plus®) administered orally to dogs naturally infested with fleas and/or ticks.

Field study to investigate the effectiveness and safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio® Plus) for the prevention of heartworm disease (Dirofilaria immitis) in client-owned dogs in the USA

BACKGROUND

Dirofilaria immitis, a globally distributed filarial parasite of dogs, is known to cause serious or fatal cardiopulmonary disease. Client-owned dogs were enrolled in a clinical field study in the USA to evaluate the clinical effectiveness and field safety of an orally administered combination investigational product (IP) containing milbemycin oxime and lotilaner (Credelio® Plus) as compared to a control product (CP) for the prevention of heartworm disease when administered monthly for 11 consecutive months.

METHODS

In this 11-month field study, 319 dogs ≥ 8 weeks old confirmed to be heartworm-negative were enrolled from eight geographically distinct US veterinary clinics, including sites in the southern USA and Mississippi River Valley. The dogs were treated with either the IP combination product at 0.75-1.53 mg/kg milbemycin oxime and 20-41.5 mg/kg lotilaner (n = 159) or the CP (Sentinel® Flavor Tabs®; milbemycin oxime/lufenuron) at the label-recommended dose rate (n = 158.) On day 330, effectiveness was evaluated in each dog using antigen and microfilarial (modified Knott's) testing to assess the establishment of any patent adult heartworm infections.

RESULTS

All dogs treated with the IP combination product and the CP tested negative (100% prevention) for heartworm infection on day 330. The IP combination product tablets containing milbemycin oxime and lotilaner were well tolerated based on the safety assessments in all treated dogs.

CONCLUSIONS

This multi-site clinical study using client-owned dogs demonstrated that monthly use of flavored, chewable tablets containing a combination of milbemycin oxime and lotilaner administered orally under end use conditions is safe for dogs. None of the enrolled dogs developed heartworm infections. Eleven consecutive monthly treatments of the IP provided 100% prevention of heartworm disease caused by D. immitis.

Effectiveness of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio® Plus) for the treatment of larval and immature adult stages of Ancylostoma caninum in experimentally infected dogs

BACKGROUND

The hookworm, Ancylostoma caninum, is a common and important zoonotic intestinal nematode parasite that infects dogs globally. Both the immature and adult stages of A. caninum ingest large volumes of blood during the feeding process and can cause severe anemia and death in young dogs, even before patent infections can be diagnosed using routine faecal examination methods. Thus, effective treatment of any pre-patent stages of immature hookworms can reduce or eliminate the risk of clinical disease in infected dogs and additionally reduce environmental contamination of eggs and infective larvae. Two randomized, blinded, GCP-compliant, pivotal laboratory dose confirmation studies were conducted to evaluate the effectiveness and safety of a new novel combination of lotilaner and milbemycin oxime tablets (Credelio Plus^®) administered orally to dogs experimentally infected with immature (L4 and immature adult [L5]) stages of A. caninum.

METHODS

Treatments using the intended global commercial tablet formulation of Credelio Plus were administered in a time frame relative to inoculation with infective larvae so that effectiveness could be assessed against each specific immature stage of A. caninum. In each study, dogs were randomized to one of six (study 1) or four (study 2) treatment groups. Each treatment group contained 8 (study 1) or 10 (study 2) dogs that had been experimentally inoculated with infective A. caninum larvae on day 0 and were dosed once on day 7 or day 11. Enrolled subjects were administered placebo tablets, Credelio Plus tablets, or lotilaner mono tablets to provide minimum dosages of 0.75 mg/kg of milbemycin oxime and 20 mg/kg of lotilaner. All dogs were necropsied 5 days after their respective treatment. All nematodes recovered from the gastrointestinal tract at necropsy were counted by species and stage.

RESULTS

For both dose confirmation studies and based on geometric mean worm counts, efficacy of Credelio Plus was ≥ 97.3% against L4 larval stage of A. caninum and ≥ 98.7% against immature adult (L5) A. caninum.

CONCLUSIONS

These studies demonstrated that the orally administered Credelio Plus combination tablet was highly efficacious in treating immature (L4 and immature adult [L5]) stages of A. caninum in experimentally infected dogs.

Effectiveness of Credelio® Plus, a novel chewable tablet containing milbemycin oxime and lotilaner for the treatment of larval and immature adult stages of Toxocara canis in experimentally infected dogs

BACKGROUND

The ascarid, Toxocara canis, is a common and important zoonotic intestinal nematode parasite that infects dogs globally. An effective treatment that kills any pre-patent stages of immature T. canis could additionally reduce or eliminate the development of patent infections that can result in clinical disease in infected dogs and would further reduce environmental contamination of eggs. Two randomized, blinded, GCP-compliant, pivotal laboratory dose confirmation studies were conducted to assess the effectiveness and safety of a new novel combination of lotilaner and milbemycin oxime tablets (Credelio Plus) administered orally to dogs that were experimentally infected with immature (L4 or immature adult [L5]) stages of T. canis.

METHODS

The commercial tablet formulation of Credelio Plus^® was administered in a time frame relative to inoculation with infective eggs. This allowed for effectiveness to be assessed against each specific immature stage of T. canis. In each study, dogs were randomized and allocated to one of four treatment groups. Each treatment group contained ten dogs that had been experimentally inoculated on Day 0 with infective T. canis eggs and then were dosed once on Day 14 or Day 24 using either placebo tablets or Credelio Plus tablets (IP) to provide minimum dosages of 0.75 mg/kg of milbemycin oxime and 20 mg/kg of lotilaner. All dogs were necropsied 5 or 6 days after their respective treatment. At necropsy, all nematodes recovered from the gastrointestinal tract were counted by species and stage.

RESULTS

In both dose confirmation studies using geometric mean worm counts, effectiveness of Credelio Plus was ≥ 98.6% and ≥ 96.8% against L4 larval stage T. canis and immature adult [L5] T. canis in both studies, respectively.

CONCLUSIONS

These studies demonstrated that the Credelio Plus combination tablet administered orally to dogs was highly efficacious against experimental infections with L4 and immature adult [L5] stages of T. canis.

Field study to investigate the effectiveness and safety of a novel orally administered combination drug product containing milbemycin oxime and lotilaner (Credelio® Plus) against natural intestinal nematode infections in dogs presented as veterinary patients in Europe

BACKGROUND

A randomised, blinded, positive controlled, multicentre, Good Clinical Practice-compliant, pivotal field study was conducted to evaluate the effectiveness and safety of a new combination of lotilaner + milbemycin oxime tablets (Credelio^® Plus; Elanco Animal Health) administered orally to client-owned dogs naturally infected with intestinal nematodes.

METHODS

Client-owned dogs presenting to veterinary clinics from households in France, Hungary and Germany were screened for intestinal nematodes. Dogs with an initial positive faecal egg count that was subsequently confirmed with a follow-up faecal examination to demonstrate the presence of naturally occurring mixed or mono-infections with Toxocara canis, Toxascaris leonina, Trichuris vulpis or Ancylostoma caninum were enrolled on Day 0 into the study. Households were randomised in an approximately 2:1 ratio to receive either an investigational product (IP; Credelio Plus tablets) or control product (CP; Nexgard Spectra^® tablets) as treatment. Dogs were administered the IP (n = 278) or CP (n = 117) once on Day 0 at a dose rate of 0.75-1.56 mg/kg bodyweight milbemycin oxime and 20.0-41.5 mg/kg bodyweight lotilaner (IP) or as recommended (CP). Effectiveness of the IP and CP treatments was based on the post-treatment reduction in geometric mean faecal egg counts on Day 8 (range Day 7-10) after treatment as compared to their pre-treatment nematode faecal egg counts.

