The immunopathogenesis of flea allergy dermatitis in dogs, an experimental study

In this study, we investigated the development of clinical disease and immune responses in the development of an experimental model of flea allergy dermatitis. Dogs were randomly divided into four treatment groups and were infested with fleas on two different feeding schedules (continuous and episodic). Group 1 consisted of four non-exposed dogs (negative controls) and Group 2 consisted of six dogs exposed to fleas continually. Groups 3 and 4 consisted of 14 dogs each that were exposed to fleas on an episodic schedule (two consecutive days every other week for 12 weeks). Group 4 also received intraperitoneal injections of a low dose of lectin (ricin) with immunomodulatory properties. The purpose of Group 4 was to investigate the effects of ricin on enhancing the development of clinical signs, flea antigen-specific IgE levels and altering the number of CD4+ and CD8+ T cell subsets in peripheral blood. Clinical signs developed in all flea exposed dogs, however, the dermatology lesion scores were less and shorter in duration for continuously exposed dogs compared to episodic exposed dogs, independent of ricin treatment. Lesion development was concentrated in the flea triangle and consisted principally of erythema, followed by alopecia, excoriation, papules, and crusts. CD4+ and CD8+ lymphocyte subsets or IgE levels were not altered by ricin treatment. Flea antigen-specific IgE values were highest in dogs exposed to fleas on a continuous basis compared to those episodically exposed. A greater percentage of clinical responder dogs with negative flea-specific IgE titers or negative intradermal test (IDT) were present in the episodic exposure groups than in the continuous exposure group. IgE titers corresponded slightly better with clinical responders than the IDT. The agreement between the IgE titers and IDT was good (weighted K = 0.67). Histopathology of skin samples were consistent with a Type I hypersensitivity. In conclusion, we were able to develop a model of flea allergy dermatitis by experimentally exposing dogs to fleas on an episodic and continuous feeding schedule. In this study, continuously exposed dogs did not develop immunotolerance, and ricin did not enhance the development of FAD.     

共免疫对跳蚤叮咬引起的猫过敏性皮炎保护效果评价

为评价共免疫r FSA1和p VAX-FSA1对于猫跳蚤过敏性皮炎(FAD)的预防免疫保护效果,用人工合成的跳蚤唾液抗原(FSA1)基因,分别构建原核表达质粒p ET28a-FSA1和真核表达质粒p VAX1-FSA1。p ET28a-FSA1转化E.coli BL21(DE3)感受态细胞,诱导表达纯化FSA1,获得r FSA1。12月龄以上猫共免疫r FSA1+p VAX-FSA1,第14天实施二免后,进行跳蚤叮咬,连续4轮,跳蚤叮咬结束后,统计皮炎评分。结果显示,第4轮攻跳蚤后共免疫r FSA1+p VAX-FSA1组的猫皮炎评分远远低于FAD对照组,说明共免疫r FSA1+p VAX-FSA1能抑制FAD症状,对跳蚤叮咬猫引起的过敏性皮炎有显著保护效果,可以作为预防猫跳蚤过敏性皮炎的良好办法。     

Induction of feline flea allergy dermatitis and the incidence and histopathological characteristics of concurrent indolent lip ulcers

The objectives of this study were to characterize the role of intermittent vs. continual flea exposure in the development of flea allergy dermatitis (FAD) in cats, assess the accuracy of intradermal skin testing (IDST) and in vitro testing, and document the incidence and histopathological features of indolent lip ulcers. Ten flea‐naive cats were divided into two groups. One group received intermittent flea exposure for 120 days. Thereafter, both groups of cats received continuous flea exposure for 120 days. In vitro testing for flea salivary antibody and IDST utilizing both whole flea antigen and flea salivary antigen were performed. Eight of 10 cats developed clinical signs of FAD within 3 months and five of these eight cats developed lip ulcers which where characterized histopathologically by ulceration with predominantly neutrophilic inflammation and surface bacterial colonization. There was no association between the presence or absence of clinical signs and positive IDST or in vitro results, and no difference in the development of clinical signs was noted between the two groups of cats.     

