Bluetongue and epizootic hemorrhagic disease virus isolation from vertebrate and invertebrate hosts at a common geographic site.

One serotype of bluetongue virus (BTV) and two serotypes of epizootic hemorrhagic disease virus (EHDV) were isolated from vertebrate and invertebrate hosts on a farm in Colorado. The isolations were from blood samples collected a week apart from a dairy heifer with stomatitis and laminitis; EHDV serotypes 1 and 2 were isolated from the first blood sample, and BTV serotype 13 and EHDV serotype 1 were isolated from the second. Antibodies to EHDV and BTV were detected in the serum from this heifer. Both EHDV serotypes and BTV serotype 13 were isolated from pools of female biting gnats (Culicoides variipennis) that had not had a recent blood meal. The BTV insect isolate was biologically transmitted by female gnats from an infected donor sheep to a recipient host sheep. Culicoides variipennis was the predominant insect collected during three nights of light trap captures at the farm.