Efficacy and safety of a sustained-release formulation of ivermectin (FILAPREV®) in preventing heartworm infection (Dirofilaria immitis) in dogs in two endemic areas of Italy

Background: Macrocyclic lactones are the only drug class currently licensed for heartworm disease prophylaxis. Macrocyclic lactones kill third- and fourth-stage larvae of the parasitic nematode Dirofilaria immitis, thus preventing the development of adult worms in dogs, which are responsible for heartworm disease, a potentially life-threatening condition. The objective of the present study was to assess the efficacy of a subcutaneous implant formulation containing ivermectin (FILAPREV®; Ceva Santé Animale, Libourne, France) compared to extended-release moxidectin (Guardian™ SR; Elanco, Indianapolis, IN, USA) to protect dogs against D. immitis infection during the entire transmission-risk season in Italy, starting in April and ending in November. Methods: A total of 114 healthy client-owned dogs were enrolled at two investigation sites located in two different regions of Italy known to be endemic for D. immitis (Lombardy and Veneto). In the spring of 2017, approximately half of the dogs from each site randomly received a single dose of FILAPREV® (ivermectin, 0.13 mg/kg as minimum standard dose); the remaining dogs were treated with a single dose of Guardian™ SR (moxidectin, 0.17 mg/kg). Antigen and Knott's tests were performed before treatment, and subsequently at 1 week and 6, 8 and 12 months post-treatment. Clinical examination, thoracic radiography and echocardiography were conducted at the same time points. Results: Of the 114 dogs enrolled in the study, 112 completed the entire study period. No adverse reactions were observed, and all dogs enrolled in the study remained heartworm-negative throughout the entire study period. Conclusions: A single subcutaneous administration of FILAPREV®, an implant containing ivermectin at the recommended dosage, prevents heartworm disease caused by D. immitis in dogs for at least 8 months, covering the full seasonal period of heartworm transmission in hyperendemic regions.