Efficacy of eprinomectin topical solution and eprinomectin extended-release injection treatments against developing larval and adult Chabertia ovina and Oesophagostomum venulosum - two less common cattle nematode parasites

The efficacy of the topical and injection formulations of eprinomectin (0.5 % w/v topical solution, EPRINEX®; 5 % w/v extended-release injection, LONGRANGE®; Boehringer Ingelheim) against larval and adult stages of the rare bovine large intestine nematodes Chabertia ovina and Oesophagostomum venulosum was evaluated in one Good Clinical Practice study compliant to World Association for the Advancement of Veterinary Parasitology and International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products anthelmintic guidelines. Forty nematode naïve induced infected Brown Swiss calves were allocated into five groups of eight completely at random. Inoculation with isolates obtained in Germany was staggered so that the parasites of the two species were, when the treatments were administered, concurrently fourth-stage larval or adult nematodes, respectively. One group served as untreated control, two groups each received eprinomectin 0.5 % w/v topical solution or eprinomectin 5 % w/v extended-release injection per product label. Animals were necropsied at one and the same day (corresponding to six weeks or two weeks after administration of treatments against fourth-stage larval or adult nematodes) for parasite recovery and count. Both C. ovina (range, 39–604) and O. venulosum (range, 3–23) were recovered from all eight controls while among the 32 calves which were administered topical solution or extended-release injection eprinomectin, only a single C. ovina specimen was isolated from one animal which received the injection product when the nematodes were adult. Eprinomectin treatments were > 99.9 % effective against fourth-stage larval or adult C. ovina and O. venulosum nematodes (p 0.001 at α = 0.05). All animals accepted the treatments well. No adverse events or other health problems were observed in the study animals.