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

Table 6 Efficacy of oral moxidectin (24 µg/kg) against ML-resistant heartworm strains compared to Heartgard® Plus or Interceptor® Plus: summary

Oral treatment^a	No. of monthly treatments^b	ZoeLA				JYD-34
		No. of infected dogs^c	Adult D. immitis worm counts		Efficacy compared to negative control (%)	No. of infected dogs^c	Adult D. immitis worm counts		Efficacy compared to negative control (%)
		No. of infected dogs^c	Range	Geometric mean	Efficacy compared to negative control (%)	No. of infected dogs^c	Range	Geometric mean	Efficacy compared to negative control (%)
Moxidectin	1	Not tested				8 of 8	7–29	16.8	53.2^d
Moxidectin	3	1 of 5	0–1	0.1	99.5^d	1 of 5	0–2	0.2	98.8^d
Moxidectin	4	5 of 6	0–3	1.1	96.8^e	5 of 6	0–4	1.3	95.9^e
Moxidectin	6	5 of 6	0–4	1.4	96.1^e	2 of 6	0–1	0.2	99.3^e
Heartgard® Plus	6	6 of 6	25–36	29.0	18.7^e	6 of 6	6–18	11.9	63.9^e
Interceptor® Plus	6	6 of 6	16–37	28.1	21.2^e	6 of 6	10–22	14.9	54.6^e

^aMoxidectin administered at exact 24 µg/kg dosage. Heartgard® Plus and Interceptor® Plus administered according to commercial label directions which resulted in administration of 6.2–15.5 µg/kg of ivermectin and 0.5–1.2 mg/kg milbemycin oxime
^bTreatment administration days: 1 monthly treatment: Day 0; 3 monthly treatments: Days 0, 28 and 56 (studies from data reference 1) or Days 0, 30, and 60 (studies from this paper); 4 monthly treatments: Days 0, 30, 60 and 90; 6 monthly treatments: Days 0, 30, 60, 90, 120 and 150
^cEach dog inoculated with 50 D. immitis L₃ on Day -30 with adult heartworm recovery at necropsy 133 to 273 days after L₃ inoculation
^dData reference: McTier et al. [4]
^eData reference: this paper

ISSN: 1756-3305