Preventive efficacy of four or six monthly oral doses of 24 µg/kg moxidectin compared to six monthly doses of Heartgard® Plus or Interceptor® Plus against macrocyclic lactone-resistant heartworm (Dirofilaria immitis) strains in dogs.

Autor: Kryda K; Zoetis, Veterinary Medicine Research and Development, 333 Portage St, Kalamazoo, MI, 49007, USA. kristina.a.kryda@zoetis.com., Holzmer S; Zoetis, Veterinary Medicine Research and Development, 333 Portage St, Kalamazoo, MI, 49007, USA., Everett WR; Bertek Inc, 104 Wilson Bottoms Rd, Greenbrier, AR, 72058, USA., McCall JW; TRS Labs Inc, 215 Paradise Blvd, Athens, GA, 30607, USA., Mahabir SP; Zoetis, Veterinary Medicine Research and Development, 333 Portage St, Kalamazoo, MI, 49007, USA., McTier TL; Zoetis, Veterinary Medicine Research and Development, 333 Portage St, Kalamazoo, MI, 49007, USA., Maeder SJ; Zoetis, Veterinary Medicine Research and Development, 333 Portage St, Kalamazoo, MI, 49007, USA.
Jazyk: angličtina
Zdroj: Parasites & vectors [Parasit Vectors] 2020 Jul 14; Vol. 13 (1), pp. 339. Date of Electronic Publication: 2020 Jul 14.
DOI: 10.1186/s13071-020-04178-z
Abstrakt: Background: Recent reports indicated that increasing the monthly oral dosage and the number of consecutive monthly doses of moxidectin improved the efficacy against macrocyclic lactone (ML)-resistant Dirofilaria immitis. The two laboratory studies reported here evaluated the efficacy of four or six monthly oral doses of 24 µg/kg moxidectin compared to six monthly doses of either Heartgard® Plus (ivermectin/pyrantel) or Interceptor® Plus (milbemycin oxime/praziquantel) against ML-resistant D. immitis strains.
Methods: Dogs were inoculated 30 days prior to first treatment with 50 third-stage (L 3 ) larvae of a ML-resistant strain of D. immitis, ZoeLA or JYD-34. In each study, dogs (six per group) were randomized to treatment with six monthly doses of placebo, four or six monthly doses of 24 µg/kg moxidectin, or six monthly doses of Heartgard® Plus or Interceptor® Plus at their label dose rates. Efficacy was evaluated by adult heartworm counts approximately nine months after L 3 inoculation.
Results: All negative-control dogs were infected with adult heartworms (geometric mean, 35.6; range, 24-41) for ZoeLA and (geometric mean, 32.9; range, 30-37) for JYD-34. Efficacies against ZoeLA for moxidectin, Heartgard® Plus and Interceptor® Plus were ≥ 96.1%, 18.7% and 21.2%, respectively. Adult counts for both moxidectin-treated groups were significantly lower than negative control (P < 0.0001), significantly lower than Heartgard® Plus and Interceptor® Plus (P < 0.0001), but not significantly different from each other (P = 0.5876). Counts for Heartgard® Plus and Interceptor® Plus were not significantly different than negative control (P ≥ 0.2471). Efficacies against JYD-34 were ≥ 95.9%, 63.9% and 54.6% for moxidectin, Heartgard® Plus and Interceptor® Plus, respectively. Counts for all groups were significantly lower than negative control (P ≤ 0.0001). Counts for six monthly doses of moxidectin were significantly lower than those for four monthly doses (P = 0.0470), and the counts for both moxidectin-treated groups were significantly lower than Heartgard® Plus and Interceptor® Plus (P ≤ 0.0002).
Conclusions: Moxidectin administered orally at 24 µg/kg to dogs for four or six consecutive months was ≥ 95.9% effective in preventing the development of two ML-resistant heartworm strains and resulted in significantly fewer adult D. immitis than in dogs treated with Heartgard® Plus or Interceptor® Plus when administered for six consecutive months at their approved label dosages in two laboratory efficacy studies.
Databáze: MEDLINE
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