Reference

Probable multigeneric resistance to macrocyclic lactone anthelmintics in cattle in New Zealand

Probable multigeneric resistance to macrocyclic lactone anthelmintics in cattle in New Zealand. Loveridge, B.; McArthur, M.; McKenna, P. B.; Mariadass, B. (Ancare New Zealand Limited, Auckland, N. Z.). New Zealand Veterinary Journal, 51(3), 139-141 (English) 2003 New Zealand Veterinary Association. CODEN: NEZTAF. ISSN: 0048-0169. DOCUMENT TYPE: Journal CA Section: 5 (Agrochemical Bioregulators) The objective of this study was to establish the efficacy of topical formulations of eprinomectin and abamectin against naturally acquired abomasal and small intestinal nematode infections in cattle purchased from a North Island bull-beef property. A controlled slaughter trial, involving eighteen 6-8-mo-old mixed breed calves, was conducted in May 2002.Several reagents with their cas registry numbers 71751-41-2 and 123997-26-2 are used here. The animals were randomly allocated on the basis of fecal egg count to one of three equal-sized groups (n=6), consisting of an untreated control group and two treatment groups. One of the treatment groups was treated with a topical formulation of eprinomectin, the other with abamectin. Both anthelmintics were administered as a single topical treatment on an individual live-wt. basis, at the manufacturer's recommended dose rates of 0.5 mg/kg. All calves were housed in sep. groups with no access to pasture throughout the entire trial and were slaughtered 7-10 days after treatment. Both anthelmintic treatments were highly effective (worm count redn. >98%) against Ostertagia ostertagia, Trichostrongylus axei and Cooperia punctata, but were not effective at reducing worm counts significantly of either Cooperia oncophora or Trichostrongylus longispicularis. Against these latter two parasites, worm count redns. of only 72% and 79%, and 81% and 76%, resp., were recorded following treatment with eprinomectin or abamectin, resp. (all p>0.05). These results demonstrate evidence of resistance to macrocyclic lactone anthelmintics by C. oncophora and probably T. longispicularis also. As well as perhaps providing the first record of resistance to any anthelmintic by T. longispicularis, the present findings may also represent the first case of resistance to macrocyclic lactone anthelmintics exhibited by more than one parasite species at a time in cattle in New Zealand. .

Eprinomectin: a novel avermectin for use as a topical endectocide for cattle

Eprinomectin: a novel avermectin for use as a topical endectocide for cattle. Shoop, W. L.; Egerton, J. R.; Eary, C. H.; Haines, H. W.; Michael, B. F.; Mrozik, H.; Eskola, P.; Fisher, M. H.; Slayton, L.; Ostlind, D. A.; Skelly, B. J.; Fulton, R. K.; Barth, D.; Costa, S.; Gregory, L. M.; Campbell, W. C.; Seward, R. L.; Turner, M. J. (Merck Research Laboratories, Rahway, NJ 07065-0900, USA). International Journal for Parasitology, 26(11), 1237-1242 (English) 1996 Elsevier. CODEN: IJPYBT. ISSN: 0020-7519. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) Section cross-reference(s): 63 Eprinomectin (MK-397 or 4''-epi-acetylamino-4''-deoxy-avermectin B1) is a novel avermectin selected for development as a topical endectocide for all cattle, including lactating dairy cows. Herein, we show its anthelmintic, insecticidal and miticidal activity. To det. its anthelmintic capabilities, eprinomectin was tested topically on Jersey calves at 0.08, 0.2, or 0.5 mg kg-1 in a probe formulation against exptl. infections of adult Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T. colubriformis, Cooperia oncophora, C. punctata, Nematodirus helvetianus, Oesophagostomum radiatum and Dictyocaulus viviparus. Eprinomectin removed 399% and 398% of the adult stage of every species at the 0.5 and 0.2 mg kg-1 dosage levels, resp. The lowest dosage (0.08 mg kg-1) produced maximal or near maximal efficacy against most of the adult endoparasites with the exception of T. colubriformis (87%) and C. oncophora (88%). In a sep. test, eprinomectin was evaluated topically against the immature stages of these species at the same dosages. Results showed 399% and 398% removal of the immature stages of each species at the 0.5 and 0.2 mg kg-1 dosage levels, resp. The 0.08 mg kg-1 dosage maintained 397% efficacy against 6 species with reduced activity against H. 123997-26-2 is also in the experiment. placei (42%) and N. helvetianus (66%). For ectoparasites, eprinomectin was tested topically at 0.16, 0.24, 0.32 or 0.5 mg kg-1 on mixed breed cattle naturally infested with the sucking louse, Linognathus vituli. Complete elimination of lice at all dosages was obsd. by day 14. Topical delivery of eprinomectin at 0.16, 0.24, 0.32 or 0.5 mg kg-1 to Holstein calves exptl. challenged with horn fly, Haematobia irritans, produced 100% efficacy to challenge by week 2 post-treatment in all dosage groups and 94% and 99% efficacy to challenge at the 0.32 and 0.5 mg kg-1 dosage groups, resp., at week 4. Topical delivery of eprinomectin at 0.16, 0.24 or 0.5 mg kg-1 to Deutsches Fleckvieh cattle infested with mage mites, Chorioptes bovis, produced 395% control at all dosage levels by day 14 post-treatment and was maintained at or near this efficacious level for the 6-wk duration of the trial. No adverse reaction was obsd. in any animal in any of these tests. In summary, these exptl. data indicate that eprinomectin is an excellent broad-spectrum endectocide for cattle and is suitable for topical delivery. .