Acute phase response in bovine coronavirus positive post-weaned calves with diarrhea.

Bovine coronavirus (BCoV) is associated with severe diarrhea in calves, winter dysentery in adult cattle, and respiratory diseases in cattle of all ages. This study aimed to investigate the relationship between white blood cell counts and haptoglobin (Hp) and serum amyloid A (SAA) levels in post-weaned calves with diarrhea caused by BCoV and those that recovered from diarrhea. Blood and fecal samples were collected twice from the same animals; 17 post-weaned calves with diarrhea (first) and 15 post-weaned calves that recovered from diarrhea (second). Real-time polymerase chain reaction revealed that all 17 fecal samples from post-weaned calves with diarrhea and one out of 15 from diarrhea-recovered calves were positive for BCoV and negative for Cryptosporidium spp., Escherichia coli K99, Salmonella spp., bovine rotavirus, and bovine viral diarrhea virus. No Eimeria oocysts were detected using the flotation method. In comparison with post-weaned calves with diarrhea, in diarrhea-recovered calves, the lymphocyte count was significantly higher (P = 0.018), and the monocyte count was significantly lower (P = 0.001); however, the number of monocytes was still high. Post-weaned calves with diarrhea had a significantly higher Hp concentration (P < 0.001) compared with diarrhea-recovered calves. The results indicated that increased Hp concentration and monocytosis but not SAA may be associated with diarrhea caused by BCoV. The present study suggests that the monitoring of Hp concentration and monocyte count is useful in the diagnosis of post-weaned calves with diarrhea caused by BCoV in this field.