Field comparison of tolerance of a collar containing 10.0% imidacloprid/4.5% flumethrin (Seresto) and a placebo collar placed on cats

Abstract

Objectives

A collar containing 10.0% imidacloprid/4.5% flumethrin (Seresto; Bayer Animal Health) controls flea and tick infestations for 8 months and is effective in preventing transmission of Bartonella henselae and Cytauxzoon felis among cats. The purpose of this study was to compare tolerance of client-owned cats for the 10.0% imidacloprid/4.5% flumethrin collar or a physically identical placebo collar.

Methods

A total of 96 client-owned cats were enrolled in the study. Cats that were systemically ill, of hairless breed or declawed in all four limbs were excluded. Cats were randomized by household to wear a placebo collar for 14 days followed by the 10.0% imidacloprid/4.5% flumethrin collar for 14 days or the 10.0% imidacloprid/4.5% flumethrin collar for 28 days. Examinations by a veterinarian were performed on days 0, 14 and 28. Owners recorded daily systemic and local health observations.

Results

All but two cats, including one that entrapped the mandible in the collar and one that developed local pyodermatitis (10.0% imidacloprid/4.5% flumethrin collar), completed the 28 day study. The majority of the local lesions or licking associated with the collars occurred in the first 14 days, and licking (but not skin lesions) was more common in cats wearing the 10.0% imidacloprid/4.5% flumethrin collars. No local lesions were reported for placebo cats after switching to the 10.0% imidacloprid/4.5% flumethrin collar, and only one cat wearing the 10.0% imidacloprid/4.5% flumethrin collar had reports of licking after day 14. Housing status, single or multiple cat household, and whether a collar had been worn previously were not associated with side effects.

Conclusions and relevance

Adverse events detected for cats wearing 10.0% imidacloprid/4.5% flumethrin collars were similar to those for cats wearing placebo collars and to cats wearing identification collars in a separate study. The data suggest that most cats originally intolerant of collars become receptive over time.

Ticks are associated with many clinical conditions in cats, including serving as vectors for Ehrlichia canis, Cytauxzoon felis and Anaplasma phagocytophilum. Fleas can also be vectors for Dipylidium caninum and Bartonella henselae, and are associated with dermatitis and blood loss anemia. Topical flea and tick control products have proven to be very efficacious and systemically safe; however, client compliance can be <100% owing to the need for monthly application of the product. A collar containing 10.0% imidacloprid/4.5% flumethrin (Seresto; Bayer Animal Health) has been evaluated in many field and research settings, and has shown high systemic safety, as well as effectiveness in preventing flea and tick infestation for up to 8 months.^1–4 Recent studies showed that cats wearing the 10.0% imidacloprid/4.5% flumethrin collar were not infected with B henselae, D caninum or C felis, proving the value of the collar in preventing vector-borne disease transmission.^1,2,5

Topical and oral medications that are provided for owners to administer can have an efficacy of <100% because of failure to administer the products properly. A major benefit for a flea and tick collar is compliance; if the collar is in place and within the expiration date, it is likely to be working. However, it is the general perception by owners and veterinarians that cats do not tolerate collars of any type. In a previous study, assessing tolerance of cats to identification collars, 9% of cats developed local cutaneous disease in the region of the collar. ⁶ In field studies conducted in Europe, a small percentage of cats developed hyperemia, alopecia, licking or pyodermatitis in the region of the 10.0% imidacloprid/4.5% flumethrin collar, but reports have been minimal. ⁷ In the multiple research studies conducted with the 10.0% imidacloprid/4.5% flumethrin collar, reports of local reactions attributed to the collar have been minimal, but large numbers of cats have not been studied. Some have questioned whether cats are intolerant of the collar itself or the active ingredients within the collar. The purpose of this study was to report side effects associated with the 10.0% imidacloprid/4.5% flumethrin collar and an identical placebo collar with no active ingredients when applied to the cats owned by veterinary healthcare providers.

Materials and methods

A total of 96 cats owned by Colorado State University veterinary students and staff were used in this double-blinded study. Exclusion criteria included cats <10 weeks of age, hairless breeds, cats that had declawed hindlimbs, cats with systemic illness and cats with known allergies. Both owner consent and approval from the International Animal Care and Use Committee (IACUC) were obtained prior to beginning the study.

Cats were randomized into two groups separated by household: placebo (48 cats) and 10.0% imidacloprid/4.5% flumethrin collar groups (48 cats). All cats in each household had the same collar type placed on day 0. Physical examinations were performed by a study veterinarian (SW) on days 0, 14 and 28, and included body weight, temperature, pulse and respiration. Presence or absence, as well as type of dermatologic lesions, were recorded. Owners were given forms to record daily health (local and systemic) observations (presence or absence) and informed to contact the study veterinarian with any concerns. On day 14, the cats wearing a placebo collar were switched to a 10.0% imidacloprid/4.5% flumethrin collar. Final observations and physical examinations were on day 28. Cats that developed significant systemic or local disease were to be removed from the study.

