Zoetis, Veterinary Medicine Research and Development, 333 Portage Street, Kalamazoo, MI, 49007, USA.
TRS Labs Inc, 215 Paradise Blvd, Athens, GA, 30607, USA.
Parasit Vectors. 2022 Mar 11;15(1):81. doi: 10.1186/s13071-022-05180-3.
Administration of four to six consecutive monthly doses of 24 µg/kg moxidectin alone shows high effectiveness in preventing the maturation of macrocyclic lactone (ML)-resistant heartworm strains, Dirofilaria immitis JYD-34 and ZoeLA. This laboratory study evaluated the efficacy of six consecutive monthly oral doses of Simparica Trio (moxidectin/sarolaner/pyrantel) compared to six monthly doses of either Heartgard Plus (ivermectin/pyrantel) or Interceptor Plus (milbemycin oxime/praziquantel) against ML-resistant D. immitis ZoeLA strain.
Beagle dogs were inoculated with 50 third-stage (L3) D. immitis larvae (ZoeLA) 30 days prior to the first treatment. Dogs were randomized to treatment (six animals in each group) with six monthly oral doses of placebo, Simparica Trio, Heartgard Plus, or Interceptor Plus at their respective label doses. Microfilaria (MF) and antigen tests were conducted periodically, and efficacy was evaluated by necropsy for adult heartworms approximately 9 months after L3 inoculation.
Adult heartworms were recovered from all six placebo dogs, with a geometric mean of 35.5 worms (range, 23-48). Five of the six dogs treated with Simparica Trio were infected with a geometric mean of 1.0 worms (range, 0-3), and all remained MF-negative. All Heartgard Plus-treated dogs (six) were infected with a geometric mean of 32.5 worms (range, 22-38); five of these dogs were MF-positive at day 236. All Interceptor Plus-treated dogs (six) were infected with a geometric mean of 22.8 worms (range, 10-34); five of these dogs were MF-positive at day 236. The efficacy of six consecutive doses with Simparica Trio, Heartgard Plus, and Interceptor Plus against ZoeLA was 97.2, 8.5, and 35.9%, respectively. Adult worm counts for the Simparica Trio-treated group were significantly lower (P < 0.0001) than placebo control, Heartgard Plus, and Interceptor Plus-treated groups. Adult worm counts for Heartgard Plus and Interceptor Plus were not significantly different from placebo (P > 0.05).
Simparica Trio prevented microfilaremia in all dogs and was highly effective (97.2%) and significantly better than either Heartgard Plus (8.5%) or Interceptor Plus (35.9%) in preventing the development of the ZoeLA ML-resistant heartworm strain when administered for six consecutive months in this comparative laboratory efficacy study.
单独给予六剂连续每月 24μg/kg 剂量的莫昔克丁可高度有效预防大环内酯类药物（ML）耐药犬恶丝虫株，即犬恶丝虫 JYD-34 和 ZoeLA 的成熟。本实验室研究评估了六剂连续每月口服 Simparica Trio（莫昔克丁/萨罗勒纳/吡喹酮）与六剂每月给予 Heartgard Plus（伊维菌素/吡喹酮）或Interceptor Plus（米尔贝肟肟/吡喹酮）相比，对 ML 耐药犬恶丝虫 ZoeLA 株的疗效。
在第一次治疗前 30 天，将 50 条第三期（L3）犬恶丝虫幼虫（ZoeLA）接种给比格犬。将狗随机分为六组，每组六只，接受六剂每月口服安慰剂、Simparica Trio、Heartgard Plus 或 Interceptor Plus，剂量为各自标签剂量。定期进行微丝蚴（MF）和抗原检测，通过接种 L3 后约 9 个月的剖检评估成虫心丝虫的疗效。
所有六只接受安慰剂治疗的狗均从心脏中回收了成虫心丝虫，几何均数为 35.5 条（范围，23-48）。Simparica Trio 治疗的六只狗中有五只感染了 1.0 条（范围，0-3），所有狗均保持 MF 阴性。所有 Heartgard Plus 治疗的狗（六只）均感染了 32.5 条（范围，22-38）；其中五只狗在第 236 天 MF 阳性。所有接受 Interceptor Plus 治疗的狗（六只）均感染了 22.8 条（范围，10-34）；其中五只狗在第 236 天 MF 阳性。六剂连续剂量的 Simparica Trio、Heartgard Plus 和 Interceptor Plus 对 ZoeLA 的疗效分别为 97.2%、8.5%和 35.9%。Simparica Trio 治疗组的成虫计数明显低于安慰剂对照组、Heartgard Plus 和 Interceptor Plus 治疗组（P<0.0001）。Heartgard Plus 和 Interceptor Plus 治疗组的成虫计数与安慰剂组无显著差异（P>0.05）。
在这项比较性实验室疗效研究中，Simparica Trio 预防了所有狗的微丝蚴血症，在预防 ZoeLA ML 耐药犬恶丝虫株发育方面非常有效（97.2%），显著优于 Heartgard Plus（8.5%）或 Interceptor Plus（35.9%），六剂连续每月给予。
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