Rotaviruses and coronaviruses are associated with severe diarrhoea in young children and the young of many animals, including calves, thus much interest is currently done to show the clinical and epidemiological aspects of these infections. The importance of these viruses in cattle industry is due to substantial economic loss, treatment costs and reduced growth rates in beef and dairy calves.Enteric infections by these viruses usually occur in calves aging up to 3 months. Mixed infection caused by rota-coronavirus in calves, can lead to severity of diarrhea and gasterointestinal infections . In Iran, several studies established the prevalence of bovine rotavirus and bovine coronavirus in calves by ELISA, RT-PCR, PAGE, and Electron Microscopy. In this study, as the first case-control study to evaluate the relationship of rotavirus and coronavirus infection with calf diarrhoea in Iran , 135 samples of healthy and 126 samples from diarrhetic calves in farms around Khorasan Razavi were collected. Bovine Rotavirus and Coronavirus were detected by Antigen Capture ELISA . The results of this study show that the prevalence of rotavirus and coronavirus infection in diarrheic calves in dairy farms around Khorasan Razavi is, 26.98% and 3.17% respectively and also the prevalence of rotavirus and coronavirus infection in healthy calves is 17.03% and 2.96% respectively. Indeed, inspite of higher prevalence of rotavirus and coronavirus infection in diarrheic calves, no significant relationship was established based on comparing the presence of rotavirus and coronavirus in fecal samples of healthy and diarrheic calves. The application of epidemiological methods could be a powerful tool to quantify the risk association between disease state and animal in a herd. According to the results of this study, it seems that in addition to the relatively high prevalence rotavirus infection, it is important to consider the situation of other enteropathogen agents in these farms.

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