Fleas that infest pets are considered important parasites of both animals and humans. These insects cause irritation and can also transmit zoonotic diseases. Research has led to a rapid expansion in the development of flea control products. In the face of a market that offers dozens of commercial ectoparasiticides for dogs and cats, pet owners and veterinarians must be provided with evidence to support their decision to select a product to control fleas. To compare the efficacy of three commercially available products against companion animal fleas, a trial was conducted on naturally-infested dogs in order to validate their pulicidal activity. Thirty-two flea-infested dogs with fleas were divided into 4 groups (n = 8) for each treatment. Group 1 received one pipette of permethrin as a spot-on dose of 650 mg/ml. The second group received 9.7% fipronil as a spot-on formulation. Group 3 was treated with a spot-on formulation of permethrin 7.40% plus piperonyl butoxide at 7.40%. Group 4 remained as the untreated control. Fleas of all experimental dogs were examined and counted on days 0, 3, 7, 14, 21 and 28 to determine the percentage of flea reduction. Results showed a 100% efficacy for all tested products. Identified species were: Ctenocephalides felis (75.7%), Ctenocephalides canis (15.9%) and Pulex irritans (9.5%). Based on these results, it was concluded that the three anti-flea products evaluated under the conditions of this study, produced an excellent efficacy as from the third day after treatment.
Despite the discovery and development of newer-generation topical (Spot-on) ectoparasiticides for dogs and cats, practitioners and researchers continue to search for products that provide increased duration and spectrum of activity. Dog and cat fleas, for example, can be a serious source of both animal and human irritation, which has led to a rapid expansion in the development of flea control products [
The present trial aimed to evaluate the effectiveness of three commercial anti-flea products on naturally-infested dogs, compared to untreated dogs, under a controlled environment. These combinations were selected because these products are the most frequently sold compounds against fleas in Mexico, and the veterinarians and pet owners need to have information that supports their efficacy and safety.
The work was carried out adhering to the guidelines of the Institutional Committee for Use and Care of Experimental Animals of the institution, according to the Mexican Official Regulation NOM-062-ZOO-1999. The study was performed during the flea season in Mexico, i.e., in late summer 2018. Thirty-two flea-infested dogs out of 124 animals were selected on day-8 based on the highest count of fleas. Dogs of different ages and breeds that harbored infestations over 50 fleas were included in this trial. They were provided by an animal control center. No medications or vaccinations had been given seven days prior to the initiation of the experimental procedures. After an acclimation period of 8 days, animals were ranked according to the number of parasites and were allocated to study groups. Dogs were fed a commercial, dry, pelleted diet according to their age and size. Water was provided ad libitum. Each animal was individually identified with a numbered tag and a colored collar.
The efficacy of the treatment of flea infestation on dogs was performed according to the World Association for the Advancement of Veterinary Parasitology guidelines [
On day 0 (day of treatment) the 32 dogs were divided into four groups of 8 animals each, using a randomized design. Dogs were weighed prior to treatment. Group 1 was treated with one pipette of 65% permethrin (ZinparÒ, Halvet, Mexico), applied once on the skin from the scapulae to the sacral region as a spot-on treatment. Pipette size was selected according to the individual body weight (1 ml/15 kg/bw) and applied following manufacturer’s instructions. Group 2 received fipronil at 9.7% (FrontlineÒ, Merial, Mexico) applied similarly as in the first group. Group 3 was treated with 7.40% permethrin plus 7.40% piperonyl butoxide (Lomo-pon-SÒ, Lapisa, Mexico) applied once as in the permethrin and fipronil treatment groups. The infested and untreated control group received only water at a volume of 1.0 ml per dog. Fleas were removed and counted by thoroughly combing animals with fine-tooth flea combs for at least 10 minutes. Fleas were considered dead if no movement was observed, thus fleas displaying abnormal movement were considered and counted as live [
Efficacy = Arithmetic mean number of flea counts ( Control ) − Arithmetic mean of flea counts ( Treated ) Arithmetic mean of flea counts ( Control ) × 100
A removal of fleas was done at day 3 on all dogs. The short-term prophylactic efficacy was measured by re-infesting all animals in each study group on days6, 13, 20 and 27 with a mixed population of 100 fleas C. felis and C. canis per dog. All dogs were combed off and fleas were counted on days 14, 21, and 28 after re-infestation. Dogs were observed constantly during and after treatments to record adverse reactions or clinical side effects. After day 28, fleas were removed from the control group to prevent a higher level of infestation that may have caused clinical signs.