IgE and IgG antibodies to flea antigen in differing dog populations

A radioimmunoassay was developed for the detection of IgG and IgE canine antibodies against partially purified flea antigen. Low background levels were found in flea naive dogs, but high levels of both IgE and IgG antibodies were found in many sera from dogs with clinical flea hypersensitivity. In sera from non-allergic dogs exposed chronically to fleas, IgE levels differed little from background, and levels of IgG anti-flea antibodies were much lower than those from the flea allergic group. The results suggest that chronic flea exposure may result in partial or complete tolerance rather than hyposensitization in the commonly accepted sense.     

Immune dysregulation in flea allergy dermatitis--a model for the immunopathogenesis of allergic dermatitis

BACKGROUND: Flea allergy dermatitis (FAD) is a common skin disease in dogs and can be induced experimentally. It often coexists with other allergic conditions. So far no studies have investigated the quantitative production of cytokine mRNA in skin biopsies and peripheral blood mononuclear cells (PBMC) in flea allergic dogs. OBJECTIVE: The aim of our study was to improve the understanding of the immunopathogenesis of allergic dermatitis as a response to fleabites. MATERIAL AND METHODS: Allergic and non-allergic dogs were exposed to fleas. Before and after 4 days of flea exposure mRNA was isolated from biopsies and PBMC. Production of chymase, tryptase, IL-4, IL-5, IL-13, TNF-alpha and IFN-gamma mRNA was measured by real-time RT-PCR. The inflammatory infiltrate in the skin was scored semi-quantitatively. The number of eosinophils, mast cells (MC) and IgE+ cells/mm2 was evaluated to complete the picture. RESULTS: FAD was associated with a higher number of MC before flea exposure and with a significant increase of eosinophils after flea exposure as compared to non-allergic dogs. The number of IgE+ cells was higher in allergic dogs before and after flea exposure. In allergic dogs mRNA for most cytokines and proteases tested was higher before flea exposure than after flea exposure. After exposure to fleas an increased mRNA production was only observed in non-allergic dogs. In vitro stimulation with flea antigen resulted in a decreased expression of most cytokines in allergic dogs before flea exposure. In contrast, in PBMC, only increased levels of IL-4 and IL-5 mRNA were observed in allergic dogs before flea exposure. However, after flea exposure and additional stimulation with flea antigen the production of mRNA for all cytokines tested was significantly increased in allergic dogs. CONCLUSION: We demonstrated that the response in biopsies and PBMC is different and that FAD is associated with a TH2 response.     

Efficacy of selamectin in the treatment and control of clinical signs of flea allergy dermatitis in dogs and cats experimentally infested with fleas

OBJECTIVE: To determine whether treatment with selamectin would reduce clinical signs of flea allergy dermatitis (FAD) in dogs and cats housed in flea-infested environments. DESIGN: Randomized controlled trial. ANIMALS: 22 dogs and 17 cats confirmed to have FAD. PROCEDURE: Animals were housed in carpeted pens capable of supporting the flea life cycle and infested with 100 fleas (Ctenocephalides felis) on days -13 and -2 and on alternate weeks with 10 to 20 fleas. On day 0, 11 dogs and 8 cats were treated with selamectin (6 mg/kg [2.7 mg/lb]). Dogs were retreated on day 30; cats were retreated on days 30 and 60. All animals were examined periodically for clinical signs of FAD. Flea counts were conducted at weekly intervals. RESULTS: Throughout the study, geometric mean flea counts exceeded 100 for control animals and were < or = 11 for selamectin-treated animals. Selamectin-treated cats had significant improvements in the severity of miliary lesions and scaling or crusting on days 42 and 84, compared with conditions on day -8, and in severity of excoriation on day 42. In contrast, control cats did not have any significant improvements in any of the clinical signs of FAD. Selamectin-treated dogs had significant improvements in all clinical signs on days 28 and 61, but in control dogs, severity of clinical signs of FAD was not significantly different from baseline severity at any time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that topical administration of selamectin, even without the use of supplementary environmental control measures and with minimal therapeutic intervention, can reduce the severity of clinical signs of FAD in dogs and cats.     

