Flea infestation remains a major clinical and public health concern in cats due to its negative impact on animal welfare and its role in the transmission of zoonotic pathogens. Effective flea control under routine field conditions is essential for integrated parasite management in companion animals. The aim of this study was to evaluate the clinical performance of a topical formulation combining ivermectin, imidacloprid, and praziquantel for flea control in domestic cats under field conditions.
A total of 142 naturally infested cats of varying ages, sexes, and body conditions were included in the study. All animals received a single topical application of the evaluated formulation. Clinical and parasitological assessments were performed on Days 0, 1, 7, 14, and 30 post-treatment using standardized flea counts, pruritus scores, and dermatological lesion scores. Treatment effectiveness was assessed using within-subject pre–post comparisons. Effective flea control was defined as a marked reduction in the proportion of flea-positive cats relative to baseline, accompanied by concurrent clinical improvement.
The proportion of cats free of detectable fleas exceeded 91% by Day 7 and approached 95% by Day 30 post-treatment. Significant clinical improvement was observed during the first two weeks, including reductions in pruritus intensity and dermatological lesion scores. Treatment response did not differ according to sex or age, indicating consistent clinical performance across diverse feline subpopulations. No adverse effects were reported throughout the study period.
The findings indicate that the evaluated topical combination provides consistent and clinically meaningful flea control in domestic cats under routine field conditions, supporting its use as part of integrated parasite management strategies in companion animals. However, the absence of a negative control or active comparator group represents a limitation of the study; therefore, treatment effectiveness was assessed using within-subject comparisons rather than established regulatory efficacy benchmarks.
Cats live in close contact with humans, with many even sleeping in the same bed as their owners. It is also common for cats to have access to outdoor areas where they face a high likelihood of exposure to ectoparasites and pathogens (
Fleas have developed multiple modes of pathogen transmission, including blood feeding, infected feces, and vertical, horizontal, and mechanical routes (
Given the high frequency of close contact between cats and their owners, as well as between cats and other domestic animals, cats may play an important role in maintaining and transmitting zoonotic agents to humans (
Imidacloprid is a well-established neonicotinoid insecticide widely used as a topical flea adulticide in cats, acting as an agonist of insect nicotinic acetylcholine receptors and producing rapid knockdown and sustained control of
The study was conducted in Mexico City, Mexico, under field (clinical) conditions. Mexico City is a high-altitude urban area (~2,240 m above sea level) characterized by a temperate subhumid climate with marked seasonal variation, including a rainy season typically extending from late spring to early autumn. Mean annual temperatures are moderate, while indoor microclimates in urban households often provide stable temperature and humidity conditions that favor the development of flea life stages throughout the year. High human and pet population density, close human–animal cohabitation, and predominantly indoor or semi-indoor pet management practices may further influence flea exposure and reinfestation dynamics in this setting. All 142 cats enrolled in the study were managed in accordance with ISFM/AAFP guidelines (
A total of 142 cats were enrolled in the study using a consecutive convenience sampling approach. All cats presented to the participating veterinary clinics during the study period were screened consecutively for eligibility, and those fulfilling the predefined inclusion criteria were enrolled until the target sample size was achieved. This recruitment strategy was selected to reflect routine clinical practice and to capture a heterogeneous population of naturally flea-infested cats under field conditions. The study population included 69 females and 73 males, comprising 49 kittens, 39 juveniles, 45 adults, and 9 senior cats. Body condition scores were classified as low (19 cats), ideal (103 cats), and high (20 cats). Ninety-six cats were gonadectomized and 46 were intact. This investigation was designed as a field-effectiveness evaluation under routine clinical conditions, focusing on cats naturally infested with fleas and presented for veterinary care. For ethical and animal welfare reasons, the inclusion of an untreated negative control group was not considered acceptable, as withholding antiparasitic treatment from cats with active flea infestation could result in sustained pruritus, dermatological lesions, discomfort, and an increased risk of pathogen transmission. Similarly, the use of an active comparator group (e.g., imidacloprid alone or another registered flea control product) would have required randomization and blinding procedures that were not compatible with the real-world clinical setting or with the primary objective of this observational study. Consequently, each animal served as its own control, and treatment response was assessed by comparing post-treatment parasitological and clinical outcomes with baseline values obtained prior to treatment administration.
Written informed consent was obtained from all owners before enrollment. To be eligible for inclusion, cats were required to be naturally infested with at least five fleas, and neither the animals nor their environment could have received any ectoparasitic treatment during the four weeks preceding enrollment. Environmental flea control measures were not standardized or actively monitored during the study period, as the investigation was designed to reflect routine clinical conditions. Owners were instructed not to apply additional ectoparasitic treatments to the animals or to the household environment during follow-up; however, environmental exposure to flea reservoirs, including immature stages present in household or peridomestic environments, could not be fully controlled. Accordingly, the study primarily evaluated the performance of the topical treatment under real-world conditions rather than under controlled environmental settings.