The primary efficacy calculations were based on arithmetic mean values with geometric mean values considered secondary. For calculation of geometric means, flea counts for each animal were transformed to the natural logarithm of (count + 1). Differences between treated and control groups were analysed statistically by an analysis of variance (ANOVA) with a treatment effect on both untransformed and logarithmic transformed data. For flea counts, a significance level of 0.05 was used and all testing was two-sided, in a two-step procedure; pair-wise comparisons were made only if the overall test of treatments was significant at a p value of 0.05.
Dogs treated with each of the three products had a more significant (p < 0.05) reduction of fleas compared with the untreated controls at each re-infestation through day 28 and a 100% anti-flea efficacy was achieved from day 3 until the end of the study, in contrast to untreated controls, which remained infested throughout the experiment. It was clearly seen that the observations made on the third day after treatment, showed only a few remaining parts of fleas or fecal detritus, but no eggs or live fleas were recorded during the trial. A 100% anti-flea efficacy was achieved at the end of the experiment in all the treated groups. Three days after treatments were applied, statistical differences were observed between the treated groups with respect to the untreated control (p < 0.01); yet the statistical analysis showed no difference among the treated groups (p < 0.01) (
A comparison made regarding sex and weight on the experimental groups showed no statistical differences among them (
Taxonomical identifications carried out on the specimens collected from the untreated control group showed that species of identified fleas were: Ctenocephalides felis (84.08%) and Ctenocephalides canis (15.92%). Even though lice treatment was not the aim of the current trial, a light infestation with Trichodectes canis was also recorded on day 3, yet these insects were completely removed after treatment.
Day | Untreated Control (n = 8) | Permethrin* | Fipronil** | Permethrin + Piperonyl Butoxide*** |
---|---|---|---|---|
Mean (% Efficacy) | ||||
−8 | 61 | 53.4 (0) | 54.8 (0) | 59.5 (0) |
0 | 41 | 50.7 (0) | 50.7 (0) | 52.8 (0) |
3 | 57.3 | 0 (100)¥ | 0 (100)¥ | 0 (100)¥ |
7 | 44.6 | 0 (100)¥ | 0 (100)¥ | 0 (100)¥ |
14 | 49.2 | 0 (100)¥ | 0 (100)¥ | 0 (100)¥ |
21 | 37 | 0 (100)¥ | 0 (100)¥ | 0 (100)¥ |
28 | 62 | 0 (100)¥ | 0 (100)¥ | 0 (100)¥ |
¥ Significantly different from untreated control (p < 0 - 0.5); *65%; **9.7%; ***7.4% + 7.4%.
Group | Male (n) | Female (n) | Total |
---|---|---|---|
Permethrin | 52.6 ± 4.2 (3) | 47.9 ± 4.1 (5) | 49.4 ± 4.1 |
Fipronil | 42.1 ± 5.1 (5) | 54.2 ± 5.8 (3) | 45.5 ± 4.9 |
Permethrin + Piperonyl Butoxide | 55.8 ± 3.6 (4) | 47.9 ± 3.5 (4) | 51.5 ± 3.5 |
Untreated control | 56.9 ± 4.4 (2) | 46.1 ± 3.8 (6) | 47.9 ± 4.1 |
*Arithmetic mean ± standard deviation.
The sale and use of ectoparasiticides for the control of arthropod parasites of domestic animals constitute a major sector of the global animal health market and their control still relies heavily on the use of chemicals of whatever origin.
