Distribution of ovine abortion virus in experimentally infected ewes and fetuses.
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During the recent devastating epidemics of foot-and-mouth disease (FMD), bluetongue (BT), the highly pathogenic avian influenza (HPAI) and New Castle disease, more than 115 million animals were culled. The mass slaughter of animals raised serious ethical questions. These epidemics showed that the use of emergency vaccination is an essential element in disease control. During the last decade the FMD antigen banks have proved to be effective and this module should be extended. An international vaccine stock should be considered for classical swine fever and HPAI. Agreements with vaccine producers should be made easily available, with instant access to a vaccine reserve for rinderpest, peste des petits ruminants, BT, African horse sickness and Rift valley fever. These vaccines should meet international standards and should allow distinction between vaccinated and infected animals. Information should be gathered proactively on the use of vaccines for lumpy skin disease, sheep and goat pox and contagious bovine pleuropneumonia.
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Scrapie first was detected in indigenous sheep in Norway in 1981, and from 1995 to 1997 an increase in the number of flocks with scrapie cases was recorded. These flocks were mainly in one geographical region. A study to identify risk factors for scrapie was conducted. The study had three frequency-matched controls selected for every case within the same Veterinary District. A questionnaire was submitted to 176 sheep flocks (42 had been scrapie flocks). The data obtained by the questionnaire were linked to data collected from governmental and industry registers. After imputing missing data using single random imputation, the statistical analysis was performed using multivariable conditional logistic regression. Purchase of female sheep from scrapie flocks, sharing of rams, or sharing of pastures between different flocks were the risk factors associated with the occurrence of scrapie. Of factors potentially sustaining and promoting the infection in the flock, number of winter-fed sheep, number of buildings for housing sheep, rams and ewes shared room during mating period and increase in the flock size were associated with scrapie. We interpret these findings to show that factors involving transfer of sheep between flocks or direct contact between sheep of different flocks are important for the spread of scrapie. Management factors are important for the development of scrapie. However, it was not possible to discriminate between the different management factors in this study at the flock level. Also, factors indicating awareness and interest of the farmer (as well as willingness to contact a veterinarian for diseased sheep) were related to the detection of scrapie in the flock.
The conversion of [1,2-3H]corticosterone to 18-hydroxycorticosterone in vitro was studied on human and animal adrenal tissue homogenates. Human adrenals were surgically resected from a patient with Cushing's disease. Sheep adrenal homogenates were prepared from the pooled glands of 20 animals. Incubations supplemented with a NADPH generating system were performed in order to evaluate the effect of aminoglutethimide and its closely related compound glutethimide on corticosterone 18-hydroxylation in vitro. Increasing concentrations of the two drugs were assayed on both human and animal adrenal homogenates. Aminoglutethimide was clearly found to inhibit corticosterone 18-hydroxylation in sheep adrenal homogenates as a 72.6% inhibition occurred in the presence of only 0.2 mumole of the drug. Inhibition reached 91.1% in the presence of 0.5 mumole aminoglutethimide. When added to the human incubated adrenal, a 59.4% inhibition occurred in the presence of 0.5 mumole aminoglutethimide. Glutethimide, a sedative of wide clinical usage, was also found to inhibit corticosterone 18-hydroxylation but the inhibitory effect occurred only in the presence of much higher concentrations. In fact, 5.0 mumoles were necessary to obtain a 43.9% inhibition of 18-hydroxycorticosterone synthesis. This study clearly demonstrates the marked inhibitory effect of aminoglutethimide on corticosterone 18-hydroxylation. Glutethimide, to a lesser extent, also inhibits 18-hydroxycorticosterone synthesis.
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BACKGROUND AND AIM OF THE STUDY: The roles of cardiac valvular interstitial cells (VIC) in extracellular matrix remodeling in fetal development, adaptation and response to injury are largely unknown. METHODS: The phenotype of VIC was studied in health (normal adult human and sheep), development (fetal human and sheep), disease (human mitral valves with myxomatous degeneration), adaptation (clinical pulmonary to aortic valve autografts) and tissue-engineered heart valves matured in vitro and remodeled in vivo. Cell phenotype was assessed using expression of vimentin (V), alpha-smooth muscle actin (SMA, A), matrix metalloproteinase (MMP)-13/collagenase-3 (M), and SMemb (S). RESULTS: VIC in normal adult valves were predominantly quiescent fibroblasts immunoreactive to vimentin (89.7 +/- 2.5%), but not MMP-13 or SMemb, with only 2.5 +/- 0.4% of alpha-SMA-positive cells ('normal/quiescent' phenotype: V+/A-/M-/S-). In contrast, fetal VIC were mostly activated myofibroblasts ('developing/activated' phenotype: V+/A+/M+/S+), with 62.1 +/- 5.0% of cells staining positive for alpha-SMA. VIC in myxomatous valves, short-term autografts and engineered valves in vitro were also activated myofibroblasts with coexpression of vimentin, alpha-SMA (36.2 +/- 3.7%, 19.3 +/- 2.4%, and 60.3 +/- 9% positive cells, respectively), strong MMP-13 activity indicative of collagen remodeling, and SMemb ('remodeling/activated' phenotype: V+/A+/M+/S+). In contrast, VIC in long-term pulmonary autografts and engineered valve explants had a mostly fibroblast-like phenotype, with sparse alpha-SMA expression (6.0 +/- 1% and 5.4 +/- 1.0% positive cells) (V+/A-/M-/S-). CONCLUSION: Most VIC in normal valves were quiescent with a fibroblast-like phenotype. VIC in developing, diseased, adapting and engineered valves adjust to a dynamic environment through VIC activation and secretion of proteolytic enzymes mediating extracellular matrix remodeling ('developing/ remodeling/activated' phenotype), followed by a normalization of phenotype.
