Viruses as a Cause of Neonatal Calf Losses

Abstract

Numerous disease agents are responsible for neonatal calf losses. Recent studies on neonatal calves with diarrhea have been reported in Nebraska (1,2,3,4,5) as being caused primarily by two viral agents. These are a reovirus-like agent and a coronavirus-like agent. Previous workers (6,7,8) have reported other viral agents as being significant in neonatal calf enteritis (scours). These agents area virus which causes calf pneumonia-enteritis and strains of bovine viral diarrhea virus (B.V.D.).

Mebus and co-workers (1) produced neonatal calf diarrhea in experimental gnotobiotic and germ free calves, one to five days of age, with field fecal material and with bacteria-free filtrates prepared from feces of the above experimental diarrheic calves. The period of incubation, age of calf, clinical signs, and mortality were identical to those observed in diarrheic calves on many of the ranches and in dairy herds. The incubation period was 12-18 hours. The clinical signs, when calves were exposed to the reovirus-like agent, were characterized by depression, inappetance, and profuse watery, yellow feces. Most affected calves drooled saliva from the commissures of the lips. Fecal material from these calves, when examined by electron microscopy, contained reovirus-likevirions with an approximate diameter of 65 nm (1,9). When fecal material or sections of the small intestine were stained by fluorescent antibody (FA) technique (1) immunofluorescent cells were observed. These cells in the feces were cast off epithelial cells. This procedure (10) is recommended for diagnosis and differentiation of reovirus-like infections and/or coronavirus-like infections in calves.