The effect of a fenbendazole treatment on cyst excretion and weight gain in calves experimentally infected with Giardia duodenalis

Vet Parasitol. 2010 Apr 19;169(1-2):18-23. doi: 10.1016/j.vetpar.2009.12.027. Epub 2009 Dec 28.


A total of 28 Holstein-Friesian calves were experimentally infected with 10(5)Giardia duodenalis cysts. Eleven days later, all animals were allocated into two groups of 14 animals each, based on the average pre-treatment cyst counts. Treatment was randomly assigned to one of the two groups, and all animals in the treatment group received a daily oral dosage of 15mg fenbendazole per kg bodyweight during 3 consecutive days. The calves in the control group received a placebo (water). From 3 days after treatment onwards, cyst excretion was determined three times a week during 4 consecutive weeks. The faecal consistency and general health were recorded on a daily basis, and all animals were weighed prior to treatment and weekly thereafter. At the end of the experimental period, there was a significant (P<0.001) reduction (98%) of the cumulative cyst excretion. There were no significant differences in general health between both groups, but faecal consistency was significantly lower (P<0.002) in the control group compared to the treatment group, although none of the animals displayed overt gastro-intestinal symptoms. Prior to treatment the weight did not differ between both experimental groups. At the end of the 4-week experimental period however, the animals in the treatment group gained on average 2.86kg (=102g per day) more than the animals in the control group (P<0.031). This study demonstrates for the first time a significant difference in weight gain between fenbendazole treated and untreated calves experimentally infected with G. duodenalis, although additional data need to confirm the need for treatment in natural conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antiprotozoal Agents / pharmacology*
  • Antiprotozoal Agents / therapeutic use*
  • Body Weight / drug effects*
  • Cattle
  • Cattle Diseases / drug therapy*
  • Feces / parasitology
  • Fenbendazole / pharmacology*
  • Fenbendazole / therapeutic use*
  • Giardia
  • Giardiasis / drug therapy
  • Giardiasis / veterinary*
  • Male
  • Random Allocation


  • Antiprotozoal Agents
  • Fenbendazole