Since the resistance problem to all chemical insecticides available is becoming more and more evident, new alternatives to control these parasites are prompted. However, the development of new drugs is a tough task mainly due to the high costs to develop a new anti-flea compound, hence pharmaceutical companies are trying to optimize the use of the currently available compounds. Among these products, fipronil, cypermethrin, permethrin and tetramethrin have been proved to be highly effective contact insecticides [
Most commercially available brands of permethrin “spot-on” products are labeled for “use in dogs only” and may be obtained over-the-counter. Permethrin toxicity usually occurs when the owner applies the dog spot-on product in cats that are in close physical contact with recently treated dogs [
Fipronil is a phenylpyrazole compound that blocks the transmissions of signals by the inhibitory neurotransmitter, GABA that is present in arthropods [
The potential benefits of a combination of products are numerous, such as prolonging the duration of activity and broadening the ectoparasiticide spectrum, hence providing a convenient single administration to treat multiple parasites at the same time. However, considering that the present study was aimed solely at determining the efficacy against fleas on naturally infested dogs, the advantage of using a combined formulation of permethrin plus piperonyl butoxide was not demonstrated since other ectoparasites from dogs and cats were not included.
In the present study, no clinical signs were observed after the treatment of dogs with either fipronil or permethrin or permethrin + piperonyl butoxide. Further studies should then be conducted to demonstrate the advantage(s) of this combined formulation.
Previous research [
In another study, 20 cats and seven dogs living in 16 homes, were topically treated according to label directions with spot-on formulations containing either fipronil (9.8%, w/w) combined with (S)-methoprene (11.8%, w/w) or fipronil (9.8%, w/w) combined with (S)-methoprene (8.8%, w/w). A single application reduced flea populations by 88.44%, within 7 days [
It must be highlighted that in the current trial, all ectoparasiticides proved to 100% control fleas after three days. Even after re-infestation, no fleas were found on counts performed on day 28. Likewise, no adverse effects observed on adults or puppies; demonstrating that they are safe when administered at the recommended dosing levels. It is important to highlight that no side effects of adverse reactions were observed. Moreover, at the end of the study, the physical appearance and health conditions of the treated dogs improved, as healthy-looking skin and shiny coat were observed. Besides, dogs recovered energy after treatment and remained playful. In contrast, dogs of the untreated group seemed depressed and even aggressive, hence, handling of these animals was difficult before treatment was administered at the end of the experiment. Regarding public and animal health issues, a previous report [
It can therefore be concluded from our findings that, under the conditions of the current trial, the three commercially available anti-flea products exerted a high and persistent efficacy during a month in naturally-infested dogs. This study can be a useful tool to ease the selection of an efficacious pulicide for dogs.
All datasets are included in this manuscript.
The authors kindly thank Laboratorios Lapisa, S.A de C.V., Mexico, for the financial support to carry out this study. The present study was carried out in accordance with the current laws of Mexico.
The authors are grateful to Nelyda Hernández Saldañafor technical assistance.
All listed authors contributed to the study design, carried out the experiments, performed laboratory analysis, collaborated with results interpretation, data analysis, manuscript revision and discussion: Performed statistical data analysis and suggested the experimental design: FIV, YVM, YAC and MFR. Wrote the paper: FIV and YAC with input from YVM Grant funding: FIV. All authors supervised the experimental procedures, read and approved the final version of the manuscript.
Not applicable.
The work was carried out adhering to the guidelines of the Institutional Committee for Use and Care of Experimental Animals of the institution, according to the Mexican Official Regulation NOM-062-ZOO-1999 and Animal Research: Reporting of In Vivo Experiments guidelines was followed.
Faculty of Veterinary Medicine. National Autonomous University of Mexico. Address: Circuito Exterior s/n. Ciudad Universitaria, Coyoacan. Mexico City, 04510, Mexico.
The authors declare that they have no competing interests.
Ibarra-Velarde, F., Vera-Montenegro, Y., Alcala-Canto, Y., Flores-Ramos, M. and Saldaña-Hernández, N. (2019) Comparative Efficacy of Three Commercial Ectoparasiticides against Fleas in Naturally Infested Dogs. Pharmacology & Pharmacy, 10, 234-243. https://doi.org/10.4236/pp.2019.105020
bw = body weight