RESULTS

Geometric mean (GM) faecal egg counts for T. canis, A caninum and T. vulpis were reduced by ≥ 97.2% in the Credelio Plus group and  by ≥ 95.3% in the afoxolaner + milbemycin oxime group. There were insufficient data to calculate a percentage reduction in GM faecal egg counts between Day 0 and Day 8 for T. leonina due to low prevalence. Credelio Plus was well tolerated in this field study. Of the 355 total doses administered, 82.3% were accepted free choice in the IP group compared to 80.8% in the CP group.

CONCLUSIONS

This study demonstrated effectiveness (≥ 97.2% reduction), safety and tablet acceptance of a combination of milbemycin oxime and lotilaner (Credelio Plus) administered orally to dogs with natural intestinal infections of T. canis, A. caninum and T. vulpis.

Effects of milbemycin oxime, combined with spinosad, when administered orally to microfilaremic dogs infected with adult heartworms (Dirofilaria immitis)

OBJECTIVE To evaluate the safety of PO administration of a milbemycin oxime (MBO) and spinosad product to heartworm (Dirofilaria immitis)-positive microfilaremic dogs. DESIGN Randomized, blinded, complete block trial. ANIMALS 32 purebred Beagles with a patent heartworm infection. PROCEDURES Dogs ranked by sex and microfilaria counts (range, 398 to 1,980 microfilaria/mL) were assigned to 4 groups of 8 to receive 3 treatments PO at 28-day intervals beginning on day 0: placebo (control group) or spinosad-MBO tablets containing MBO at the upper end of the label dose range (0.75 to 1 mg/kg [0.34 to 0.45 mg/lb]; 1× group) or 3 (3× group) or 5 (5× group) times that dose. Blood samples were collected at various points for adult heartworm antigen and Knott tests. Necropsies were performed on day 65, and recovered adult heartworms were counted. RESULTS 1 control dog died from heartworm-associated complications. Other adverse events included mild, transient emesis (1 dog in each of the 1× and 5× groups and 3 dogs in the 3× group). Similar adult heartworm counts (range, 13 to 41) were obtained for all 4 groups. Results of blood antigen and microfilaria tests were positive throughout the study, with 1 exception in each of the 3× and 5× groups. Mean microfilaria counts increased with time in the control group, whereas reductions from baseline in treated groups ranged from 61.5% to 96.4%. CONCLUSIONS AND CLINICAL RELEVANCE The evaluated MBO-spinosad formulation caused no severe adverse events when administered PO to microfilaremic dogs. Although microfilaria counts decreased following treatment, repeated monthly MBO treatments were incompletely microfilaricidal, suggesting MBO should not be used as a microfilaricide.

Efficacy of lotilaner (Credelio™), a novel oral isoxazoline against naturally occurring mange mite infestations in dogs caused by Demodex spp

BACKGROUND

The oral systemic efficacy of lotilaner (Credelio™, Elanco) was evaluated against Demodex spp. in naturally infested dogs with generalized demodicosis.

METHODS

In this study, 10 dogs with clinical signs of generalized demodicosis and positive for Demodex spp. mites based on skin scrapings were assigned to a single group orally treated with lotilaner (minimum dose of 20 mg/kg) on Days 0, 28 and 56.

RESULTS

For lotilaner-treated dogs, pre-treatment mite counts based on skin scrapings performed at five different sites were reduced by > 99.9% (P < 0.0001) up to 56 days after the first and second monthly doses. No live mites were detected after Day 56 out to and including Day 84 post-treatment for 100% efficacy of each dog's Demodex mite infestation. Nine of 10 dogs were 100% mite-free from Day 28 (first evaluation) through Day 84 (end of study) and live mites were only found once on one dog (Day 56) following treatment with lotilaner. All dogs in the lotilaner-treated group showed marked improvement in the clinical signs of demodicosis and there were no drug associated adverse events. A marked improvement in hair re-growth was observed in all the dogs from 6 weeks following initiation of treatment.

CONCLUSIONS

In this study lotilaner administered at a minimum oral dose of 20 mg/kg was highly effective in reducing and eliminating live mite counts in dogs with natural infestations of Demodex spp.

Effectiveness and residual speed of flea kill of a novel spot on formulation of spinetoram (Cheristin®) for cats

Background

A spot-on spinetoram formulation (Cheristin^®) was developed to eliminate fleas from infested cats. This paper describes three spinetoram studies: two for registration (Studies 1 and 2), and one comparing residual speed of kill (SOK) with topically applied fipronil/(S)-methoprene (FSM) and imidacloprid (Study 3).

Methods

Cats were randomized to treatment based on flea counts from infestations placed within 2 weeks prior to treatment. In Studies 1 and 2, groups were untreated control and spinetoram; in Study 3, groups were untreated control, spinetoram, FSM and imidacloprid, all applied per label on Day 0. Cats were infested the day before treatment. In Studies 1 and 2, counts were completed 48 h post-treatment and after weekly challenges through 5 weeks. In Study 3, infestations were completed weekly through Day 28, with counts 1, 4, 8 and 12 h after treatment or post-infestation (PI). Efficacy was determined on geometric mean flea count reductions compared with controls, and in Study 3 mean flea counts in spinetoram-groups were compared with those in FSM and imidacloprid groups.

Results

In Studies 1 and 2, spinetoram effectiveness was 100% against existing infestations, and at least 96% through Day 37. In Study 3 mean counts were not significantly different from controls in any group until 8 h post-treatment when imidacloprid counts were significantly lower than spinetoram counts, which were in turn significantly lower than FSM counts (P < 0.05). At 1 h PI spinetoram-group counts were significantly lower (P < 0.05) than counts in: controls, all days; imidacloprid, Days 7, 14, and 28; FSM, Days 14 and 28. At 4 h PI, spinetoram mean counts were significantly lower (P < 0.05) relative to: controls, all days; imidacloprid, Days 7, 14 and 21; FSM, Days 7, 14, 21 and 28 (P < 0.05). On multiple occasions, at 8 and 12 h PI, mean counts were significantly lower (P < 0.05) for spinetoram than for imidacloprid and FSM; at no point were FSM or imidacloprid significantly more effective than spinetoram against new infestations. All treatments were well tolerated.

Conclusions

Spinetoram was highly effective for at least 1 month post-treatment and provided more rapid month-long residual SOK than FSM or imidacloprid.

