Doramectin, a new avermectin highly efficacious against gastrointestinal nematodes and lungworms of cattle and pigs: two studies carried out under field conditions in Germany

Two field studies were carried out to confirm the efficacy of doramectin in cattle and pigs in Europe. A total of 40 cattle harbouring naturally acquired infections of gastrointestinal nematodes, including Ostertagia spp., Oesophagostomum spp., Cooperia spp., Haemonchus spp., Nematodirus spp. and Trichuris spp., were allocated to a treated or a control group (20 animals/group), and 100 harbouring naturally acquired infections of gastrointestinal nematodes and lungworms, including Oesophagostomum spp., Metastrongylus spp., Ascaris suum and Trichuris suis, were allocated to either a treated (60 pigs) or a control (40 pigs) group. Animals in the treated groups received an injection of doramectin at 200 micrograms/kg (1 ml/50 kg) for cattle or 300 micrograms/kg (1 ml/33 kg) for swine. Animals in the control groups received saline at 1 ml/50 kg for cattle or 1 ml/33 kg for swine. The cattle were injected by the subcutaneous route in the lateral mid-line of the neck and the pigs were injected intramuscularly in the neck. Faecal egg counts were determined for all animals on days--7, 0, 7, 14 and 21 of the studies, where day 0 was the day of treatment. The mean daily weight gain of doramectin-treated animals was significantly higher than that of the control animals over the 21 days of the studies (P < 0.0007 for cattle and P = 0.0001 for swine). At 21 days after treatment, the mean faecal egg counts of the doramectin-treated animals were significantly lower than those of the control animals and were reduced by 100% as compared with pretreatment levels. No adverse reaction to treatment was observed in any animal during either study.