Rotavirus disease amplifies within a herd when infected calves shed the pathogen into the environment, thereby exposing and potentially infecting herd mates. This environmental pathogen load builds up to a level which can overwhelm the immune status of herd mates, creating significant illness and death loss.
A core driver of new rotavirus infections is large exposure to the pathogen shed into the environment over a short span of time, particularly under conditions of stress. It has been suggested that the major mode of rotavirus spread is from actively infected calves to susceptible ones.
Increasing environmental contamination will amplify diarrheal disease in calves (Holland, 1990). Calves will excrete rotavirus in feces starting the second day of infection.
The virus survives in feces for several months and is resistant to many disinfectants. This suggests that prevention, versus treatment, is vital to decreasing pathogen load in the environment (Radostits et al 2007).
It is crucial, then, to reduce the number of intestinal cells infected and the quantity of virus shed. Doing so could not only impact individual calf health but also would provide partial herd immunity in controlling the lateral spread of disease through less environmental contamination.
To learn more, read this research on reducing rotavirus shedding in newborn calves.