Experimental inoculation of heifers with bovine adenovirus type 3.

Nine 2-year-old heifers having BAd3-neutralizing antibody titers between 1:120 and 1:1080 were individually exposed intranasally to an aerosol of 10(8) pfu of wild type (wt) bovine adenovirus type 3 (BAd3). Four animals were kept as non-inoculated controls. The heifers were examined daily for rectal temperature, weight gain/loss, nasal and ocular discharges, and other clinical signs for 10 d post-inoculation. None of the animals showed any sign of clinical disease. Virus excretion was observed in one animal only on Day 3 post-inoculation. All BAd3-inoculated heifers demonstrated a significant (P < 0.005, paired t-test) rise in BAd3-specific serum IgG, IgG1, or IgG2 ELISA titers and virus-neutralizing antibody titers compared to the titers before inoculation. All virus-inoculated animals demonstrated increased levels of BAd3-specific IgA ELISA titers in nasal secretions. These results suggest that in the presence of circulating BAd3-neutralizing antibodies, intranasal inoculation of cattle with wt BAd3 would result in inapparent infection.