Changes in flea and tick infestation following topical fipronil, permethrin, piperonyl butoxide, and pyriproxyfen in naturally infested dogs: an exploratory uncontrolled field study

Background Flea and tick infestations impair canine welfare and may have public-health relevance in rural settings. Objective To describe temporal changes in ectoparasite infestation and associated clinical signs after a single topical application of fipronil, permethrin, piperonyl butoxide, and pyriproxyfen (PROTECH) in naturally infested dogs. Methods This prospective, uncontrolled exploratory field study enrolled 44 privately owned dogs in Tahdziú, Yucatán, Mexico. Dogs received one topical application at Day 0 and were reassessed on Days 15 and 30. An approximately 5-min whole-body examination documented ectoparasite presence or absence. Field-recorded numerical skin-lesion and pruritus scores and observed adverse events were summarized. Results Among dogs with flea-only infestation ( n = 18), positivity decreased from 18/18 at Day 0 to 0/18 at Days 15 and 30. Among tick-only dogs ( n = 11), positivity decreased from 11/11 to 0/11 and 1/11, respectively. In mixed infestations ( n = 15), positivity decreased from 15/15 to 3/15 and 2/15. Mean lesion and pruritus scores also declined in all subgroups. No adverse reactions were observed. Conclusions A single application was followed by marked temporal reductions in ectoparasite positivity and clinical signs through Day 30. Because the study lacked a comparator and used non-validated clinical scores, the findings are descriptive and exploratory; they do not establish a causal treatment effect or comparative efficacy.