Epidemiological Survey on Eimeria spp. Associated with Diarrhea in Pre-weaned Native Korean Calves

Bovine coccidiosis is one of the most important parasitic diseases affecting calf productivity. Here, we investi- gated the prevalence of Eimeria spp. in pre-weaned native Korean calves and determined the correlation between diar- rhea and Eimeria spp. Fecal samples were collected from individual calves (288 normal and 191 diarrheic) in 6 different farms. Of the 479 samples, Eimeria oocysts were detected in 124 calves (25.9%). Five Eimeria spp. were identified; E. zuernii (18.8%) was the most prevalent, followed by E. auburnensis (12.5%), E. bovis (7.5%), E. subspherica (5.8%), and E. bukidnonensis (1.0%). A significant correlation was observed between diarrhea and mixed infection with more than 2 Eimeria spp. (odds ratio [OR]=2.21; 95% confidence interval [CI]: 1.09-4.49; P=0.03) compared to single infection (OR = 1.29; 95% CI: 0.77-2.15; P = 0.33). Of the 5 Eimeria spp. identified, E. subspherica (95% CI: 1.24-5.61; P = 0.01) and E. bukidnonensis (95% CI: 825.08-1,134.25; P = 0.00) strongly increased the risk of diarrhea by 2.64-fold and 967.39-fold, respectively, compared to other species. Moreover, mixed infection with E. auburnensis and E. bukidnonensis was significantly associated with diarrhea (OR = 2,388.48; 95% CI: 1,009.71-5,650.00; P < 0.00) in pre-weaned native Korean calves. This is the first report to demonstrate the importance of E. bukidnonensis associated with diarrhea in pre-weaned native Korean calves. Further epidemiological studies should investigate the prevalence of E. bukidnonensis and the association between E. bukidnonensis and diarrhea.