Efficacy of fenbendazole for treatment of giardiasis in calves.
OBJECTIVE
To determine efficacy of fenbendazole for treatment of giardiasis in calves.


METHODS
Twenty male and 15 female Holstein calves (100 to 180 kg), naturally infected with Giardia sp.


METHODS
In vitro fenbendazole susceptibility and resistance development was determined for a ruminant Giardia isolate by use of an adherence assay. Calves were treated as follows: group 1, a single administration of 5 mg of fenbendazole/kg of body weight; group 2, a single administration of 10 mg of fenbendazole/kg; group 3, 5 mg of fenbendazole/kg, every 24 hours for 3 days; group 4, 10 mg of fenbendazole/kg, every 24 hours for 3 days; group 5, 20 mg of fenbendazole/kg, every 24 hours for 3 days; group 6, 0.833 mg of fenbendazole/kg, every 24 hours for 6 days; and group 7, saline solution. Fecal Giardia cysts were counted on days -3 through -1 and 1 through 7, 9, 11, 13, 21, and 28 by use of sucrose gradient concentration and staining with a fluorescent monoclonal antibody.


RESULTS
The 50% adherence inhibition concentration was 0.024 +/- 0.002 microgram/ml, and resistance could not be detected after 5 weeks of continuous culture at sublethal concentration of fenbendazole (0.01 microgram/kg). Fenbendazole was 100% effective in eliminating cysts from the feces within 6 days for calves in treatment groups 2-6. Reinfection was observed in some calves within the 28-day study period.


CONCLUSIONS
Fenbendazole is effective in the elimination of Giardia infections in calves, but repeat treatments may be required in reinfected animals.


CONCLUSIONS
Fenbendazole is an effective and economical treatment for Giardia-associated diarrhea and growth rate reduction in calves.
O'Handley
R M
RM
Gastrointestinal Research Group, University of Calgary, Alberta, Canada.
Olson
M E
ME
McAllister
T A
TA
Morck
D W
DW
Jelinski
M
M
Royan
G
G
Cheng
K J
KJ
D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology / Q000592:standards / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000503:physiopathology / Q000517:prevention & control; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000469:parasitology; D005260:Female; D005273:Fenbendazole / Q000494:pharmacology / Q000592:standards / Q000627:therapeutic use*; D005872:Giardia / Q000187:drug effects / Q000302:isolation & purification; D005873:Giardiasis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D008297:Male
D000981:Antiprotozoal Agents; D005273:Fenbendazole