Initial evaluations of the effectiveness of spinetoram as a long-acting, oral systemic pulicide for controlling cat flea (Ctenocephalides felis) infestations on dogs

Spinetoram is a semi-synthetic, spinosyn class natural product derived from fermentation by the actinomycete, Saccharopolyspora spinosa. Based on LD₅₀ (50% lethal dose) values against adult cat fleas (Ctenocephalides felis) using an in vitro contact assay, spinetoram was approximately 4-fold more potent than spinosad. Subsequently, two parallel-arm, randomized block design laboratory studies were conducted to evaluate the effectiveness of orally administered spinetoram against experimental C. felis infestations on dogs, when administered as a single dose or multiple doses over a 6-12h interval. In the first study, 16 mixed-breed dogs were allocated to two treatment groups of eight dogs each, based on pre-treatment flea retention rates: negative (placebo) control; and a single dose of spinetoram at 30mg/kg. In the second study, 32 mixed- and pure-breed dogs were allocated to four treatments groups of eight dogs each, based on pre-treatment flea retention rates: negative (placebo) control; a single dose of 60mg/kg; three sequential 20mg/kg oral doses evenly administered over a 6h period; and three sequential 20mg/kg oral doses evenly administered over a 12h period. In both studies, treatments were administered to dogs in a fed state in order to enhance absorption of spinetoram. Therapeutic efficacy was assessed 24h after treatment and persistent efficacy was assessed 48h after each subsequent flea infestation. The duration of effectiveness was assessed at approximate weekly intervals beginning on Day 5 through Day 56 in the first study, or through Day 105 in the second study. In both studies, treatment efficacy was ≥99% (geometric means) through 44 d, with ≥99% efficacy continuing through 72 d for all three treatments in the second study. Efficacy remained ≥90% for at least 8 weeks with a single 30mg/kg dose; through 13 weeks with three sequential 20mg/kg doses; and through 15 weeks with a single 60mg/kg dose. For all time points and in both studies, spinetoram-treated groups had significantly fewer live fleas relative to their respective negative control group (p<0.05). The pharmacokinetic profile in dogs revealed that the mean plasma concentration of spinetoram required for effectiveness against fleas was maintained for at least 3 months regardless of whether the 60mg/kg total body dose was administered as a single bolus or in three sequential 20mg/kg doses administered over a 6-12h period of time. The results of preliminary in vitro and in vivo studies demonstrate that orally administered spinetoram was well tolerated, and provides long lasting effectiveness against C. felis infestations on dogs.

Speed of flea knockdown of spinosad compared to afoxolaner, and of spinosad through 28 days post-treatment in controlled laboratory studies

BACKGROUND

The speed of flea knockdown by different products and their duration of effectiveness are factors which affect veterinarian prescribing decisions. To further validate the month-long pulicidal effectiveness of spinosad and determine its rate of flea knockdown to that of afoxolaner, three studies were conducted in two laboratories in the United States, utilizing flea infestations from colonies which are regularly refreshed through introduction of locally caught fleas.

METHODS

All study assessors were blinded, dogs were ranked by pre-study flea counts and randomized accordingly, and treatments administered on Day 0. All studies included a negative control group; two also included an afoxolaner group. In one study, flea challenges for treated and control dogs (10 per group) were completed 21 and 28 days after treatment and counts were performed 24 h later. In each of two speed-of-knockdown (SOK) studies, 36 dogs were randomized, six dogs per group, to: untreated controls; administered oral afoxolaner (2.6-6.2 mg/kg); or oral spinosad (32.1-59.2 mg/kg). In the SOK studies, live fleas from Day -1 infestations were counted after being combed off at 1 and 3 h after treatment, and after reinfestations on Day 7.

RESULTS

There were no treatment-related adverse events. Spinosad was 98.6% effective at 28 days post treatment. For SOK, geometric mean live flea counts for afoxolaner were not different from controls at any assessment. For spinosad, all mean counts were significantly lower than in controls (p ≤ 0.0128) except at 1 h post treatment in both studies. Spinosad was significantly more effective than afoxolaner in both studies at 3 h post treatment (p ≤ 0.0065) and post-Day 7 infestation (p ≤ 0.0054), and at 1 h post treatment (p = 0.0276) and post-Day 7 infestation in one study.

CONCLUSIONS

These data validate spinosad's faster onset of flea knockdown than afoxolaner against infestations present at the time of treatment, and faster residual speed of flea knockdown for at least 7 days post treatment, and confirm spinosad's extended residual speed of kill for at least 28 days post treatment.

Field evaluation of the efficacy and safety of a combination of spinosad and milbemycin oxime in the treatment and prevention of naturally acquired flea infestations and treatment of intestinal nematode infections in dogs in Europe

Two separate randomised, blinded, multicentre field trials were conducted to evaluate the efficacy and safety of a combination of spinosad and milbemycin oxime (MO) (Trifexis(®), Elanco Animal Health) in the treatment and prevention of naturally acquired flea infestations and intestinal nematode infections in European dogs. Treatments using Trifexis(®) and each control veterinary product (CVP) were administered once on Day 0 in both field studies. In the flea field trial, 11 veterinary clinics in France participated in the study. On Day 0, whole body flea comb counts were conducted on all dogs being evaluated for enrolment. Dogs with ≥7 fleas on Day 0 were enrolled, treated once on Day 0 with spinosad/MO or the CVP (Stronghold(®); selamectin) and then underwent post-treatment flea counts on Days 14 and 30. There were 150 spinosad/MO treated dogs and 71 CVP treated dogs included in the flea effectiveness population. Effectiveness against fleas (% reduction in geometric means; GM) was 98.97% and 97.37% for the spinosad/MO treated dogs, and 97.43% and 93.96% for the CVP dogs on Days 14 and 30, respectively, compared to the pre-treatment baseline flea counts. Of the spinosad/MO dogs, 89.3% and 80.0% had no live fleas on Days 14 and 30, compared to 77.5% and 70.4% of the CVP dogs, respectively. In the nematode field trial, data from 10 veterinary clinics in France and 19 in Ireland were pooled. Faecal samples from dogs at each clinic were analysed. A positive result at screening (parasite eggs from Toxocara canis, Toxascaris leonina, Trichuris vulpis or Ancylostoma caninum) allowed for enrolment. Dogs were randomised to spinosad/MO or the CVP (Milbemax(®); MO/praziquantel). On Day 8, a post-treatment faecal sample was taken and analysed. Of 2333 dogs screened for nematode eggs, 238 dogs were positive with one or more of these nematodes, and 229 were enrolled in the study. Of the 229 dogs, 151 were treated with a single dose of spinosad/MO, and 77 were treated with a single dose of CVP. Post-treatment effectiveness against all nematodes (% reduction GM) was achieved with reductions of 98.57% and 97.57% for the spinosad/MO treated dogs and CVP dogs, respectively, as compared to the pre-treatment baseline faecal egg counts. Trifexis(®) was shown to be safe and effective against natural infestations of fleas as well as mixed and single intestinal nematode infections in client owned dogs in Europe when administered as a single oral administration at the recommended dose.

Safety and efficacy of spinosad chewable tablets for treatment of flea infestations of cats

OBJECTIVE

To compare safety and efficacy of spinosad and selamectin and determine effects of those products on flea allergy dermatitis (FAD) in cats.

DESIGN

Randomized clinical trial. Animals-211 client-owned cats.

PROCEDURES

Cats with ≥ 5 fleas evaluated at 8 veterinary clinics were allocated to receive spinosad (50 to 100 mg/kg [22.7 to 45.5 mg/lb], PO; n = 139) or selamectin (≥ 6 mg/kg [≥ 2.7 mg/lb], topically; 72) once per month. Flea comb counts and FAD scores were determined on day -1, between days 27 and 33, and between days 85 and 95 (evaluations 1, 2, and 3, respectively); day 0 was the first day of drug administration.

