The efficacy of an ivermectin/closantel injection against experimentally induced infections and field infections with gastrointestinal nematodes and liver fluke in cattle.

Three studies were performed to test the efficacy of an ivermectin/closantel injection (200 microg/kg(-1) ivermectin and 5 mg/kg(-1) closantel) in cattle. Two were experimentally induced infections of Ostertagia ostertagi, Cooperia oncophora and Fasciola hepatica in calves, and the third had natural field infections in cattle with several species of gastrointestinal nematodes and F. hepatica. In the two studies with artificial infections, four groups of 8 calves were used. All calves were infected with metacercariae on Day 0. Infection with the nematodes took place on Day 33 in groups 1 and 2 and on Day 54 in groups 3 and 4. Treatment was given to calves of group 1 on Day 63 and to calves of group 3 on Day 84. Calves of groups 2 and 4 served as untreated control groups. Calves of groups 1 and 2 were sacrificed on Day 84, calves of groups 3 and 4 on Day 105. The field study was carried out on a commercial farm in the Netherlands. Six groups of cattle were used. Groups A and B consisted of 10 parasite free calves, introduced to the farm and grazed for four weeks on pastures naturally infected with gastrointestinal nematode larvae and liver fluke metacercariae. Group C were the farmers own calves (15), group D heifers (10), group E dry cows (6) and group F milking cows (20). Treatment was given to animals of group A, C, D and E 10 weeks after housing of group A and B. Animals of groups B and F served as untreated controls. Calves of groups A and B were sacrificed 14 days after treatment. The efficacy of the treatment was calculated on basis of the post-mortem fluke and nematode worm counts in the first two studies and on a combination of post-mortem fluke and nematode worm counts and faecal egg output in the field study. In the two experimental studies, the efficacy of the treatment against F. hepatica was 99.2% and 94.5% for 9-week-old flukes and 98.4% and 99.5% for 12-week-old flukes. For O. ostertagi in both studies efficacy was 100% and against C. oncophora in both Groups 1 efficacy was 84.9% and 99.0% and in Groups 3 85.0% and 99.4%. In the field study, based on the post mortem fluke and nematode worm counts in groups A and B, efficacy against F. hepatica was 98.4%, O. ostertagi 100%, C. oncophora 99.4%, C. punctata 100%, Nematodirus helvetianus 60.8%, Trichuris spp. 100% and against larval intestinal nematodes 100%. The results of the faecal examinations 14 days after treatment confirmed the post-mortem results with 100% reduction of egg output for O. ostertagi, C. punctata, Trichostrongylus spp. and Trichuris spp. and low egg output of C. oncophora and N. helvetianus.