The Efficacy of a Topically Applied Imidacloprid 10 % / Moxidectin 2.5 % Formulation (Advocate®, Advantage® Multi, Bayer) against Immature and Adult Spirocerca lupi Worms in Experimentally Infected Dogs

Abstract

This study investigated the efficacy and safety of an imidacloprid 10 %/moxidectin 2.5 % spot-on combination (Advocate ® , Advantage ® Multi, Bayer) against immature and mature stages of Spirocerca lupi in experimentally infected dogs. 24 dogs were allocated to 3 groups and infected with approximately 10 L3 larvae of S. lupi orally on study day (SD) +2, +14, +28 and +42. Group 1 remained as untreated control group. Group 2 dogs were treated on SD -28, 0, and thereafter monthly until Day 280 (12 treatments). Group 3 dogs were treated weekly on 19 occasions starting on SD +170. The dosage for all treatments was the licensed dose of 10-25 mg imidacloprid/2.5-6.25 mg moxidectin per kg body weight. All dogs were examined on SD +169 or +176 by endoscopy. Group 3 dogs were additionally examined approximately every two weeks up to Day 296. On Day +308 or +310, all dogs were necropsied to recover S. lupi worms and to quantify lesions in the thoracic aorta and oesophagus. Dogs in the control group were adequately infected with S. lupi, demonstrated by the extensive damage to the thoracic aorta, the nodules in the oesophagus and the large numbers of worms recovered. In total 144 worms were collected (geometric mean of 16.8 worms per dog). Dogs in group 2 had no or very slight damage to the thoracic aorta and no nodules or worms in the oesophagus, indicating 100 % efficacy of the monthly treatments. Dogs in group 3 were also adequately infected, showing nodules in the oesophagus before initiation of weekly treatment, and at necropsy extensive damage was seen S92 EndoparasitEs in the thoracic aorta. After treatment, three dogs of 8 still had a few nodules and in total three worms (GM of 0.25 per dog) were recovered, demonstrating an efficacy of 98.5 % against adult S. lupi. All dogs tolerated the treatment well and no treatment-related adverse events occurred.

Occurrence of Spirocerca lupi Infection in Hungarian Dogs Referred for Gastroscopy

“…Some literature resources claim disophenol to be the only confirmed adulticide drug, but it does not affect juvenile worms and is not available on the market (Lobetti 2013). Other sources claim that macrocyclic lactones are an effective treatment for benign esophageal alterations caused by Spirocerca lupi (Berry 2000, Kelly et al 2008, Lobetti 2012, Austin et al 2013), while effective prevention is possible with avermectins, milbemycin and moxidectin , Kelly et al 2008, Kok et al 2010, 2011, Le Sueur et al 2010, Nolan et al 2012). In our experience, doramectin-treated patients become symptomfree, but use of the drug is greatly hindered by off-label application and the risk of complications.…”

“…Based on literature data, it is 100 % effective in preventing Spirocerca lupi-induced esophageal granulomas in dogs. In experimentally infected dogs it was also effective against adult Spirocerca lupi forms in 98.5 % of cases, without the patients showing adverse effects, when applied weekly for 19 weeks (Austin et al 2013). The efficacy of Advocate spot-on should therefore also be examined in a clinical case load.…”

“…The toxicity depends on the mutation of the MDR-1 Δ gene and the expression of protective glycoprotein P (Lobetti 2013). Milbemycin oxime, applied at 0.5 mg/kg for 28 days (Beugnet et al 2016, Kok et al 2010, 2011, or spot-ons containing a combination of imidacloprid and moxidectin are both confirmed as being suitable for spirocercosis prevention (Austin et al 2013, Le Sueur et al 2010. Although the esophageal granulomas caused by Spirocerca lupi can be successfully treated with doramectin, sarcomas require surgical and oncological treatment (Willard 2013).…”

Clinical spirocercosis in a dog in the UK

“…The authors also consider the possibilities that undetected gastrointestinal malabsorptive disease or lack of owner compliance could have impacted the efficacy of milbemycin oxime preventative therapy. Although various protocols of milbemycin oxime and doramectin administration to treat spirocercosis have been described,3 13–17 we opted to treat our patient with Advocate (10% imidacloprid and 2.5% moxidectin) postoperatively due to a combination of factors including lack of availability of doramectin, the patient’s history of developing spirocercosis despite milbemycin oxime therapy and published efficacy of Advocate® for treating spirocercosis 18 19…”

Triple Phase Dynamic Computed Tomographic Perfusion Characteristics of Spirocercosis Induced Esophageal Nodules in Non‐neoplastic Versus Neoplastic Canine Cases

“…Benign lesions can be successfully treated with avermectins. [2,12,13] However malignant transformation can only be treated surgically with or without chemotherapy and generally with poorer outcomes. [8] These differences emphasize the need for improved methods to distinguish non-neoplastic from neoplastic nodules ante-mortally to enable early treatment options for malignant cases as well as to get a better understanding of the pathophysiology of neoplastic transformation.…”