Minimum intravenous infectious dose of ovine progressive pneumonia virus (OPPV)

The minimum intravenous infectious dose for ovine progressive pneumonia virus (OPPV) WLC1 was determined using twenty-four 6month-old lambs. Twelve groups of two 6month-old lambs were inoculated intravenously (i.v.) with tissue culture fluid containing ovine progressive pneumonia virus (OPPV) WLC1 titers ranging from 107.6 TCID50/lamb down to 10−3.4 TCID50/lamb and were monitored for seroconversion using the OPPV agar gel immunodiffusion assay (AGID). Fifteen of the 16 lambs given equal or greater than 100.6 TCID50 seroconverted, and virus could be isolated from peripheral blood leukocytes in 13 out of the 15 of these lambs. None of the eight lambs receiving less than 100.6 TCID50 seroconverted during the 12months. The results of this study indicated that 100.6 or 4 TCID50/lamb given i.v. was capable of establishing infection.