Treatment of Neotrombicula species infestation in cats using a 10% (w/v) fipronil topical spot-on formulation: a pilot study

OBJECTIVES: Few data are available concerning therapeutic aspects of feline trombiculiasis. This study evaluated the efficacy of a 10% w/v fipronil-based spot-on solution in 15 cats with natural Neotrombicula species infestation. METHODS: Ten cats received 1 drop per affected site on day (D)0 and D14, with the rest of the 0.5 ml pipette applied on the skin between the shoulders. Five cats served as non-treated controls. Parasite score (0 = absent; 3 = severe, >10 parasites/zone) was assessed on D0, D14 and D28 on all animals. Skin lesions (SCORing Feline Allergic Dermatitis lesion severity scale [SCORFAD]) and investigator pruritus scale (IPS; 0 = cat comfortable, grooming like any normal cat; 4 = cat uncomfortable, pruritic all the time) were assessed on treated cats on the same days. Global assessment of efficacy, tolerance and ease of use (GAS; 1 = very poor; 5 = excellent) was assessed on D28. RESULTS: All the cats completed the study. Parasite scores of the control cats were maintained throughout the trial (mean ± SD: D0 4 ± 0.7, D14 3.2 ± 1.1 and D28 3.2 ± 0.4). In treated cats, SCORFAD (D0 3.2 ± 5.4, D14 1.1 ± 2.1 [P <0.002] and D28 0.5 ± 1.3 [P <0.002]), parasite (D0 3.9 ± 1.3, D14 1.2 ± 0.8 [P <0.005] and D28 0.4 ± 0.5 [P <0.005]) and IPS (D0 1 ± 1.2, D14 0.5 ± 1.1 [P <0.05] and D28 0.3 ± 0.7 [P <0.05]) scores significantly decreased throughout the trial. On D28, the GAS was 4.2 ± 0.9. There were no adverse effects from treatment. CONCLUSIONS AND RELEVANCE: The 10% w/v fipronil preparation appeared to be effective, safe and practical in the treatment of localised Neotrombicula species infestation in these cats.