Field efficacy and safety of an oral formulation of the novel combination anthelmintic, derquantel-abamectin, in sheep in New Zealand

Abstract

AIM: To evaluate the efficacy and safety of the novel anthelmintic combination, derquantel-abamectin, against gastrointestinal nematode populations in sheep, under field-use conditions.METHODS: Controlled faecal egg count reduction tests (FECRT) were conducted in New Zealand in 14 trials, covering a range of geographic locations, farming enterprises, breeds, nematode populations, and anthelmintic-resistance profiles. Enrolled animals were naturally infected with mixed populations of gastrointestinal nematodes. All trials included a group treated with derquantel-abamectin, and a negative control group. Nine trials included additional groups each treated with a single- or dual-active oral reference anthelmintic, selected from albendazole, levamisole, albendazole-levamisole, ivermectin, abamectin and moxidectin. A total of 838 animals were enrolled across all trials, and were randomly allocated to treatment groups within blocks defined by faecal nematode egg counts (FEC) pre-treatment. On Day 0 derquantel-abamectin was administered orally at 1 ml/5 kg bodyweight (2 mg/kg derquantel, 0.2 mg/ kg abamectin), and each reference anthelmintic was given at the recommended label dose. Faecal samples were collected on Day 14 (± 1 day), to determine the percentage reduction in mean FEC for each anthelmintic tested. Larval differentiation was also performed post-treatment, to estimate efficacy at the genus level. Animals were weighed on or before Day 0, and on Day 14 (± 1 day) in 13 trials.RESULTS: The efficacy of derquantel-abamectin against mixed strongyle populations was ≥99.2%, based on the percentage reduction in geometric mean FEC. Nematodirus sp. was present in six trials at a level sufficient for efficacy calculations to be conducted; in all cases, the efficacy of derquantel-abamectin was 100%. In those trials where the efficacy of at least one reference anthelmintic was <95% against strongyles and/or Nematodirus sp., derquantel-abamectin was 100% effective. In five trials, the mean gain in bodyweight was significantly greater in the derquantel-abamectin group than the negative controls.CONCLUSIONS AND CLINICAL RELEVANCE: When administered orally at 1 ml/5 kg bodyweight, derquantel-abamectin is highly effective for the treatment of gastrointestinal nematodes in sheep, including populations of strongyles and Nematodirus sp. with resistance to one or more single- or dual-active anthelmintics. Derquantel-abamectin presents sheep producers with a unique opportunity to introduce a new class of anthelmintic to their nematode control programmes, with the added benefits offered by a combination anthelmintic.

Overview of anthelmintic resistance of gastrointestinal nematodes of small ruminants in Brazil

“…Recently, two new classes of anthelmintics were launched, a derivative of aminoacetonitrile with broad-spectrum activity, monepantel, Zolvix® (KAMINSKY et al, 2008) and derquantel (Startect®), a medium-spectrum semisynthetic spiroindolone, which was marketed in association with abamectin (LITTLE et al, 2010(LITTLE et al, , 2011. Sager et al (2012) found 100% and 95% effectiveness, respectively, for these two products against Haemonchus contortus strains resistant to other drugs.…”

“…Macrocyclic lactones were launched on the market in the 1980s (CHABALA et al, 1980), but just a few years later, there were reports of the loss their efficiency in Brazil (ECHEVARRIA & TRINDADE, 1989). Recently, two new classes of anthelmintics were launched, an amino-acetonitrile derivative, monepantel (KAMINSKY et al, 2008), and derquantel, which was marketed in association with abamectin (LITTLE et al, 2010). However, there have been reports of resistance to monepantel (SCOTT et al, 2013;MEDEROS et al, 2014a; VAN DEN BROM et al, 2015) and to derquantel (KAMINSKY et al, 2011), indicating the high vulnerability of these drugs.…”

Resistência anti-helmíntica em nematoides gastrintestinais de pequenos ruminantes: avanços e limitações para seu diagnóstico

“…O controle químico continua a ser preocupante, pois é praticado com medicamentos contendo alta concentração ou mesmo com o uso da combinação de medicamentos, muitas vezes sem critério de produção e/ou indicação para sua ampla utilização. Recentemente, duas novas classes de anti-helmínticos -monepantel (Kaminsky et al 2008) e derquantel, este em combinação com a abamectina (Little et al 2010) -, com novos modos de ação, foram lançados no mercado na Nova Zelândia, sendo uma alternativa promissora para o futuro do controle de nematoides gastrintestinais.…”

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) Guideline: Anthelmintic combination products targeting nematode infections of ruminants and horses

“…For example, a new anthelmintic, derquantel (spiroindole class), has recently been approved for use in some countries as a combination anthelmintic product with abamectin (ML class). By adding abamectin to derquantel, the spectrum of parasite species against which this combination exhibits ≥95% efficacy is significantly increased (Little et al, 2010(Little et al, , 2011.…”