The effect of levamisole on the development of Ostertagia circumcincta in lambs

The majority of third-stage Ostertagia circumcincta larvae exposed to 0·5% levamisole failed to infect lambs even though the worms regained some activity after repeated washings in balanced saline. A low level of efficiency was recorded against 4·5-day-old O. circumcincta when lambs were treated with levamisole at 7·5 mg per kg. Nine-day-old worms from hosts which received anthelmintic on day 4·5 were at the same stage of development as those from untreated control lambs.

The anthelmintic activity of cambendazole in calves and lambs

Tests were carried out on the efficacy of Cambendazole (5-isopropoxy carbonylamino-2-(4-thiazolyl) benzimidazole) against lungworm and gastrointestinal parasites of calves and lambs. Against Dictyocaulus viviparus the compound was highly effective (80%) against mature worms at levels of 35 mg/kg and over and immature "arrested" worms at 60 mg/kg (71% efective). In the Calves the compound was very effective (90 to 99%) against adult Haemonchus placei, Ostertagia spp., Trichostrongylus axei and Cooperia oncophora at all levels tested (15, 20, 25, 30, 40 and 60 mg/kg). Against adult Nematodirus spp. dosages of 30, 40 and 60 mg/kg were 81%, 94% and 99% effective respectivelyAgainst arrested Ostertagia spp. larvae, a dosage of 60 mg/kg was 90% effective. Immature stages of Cooperia spp. were susceptible at all levels used but those of Nematodirus spp. required levels of 60 mg/kg for 99% removal. In the lambs the compound was highly effective against immature and mature nematodes when given orally at all levels tested from 15 mg/kg to 30 mg/kg. Significant reductions (81%) in Moniezia expansa scolices were also observed at dosages from 15 mg/kg to 30 mg/kg.

Effects of thiabendazole treatment on weight gains by Nebraska range cattle

The results of these studies indicate that a high percentage of Nebraska range cattle are infected with gastrointestinal parasites, but at a subclinical level of infection. However, significant differences were not observed in average daily gain between thiabendazole-treated range cattle and unmedicated controls in three of four field trials. In the three trials the average improvement in daily gain in animals receiving thiabendazole once averaged .01 lb greater than untreated controls. During a 120 day grazing period this improvement would not be sufficient to pay for the wormer or cost of additional labor.