RESULTS

The most common adverse event was vomiting (14.3% and 2.4% of spinosad- and selamectin-treated cats, respectively). Evaluation 2 and 3 geometric mean flea counts for spinosad-treated cats were significantly lower than those for selamectin-treated cats. Percentage reductions in flea counts for the spinosad and selamectin groups were 97.5% and 88.8% (evaluation 2) and 99.3% and 97.7% (evaluation 3), respectively. At evaluations 2 and 3, 70.6% and 92.6% of spinosad-treated cats and 29.4% and 64.7% of selamectin-treated cats were free of fleas, respectively. Weighted FAD scores for spinosad- and selamectin-treated cats decreased 94.2% and 80.0% during the study, respectively. Spinosad tablets were successfully administered during 98.1% of treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study indicated spinosad and selamectin both reduced flea counts and FAD scores for cats, although spinosad was more effective. Monthly oral administration of spinosad may be practical for treatment of flea infestations and FAD in cats.

Speed of kill efficacy and efficacy of flavored spinosad tablets administered orally to cats in a simulated home environment for the treatment and prevention of cat flea (Ctenocephalides felis) infestations

The efficacy of spinosad against adult fleas (Ctenocephalides felis) on cats was evaluated in two separate controlled, blinded studies-one to determine flea knockdown and speed of flea kill (SOFK) on experimentally infested cats, another to assess the ability of spinosad to prevent flea infestations in a simulated home environment (SHE) study design. In each study, pre-treatment live flea counts were used as a blocking factor to randomize cats to treatment, and treated in the fed state, with flavored tablets containing either no active ingredient (control) or spinosad (50-100mg/kg in the SOFK study; 50-75 mg/kg body weight in the SHE study). In the SOFK study, 6 cats per group were infested with unfed adult fleas on Day -1. Groups 1-5 received control tablets; groups 6-10 received spinosad tablets. Flea counts were conducted at 0.5, 2, 4, 8 and 24h post-dosing. In the SHE study, 12 flea-free cats per group, treated on Days 0, 30 and 60, were maintained in solid-sided cages with solid carpeted floors. Each cat was infested on Days 1, 7 and 14 with 100 unfed adult fleas. Individual flea comb counts were performed on Days 3, 9, 16, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91 and 95. After each count, except Day 95, up to 300 live fleas were replaced on each cat. To augment flea challenge, the carpeted area in each cage was sprinkled weekly with larval flea growth media (dried blood, yeast). In the SOFK study, reductions in mean flea counts in the spinosad groups were observed at all post-treatment assessments, beginning at 0.5h post-infestation with significant differences (p<0.0001) from vehicle-treated cats from 2h post-treatment when efficacy was >90%, through the final flea counts 24h post-infestation when no fleas were found on spinosad treated cats. In the SHE study, GM post-treatment flea counts in the control group ranged between 38.9 and 107.0 (arithmetic means 58.8-118.1); no live fleas were combed from spinosad-treated cats (100% effectiveness) at any time point post-treatment. No adverse events that were attributable to the treatments were observed in either study. These studies demonstrated that spinosad administered orally to cats is safe and effective, providing >90% efficacy from 2h post-dosing and 100% knockdown at 24h, and preventing infestations over a 95 day study period from a flea-contaminated simulated home environment.

Assessment of owner-administered monthly treatments with oral spinosad or topical spot-on fipronil/(S)-methoprene in controlling fleas and associated pruritus in dogs

Monitoring of the performance of flea control products under conditions of natural challenge is valuable in assessing continued effectiveness and determining the ongoing relevance of laboratory studies. A multi-clinic, investigator-blinded study was undertaken in client-owned dogs to investigate and compare the flea control provided by 3 consecutive monthly treatments of oral spinosad (SPN) or fipronil/(S)-methoprene topical (FSM) spot-on. The first household dog meeting enrollment criteria and with at least 10 fleas (whole-body flea count) served as the index dog in a household against which primary objectives were set. Stratification was based on pruritus scores at the enrollment visit and on single or multiple pet household. Index pets were randomized to treatment with either SPN or FSM, dispensed on day 0 for at-home administration by owners. All other household dogs and cats, maximum 4 pets per household, were dispensed the same treatment as the index dog (spinetoram was dispensed for cats in SPN households). Subsequent treatments were dispensed when index dogs were returned for whole-body flea counts and pruritus-scoring at visits on days 30 and 60, with final assessments on day 90 (±5 days on each occasion). Primary endpoints were the number of flea-free index dogs in each group one month after the final treatment, the reduction in owner-reported pruritus, and the reduction from baseline mean flea counts. One hundred twenty eight index dogs were enrolled (65 in the SPN arm; 63 in the FSM arm) at 10 clinics in FL (6), NC (2), LA (1), and TX (1). On day 0, geometric mean flea counts were 57.7 (range: 10-1469) and 44.8 (10-717) for the SPN and FSM groups, respectively. On Day 90, 55 of 58 (95%) and 21 of 55 (38%) index dogs completing the study were flea-free in SPN and FSM groups, respectively; mean SPN pruritus scores declined to 0.92 (6.67 on day 0), and to 3.83 (6.33 on day 0) for FSM; geometric mean flea counts (% control) were 0.08 (99.9%) and 5.19 (88.4%), for SPN and FSM groups, respectively. Between-treatment differences were highly statistically significant (p<0.0001). In conclusion, SPN provided reliable flea control in client-owned dogs, regardless of challenge level.

Dose confirmation and non-interference evaluations of the oral efficacy of a combination of milbemycin oxime and spinosad against the dose limiting parasites, adult cat flea (Ctenocephalides felis) and hookworm (Ancylostoma caninum), in dogs

Two separate controlled and blinded studies were conducted to confirm the dose and non-interference of spinosad and milbemycin oxime (MO) administered orally in combination or alone to dogs for the treatment and control of experimentally induced flea infestations (Ctenocephalides felis) and adult hookworm infections (Ancylostoma caninum). For each study, dogs were allocated randomly based on pre-treatment adult flea and hookworm egg counts to one of four treatment groups of 10 animals each. In each study, spinosad and MO in combination, using the lower half (30-45 mg/kg spinosad; 0.5-0.75 mg/kg MO) of the US commercial dose band (30-60 mg/kg spinosad; 0.5-1.0mg/kg MO) of each active ingredient, or individually alone using the full dose range, were given orally to dogs on Day 0 using a tablet formulation. A placebo control was treated similarly. In one study, on Days -1, 5, 12, 19, 28 and 35 each dog was infested with approximately 100 unfed adult C. felis obtained from the investigator's established flea colony. All dogs were infested via the same method. Forty-eight hour post-infestation flea comb counts were conducted on Days 1, 7, 14, 21, 30 and 37 and were used to determine the knockdown and residual flea activity. In the second study, on Day -27 each of 48 dogs were experimentally inoculated with 100 third-stage infective larvae of the hookworm, A. caninum. Dogs were treated on Day 0 and necropsied on Day 7 or Day 8. All nematodes in the intestinal tract were collected on Day 7 or Day 8, identified and counted by species and stage. Post-treatment, the geometric mean live flea counts were significantly different (p-value<0.0001) between the spinosad/MO combination and the spinosad only treatment groups as compared to the vehicle control group. The flea counts in the MO only group and the control group were not statistically different. The spinosad and MO combination group and the spinosad only treatment group demonstrated significantly different knockdown (100%) and post-treatment residual flea efficacy at Day 30 was 100% for both groups as compared to the vehicle control. The presence of MO in combination with spinosad did not interfere with the flea efficacy of spinosad as compared to the spinosad only group. MO alone did not demonstrate any flea efficacy. Post-treatment, the geometric mean A. caninum worm counts were significantly different (p-value<0.0001) between the spinosad and MO combination group as compared to the vehicle control group. The worm counts in the MO only group and the combination group were not statistically different. The spinosad and MO combination group (99.8% reduction) and the MO only treatment group (99.5% reduction) both demonstrated significantly different hookworm efficacy as compared to the vehicle control group. The presence of spinosad in combination with MO did not interfere with the hookworm efficacy of MO as compared to the MO only group. Spinosad alone did not demonstrate any hookworm efficacy. In summary, flavored spinosad and MO combination tablets administered orally to dogs at the lower end (30-45 mg/kg spinosad; 0.5-0.75 mg/kg MO) of the US commercial tablet unit dose range (30-60 mg/kg spinosad; 0.5-1.0mg/kg MO) were both safe and highly efficacious delivering 100% knockdown and 30 days of residual adult flea control on experimentally infested dogs as well as >99% adult hookworm efficacy evaluated under laboratory conditions. Interference between either drugs was not demonstrated for both of these dose limiting parasites.

