Four poll Dorset sheep and four Holstein‐Friesian cattle were infected with the northern European strain of bluetongue virus ( btv ), btv‐8 , to assess its pathogenicity in uk breeds. The time course of infection was monitored in both species by using real‐time reverse transcriptase‐ pcr ( rt‐pcr ), conventional rt‐pcr and serology. Two of the sheep developed severe clinical signs that would have been fatal in the field; the other two were moderately and mildly ill, respectively. The cattle were clinically unaffected, but had high levels of viral rna in their bloodstream. Real‐time rt‐pcr detected viral rna as early as one day after infection in the cattle and three days after infection in the sheep. Antibodies against btv were detected by six days after infection in the sheep and eight days after infection in the cattle. Postmortem examinations revealed pathology in the cattle that was more severe than suggested by the mild clinical signs, but the pathological and clinical findings in the sheep were more consistent.

The aim of this study was to assess the mechanisms of transmission of bluetongue virus serotype 26 (BTV-26) in goats. A previous study, which investigated the pathogenicity and infection kinetics of BTV-26 in goats, unexpectedly revealed that one control goat may have been infected through a direct contact transmission route. To investigate the transmission mechanisms of BTV-26 in more detail an experimental infection study was carried out in which three goats were infected with BTV-26, three goats were kept uninfected, but were housed in direct contact with the infected goats, and an additional four goats were kept in indirect contact separated from infected goats by metal gates. This barrier allowed the goats to have occasional face-to-face contact in the same airspace, but feeding, watering, sampling and environmental cleaning was carried out separately. The three experimentally infected goats did not show clinical signs of BTV, however high levels of viral RNA were detected and virus was isolated from their blood. At 21 dpi viral RNA was detected in, and virus was isolated from the blood of the three direct contact goats, which also seroconverted. The four indirect barrier contact goats remained uninfected throughout the duration of the experiment. In order to assess replication in a laboratory model species of Culicoides biting midge, more than 300 Culicoides sonorensis were fed a BTV-26 spiked blood meal and incubated for 7 days. The dissemination of BTV-26 in individual C. sonorensis was inferred from the quantity of virus RNA and indicated that none of the insects processed at day 7 possessed transmissible infections. This study shows that BTV-26 is easily transmitted through direct contact transmission between goats, and the strain does not seem to replicate in C. sonorensis midges using standard incubation conditions.