Wavelength of ultraviolet radiation that enhances onset of clinical infectious bovine keratoconjunctivitis.

Cellulose acetate filtered ultraviolet (UV) radiation and unfiltered UV radiation were used on calves that were subsequently challenge exposed with Moraxella bovis. The onset, course, and severity of infectious bovine keratoconjunctivitis (IBK) were studied. Ten calves irradiated with unfiltered UV had the disease 1 to 2 days after M bovis challenge exposure; all 10 calves had moderate to severe IBK. Ten calves irradiated with filtered UV and 10 calves not irradiated manifested IBK in a similar manner. The date of onset and severity of the disease varied. Evidence is presented to support the contention that the wavelengths (around 270 nm) which are eliminated by cellulose acetate enhance the course of IBK. The effects on IBK of environmentally increased solar UV radiation is also discussed.