Ivermectin and milbemycin oxime in experimental adult heartworm (Dirofilaria immitis) infection of dogs

BACKGROUND

The US Food and Drug Administration reports an increase in the frequency of reports of lack of effectiveness claims for heartworm (HW) prevention products.

HYPOTHESIS

At their labeled doses, single doses of commercially available HW prevention products are not completely effective against all field isolates of HW.

ANIMALS

Forty-two HW-free dogs experimentally inoculated with a recent HW field isolate.

METHODS

Placebo-controlled, blinded laboratory clinical trial. Dogs randomly allocated to 1 of 3 treatment groups with 14 dogs per group. Groups were untreated control or p.o. dosed with milbemycin oxime (MBO) or ivermectin (IVM). Dogs were inoculated with 50 HW third stage larvae 30 days before dosing and necropsy was performed on Day 123 after treatment to enumerate adult HW.

RESULTS

Thirteen of 14 control dogs had adult HW detected at necropsy with a geometric mean worm count of 22.3. One HW was found in 1 dog in each of the MBO and IVM treatment groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

Two currently approved macrocyclic lactone HW preventives used at their labeled dose rates were <100% effective against a recent HW field isolate, supporting the hypothesis that the effectiveness of a single dose of these preventives can vary. This is important in guiding clients on expectations of product effectiveness.

Effects of orally administered spinosad (Comfortis) in dogs on adult and immature stages of the cat flea (Ctenocephalides felis)

The efficacy of spinosad against adult fleas (Ctenocephalides felis) on dogs was evaluated in three controlled, blinded studies. One study was conducted to determine speed of kill on experimentally infested dogs. Two additional studies were designed to assess the efficacy of spinosad in preventing environmental contamination with flea eggs (USA study and EU study). An additional objective of the USA study was to assess the effects of skin and hair-coat debris from spinosad-treated dogs on eggs and larvae of C. felis. Dogs were randomly allocated to treatment with beef-flavored spinosad tablets, administered orally at a minimum dosage of 30mg/kg, or placebo. In the first study, speed of kill was determined by flea comb counts performed at 0.5, 1, 2, 4, 8, 12, 24 and 48h after spinosad treatment. Reductions in geometric mean flea counts for spinosad-treated dogs, compared to placebo were 53.7% at 0.5h, 64.2% at 1h, 85.8% at 2h and 100% at 4 through 48h post-treatment (p<0.05 at 1h and beyond). In the 2 flea egg production studies, dogs were treated (spinosad or placebo) once on day 0, infested with 600 fleas approximately 3h post-treatment and reinfested with approximately 600 fleas at intervals over 1 month. Flea eggs were collected starting at approximately 72h after each infestation. Eggs were examined for any effects of spinosad on egg viability. Efficacy of spinosad was also evaluated against environmental eggs and larvae exposed to canine hair-coat debris collected on days 3, 7, 14, 21, and 30. Spinosad was highly effective in reducing flea egg production (>99.8% across the entire study period) compared to control dogs in both egg collection studies. Insufficient numbers of eggs were recovered from spinosad-treated dogs to determine the viability of those eggs. There was no evidence of any effect on environmental flea stages, indicating that spinosad was not present in the skin debris of spinosad-treated dogs. The capability of spinosad to quickly kill adult fleas, and to greatly reduce egg production following challenge with high numbers of adult fleas is important in breaking the flea life cycle and preventing the introduction and establishment of new flea infestations in the household.

Clinical field study of the safety and efficacy of spinosad chewable tablets for controlling fleas on dogs

Preliminary studies showed spinosad to be rapidly effective and safe in controlling fleas on dogs. To validate these studies, a clinical trial was undertaken using 470 flea-infested client-owned dogs allocated to receive three monthly treatments with either beef-flavored chewable spinosad tablets (30-60 mg/kg) or selamectin applied according to label instructions. Flea counts 15 days after enrollment were reduced by 98.6% and 90.9% for spinosad- and selamectin-treated dogs, respectively; at 90 days, flea count reductions were 99.9% and 98.9%, respectively. Compared with baseline, all flea reductions were significant (P < .001) for both products and spinosad was significantly (P ≤ .0172) more effective than selamectin at each postenrollment flea count.

Knockdown and mortality comparisons among spinosad-, imidacloprid-, and methomyl-containing baits against susceptible Musca domestica (Diptera: Muscidae) under laboratory conditions

The activity of spinosad, imidacloprid, and methomyl baits and technical actives were assessed against susceptible house flies, Musca domestica L. (Diptera: Muscidae). In a feeding assay, imidacloprid affected flies more rapidly than methomyl or spinosad, but spinosad was 2.7 times more potent than methomyl and 8 times more potent than imidacloprid. The profile of technical actives correlated with their respective fly bait formulations in laboratory assays. Although having the most rapid onset of activity in laboratory tests, up to 50% of flies remained alive after exposure to imidacloprid bait. In contrast, <5% of flies survived 24-h exposure to spinosad or methomyl baits. High temperature reduced the knockdown activity of imidacloprid bait and slowed the speed of kill for spinosad and methomyl baits over a 24-h exposure period. Spinosad and methomyl baits were also superior to imidacloprid when applied to the floors of environmentally controlled rooms at label recommended rates, providing good fly control for up to 21 d. The fact that a significant percentage of flies exposed to imidacloprid were rapidly knocked down but subsequently remained alive in all of the assays suggested that flies were recovering from initial exposure to this compound. Given its favorable safety profile, a high degree of initial and residual activity comparable with methomyl and lack of cross-resistance to other chemistries, spinosad bait may be a valuable component of house fly control programs to help control or delay the emergence of resistant populations.

Therapeutic and persistent efficacy of spinosad applied as a pour-on or a topical spray against natural infestations of chewing and sucking lice on cattle

Studies were conducted in Wisconsin and Illinois, USA, to assess and compare the therapeutic and persistent efficacy of spinosad when applied as either a pour-on or topical spray and compared with cyfluthrin pour-on and coumaphos topical spray for controlling natural infestations of chewing (Bovicola bovis) and sucking (Linognathus vituli, Solenopotes capillatus and Haematopinus eurysternus) lice on cattle. Thirty-five animals at each trial site were blocked according to pre-treatment lice counts and randomly allocated to one of five treatment groups: single treatments of spinosad (25 g/L), diluted with water to 0.04% active ingredient and applied as a whole-body topical spray; spinosad (25 g/L) applied as a neat pour-on at 2 mg/kg body weight; Co-Ral Emulsifiable Livestock Insecticide (5.8% coumaphos), diluted to 0.03% active ingredient and applied as a whole-body topical spray; CyLence Pour-on Insecticide (1% cyfluthrin), applied as a neat pour-on at the manufacturer's recommended use rate for lice; and untreated control. Both spinosad treatments and cyfluthrin provided > or =96% control of B. bovis for up to 7 weeks, whereas the efficacy of coumaphos dropped to <90% after week 5 at one site. Spinosad spray had the best therapeutic and residual control of all treatments against L. vituli, > or =98% for at least 5 weeks at both sites, compared with 3 weeks for coumaphos at one site. Spinosad and coumaphos sprays provided 100% control of S. capillatus for at least 8 weeks compared with > or =97% control for spinosad and cyfluthrin pour-on treatments over the same interval. While H. eurysternus burden was low and limited to one study site, all four treatments provided 100% control for at least 6 weeks. These studies showed that topically applied spinosad provided a high degree of therapeutic and residual control against both sucking and chewing lice.