Day 0 was defined individually as the day on which each animal was assessed and confirmed as eligible for enrollment. On Day 0, all required parasitological and clinical examinations were performed. Flea counts were conducted following a standardized protocol (
Adverse events were monitored using a combined approach consisting of (i) active veterinary clinical assessment at each scheduled evaluation (Days 0, 1, 7, 14, and 30) and (ii) structured owner-reported follow-up. At each visit, cats underwent a brief physical examination and targeted neurologic observation (mentation, gait/ataxia, tremors, pupil size, hypersalivation). Owners were asked standardized questions using a checklist addressing potential post-treatment events, including hypersalivation, vomiting, diarrhea, lethargy, anorexia, exacerbation of pruritus, erythema at the application site, ataxia, tremors, and mydriasis. Any suspected adverse event was recorded with respect to onset time, duration, severity, and outcome. Owners were instructed to contact the clinic immediately if abnormal clinical signs occurred between scheduled visits. Flea control effectiveness was determined by comparing the presence of live fleas before treatment with findings obtained during post-treatment evaluations. No medications that could influence parasitological or clinical assessments were permitted during the study period.
After parasitological and clinical evaluations were completed, each cat received treatment with Feline Full Spot® (Imidacloprid 11 g, Ivermectin 0.2 g, and Praziquantel 7.5 g/100ml). A single dose was applied directly onto the skin at three points along the dorsal midline, from the nape of the neck to the withers, to minimize the risk of licking. No patient received any additional topical or systemic treatment during the evaluation period.
A Shapiro–Wilk normality test was performed to assess data distribution. Because the data were not normally distributed, non-parametric tests were used. A matched-pairs test was applied to compare pruritus scores and lesion scores across time points. For epidemiological variables, a chi-square test was used to evaluate associations between host-related variables and flea presence. In addition to hypothesis testing, descriptive effect estimates were calculated to support the interpretation of results. Proportions of flea-positive and flea-free cats at each evaluation time point were accompanied by 95% confidence intervals (CI) calculated using exact binomial methods. Because the study was designed as an exploratory field-effectiveness evaluation with a limited number of predefined within-subject comparisons, no formal correction for multiple comparisons was applied; results were interpreted with emphasis on effect magnitude and consistency across time points rather than on isolated p-values. All analyses were conducted using JMP statistical software version 8.0.
All cats (n = 142) were infested with fleas at baseline (Day 0). Treatment effectiveness was assessed using within-subject comparisons between baseline and post-treatment evaluations. In this study, effective flea control was defined as a reduction in the proportion of cats with detectable live fleas relative to Day 0, together with concurrent improvement in clinical parameters. Flea infestation was analyzed as a binary outcome (presence or absence of live fleas) rather than as mean flea counts. This approach was selected to reflect a clinically relevant endpoint in routine veterinary practice, where flea-free status and resolution of clinical signs are primary indicators of treatment success. Additionally, binary outcomes reduce variability associated with flea counting techniques under field conditions and facilitate interpretation of effectiveness in heterogeneous patient populations. Using these criteria, the proportion of flea-positive cats decreased from 100% at baseline to 8.39% (11/142) by Day 7, corresponding to a reduction of 91.61%. On Days 14 and 30, fleas were detected in 8 (5.97%) and 7 (5.18%) cats, representing reductions of 94.03% and 94.82%, respectively (
Proportion and percentage of cats with fleas following treatment with FELINE full spot®.
| Cats (n = 142) | Day 1 | Day 7 | Day 14 | Day 30 |
|---|---|---|---|---|
| Presence/absence of fleas | 142/0 | 11/131 | 8/134 | 7/135 |
| % presence of fleas | 100 | 8.39 | 5.97 | 5.18 |
| % reduction vs. baseline | 0 | 91.61 | 94.03 | 94.82 |
a Reduction percentages were calculated relative to baseline (Day 0).
b Flea infestation was analyzed as a binary outcome (presence/absence of live fleas).
c Flea-positive proportions are reported with 95% confidence intervals (exact binomial) in the Results section.
The proportion of flea-positive cats at each time point was further characterized by 95% confidence intervals to quantify the precision of the estimates. At Day 7, the flea-positive proportion was 8.39% (11/142; 95% CI: 4.25–14.50%), decreasing to 5.97% at Day 14 (8/142; 95% CI: 2.60–11.39%) and to 5.18% at Day 30 (7/142; 95% CI: 2.10–10.41%). These intervals indicate a consistent and sustained reduction in flea infestation relative to baseline.