Diagnosis of flea allergy dermatitis: comparison of intradermal testing with flea allergens and a FcepsilonRI alpha-based IgE assay in response to flea control

The objective of this study was to evaluate the accuracy of in vivo and in vitro tests in the diagnosis of flea allergy dermatitis in comparison with history, clinical signs and response to flea control. Intradermal testing using four different sources of flea allergens and FcepsilonRIalpha-based immunoglobulin (Ig)E assays were performed in 15 flea-allergic dogs, 15 atopic dogs and 15 dogs infested with fleas but showing no clinical signs of skin disease. Sensitivity, specificity, negative predictive value, positive predictive value and accuracy were calculated for all five tests and results varied greatly. Sensitivity, specificity and overall accuracy were 27, 83 and 64%, respectively, for one extract (Isotec), 67, 90 and 82% for another extract (Greer), 93, 90 and 91% for flea saliva, 40, 90 and 73% for the recombinant Cte f 1 both produced by Heska Corp. and 87, 53 and 64% for a FcepsilonRIalpha-based IgE assay. These results indicate that intradermal testing with flea extracts is more accurate in the diagnosis of flea allergy dermatitis than in vitro tests. Moreover, pure flea saliva used as a reagent for intradermal testing provided the best results in terms of sensitivity, specificity and overall accuracy although the Greer extract, a whole body flea extract, also allowed a good correlation between intradermal testing results and clinical approach to flea allergy dermatitis diagnosis.     

Efficacy of pre-treatment with lufenuron for the prevention of Microsporum canis infection in a feline direct topical challenge model

Oral lufenuron is reportedly an effective treatment for some cats with dermatophytosis. The purpose of this study was to determine if lufenuron, when used as a pre-treatment prior to challenge exposure, would be protective against the development of infection after the direct topical application of fungal macrocondia (Microsporum canis spores). Three groups (n = 6/group) of juvenile cats were treated with either monthly oral lufenuron (30 or 133 mg/kg) or placebo. After 2 months of treatment, kittens were challenged using 10(5)Microsporum canis spores applied to the skin under occlusion. Cats were examined weekly and the following data collected: Wood's lamp examination; scoring for scale/crust, erythema and induration; lesion size; and the development of satellite lesions. Fungal cultures were performed bi-weekly. All cats became infected; the infections progressed, and then regressed, in a similar fashion in all groups. There were no consistent statistically significant differences in weekly infection scores between treated and untreated cats throughout the study. Treated cats did not recover faster than untreated cats. We conclude that oral lufenuron at the dosing schedule and conditions used in this study did not prevent dermatophytosis or alter the course of infection by direct topical challenge.     

The effects of endoparasitism on the immune response to orally administered antigen in cats

The aim of the study was to assess whether infection with Toxocara cati (T. cati) facilitates the induction of immunoglobulin (Ig) E or other antibody responses to a specific antigen administered with food in kittens. Two groups of 10 cats each, either experimentally infected with T. cati or parasite-free, were dosed with human serum albumin (HSA) added daily to their food from day 7 to 28 inclusive. Levels of HSA-specific IgE, IgG, IgA and IgM were assessed in the serum by enzyme-linked immunosorbent assay (ELISA) in both groups of cats at weeks 0, 2, 4 and 8. Although weak, an IgE response was detected in most of the cats 1 week after exposure to HSA. However, HSA-specific IgG and IgA could only be detected from the third week after exposure to HSA. The group of parasitized cats had significantly higher levels of HSA-specific antibodies of the IgG and IgA at weeks 4 and 8 (p<0.05 by Mann-Whitney) and IgE isotypes at weeks 2 and 4 (p<0.05 by analysis of variance (ANOVA)) than did the group of parasite-free cats. Specific IgM antibody was not detected in the sera of any of the 20 cats. These findings are supportive of a role of T. cati infection in enhancing the IgE response to orally administered antigens, and hence possibly, in genetically susceptible individuals, in the development of food hypersensitivity.     

