Evaluation of Side Effects and Long-Term Protection of a Sustained-Release Injectable Moxidectin Formulation against Dirofilaria immitis Infection in Dogs: An Observational-In Field Multicentric Study

The sustained-release moxidectin formulation Afilaria SR is a relatively new product and has been labelled to prevent Dirofilaria immitis infection in dogs for a six months-period. An observational, in field multicentric study was performed, aiming to evaluate the tolerability and the long-term prevention of Afilaria SR in Italy, a country where filariasis is endemic. The study was designed to include not less than 300 dogs, older than 6 months, of any breed. Side effects were recorded by veterinarians and antigenic tests were performed after 210, 365, 730, and 1095 days after the administration of the drug. A total of 583 dogs were recruited from 2018 to 2021 and all of them were negative with respect to antigenic tests at all time points, indicating that 100% of protection was achieved. Ranking of adverse reactions and correlation to patient features were analyzed using descriptive statistics and χ2 square test, respectively. Afilaria SR was well tolerated: 13% of dogs experienced mild reactions and only two dogs out of 583 (0.3%) demonstrated anaphylactoid/angioneurotic reactions, resolved administering corticosteroids. These data support that Afilaria SR prevented Dirofilaria immitis disease in all enrolled dogs and the low number and the low grade of side effects indicate the high safety profile of the product.