DISTRIBUTION OF BLUETONGUE VIRUS IN TISSUES OF EXPERIMENTALLY INFECTED PREGNANT DOGS AS DETERMINED BY IN-SITU HYBRIDIZATION

Six female dogs (four pregnant and two nonpregnant) were inoculated wi th bluetongue virus (BTV), serotype 11. Pregnant animals and one nonpr egnant dog received 5.5-6.3 log(10) of cell culture-adapted virus. The other nonpregnant dog received a modified live vaccine contaminated w ith bluetongue virus. The nonpregnant animals never became clinically ill and were euthanatized 35 days post-inoculation. Three of the four pregnant dogs aborted, and all four died or were euthanatized 5-10 day s post-inoculation. The predominant pathologic feature in the adults w as severe pulmonary edema. Various tissues from the bitches and fetuse s were examined by in situ hybridization using a digoxigenin-labeled p robe corresponding to the nonstructural protein-1 gene of BTV-17. By t his technique, viral nucleic acid was detected predominantly in endoth elial cells of lung of all four dogs, with lesser amounts in capillari es of uterus, spleen, and kidney in some of the dogs. In two adult dog s, bluetongue viral nucleic acid was detected in mononuclear cells of the periarteriolar lymphoid sheaths of spleen. There was minimal stain ing of capillaries in placentae in three of the five fetuses examined. There was no viral nucleic acid detected in any of the other fetal ti ssues.