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Four trials, using 48 European breed cattle, were conducted to evaluate the efficacy of abamectin against the louse species Linognathus vituli, Haematopinus eurysternus and Damalinia bovis and against the mange mites Sarcoptes scabiei var bovis and Psoroptes ovis. Animals were allocated by restricted randomisation based on parasite counts to treatment with abamectin at a dose of 200 micrograms/kg given subcutaneously or to an untreated control group. Ectoparasites were counted before treatment and at weekly intervals thereafter for eight weeks. L. vituli, H eurysternus and S scabiei var bovis were eliminated (P < 0.05) by day 7 after abamectin treatment. An efficacy of more than 99 per cent was recorded against P ovis mange mites. The biting louse D bovis was not controlled. Abamectin treatment increased the weight gain of cattle infested with ectoparasites.

Eight controlled trials were conducted, using 96 cattle of European breeds, to evaluate the efficacy of abamectin against natural and artificially acquired infections of adult and fourth-stage larvae of all the economically important gastrointestinal nematodes and lungworms in Germany and the United Kingdom. Half the animals were treated on one occasion with abamectin at a dose of 200 micrograms/kg bodyweight given subcutaneously while the other half remained untreated. Worms were counted 14 or 21 days after treatment or 28 days after the last infection. The treatment was highly effective (> 99 to 100 per cent) (P < 0.05) at removing immature (L4) stages and adult worms of the following species: Ostertagia ostertagi (inhibited larvae included), Trichostrongylus axei, Haemonchus contortus, Bunostomum phlebotomum, Cooperia species Oesophagostomum radiatum and Dictyocaulus viviparus. Naturally acquired adult C surnabada and Trichuris discolor infections were also significantly (P < 0.05) reduced. For Nematodirus helvetianus the efficacy varied from 89.8 to > 99 per cent (P > 0.1 to < 0.01). Abamectin gave full protection against the gastrointestinal nematodes O ostertagi, H contortus, Cooperia species and O radiatum for at least seven days and against the lungworm D viviparus for at least 14 days after treatment.