The efficacy of a treatment with fenbendazole against an experimental Giardia duodenalis infection in lambs

The aim of the present study was to evaluate the efficacy of fenbendazole (Panacur 2.5%; Intervet/Schering-Plough) at 15 mg/kg/day during 3 consecutive days in lambs experimentally infected with Giardia duodenalis, and to evaluate the benefit of the treatment with fenbendazole on growth, faecal consistency and general health. To this end, 42 weaned (∼12 weeks of age) and healthy lambs were selected and housed into three experimental groups based on weight. One group of 14 lambs remained uninfected (group 1: negative control group), while the other 28 lambs were infected with a total of 105G. duodenalis cysts, 11 days prior to treatment (D11). Based on the average individual cyst counts between D4 and D2, the infected animals were allocated on D1 into two groups of 14 animals each. Treatment was randomly assigned to one of these two groups, and all animals in the treatment group (group 3) were orally treated with fenbendazole at 15 mg/kg/day during 3 consecutive days starting from D0 (day of treatment). The lambs in the positive (group 2) and negative control group received a placebo (water). From 3 days after treatment (D3) onwards, cyst excretion was determined three times a week during 4 consecutive weeks after the start of the treatment. The faecal consistency and general health were recorded at each sampling day. The weight was recorded prior to treatment and at the end of each week throughout the experimental period. During the experimental period, there was a high (≥97.8%) and continuous reduction in cyst excretion in the treatment group compared to the positive control group for 12 days, resulting in a significant (P < 0.001) reduction of the cumulative cyst excretion until D21. There were no significant differences in general health and faecal consistency between the three groups, as there were no overt clinical symptoms in any of the infected animals. Prior to treatment the weight did not differ between the three groups. Although not significantly different, the animals in the treatment group gained on average 4.23 kg over the 4-week period, while the infected and non-infected animals gained 3.78 kg and 3.52 kg, respectively.