Evaluation and development of spinosyns to control ectoparasites on cattle and sheep

The spinosyns are a novel family of fermentation-derived natural products that exhibit potent insecticidal activities. Spinosad, a naturally-occurring mixture of spinosyn A and spinosyn D, has successfully established its utility for crop protective applications in the agrochemical field. Potential applications of this unique chemical family of macrolides also have been investigated in the field of animal health. Applications for the control of blowfly strike and lice on sheep have now been commercially developed and registered in Australia and potential applications for the control of ectoparasites on cattle are being studied.

Efficacy of a single whole-body spray treatment of spinosad, against Boophilus microplus (Acari: Ixodidae) on cattle

The efficacy of a single whole-body spray of spinosad, a naturally derived control agent, applied at three concentrations was evaluated against cattle infested three separate times prior to treatment and at four weekly intervals following treatment with Boophilus microplus (Canestrini). At 0.0167% active ingredient (AI) both tick numbers (1894 ticks per calf) and index of fecundity (IF) of females (258.3) were no different than that of the control group. However, spinosad treatment at both 0.05 and 0.15% AI resulted in fewer ticks per calf (600 and 935, respectively) with lower IF values for females (43.4 and 38.4, respectively). The percent control of ticks on the animals at the time of treatment (acute efficacy) was dramatically lower at 0.0167% AI (21.4%) than at 0.05 (86.3%) and 0.15% AI (87.9%). Spinosad treatments appeared to be more effective against immature stages (nymphs and larvae) than against adult ticks that were on the animals at the time of treatment. The mean weight of females that survived to repletion was similar (322-348 mg) in all groups. By contrast, the mean weight of egg masses produced by females was highest in the control group (155 mg), whereas each increase in spinosad concentration resulted in a substantial decrease in egg mass weight, with the 0.15% AI group averaging only 73 mg. The hatch rate of eggs derived from females ranged from 93.4% in control females down to 53.9% hatch for females treated at 0.15% AI spinosad. The residual efficacy of spinosad at 0.0167% AI was poor even at 1 week following treatment, resulting in 101 ticks per calf and a level of control of only 66.4%. At 0.05% AI, protection against successful reinfestation was high at 1-week post-treatment where only five ticks per calf reached repletion, and control of the IF of these females was 99.3%. The 0.15% AI treatment provided almost complete protection against reinfestation for 2 weeks following treatment (< or =5 ticks per calf), and control of the IF of these ticks was >99.9%. Thus, the use of spinosad at US ports-of-entry would be unacceptable because of the critical necessity of achieving 100% control with a single treatment to prevent the reintroduction of ticks. However, it is likely ticks could be eradicated using spinosad in tick infested areas of the US if repeated (systematic) treatments were applied to cattle maintained on the premises.

A retrospective histopathological survey of capillariasis in raccoons (Procyon lotor) from Oregon

A 2-yr retrospective survey (1995-1998) of 63 adult raccoons (Procyon lotor) from Oregon, northwestern United States, was conducted by histopathological examination of various tissues. An overall prevalence of capillariasis was recorded in 52% of the raccoons. Highest prevalence of nematodes (29/30, 97.7%) was present in the anal sacs, where variable numbers of nematodes, their ova, and extensive diffuse inflammatory cellular infiltrate were evident. Lesser numbers of nematodes were also seen in the mucosa of the anterior alimentary tract (mouth 2/63, tongue 10/62, esophagus 2/63) and in the urinary bladder (7/63). However, at these sites, there was a paucity of inflammatory infiltrate. The findings of this study indicate that capillariasis of the anal sacs is commonly seen in free-ranging raccoons in Oregon, and the infection is essentially subclinical because only 1 case of anal sac impaction has been reported. Measurements of the nematode and their ova from the anal sacs indicate that it is most likely a new capillariid species, which to date has not been fully described in raccoons. It is speculated that the high prevalence of anal sac infection by a Capillaria sp. in Oregon raccoons may also be true for raccoons in other parts of North America and in parts of Europe and Asia where this species has been introduced.

Cerebral larva migrans in a raccoon (Procyon lotor)

During 1997, gross and histopathologic examinations were performed on an adult female raccoon (Procyon lotor) that was live-trapped in Corvallis, Oregon. Multifocal eosinophilic granulomas indicative of neural and visceral larva migrans were observed. However, within these granulomas, the presence of parasitic larva was seen only in the cerebrum. Morphologic characteristics indicated that the nematode was an ascarid larva. However, it was smaller than the larva of Baylisascaris sp. This appears to be the first documented case of cerebral larva migrans in a raccoon.

Synthesis and endectocidal activity of novel 1-(arylsulfonyl)-1-[(trifluoromethyl)sulfonyl]methane derivatives

We have recently synthesized a series of novel disulfonylmethane compounds that have shown anthelmintic and insecticidal (endectocidal) activity. Several analogues have shown activity against the internal nematode Haemonchus contortus. In sheep studies, these analogues have shown 100% control of this internal parasite at a 10 mg/kg rate. In vitro activity against the biting flies, Stomoxys calcitrans and Haematobia irritans, has been observed at rates as low as 25 and 2.3 ppm, respectively. Only marginal activity against the liver fluke Fasciola hepatica and Trichostrongylus colubriformis was seen. Respiratory control index values on rat liver mitochondria for this series suggested uncoupling of oxidative phosphorylation as a mechanism of action. Compound 1 is considered to be a promising agent for treatment of parasitized sheep.

Biochemical, biological, and genetic characterization of a sylvatic isolate of Trichinella

Biological, biochemical, and genetic relationships of Trichinella isolates were assessed and compared from 3 species of Illinois fur-bearing mammals. Tongue muscle collected from 1987 through 1989 from 323 raccoons (Procyon lotor), 9 red fox (Vulpes fulva), and 1 coyote (Canis latrans) were digested and Trichinella muscle larval prevalences and mean intensities (larvae/g) determined. The prevalence and mean intensity of tongue muscle-stage larvae were 2.8% and 44.4% and 326 and 2 larvae/g for raccoon and red fox, respectively. The single coyote examined for muscle larvae was negative. Seven of 13 Trichinella isolates (5 raccoon, 2 red fox) were maintained and amplified in mice. Comparative analyses of DNA from larvae of these isolates and from other Trichinella isolates were performed by dot-blot hybridization using specific repetitive DNA probes. DNA from the 7 Illinois sylvatic isolates reacted with the Trichinella T5 isolate DNA probe pUPB-3.7 and did not cross-react with the Trichinella spiralis probe pBP-2. The sylvatic isolates of Trichinella were also analyzed using 27 allozymes. Their allozymic patterns were similar to Trichinella reference strain T5 from Pennsylvania, except for mannose phosphate isomerase. These results suggest that the Illinois wildlife isolates belong to the Trichinella T5 genotype according to the classification system established by the International Trichinella Reference Centre and as defined here by positive hybridization to the pUPB-3.7 probe. Results from Southern blot analyses using rRNA as a probe and allozyme patterns revealed some heterogeneity among geographical isolates of the T5 genotype.

