Viral enteritis in calves.

A complex community of bacteria, viruses, fungi, protists, and other microorganisms inhabit the gastrointestinal tract of calves and play important roles in gut health and disease. The viral component of the microbiome (the virome) is receiving increasing attention for its role in neonatal calf diarrhea (NCD). Rotavirus and coronavirus have for a long time been associated with NCD and commercial vaccines have been produced against these agents. Recently, several other viruses which may play a role in diarrhea have been discovered in calf fecal samples, mostly by sequence-based methods. These viruses include torovirus, norovirus, nebovirus, astrovirus, kobuvirus, and enterovirus. Most studies have involved epidemiologic investigations seeking to show association with diarrhea for each virus alone or in combination with potential pathogens. However, determining the contribution of these viruses to calf diarrhea has been challenging and much uncertainty remains concerning their roles as primary pathogens, co-infection agents, or commensals.