Statistical analysis

All reports of abnormalities were recorded and reported, and analysis performed by group as prevalence rates on those deemed potentially related to the collars. Prevalence rates for each report were compared by Fisher’s exact test. Logistic regression was also performed. For univariate analyses, significance was defined as P <0.25; for the final model, significance was defined as P <0.05. Parameters assessed in the univariate analysis included indoor/outdoor status, whether it was a single or multiple cat household, the age of the cats (⩽1 year or >1 year) and whether a collar (any type) had previously been worn. Only parameters shown to be statistically significant in univariate analysis were added to the final logistic regression model. All statistical analysis was performed using Stata 11.2.

Results

Of the 96 cats, 36 (37.5%) were female and 60 (62.5%) were male. A total of 64 cats (66.6%) had worn a collar of any type prior to the beginning of the study. Cats that had previously worn flea collars were not differentiated from those that worn identification collars. The majority of the cats (81/96; 84.4%) lived in households with at least one other cat and was housed indoors. There were no systemic clinical signs of disease attributed to the collars. One cat in the 10.0% imidacloprid/4.5% flumethrin collar group had the collar entrapped over the mandible twice in the first several days of the study, and thereafter was excluded from the study; the other 95 cats completed the 28 day study. The cat with mandibular entrapment of the collar was able to loosen the collar enough to entrap the lower jaw while attempting to remove the collar.

In the first 14 days of the study, the prevalence of crusts (placebo collar = 2.1%; 10.0% imidacloprid/4.5% flumethrin collar = 4.6%), erythema (placebo collar = 4.2%; 10.0% imidacloprid/4.5% flumethrin collar = 6.4%), alopecia with erythema (placebo collar = 2.1%; 10.0% imidacloprid/4.5% flumethrin collar = 4.3%), alopecia with crusts (placebo collar = 4.2%; 10.0% imidacloprid/4.5% flumethrin collar = 2.1%) or any skin lesion (placebo = 12.5%; 10.0% imidacloprid/4.5% flumethrin collar = 17%) was not statistically different between groups (P >0.05). Owner reports of the cat licking the collar were statistically different between the groups (placebo collar = 8.3%; 10.0% imidacloprid/4.5% flumethrin collar = 27.7%) during the first 14 days of the study. Four cats were excluded from the logistic regression model because of missing data. The results of the univariate analysis showed only the history of wearing a collar and age class to be significant covariates, and so these were included in the final logistic regression model. When the presence of skin lesions were compared between groups in the final model while controlling for age and previous collar history, there were no significant differences. When owner-reported licking was included, the model showed there was a significant difference (P = 0.023) between groups; cats wearing a 10.0% imidacloprid/4.5% flumethrin collar were 3.46 times (95% confidence interval 1.18–10.12) more likely to have a report of licking or a skin lesion than cats with the placebo collars.

None of the placebo cats had reports of local lesions after crossing to the 10.0% imidacloprid/4.5% flumethrin collar, and only one 10.0% imidacloprid/4.5% flumethrin collar cat had a reported side effect after day 14 (owner reported licking). One cat required removal of the collar for treatment (10% imidacloprid/4.5% flumethrin collar) for local pyodermatitis, which resolved with routine treatments.

Discussion

The presence or absence of skin lesions were not significantly different between cats wearing 10% imidacloprid/4.5% flumethrin collars or placebo collars, and the presence of skin lesions was similar to cats wearing identification collars reported in a previous study. ⁶ In a previous study assessing the possible effects of identification collars in cats, 9% developed cutaneous reactions at the collar placement sites. ⁶ Overall prevalence of skin lesions in this study was comparable but slightly higher in the placebo and 10.0% imidacloprid/4.5% flumethrin collar groups, with prevalence rates of 12.5% and 17.0%, respectively. The only significant difference between the two groups of cats was only recognized when owner-reported licking was included in the analysis of the first 14 days of the study and was associated with the 10.0% imidacloprid/4.5% flumethrin collar. While these results could imply that the active ingredients in the collar induced licking, the effect was not observed in the large majority of the cats when the placebo collar was removed and the 10.0% imidacloprid/4.5% flumethrin collar applied. Taken together, it appears that local reactions to the active ingredients in the 10.0% imidacloprid/4.5% flumethrin collar are not the direct causative agent of skin lesions that may develop with collar wear. This is suggestive that irritation is caused by the presence of a collar, and that cats originally intolerant of collars will become more receptive over time.

Owner reports of getting mouth or forelimbs caught on their collar were similar among both placebo (0%) and 10.0% imidacloprid/4.5% flumethrin collar groups (2%), and similar to a previous study assessing tolerance of inactive collars (5%). ⁷ None of the owners reported that the cats caught the collars on furniture or other projections, and none of the cats spontaneously removed the collars. The 10.0% imidacloprid/4.5% flumethrin collar has a safety mechanism designed to prevent choke injury (http://bayer.naccvp.com). Owners should follow the product insert instructions for proper collar placement.

Conclusions

The results of this study indicate that the 10.0% imidacloprid/4.5% flumethrin collar does not frequently induce skin lesions in cats. When combined with the high degree of compliance and efficacy results in other studies, these results support the use of this collar in cats for flea and tick control, and to block the transmission of some vector-borne diseases like B henselae and C felis for a period of up to 8 months.