Epidemiology of Ostertagia ostertagi in cow-calf herds in the southeastern USA

Ostertagia ostertagi is commonly found in the brood cow and nursing calf in the southeastern USA, this information being derived from fecal egg counts, coproculture and necropsy results; however, clinical disease and large burdens of this parasite are rarely reported. Fecal egg counts in brood cows are routinely low and are generally reported to be 10 eggs per gram of feces (EPG) or less. Nematode egg counts in spring-born calves are also generally low prior to weaning; they increase steadily during the spring and summer and peak from late summer to fall weaning. That egg counts in spring-born calves are low for several months after birth is probably a reflection of minimal grazing activity. It appears that Ostertagia ostertagi may be of equal or less importance than other nematode genera for spring-born calves in the southeastern USA. The role that Ostertagia ostertagi plays in fall-born calves or in year-round calving herds has not been adequately investigated. Also, the role that the adult cow plays, with low egg counts and small Ostertagia ostertagi burdens, in contamination of pasture is not understood during either lactation or dry periods. Treatment of beef calves prior to, or at weaning can reduce contamination and transmission of gastrointestinal parasites on pastures which may be subsequently grazed by these or other weaned calves. Data on parasite population dynamics from tracer calf studies in cow-calf herds in the southeastern USA have identified peak periods of transmission and incidence of specific genera or stages. This information, in conjunction with routinely used cattle production and management practices such as time of calving, should provide means to more accurately define optimal timing for strategic parasite treatment programs and their overall effect on beef production in the southeastern USA.

First report of a Demodex sp. in raccoons (Procyon lotor)

Demodex spp. mites were seen in skin sections of 5 of 53 raccoons (Procyon lotor) necropsied on Parramore Island, Virginia (USA). In all infections, mites were present in the skin over the lower legs; in one raccoon they also were located in a follicle of a vibrissa. None of the raccoons had Demodex-related gross lesions. Histopathologically, minimal lesions were seen in the affected follicles. This is the first documentation of Demodex spp. in raccoons.

Helminth parasites of the raccoon (Procyon lotor) from north-central Arkansas

Twenty-three species of helminths (4 trematodes, 2 cestodes, 14 nematodes, and 3 acanthocephalans) were found in the gastrointestinal tract, lungs, pancreas, tongue, urinary bladder, and subcutaneous tissues of 30 live-trapped or hunter-shot raccoons from north-central Arkansas between November 1989 and April 1990. Helminths were not detected in the brain, diaphragm, gallbladder, heart, liver, reproductive system, or trachea. Each raccoon examined was infected with 3 or more of the following helminths: Brachylaima virginiana, Eurytrema procyonis, Fibricola cratera, Pharyngostomoides procyonis, Atriotaenia procyonis, Mesocestoides spp., Arthrocephalus lotoris, Capillaria aerophila, Capillaria plica, Capillaria procyonis, Capillaria putorii, Crenosoma goblei, Cruzia americana, Dirofilaria tenuis, Dracunculus insignis, Enterobius sp., Gnathostoma procyonis, Molineus barbatus, Physaloptera rara, Trichinella spiralis, Centrorhynchus wardae, Macracanthorhynchus ingens, and Oligacanthorhynchus tortuosa. All helminths collected with the exception of D. insignis constitute new geographic distribution records. Occurrences of C. aerophila, C. wardae, and O. tortuosa are new host records. One nymphal pentastome, Porocephalus crotali, was found in the liver of 1 raccoon, constituting a new host record.

Prerequisites for oral immunization of free-ranging raccoons (Procyon lotor) with a recombinant rabies virus vaccine: study site ecology and bait system development

A model baiting system suitable for the delivery of an oral rabies vaccine to free-ranging raccoons (Procyon lotor) was developed and tested on barrier islands in South Carolina (USA). Features of barrier island physiography and ecology were studied relative to selective bait deployment and site biosecurity. Capture-mark-recapture data were obtained from 228 raccoons. Raccoon density estimates, using a modified census assessment technique, were one raccoon per 1.8 to 2.7 ha. Mean (+/- SE) and range home area estimates of radio-collared raccoons were 84 (+/- 15.6) ha (27 to 176 ha) by a minimum convex polygon method and 138 (+/- 22.8) ha (43 to 241 ha), by a harmonic mean transformation method. Habitat utilization determinations of radio-collared raccoons were conducted to identify study areas to potentially maximize selectivity of bait towards raccoons and to reduce the absolute number of baits deployed. Island raccoons showed a habitat preference for maritime forest, maritime shrub and marsh areas. Additionally, there was no evidence of inter-island or mainland exchange of ear-tagged or radio-collared raccoons. A disease and mortality survey was conducted to identify baseline pathology and incidental lesions in the target raccoon population, prior to actual vaccination initiation. Thirty-eight percent of 30 clinically suspect raccoons sampled had intracytoplasmic eosinophilic inclusions diagnostic of canine distemper; no other lesions suggestive of viral etiologies were found. Serological surveys for raccoon poxvirus and rabies virus antibodies were negative. Antibody titers to canine adenovirus 1 and 2 indicated a moderate level of exposure (approximately 10 to 16%) in the raccoon population. Overall, 93 to 100% of placebo baits were consistently disturbed by 7 days post-bait deployment, and bait acceptance rates by raccoons ranged from 49 to 85%, by using a modular systems approach to select the optimum combination of bait attractant, biomarker, matrix, density, and distribution. These results suggest that a large proportion (up to 85%) of a free-ranging island raccoon population can be selectively and safely targeted, marked and monitored utilizing a proposed oral bait delivery system for recombinant or other rabies vaccines.

Notoedric acariasis in the porcupine (Erethizon dorsatum)

Six of 16 porcupines (Erethizon dorsatum) live-trapped in Sullivan County, Pennsylvania were infested with the mite Notoedres douglasi. Alopecia was evident in the ventral inguinal area and the infested skin was thickened, wrinkled and had multifocal areas of extensive hyperkeratosis. Microscopically the skin lesions consisted of extensive acanthosis and hyperkeratosis with variable cellular infiltrate in the dermis. Mites were seen in tunnels in the hyperkeratotic skin sections. This is the first report of notoedric acariasis in the porcupine.

Pancreatic duct hyperplasia in a raccoon (Procyon lotor) caused by Atriotaenia procyonis

A raccoon (Procyon lotor) live-trapped in Philadelphia, Pennsylvania was heavily infected with the tapeworm Atriotaenia procyonis. Histopathologic examination of the duodenum revealed this tapeworm attached to the mucosa; the mucosa was mildly hyperplastic without a significant inflammatory infiltrate. This tapeworm was seen also within the proximal pancreatic duct and histopathologic lesions associated with its presence consisted of marked hyperplasia of mucosal cells, causing the formation of an extensive papillary projection into the duct lumen. Inflammatory cellular reaction was minimal, consisting primarily of lymphocytes, and was seen in the mucosa and submucosa of the duct. The presence of A. procyonis in the pancreas of this raccoon is considered to be an aberrant location for this parasite and has not been reported previously.

