Preventive efficacy of six monthly oral doses of Simparica Trio®, Heartgard® Plus, and Interceptor® Plus against a macrocyclic lactone-resistant strain (ZoeLA) of heartworm (Dirofilaria immitis) in dogs

Table 4 Efficacy of oral moxidectin against ML-resistant heartworm strains compared to Simparica Trio^®, 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
Simparica Trio	6	5 of 6	0–3	1.0	97.2^g	na	na	na	na
Heartgard Plus	6	6 of 6 6 of 6	25–36 22–38	29.0 32.5	18.7^e 8.5^g	6 of 6 6 of 6 6 of 6	6–18 12–29 19–34	11.9 21.7 26.8	63.9^e 37.7^f 10.5 ^f
Interceptor Plus	6	6 of 6 6 of 6	16–37 10–34	28.1 22.8	21.2^e 35.9^g	6 of 6 6 of 6 6 of 6	10–22 14–37 13–35	14.9 22.7 25.5	54.6^e 34.9^f 14.6^f

^aMoxidectin administered at exact 24 µg/kg dosage. Simparica Trio (24 µg/kg moxidectin + 1.2 mg/kg sarolaner + 5 mg/kg pyrantel), Heartgard Plus (6 µg/kg ivermectin + 5 mg/kg pyrantel), and Interceptor Plus (500 µg/kg milbemycin oxime + 5 mg/kg praziquantel) administered according to commercial label directions, which resulted in administration of 24 to 48 µg/kg moxidectin, 6.2–15.5 µg/kg of ivermectin and 0.5 to 1.2 mg/kg milbemycin oxime
^bTreatment administration days: one monthly treatment: day 0 [4]; three monthly treatments: days 0, 28, and 56 [4]; four monthly treatments: days 0, 30, and 60 [9], six monthly treatments: days 0, 30, 60, 90, 120, and 150 [9, 10, studies from this paper], and for one study, six monthly treatments were provided prior to and after inoculation on day 165 (treatments on days 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330) [10]
^cEach dog inoculated with 50 D. immitis L3 on day -30, with adult heartworm recovery at necropsy 133–273 days after inoculation
^dData reference: McTier et al. [4]
^eData reference: Kryda et al. [9]
^fData reference: McTier et al. [10]
^gData reference: this paper

ISSN: 1756-3305