Safety of a topically applied metaflumizone spot-on formulation for flea control in cats and kittens

Four laboratory studies were conducted in cats of various ages to evaluate the safety of a novel low-volume topical spot-on containing 20% metaflumizone (ProMeris for Cats, Fort Dodge Animal Health, Overland Park, KS) when used in cats according to the recommended minimum dosage of 40mg metaflumizonekg(-1) delivered via fixed volume doses of 0.8ml for cats 4.0kg. Study parameters included body weight, food consumption, clinical, physical and neurological examinations, and clinical pathology including complete hematology, coagulation, clinical chemistry and urinalysis. Exaggerated and repeated topical applications of metaflumizone at 1x, 3x and 5x the proposed recommended dose in adult cats and kittens 8 weeks of age had no effect on mortality, body weight, food consumption, clinical, physical or neurological examinations, or clinical pathology parameters. Transient salivation was sporadically noted following some, but not all treatment applications. It occurred and resolved within minutes of treatment application in all groups, including cats treated with placebo. Consequently, it was not considered a direct result of treatment with the active ingredient, metaflumizone. Cats orally administered 10% of the recommended topical dose exhibited considerable avoidance behaviors including spitting, head shaking, and salivation. Therefore, voluntary oral exposure is unlikely. No other adverse signs were observed. Repeated use of metaflumizone caused no adverse health effects when administered at 5x the recommended dose and is safe when used as directed, even on kittens as young as 8 weeks of age.     

Efficacy and safety of selamectin against fleas and heartworms in dogs and cats presented as veterinary patients in North America

A series of randomized, controlled, masked field studies was conducted to assess the efficacy and safety of selamectin in the treatment of flea infestations on dogs and cats, and in the prevention of heartworm infection in dogs. In addition, observations were made on the beneficial effect of selamectin treatment on dogs and cats showing signs of flea allergy dermatitis (FAD). In all studies selamectin was applied topically, once per month, in unit doses providing a minimum dosage of 6mgkg(-1). Dogs and cats with naturally occurring flea infestations, some of which also had signs associated with FAD, were assigned randomly to receive three months of topical treatment with selamectin (220 dogs, 189 cats) or a positive-control product (dogs: fenthion, n=81; cats: pyrethrins, n=66). Selamectin was administered on days 0, 30, and 60. Day 0 was defined as the day that the animal first received treatment. Flea burdens were assessed by flea comb counts and clinical evaluations of FAD were performed before treatment, and on days 14, 30, 60, and 90. On days 30, 60, and 90, mean flea counts in selamectin-treated dogs were reduced by 92.1, 99.0, and 99.8%, and mean flea counts in fenthion-treated dogs were reduced by 81.5, 86.8, and 86.1%, respectively, compared with day 0 counts. Also, on days 30, 60, and 90, mean flea counts in selamectin-treated cats were reduced by 92.5, 98.3, and 99.3%, and mean flea counts in pyrethrin-treated cats were reduced by 66.4, 73.9, and 81.3%, respectively, compared with day 0 counts. Selamectin also was beneficial in alleviating signs in dogs and cats diagnosed clinically with FAD. A total of 397 dogs free of adult heartworm infection from four heartworm-endemic areas of the USA were allocated randomly to six months of treatment with selamectin (n=298) or ivermectin (n=99). Selamectin achieved a heartworm prevention rate of 100%, with all dogs testing negative for microfilariae and adult heartworm antigen on days 180 and 300. Selamectin was administered to a total of 673 dogs and 347 cats having an age range of 6 weeks to 19 years (3954 doses). The animals included 19 purebred or crossbred Collies (Bearded, Border, and unspecified). There were no serious adverse events. Results of these studies indicated that selamectin was highly effective in the control of flea infestations in dogs and cats without the need for simultaneous treatment of the environment or of in-contact animals and also was beneficial in alleviating signs associated with FAD. Selamectin also was 100% effective in preventing the development of canine heartworms and was safe for topical use in dogs and cats.     