Lesions associated with pulmonary parasites in bobcats (Felis rufus) from Arkansas

Two of five bobcats (Felis rufus) from southwestern Arkansas had natural pulmonary infections of Paragonimus kellicotti and Filaroides rostratus. Pairs of P. kellicotti were found in spherical cyst-like structures approximately 1 cm in diameter. Filaroides rostratus were seen as serpentine pale white areas on the pleural surface and also firmly embedded in fibrous capsules in the pulmonary parenchyma. Histologic lesions associated with the presence of these parasites consisted primarily of a verminous bronchitis. Clinical signs or compromised pulmonary function were not associated with these infections.

Lung lesions in an opossum (Didelphis virginiana) associated with Capillaria didelphis

An opossum (Didelphis virginiana) live-trapped on Parramore Island, Virginia was infected with the lung parasite Capillaria didelphis. Lung lesions associated with this parasite were extensive and consisted of numerous areas with central necrosis deep within the parenchyma. Necrotic foci were present around airways and consisted of a mixture of inflammatory cells and cellular debris, adult nematodes and many bipolar eggs. This parasite causes severe verminous pneumonia in the opossum.

Sarcocystis kirkpatricki n. sp. (Apicomplexa: Sarcocystidae) in muscles of raccoons (Procyon lotor) from Illinois

Sarcocysts of Sarcocystis kirkpatricki n. sp. (Apicomplexa: Sarcocystidae) are described from the skeletal and heart musculature of 66 (66%) of 100 raccoons (Procyon lotor) from Illinois. Histologic examination of muscle tissues from tongue, diaphragm, esophagus, and heart revealed that 61%, 47%, 32%, and 2%, respectively, contained sarcocysts of this species. Juvenile raccoons (less than 1 yr old) were more likely (P less than 0.01) to have sarcocysts in the tissues examined (52/60 or 87%) than were adults (14/40 or 35%). Histologically, sarcocysts in the 4 tissues were similar: the cyst wall was 2-3 microns thick, PAS negative, and had fine hairlike surface projections; interior septa were indistinct. Ultrastructurally, sarcocyst walls had short (mean = 2.8 microns), straight to sloping, villuslike projections. Longitudinal tubular filaments inside these projections extended from the tips to the base, where they terminated in a granular electron-dense layer of the primary cyst wall. Thin septa were within the sarcocysts. Feeding experiments utilizing dogs and cats as potential definitive hosts were negative.

Proposed field evaluation of a rabies recombinant vaccine for raccoons (Procyon lotor): site selection, target species characteristics, and placebo baiting trials

Prior to a limited field application of an orally-administered vaccinia-rabies glycoprotein (V-RG) recombinant virus vaccine for wildlife, background data were obtained for the proposed site on Parramore Island, Virginia (USA). Mammalian target and nontarget species, potentially at risk for exposure to vaccine were inventoried. Placebo baiting trials with a fishmeal polymer bait resulted in high bait disturbance (88 to 100%), primarily by raccoons (Procyon lotor), with infrequent visitation and no evidence of bait consumption by deer (Odocoileus virginianus), small mammals or avian species. Definitive bait acceptance rates by raccoons (indicative of bait ingestion) were difficult to accurately determine based exclusively on premolar and vibrissae samples collected antemortem from live-trapped raccoons for tetracycline and rhodamine B biomarker analyses, respectively. Bait acceptance rate was more accurately determined during a pilot baiting trial conducted on North Island, South Carolina, when mandibles (postmortem samples) were examined for tetracycline incorporation. Parasitologic findings in raccoons on Parramore Island included Hepatozoan procyonis, Phagicola angrense and Physaloptera rara and a variety of incidental microscopic lesions, and provided baseline pathological data for comparison subsequent to V-RG vaccine application. A population density estimate of one raccoon/2.7 ha was calculated using mark-recapture data for comparison after vaccine deployment. Limited reproductive data, including estimates of pregnancy rates by palpation, the number of live kits/litter live-trapped with previously pregnant raccoons or observed in the dens of radio-collared raccoons, was gathered to assess the effect of proposed oral vaccination with V-RG vaccine. Home ranges were assessed by radio-telemetry of 15 raccoons; all radio-collared raccoons currently reside on Parramore Island.(ABSTRACT TRUNCATED AT 250 WORDS)

Dirofilaria immitis in a river otter (Lutra canadensis) from Louisiana

A single adult male river otter (Lutra canadensis) from Louisiana was found naturally infected with Dirofilaria immitis. One adult male nematode was found in the heart; lesions attributable to the presence of the parasite were not found. This is the first report of D. immitis in the river otter in North America.

Scanning electron microscopic observations of adult Baylisascaris procyonis (Nematoda)

The scanning electron microscope was used to illustrate the microtopographic features of the caudal end of adult male Baylisascaris procyonis. The male tail was relatively long, smoothly attenuated and often had a small button-like or mucronate termination. The preanal papillae were situated ventrally in two slightly divergent and somewhat irregularly spaced rows. Anterior and posterior to the anus were two slightly raised roughened patches consisting of several rows of small spines. Just anterior to the anus along the outer margin of the preanal roughened patch was a large double medioventral papilla. There were five pairs of postanal papillae with the first pair just posterior to the anus being double while the remaining four pairs were more closely associated in a group near the tail end. The second pair were also double papillae; however, in a few specimens they were not fused and appeared as two single closely associated papillae. The last three pairs of papillae were single. The fourth pair of caudal papillae were the phasmids and in the center of each was a ringed pore-like opening. The spicules of the male had a highly sculptured surface with a pincher-like terminal end.

An American Board of Orthodontics case report

A case report is presented of an Angle Class I dental malocclusion, significant bimaxillary dentoalveolar protrusion, anterior open bite, and spacing of the maxillary and mandibular incisors. [This case was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.]

Phagicola angrense (Digenea: Heterophyidae) as a cause of enteritis in a raccoon (Procyon lotor)

Numerous Phagicola angrense were associated with enteritis in a single male juvenile raccoon (Procyon lotor) live-trapped on Parramore Island, Virginia (USA). The raccoon was weak, ataxic and had melenic soft feces. The carcass was emaciated, pale and had ascites. Mesenteric vessels appeared prominent and the stomach and the intestines contained fetid bloody material. The small intestinal mucosa contained three locally extensive sites of necrosis. Histopathologically, there were numerous small digeneans both attached to the mucosa and free within the lumen. Digeneans were usually found deep within the crypts where the epithelium was markedly attenuated and devoid of epithelial cells at the point of parasite attachment. In the lamina propria there were areas of acute hemorrhage and infiltration with plasma cells and eosinophils. This appears to be the first record of severe enteritis in the raccoon caused by this digenean.

New information on the location of Capillaria procyonis (Nematoda: Trichuroidea) in the tongue of a raccoon (Procyon lotor)

Histologic examination of the tongue of one juvenile male raccoon demonstrated the presence of adults and unembryonated eggs of the nematode Capillaria procyonis within parasite-induced tunnels in the stratified squamous epithelium. There was no inflammatory infiltrate within the epithelium or the subjacent lamina propria. The shape of tunnels approximated that of the resident nematodes and were lined by flattened and attenuated epithelial cells. Therefore, the site of infection of C. procyonis in the raccoon includes the oral, lingual and pharyngeal epithelium in addition to the esophagus.