Duration of bluetongue viremia in experimentally infected American bison

Six yearling American bison (Bison bison bison) bulls and one yearling ewe (Ovis alles) were inoculated intradermally and subcutaneously with 2 x 10(5 ) plaque forming units (pfu) of bluetongue (BT) virus serotype 11. Two unin oculated yearling bison bulls served as negative controls. Blood samples we re collected for serology and virus isolation on 0, 4, 7, 11 and 14 days po st-inoculation (dpi) and every 2 wk thereafter to 127 dpi. Every 4 wk a new ewe was inoculated with a pooled sample of whole blood from the six infect ed bison, and each sheep was monitored for 28 days for clinical signs of BT and seroconversion. Bluetongue viremia was detected in all six inoculated bison starting at 4 to 28 dpi and was no longer detectable from 42 dpi onwa rd. Pooled blood samples collected at 28, 56, 84 and 112 dpi from the six i nfected bison were not infectious for sheep. The six infected bison serocon verted by 11 to 28 dpi on a competitive enzyme-linked immunosorbent assay a nd by 28 dpi on the serum neutralization test, and all remained seropositiv e thereafter. No clinical signs or lesions attributable to BT were observed in the infected bison or controls. There was evidence that a small amount of epizootic hemorrhagic disease virus type 2 had been present in the BT vi rus inoculum; reasons are given for concluding that this did not affect die results of the BT study.