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SUMMARYThe morphology of border disease virus and bovine virus diarrhoea virus in infected bovine embryonic testis cells was examined by electron microscopy. Particles which appeared to be mature virions of both viruses were similar, being roughly circular and approximately 46 nm in diameter with a 20 to 25 nm core. Virus replication took place totally within the cytoplasm in association with structures formed from modified endoplasmic reticulum.

Bulk tank milk samples were collected from 374 dairy farms in Scotland in 2007/2008 along with questionnaire data relating to the management of the farm. Milk samples were tested for antibodies to bovine viral diarrhoea virus (BVDV) using a commercially available (Svanova) kit and percentage positivity scores calculated according to the manufacturer's guidelines. There were 220 farms that did not routinely vaccinate for bovine viral diarrhoea (BVD), and these were distributed according to the Swedish BVD eradication classes as 12.7 per cent, 22.3 per cent, 44.5 per cent and 20.5 per cent for Classes 0, 1, 2 and 3, respectively. A more sophisticated statistical method (finite mixture modelling) which does not depend on arbitrary thresholds and categories suggested a 73 per cent prevalence of herds with high mean levels of antibodies. Risk factor analysis suggested that routine vaccination for BVD, suspicion of BVD, housing of pregnant cows with calves, total number of cows and the proportion of cows that were dry were all associated with increased BVDV antibodies in bulk milk. The inclusion of BVD within the farm's health plan was associated with decreased BVDV antibodies in the bulk milk.

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A serological survey of the prevalence of a new herpesvirus isolated from red deer (Cervus elaphus), tentatively designated herpesvirus of Cervidae type 1 (HVC-1), has shown that the virus is widespread in free-living and farmed red deer. Neutralising antibodies were detected in hill deer culled at three different locations in the north of Scotland, in farmed deer on five of eight Scottish farms and in four of 12 groups of English farmed or park deer. Fifty-eight of 145 (40 per cent) hill deer, 67 of 203 (33 per cent) Scottish farmed deer and 26 of 172 (14 per cent) English deer had antibody, the overall prevalence being 29 per cent. Further outbreaks of ocular disease in farmed red deer calves caused by HVC-1 were investigated. Deer sent to an auction from one farm were found after sale to have been incubating the disease and it was thus spread to seven deer farms. Despite a high incidence of clinical disease in the calves from the original farm, few in-contact deer showed clinical signs.

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Investigation of a sight defect in a pedigree bull, born as a result of artificial insemination and ovum transplantation, led to the finding that the animal was persistently infected with bovine virus diarrhoea virus. Virus was cultured from blood and from nasal and ocular swabs and was present in semen in high titre. At necropsy, virus was cultured from a wide range of tissues. The pathological findings are described and discussed as are the potential hazards of such infections.

The growth rate, feed consumption and carcase composition of nine untreated wether lambs (controls) were compared with those of lambs in which a chronic pneumonia had been experimentally induced. Six pneumonic lambs (group 1) were killed with the controls on day 109 and eight (group 2) lambs were killed when they had a similar mean liveweight to the controls (42 kg) on day 172. The mean liveweight gain of infected animals to day 108 was 59 per cent, the mean feed intake 69 per cent and the mean carcase weight of group 1 was 73.5 per cent that of the controls. Group 2 lambs required 25 per cent more feed and nine weeks longer than the controls to reach similar live and carcase weights. This depression of appetite and growth rate was most marked in the first 35 days after inoculation, but growth rates of infected lambs continued to be lower than those of the controls throughout the experiment. At slaughter, all infected lambs had consolidated lesions of pneumonia and a significant correlation was noted between the extent of lung lesions and total liveweight gain in individual lambs. Carcases of group 1 lambs had a proportionately low fat, high lean meat and bone content, indicative of immature development and consistent with a lowered feed intake. Carcases of group 2 lambs showed a similar trend but differences from the controls were not significant.