An assessment of canine ectoparasiticide administration compliance in the United States based on timing of ectoparasiticide purchases recorded in veterinary hospital transactions

Background: This study evaluated the timing of dog owner ectoparasiticide purchases to estimate administration compliance and assess the consequent impact of dose purchase gaps on the proportion of time that dogs are protected over a 12-month period. Methods: Ectoparasiticide purchase transactions over a 12-month period were evaluated for dogs from 626 U.S. veterinary hospitals to determine dose purchase timing and identify consequent gaps between dose administration. Orally administered prescription ectoparasitic medications with active ingredients from the isoxazoline family (afoxolaner, fluralaner, lotilaner, or sarolaner) are included in the analysis. A period was calculated for each of the four isoxazoline-containing medications that represented the duration of protection provided by two doses of ectoparasiticide plus the average gap between these two doses. The maximum percentage of time possible for ectoparasiticide protection for this aggregate period was then calculated for each active. Results: Ectoparasiticide transaction records were analyzed for 506,637 dogs. Of these, 43% of dog owners purchased just one dose over the 12 months. If a dog owner purchased more than one dose, then the timing of these transactions could create a time gap between the completion of ectoparasite protection from the first dose and onset of protection from the subsequent purchase and administration of the second dose. Such gaps were observed in purchases made by 31-65% of dog owners depending on the selected active ingredient and number of doses. The average gap duration between dose purchases was calculated for all possible dose combinations over 12 months of ectoparasite protection. Time gaps between the first and second doses are as follows: for sarolaner (20.3 weeks), afoxolaner (12.9 weeks), fluralaner (12.8 weeks), and lotilaner (8.9 weeks). The proportion of time when protection was provided during the aggregate period between administration of the first and second doses was fluralaner 65%, lotilaner 49%, afoxolaner 40,% and sarolaner 30%. Conclusions: Dog owner ectoparasiticide purchase transactions show that there are time gaps between doses leading to reduced ectoparasite protection. The longer re-administration interval of fluralaner, which results from its extended duration, results in dog owners gaining the greatest proportion of ectoparasite protection time compared with shorter-acting monthly re-treatment medications.