Elimination of Dirofilaria immitis Infection in Dogs, Linosa Island, Italy, 2020-2022

On Linosa Island, Italy, Dirofilaria immitis infection has been hyperendemic in dogs and seroprevalent among islanders. In 2020, we implemented a heartworm dis-ease elimination program on Linosa Island. Of 54 dogs tested for D. immitis antigen and microfilariae, 28 had positive results and received treatment with oral doxy-cycline twice daily for 4 weeks plus topical imidacloprid/ moxidectin monthly for 12 months. The 26 dogs with negative results received monthly topical imidacloprid/ moxidectin as preventive. During month 1, the number of microfilaremic dogs was reduced by 76.5%. From month 2 on, all animals were microfilariae negative, and dur-ing months 3 to 9, the number of antigen-positive dogs decreased progressively. Treatment of positive dogs coupled with chemoprophylaxis for noninfected dogs was effective, protecting them from new infections. The elimination program reduced the risk for human infec-tion, representing a One Health paradigm. Monitoring and chemoprophylaxis are advocated to maintain the status of heartworm disease-free area.