Comparison of mean pruritus scores and lesion scores in cats with flea infestation treated with FELINE full spot®.
| Variable | Day 1–7 | Day 7–14 | Day 14–30 |
|---|---|---|---|
| Pruritus (mean score) | 5.30 → 0.33 | 0.33 → 0.24 | 0.24 → 0.23 |
| P-value | < 0.0001* | 0.02* | 0.42 |
| Lesions (mean score) | 72.70 → 5.59 | 5.59 → 1.64 | 1.64 → 1.57 |
| P-value | < 0.0001* | 0.004* | 0.43 |
*Matched-pairs test, 95% confidence level; significant.
General characteristics of the cats and their association with flea presence during 133 evaluations.
| Evaluation day | Variable | χ² | P-value | OR | 95% CI |
|---|---|---|---|---|---|
| Day 7 | Sex | 0.047 | 0.82 | 1.14 | 0.33–3.94 |
| Day 7 | Age | 2.83 | 0.41 | — | — |
| Day 14 | Sex | 0.007 | 0.93 | 0.86 | 0.63–1.19 |
| Day 14 | Age | 3.27 | 0.35 | — | — |
| Day 30 | Sex | 0.21 | 0.64 | 0.86 | 0.63–1.19 |
| Day 30 | Age | 2.04 | 0.56 | — | — |
*Chi-square test; OR = odds ratio; 95% CI = 95% confidence interval; significant
No statistically significant associations were detected between flea presence and sex or age at any evaluation time point.
The findings of this study demonstrate that the topical combination of imidacloprid, ivermectin, and praziquantel (Feline Full Spot®) provides consistent and clinically meaningful control of
In parallel with the parasitological response, a statistically significant improvement in clinical parameters was observed during the first two weeks following treatment. Reductions in pruritus intensity and dermatological lesion scores indicate not only successful flea control but also an improvement in animal welfare, which is a central objective in contemporary feline medicine (
The findings of this study should be interpreted in light of the climatic, ecological, and management characteristics specific to Mexico City. Flea development and survival are strongly influenced by temperature, humidity, and the availability of suitable microhabitats, particularly indoor environments that may buffer seasonal climatic extremes (
Despite the overall level of effectiveness observed, a small proportion of cats exhibited persistent or possibly new flea infestations by Day 30. The presence of fleas in this subset of animals should be interpreted in the context of uncontrolled environmental exposure. Flea life stages developing in household and peridomestic environments are a well-recognized source of reinfestation, particularly when environmental treatments are not concurrently implemented. Because environmental control measures were not standardized or actively monitored in this study, residual flea presence may reflect ongoing exposure to environmental reservoirs rather than reduced product effectiveness. These findings underscore the importance of integrated flea management strategies that combine on-animal treatment with environmental interventions to achieve sustained control, especially in endemic settings (
Although the formulation evaluated combines imidacloprid, ivermectin, and praziquantel, the present study design does not allow differentiation of the individual contributions of each active ingredient to the observed flea control. Imidacloprid is recognized as the primary flea adulticide within the formulation, and its efficacy as a standalone compound against
The effectiveness observed in this study should therefore be interpreted within the context of the predefined evaluation criteria and study design. Terms such as “effective” or “rapid reduction” refer to the magnitude of change observed in flea presence and clinical scores when compared with baseline values within the same animals, rather than to established regulatory efficacy thresholds derived from controlled comparative trials. Accordingly, the results demonstrate a consistent and clinically meaningful reduction in flea infestation and associated clinical signs under routine clinical conditions, while avoiding direct inference regarding regulatory-level or comparative efficacy. Future randomized controlled studies incorporating active comparators would be necessary to further define relative efficacy and the individual contribution of each component of the formulation.
Although no adverse events were detected in the present study, safety considerations remain important when macrocyclic lactones such as ivermectin are used in cats. Reported adverse effects associated with ivermectin exposure are typically linked to overdose, inappropriate formulations, or accidental ingestion and primarily involve neurologic signs due to central nervous system penetration, including lethargy, ataxia, hypersalivation, mydriasis, tremors, seizures, and coma (
The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.
The animal study was approved by Centro Universitario UAEM Amecameca. The study was conducted in accordance with the local legislation and institutional requirements.
CR-N: Conceptualization, Writing – original draft, Formal analysis, Funding acquisition, Methodology, Writing – review & editing. AF-O: Conceptualization, Writing – original draft, Supervision, Validation. RH-C: Conceptualization, Data curation, Investigation, Methodology, Writing – original draft. ES-G: Investigation, Supervision, Project administration, Writing – original draft.
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The author(s) declared that generative AI was not used in the creation of this manuscript.
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