Pilot study: prevalence of positive aeroallergen reactions in 10 cats with small-airway disease without concurrent skin disease

The purpose of this study was to determine the prevalence of positive allergen reactions in cats with small-airway disease (i.e. 'feline asthma', 'feline allergic bronchitis', 'feline bronchial disease'). Intradermal skin tests (IDT) and serum immunoglobulin E (IgE) tests were performed in 10 cats with idiopathic small-airway disease and in 10 normal cats without a history of respiratory disease. None of the cats had a history of skin disease or clinical signs of skin disease at the time of testing. Significantly more individual positive allergen reactions were found on serum IgE tests than on IDT in both groups of cats. Affected cats had significantly more individual positive allergen reactions on both tests than unaffected cats. Both IDT and serum IgE tests resulted in more individual positive allergen reactions to weeds, trees, grasses, and/or moulds in affected cats than in normal cats. Significantly more positive allergen reactions to house dust mites were found in affected compared to non-affected cats by IDT but not by serum IgE testing. One unexpected obstacle to inclusion of more affected cats in the study was the concurrent presence or history of suspect or known allergic skin disease. Concurrent allergic skin disease has not been reported in association with small-airway disease in cats. The increased prevalence of individual positive allergen reactions in affected cats may be due to increased immunological reactivity in these cats. Further studies are needed to answer this question and to determine what role, if any, aeroallergens have in the pathogenesis of this complex feline disease.     

Clinical and histological evaluation of immediate and delayed flea antigen intradermal skin test and flea bite sites in normal and flea-allergic cats

Seven cats diagnosed as flea allergic by specific criteria and seven normal control cats were exposed to flea bites in a controlled manner and were given intradermal injections of 1:1000 w/v flea antigen. Subjective evaluation of gross lesions and documentation of histological changes at flea antigen intradermal skin test (IDST) and flea bite sites were performed at 15 min, 24 h and 48 h after IDST or flea exposure. Control cats did not develop an immediate gross reaction to either flea bites or the intradermal injection of flea antigen. All seven flea-allergic cats had an immediate gross reaction at the site of IDST with flea antigen; five of these cats also developed immediate gross reactions to flea bites. Three of seven flea-allergic cats developed a gross 24 h and/or 48 h delayed reaction at the flea antigen IDST sites. These three and one other cat had both an immediate and delayed gross reaction to flea bites. Histological examination of 15 min skin specimens from IDST and flea bite sites of flea-allergic cats were similar with a mild lymphocytic, histiocytic and mastocytic superficial perivascular dermatitis. Histological examination of 24 h and 48 h skin specimens from IDST and flea bite sites of flea-allergic cats showed that they were often indistinguishable. Histological features of IDST and flea bite sites of flea-allergic cats at 24 h consisted of a perivascular to diffuse predominately eosinophilic dermatitis and mural folliculitis with variable epidermal necrosis and ulceration.     

Immediate intradermal flea antigen reactivity in clinically normal adult dogs from south Florida, USA

Eighty-six clinically normal adult dogs from southern Florida, USA, with no history of dermatitis, were intradermally skin tested with Greer flea antigen 1:1000 w/v to determine the prevalence of positive immediate intradermal reactivity. This study describes the test group of animals and reports the prevalence of sensitivity to the Greer whole-body flea antigen in normal dogs living in a flea-rich environment. Similar to previous research, the highest prevalence of reactivity to flea antigen occurred at 3–4 years of age. The results indicate that 24% of clinically normal dogs from a flea-rich environment exhibited positive immediate skin test reactivity. These dogs had no clinical signs of flea allergic dermatitis (FAD) in spite of ongoing flea exposure. A 2-year follow-up telephone call to the owners of these flea antigen intradermal skin test (IDST)-positive dogs indicated that only two of 21 dogs had developed clinical signs of FAD.     

