Efficacy of a combination of imidacloprid 10%/moxidectin 2.5% spot-on (Advocate® for dogs) in the prevention of canine spirocercosis (Spirocerca lupi).

The nematode Spirocerca lupi is a major canine parasite in warm regions of the world, classically causing parasitic nodules in the esophagus, aortic aneurysms, and spondylitis. This study evaluated the preventive efficacy of monthly treatment with imidacloprid 10%/moxidectin 2.5% spot-on (Advocate® for dogs) administered over a period of 9 months in young dogs naturally exposed to S. lupi on Réunion island. One hundred and twelve puppies, aged from 2.0 to 4.0 months and with a negative spirocerca fecal examination at inclusion, completed the study. They were randomly allocated to two groups. Group A puppies (n=58) received nine spot-on treatments with Advocate® at the minimum dose of 2.5 mg moxidectin/kg bw at monthly intervals. Control group B puppies (n=54) received no treatment for S. lupi. During the study, regular clinical and fecal examinations were performed, as was final upper gastrointestinal endoscopy. Endoscopy showed that 19 dogs from group B had spirocerca nodules, corresponding to a prevalence of 35.2% in dogs aged 12 to 14 months. In contrast, only one dog from group A had a nodule, corresponding to a preventive efficacy of 94.7% (p<0.0001). None of the 378 fecal examinations were positive for spirocerca. This study confirms a high prevalence of canine spirocercosis on Réunion and shows that infestation occurs in very young puppies. Furthermore, it demonstrates that monthly spot-on administration of a combination of imidacloprid 10%/moxidectin 2.5% (Advocate® for dogs) in puppies starting at the age of 2 to 4 months achieves effective and safe prevention of canine spirocercosis.