Clinical assessment of heartworm-infected Beagles treated with a combination of imidacloprid/moxidectin and doxycycline, or untreated.

Abstract

BACKGROUND: Administration of moxidectin topically and doxycycline PO has been utilized experimentally as an alternative treatment for heartworm disease. However, clinical effects of this protocol remain poorly characterized. OBJECTIVE: To evaluate the clinical and postmortem findings associated with administration of doxycycline and monthly 10% imidacloprid&#x2009;+&#x2009;2.5% moxidectin (IMD&#x2009;+&#x2009;MOX, Advantage Multi/Advocate) to Dirofilaria immitis-experimentally infected as compared to nontreated control dogs. ANIMALS: Sixteen purpose-bred, female, Beagle dogs. METHODS: Prospective, blinded, experimental study. Animals with surgically transplanted adult heartworms were randomized into 2 study groups of equal size: a nontreated control group (n = 8) and an IMD&#x2009;+&#x2009;MOX and doxycycline-treated group (n = 8). Randomization was performed using a complete block design according to circulating microfilarial concentrations, measured before treatment. Serum biochemical profiles, CBCs, thoracic radiographs and echocardiograms were performed prior to and 3&#x2009;weeks after transplantation, and monthly for 10 months. Postmortem gross and histopathologic evaluations were performed. RESULTS: Compared to control animals, mean&#x2009;&#xb1;&#x2009;SD serum alanine aminotransferase (181&#x2009;&#xb1;&#x2009;203&#x2009;U/L vs 33&#x2009;&#xb1;&#x2009;7 U/L; P&#x2009;<&#x2009;.0001) and alkaline phosphatase (246&#x2009;&#xb1;&#x2009;258&#x2009;U/L vs 58&#x2009;&#xb1;&#x2009;19&#x2009;U/L; P&#x2009;<&#x2009;.0001) activities were significantly higher in the treated group on day 28. Radiographic and echocardiographic evidence of heartworm disease was observed in both groups; however, no significant differences in these variables were noted between groups. Mean&#x2009;&#xb1;&#x2009;SD pulmonary arterial thrombus score was significantly higher in the treated vs nontreated group (3.9&#x2009;&#xb1;&#x2009;0.4 and 1.5&#x2009;&#xb1;&#x2009;2.1, respectively; P = .01). CONCLUSIONS AND CLINICAL IMPORTANCE: The treatment protocol was well-tolerated with no clinically relevant adverse effects for any variable evaluated during the observational period.