Effect of topical application of fipronil in cats with flea allergic dermatitis

OBJECTIVE: To determine whether topical application of a 10% fipronil solution would control signs of flea allergic dermatitis in cats housed under natural conditions. DESIGN: Multicenter open clinical trial. ANIMALS: 42 client-owned cats with flea allergic dermatitis. PROCEDURES: Study cats along with all other cats and dogs living in the same houses were treated with 10% fipronil solution topically on days 0, 30, and 60. Flea counts and clinical assessments were performed on study cats on days 0, 14, 30, 60, and 90. RESULTS: Percentage reductions in geometric mean flea counts on days 14, 30, 60, and 90, compared with day-0 geometric mean count, were 75, 73, 85, and 94%, respectively. Pruritus score was significantly improved at each examination after day 0, and pruritus was reduced or eliminated in 31 of 40 (78%) cats at the final examination. Similarly, scores for severity of miliary dermatitis and alopecia were significantly improved at each examination, except for alopecia score on day 14. Overall treatment efficacy, assessed on day 90, was excellent for 28 (70%) cats, good for 6 (15%), moderate for 3 (7.5%), and poor for 3 (7.5%). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that monthly topical application of fipronil is effective for treatment of flea allergic dermatitis in cats housed under natural conditions.     

Insecticidal activity of propoxur- and carbaryl-impregnated flea collars against Ctenocephalides felis.

Ten dogs were fitted with 10% propoxur-(0-isopropoxyphenyl methylcarbamate) and 10 dogs were fitted with 16% carbaryl-(1-naphthyl-N-methylcarbamate) impregnated flea collars. Ten cats were fitted with carbaryl-impregnated flea collars. There were 5 control animal for each trial. Insecticidal activity against experimental infestations with the cat flea (Ctenocephalides felis) was evaluated. The propoxur collars on dogs reduced the flea populations by 90% within 2 days of infestation for at least 13 weeks. By the 16th week, the flea population was reduced 65% in 2 days and 87% in 7 days. In subsequent infestations, efficiency was less than 80% after 7 days. Carbaryl collars on dogs reduced the flea population by as much as 80% in 2 days for a period of 16 weeks. An efficiency of at least 80% at 7 days was maintaned for 17 weeks. Carbaryl collars on cats reduced the flea population within 2 days by 80% or more for a period of at least 19 weeks--the last experimental infestation.     

Evaluation of the CatanDog's tag to prevent flea infestations, inhibit flea reproduction or repel existing flea infestations on cats

To evaluate the ability of the CatanDog's tag to eliminate fleas, inhibit egg production and prevent flea infestations, six domestic shorthaired cats were randomly allocated to two treatment groups and housed individually in stainless steel metabolic cages. Three cats were each fitted with a CatanDog's tag; the other three cats were not fitted with tags and served as controls. Following a 42-day acclimation period, each of the six cats was infested with 100, 1-3 day post-emergence, adult Ctenocephalides felis felis (Bouché) on days 0, 7, 14, 21, and 27. Flea egg production was determined by collecting and enumerating eggs 2, 4 and 6 days after each infestation. Viability of eggs was determined by placing 100 eggs recovered from each cat in rearing media in an insect rearing chamber and determining adult emergence at 28 days. Adult fleas were recovered from cats 6 days post-infestation by thoroughly combing each cat to remove fleas. To determine if the tags provided protection from infestation, the six cats were placed into a 8.53mx4.36 m room with 400 cat fleas for 3h. Cats were then combed to remove and enumerate fleas. The CatanDog's tags had no significant effect upon egg production, egg viability, or adult fleas infesting cats. In addition there was no difference in the numbers of fleas recovered from the cats placed in the flea-infested room.     

