Effect of fenbendazole on shedding and embryonation of Ascaris suum eggs from naturally infected sows

Materials and methods: Five shedding and three embryonation experiments across three commercial sow farms were conducted. Ascaris suum-infected sows were allocated to four treatments: untreated controls; 545.5 mg fenbendazole, 1 day (Treatment 1); 545.5 mg fenbendazole, 3 consecutive days (1636.5 mg total) (Treatment 2); and 1636.5 mg fenbendazole, 1 day (Treatment 3). Fecal samples were collected and evaluated by a standard flotation method (shedding study) or eggs were isolated and incubated (embryonation study) to determine embryonation rates. Groups were compared for time-to-negative (Kaplan-Meier survival analysis); percent negative (chi-square analysis); environmental burden (analysis of variance); and embryonation rates (analysis of variance).