Two male calves infected with non-cytopathic (ncp) bovine viral diarrhea virus (BVDV) BVDV-1c in survey study were donated and superinfected experimentally with cytopathic (cp) BVDV-1a via the intranasal (calf 1) or intravenous (calf 2) route to perform clinical, pathological, and serological evaluation using different inoculation routes. Both calves were moribund and euthanized at post-inoculation days (PID) 30 and 38 without diarrhea, respectively. Gross and histopathological lesions were not prominent in calf 1, and the cp BVDV could not be isolated from samples from this calf. More severe and characteristic upper gastrointestinal lesions, including deep ulceration and lymphocytic inflammation in the digestive system, were noted in calf 2 than in calf 1. Moreover, the cp BVDV-1 was isolated from various organs or tissues in calf 2. These results indicate that the inoculation route of cp BVDV-1 could be an important factor in the induction of mucosal disease in PI calves.

Key words: BVDV, Cattle, Inoculation route, Mucosal disease, Persistent infection