Comparison of intradermal and serum testing for allergen-specific IgE using a Fcepsilon RIalpha-based assay in atopic dogs in the UK

Atopic dermatitis in dogs is a common allergic skin disease that affects substantial numbers of dogs in the UK. The purpose of this study was to compare the results of an intradermal test (IDT) and an in vitro test in a large cohort of dogs. Dogs were intradermal tested with Greer allergens (Greer Labs Inc, Lenoir, NC, USA) using standard techniques. At the same time blood samples were drawn and submitted for evaluation by ELISA using the ALLERCEPT Definitive Allergen Panels for allergen-specific IgE, a commercial assay that uses a biotinylated recombinant extracellular domain of the high affinity Fc-epsilon receptor alpha chain protein (Fcepsilon RIalpha). The allergens used in the two tests included grass, tree and weed pollens, moulds, flea saliva/whole flea extract and house dust mite species. The optical density readings from the ELISA for each allergen were compared with the results of the IDT for 265 dogs. The prevalence of positive reactions in the ELISA was equal to or greater than the results of the IDT in the case of almost all of the allergens, but two notable exceptions were the house dust mites Dermatophagoides farinae and Dermatophagoides pteronyssinus. These two allergens were the most common positive reactions by IDT (prevalence D. farinae 78.9%, D. pteronyssinus 66.4%). The results of the two tests were significantly different (McNemar's test, P<0.05) for 16 of the 22 allergens. The sensitivities of the ELISA compared to the IDT (where there were more than 3 dogs with positive reactions in both tests) varied between 19.3 and 77.1% (D. pteronyssinus 19.3% and D. farinae 67.9%) and the specificities varied between 64.2 and 96.6% (D. pteronyssinus 96.6% and D. farinae 89.3%).     

Efficacy of a topically applied formulation of metaflumizone on cats against the adult cat flea, flea egg production and hatch, and adult flea emergence

A spot-on metaflumizone formulation was evaluated to determine its adulticidal efficacy, effect upon egg production, and ovicidal activity when applied to flea infested cats. Eight male and eight female adult domestic shorthair cats were randomly assigned to either serve as non-treated controls or were treated topically with a minimum of 40mg/kg metaflumizone in single spot-on Day 0. On Days -2, 7, 14, 21, 28, 35, 42, 49, and 56, each cat was infested with approximately 100 unfed cat fleas, Ctenocephalides felis felis. On Days 1, 2, and 3, and at 48 and 72h after each post-treatment reinfestation, flea eggs were collected and counted. At approximately 72h after treatment or infestation, each cat was combed to remove and count live fleas. Egg viability was determined by examining hatched eggs after 5 days and adult emergence was determined 28 days after egg collection. Metaflumizone provided >/=99.6% efficacy against adult fleas from Days 3 to 45 following a single application. Following treatment, egg production fell by 51.6% within 24h and 99.2% within 48h. Following subsequent weekly infestations egg production from treated cats was negligible out to Day 38, with >/=99.5% reduction relative to non-treated cats. Where there were eggs to evaluate, metaflumizone treatment did not have any apparent effect on the hatching of eggs or on the development and emergence of adult fleas from the eggs produced by fleas from treated animals.     

Evaluation of the comparative efficacy of selamectin against flea (Ctenocephalides felis felis) infestations on dogs and cats in simulated home environments

The comparative efficacy of monthly administration of selamectin or lufenuron against Ctenocephalides felis felis on dogs and cats was evaluated over a 5-month period in flea-infested environments. Twenty-four dogs and 32 cats were randomly allocated to receiving a topical treatment with selamectin or an oral administration of tablets containing lufenuron/milbemycin oxime (for dogs) or lufenuron only (for cats). Each product was administered in accordance with the manufacturer's label recommendations. Eight dogs and four cats served as untreated sentinels. Treatments were administered on days 0, 30, 60, 90, and 120. Each animal received an application of 100 fleas on days -28 and -21, and then weekly applications of 20 fleas from days 91 through 147. Flea comb counts were performed on day -6, and every 2 weeks after day 0. From day 29 (dogs) or day 44 (cats) to day 150, geometric mean flea counts for selamectin were < or =0.4. Mean flea counts for animals assigned to treatment with selamectin were significantly lower (P=0.0001) than for animals assigned to treatment with lufenuron at all assessments after day 0.