Incidence of Bovine Enterovirus, Coronavirus, and Group A
Rotavirus, and Concentration of Total Coliforms in Midwestern
The occurrence of bovine enteric pathogens and total coliform contamination in streams of 13 Midwestern cow/calf pastures was studied during the 2007-2009 grazing seasons. Water samples (n=1274) were collected biweekly at up- and downstream locations on each stream. Incidence of Bovine Enterovirus (BEV), Coronavirus (BCV), and group A Rotavirus (BRV), and concentrations of total coliforms (TC) were evaluated. The mean incidences of BEV, BCV, and BRV in all samples were 3.91, 1.12, and 0.49%, respectively, over the three grazing seasons. There were no differences between farms for BEV (P=0.1163), BCV (P=0.2977), and BRV (P=0.5040) incidences, and there were no differences (P=0.3023, P=0.5868, P = 0.1008) for the BEV, BCV, and BRV incidences between samples collected from up- or downstream locations. Incidence of BEV in up- and downstream samples were related to cattle presence in the pasture on the day, three days, and four days prior to sampling (P=0.0130, P=0.0283, P=0.0300, respectively), and tended to be related to cattle presence in the pastures two days, five days, and six days prior to sampling, (P=0.0603, P=0.0603, P=0.0516, respectively), but were not related to cattle presence seven days prior to sampling (P=0.2312). However, incidences of BCV or BRV were not related (P>0.10) to cattle presence in the pastures at any time throughout the grazing seasons. In downstream samples, cattle presence in the pasture on the day of sampling only tended (P = 0.0875) to be related to BEV incidence. Whereas, in upstream samples, BEV tended (P = 0.0688, P = 0.0710, P = 0.0710; respectively), to be related to cattle presence in the pasture on the day, and 2 and 4 days prior to sampling. Mean TC were 1269 and 1417 colony-forming units (CFU)/100ml, respectively, for up- and downstream samples. Differences (P = 0.0179) were observed between farms, but not between sites on farms (P = 0.3091), for concentrations of TC. Preliminary results indicate that the timing and management of grazing may be beneficial in decreasing the incidence of enteric viral pathogens and concentrations of TC in Midwestern pasture streams.