This study was carried out to investigate the association between infection to Giardia sp. and occurrence of diarrhea in Urmia, Iran. Fecal samples were collected from 246 calves (34 diarrheic and 212 non-diarrheic) and examined for the presence of Giardia spp. cysts using a quantitative centrifugation concentration zinc sulfate flotation technique. Analysis of data showed that the relative frequency of infection to Giardia cysts is significantly (p<0.001) more in diarrheic calves (35.3%) than in non-diarrheic ones (8%). Epidemiologic measures of association, i.e., odds ratio, population odds ratio, attributable risk, attributable fraction, population attributable rate, population attributable fraction were 6.26, 1.42, 31.2, 3.7, and 0.27, respectively. The results would suggest that there is a significant association between infection Giardia spp. and occurrence of diarrhea in Urmia district. However, more studies are required to establish a cause-effect relationship.
Key words: Giardia, calf diarrhea, odds ratio.