Isolation of bluetongue virus from bull semen

The efficacy of inoculation of Vero cell cultures or intravenous inoculation of chicken embryos in the isolation and titration of seminal bluetongue virus (BTV) was studied, as was the toxicity of bull semen for these 2 isolation systems. Frozen and thawed BTV-contaminated ejaculates collected during periods of viremia from 2 bulls experimentally infected with cell culture-adapted BTV serotype 17 were used in isolation, titration and fractionation studies. Blood collected from the 2 bulls concurrently with the semen was titrated in chicken embryos. Bull semen was toxic for both isolation systems. Toxicity was associated with both the spermatozoa and seminal plasma. Dilution of the semen at least 1:25, addition of peptone or tryptose broth to the diluent, limitation of adsorption time and postinoculation washing of cell culture monolayers all reduced the destructive effects of semen. Isolation of BTV was successful from 11 ejaculates and was titratable in 9 of these. Blind passage of surviving embryos or cell cultures at the endpoints of the titrations produced BTV isolations in 4 instances. The virus was never isolated from semen in the absence of concurrent viremia. Peak seminal BTV titers of 10(5.5) CEIVLD50/ml and 10(5.7) TCID50/ml were observed.(ABSTRACT TRUNCATED AT 250 WORDS)