Influence of outdoor winter environment on the course of infectious bovine keratoconjunctivitis.

The effect of environmental conditions on the onset, severity, and duration of Moraxella bovis infection and subsequent clinical disease was studied. Twelve calves were used; 6 were maintained under usual isolated experimental conditions (inside), and 6 were kept under normal feedlot conditions (outside) during the winter (-20 to +15 C). The cattle housed inside had a higher infection rate, a milder disease, and longer duration of infection than did the cattle kept out side. Seemingly, the stress of the cold weather caused a more severe disease of shorter duration.