Preventive efficacy of six monthly oral doses of Simparica Trio ® , Heartgard ® Plus, and Interceptor ® Plus against a macrocyclic lactone-resistant strain (ZoeLA) of heartworm (Dirofilaria immitis) in dogs.

Simparica Trio prevented microfilaremia in all dogs and was highly effective (97.2%) and significantly better than either Heartgard Plus (8.5%) or Interceptor Plus (35.9%) in preventing the development of the ZoeLA ML-resistant heartworm strain when administered for six consecutive months in this comparative laboratory efficacy study.