Abstract
BackgroundInfection of dogs with the cardiopulmonary nematode Angiostrongylus vasorum may result in severe clinical disease therefore adequate prevention is necessary. A randomized, negative control, blinded study was conducted to evaluate the efficacy in the prevention of canine A. vasorum infection after monthly administrations of NexGard Spectra®, a novel chewable tablet formulation combining the insecticide and acaricide afoxolaner and the anthelmintic milbemycin oxime, in a multiple challenge (trickle infection) model.MethodsTwenty beagle dogs were challenged orally with doses of approximately 32–43 third-stage larvae of A. vasorum once every other week on seven occasions (Study Days -7, 7, 21, 35, 49, 63 and 77). Ten dogs were administered NexGard Spectra® as close as possible to the minimum recommended dose of afoxolaner and milbemycin oxime, i.e. 2.5 mg/kg body weight and 0.5 mg/kg body weight, respectively, four times at monthly intervals (Study Days 0, 28, 56 and 84) while the remaining ten dogs served as untreated controls. For parasite recovery and count, dogs were euthanized humanely and necropsied six to eight days following the last treatment (Study Days 90–92). Beginning six weeks after first inoculation, faeces were collected on a bi-weekly basis and examined for first-stage larvae of A. vasorum.ResultsUntreated dogs harboured 39–95 adult A. vasorum (geometric mean, 66.4), while zero to 24 adult A. vasorum were recovered from the treated dogs (geometric mean, 3.4; P < 0.0001). Thus, efficacy of NexGard Spectra® administered at monthly intervals against incoming A. vasorum was 94.9 %. Compared to the untreated controls, larval excretion of the treated dogs was reduced by 99.9 % (P < 0.0001).ConclusionResults of this study demonstrate that NexGard Spectra®, when administered at monthly intervals, can effectively prevent canine A. vasorum infection.
Highlights
Infection of dogs with the cardiopulmonary nematode Angiostrongylus vasorum may result in severe clinical disease adequate prevention is necessary
Angiostrongylus vasorum were recovered from all untreated dogs, with 39 to 95 adult worms recovered per dogs, corresponding to individual establishment rates ranging from 15 to 36.5 %
Dogs treated with NexGard Spectra® harbored 0 to 24 adult A. vasorum
Summary
Infection of dogs with the cardiopulmonary nematode Angiostrongylus vasorum may result in severe clinical disease adequate prevention is necessary. In the United Kingdom, hyper-endemic foci have been identified where practitioners reported more than 20 cases per year Veterinary practices in those areas are 15 to 16 times more likely to see clinical angiostrongylosis than anywhere else [2, 3, 6]. Adult A. vasorum reside in the right heart and pulmonary arterial tree of dogs and other canids. Dogs become infected by ingestion of intermediate or paratenic hosts containing the infectious third-stage (L3) larvae. Following ingestion by a canid, larvae penetrate the intestinal wall, enter the visceral lymph nodes and are carried via the hepatic portal vein to the heart and pulmonary arterial system where first immature worms arrive 10 days following infection and develop into mature adults [10, 11]. In recently reported studies, excretion of L1 larvae was observed to commence in most dogs six to eight weeks after single challenge infection [12,13,14]
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