Abstract. Six female dogs (four pregnant and two nonpregnant) were inoculated with bluetongue virus (BTV), serotype 11. Pregnant animals and one nonpregnant dog received 5.5-6.3 log,, of cell culture-adapted virus. The other nonpregnant dog received a modified live vaccine contaminated with 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 days post-inoculation. The predominant pathologic feature in the adults was severe pulmonary edema. Various tissues from the bitches and fetuses were examined by in situ hybridization using a digoxigenin-labeled probe corresponding to the nonstructural protein-1 gene of BTV-17. By this technique, viral nucleic acid was detected predominantly in endothelial cells of lung of all four dogs, with lesser amounts in capillaries of uterus, spleen, and kidney in some of the dogs. In two adult dogs, bluetongue viral nucleic acid was detected in mononuclear cells of the penarteriolar lymphoid sheaths of spleen. There was minimal staining of capillaries in placentae in three of the five fetuses examined. There was no viral nucleic acid detected in any of the other fetal tissues.Key words: Bluetongue virus; dogs; in situ hybridization.Beginning in late 1992, a multicomponent modified live virus vaccine containing canine distemper virus, canine parainfluenza virus, canine adenovirus-2, and canine parvovirus was reported to be causing clinical disease and death when used during late-term pregnancy in d o g~.~,~J Bluetongue virus (BTV), serotype 11, was isolated from the tissues of some of the vaccinated dogs as well as from the vaccine.l' This virus was then propagated, and the dogs were inoculated with it to confirm its pathogenicity. This report details the pathologic findings and the distribution of virus, as determined by in situ hybridization, in experimentally infected dogs.
Materials and Methods
VirusBluetongue virus, serotype 11, was isolated from a multicomponent modified live vaccine containing canine distemper, canine parainfluenza virus, canine adenovirus-2, and canine parvovirus. The BTV was isolated in Vero cells and expanded in baby hamster kidney cells.iL
DogsFour late-term pregnant Beagle dogs were inoculated with BTV. Two (Nos. 1, 2) received 6.3 log,, TCID,, BTV, and two (Nos. 3, 4) received 5.6 log,, TCID,, BTV, all intramuscularly. A fifth pregnant dog (No. 5) received 1.0 ml of noncontaminated multicomponent vaccine, given subcutaneously. One 12-week-old female dog (No. 6) was inoculated with 5.5 log,, TCID,, BTV; another 12-week-old female dog (No. 7) was inoculated with 1 .O ml of the contaminated vaccine. Animals were monitored clinically daily and euthanatized with an overdose of barbiturate when they became severely clinically ill.
Pathologic FindingsAll dogs were necropsied, and tissues were fixed routinely in formalin for histopathology. Paraffin sections were cut at 4-5 pm and stained with hematoxylin and eosin...