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An increased level of procoagulant activity (PCA) in leukocytes of pigs with acute classical swine fever (CSF) was observed on day 4 postinfection; PCA level normalized during the moribund state. CSF vaccine strain either did not induce an increase of PCA level or induced an increase that persisted for at least 11 days. Time course of PCA changes in the leukocytes from sheep infected with borderline sheep disease was similar to the time course of PCA in acute CSF. In vitro each of the pestiviruses induced an increase in PCA in homologous and heterologous leukocytes.
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The epidemic of bovine spongiform encephalopathy which is currently afflicting British cattle probably represents transmission of the sheep disease, scrapie, to bovines. Epidemiological evidence suggests that the source of the infection was dietary, and implicates commercial cattle rations containing meat and bone meal. Although this product is manufactured worldwide from waste animal tissues, only sporadic cases of the cattle disease have occurred outside Great Britain where a unique combination of factors is considered to be involved; this includes changes in manufacturing methods together with the greater use of ovine raw material, an increasing proportion of which was probably scrapie-infected. A number of legislative measures have been introduced which should lead to the eventual elimination of the disease and prevent the occurrence of analogous diseases in other species. Meanwhile, pilot-scale spiking studies are underway to determine the relative decontamination efficiencies of various procedures used throughout the EC to manufacture meat and bone meal; more rigorous methods which are not currently employed are also being assessed.
Rift Valley fever is the most important bunyaviral disease of animals in Africa. The virus, transmitted by mosquitoes, causes abortions and mortality in young animals in addition to haemorrhagic fevers in humans. Although vaccines against this virus are available, the uses of these vaccines are limited because of deleterious effects or incomplete protection, justifying further studies to improve the existing vaccines or to develop others. Nairobi sheep disease is transmitted by ticks. The disease is endemic in East Africa and sporadic cases are reported in India and Sri Lanka. Other viruses transmitted by mosquitoes or midges are teratogenic in cattle or sheep, these include Akabane and related viruses in Asia, Australia and the Middle East, and Cache Valley in North America. The Marburg and Ebola viruses of the genus Filovirus are associated with epidemics in Central Africa with high fatality rates in humans; some outbreaks were related to contact with monkeys. Another subtype of Ebola virus was first described in a quarantine facility in the United States of America among cynomolgus monkeys (Macaca fascicularis) from the Philippines. The reservoir of these viruses remains unknown.
Eight 2-month-old merino lambs were inoculated intranasally with different (10(2.0)-10(5.0)TCID50) amounts of Aujeszky's disease virus (ADV). Electron microscopic studies indicated that ADV replicated in extra-neural sites, in the epithelial cells of the mucosa of the upper and lower respiratory tract. Although the virus was excreted continuously in nasal discharges, horizontal transmission to contact lambs failed. The surviving exposed and contact lambs had no demonstrable antibodies against ADV and they were susceptible when challenged by ADV. However, the virus was transmitted to susceptible pigs in contact with the exposed lambs. One of the five contact pigs showed characteristic clinical signs of Aujeszky's disease, developed a nonsuppurative meningoencephalomyelitis and ADV was recovered from the brain, nasal discharge and other organs. Restriction enzyme analysis of DNA from this virus confirmed the sheep origin of the isolate. The other 4 pigs seroconverted. ADV infection in sheep is therefore a possible source of infection for pigs, but the lack of horizontal transmission in sheep was confirmed.
The sheep disease maedi-visna (MV) was introduced into Finland in 1981 and had spread to eight flocks in the southwestern part of the country when first detected in a survey in 1994. Six more seropositive flocks were subsequently traced, bringing the total to 14. MV has a notifiable disease status in Finland that provides for official restrictive measures to which all infected herds are subject. These measures are withdrawn once the seropositive animals and their progeny are culled and the flock has showed negative signs in the test done twice, or after total culling. A voluntary control programme was initiated in January 1995 to extend official control efforts. The programme furnishes a guideline for culling, restrictions on contacts, and a timetable for testing the flock to attain MV-free status. Seven flocks of the 14 were slaughtered either immediately or after a period under restrictive measures. One flock finished sheep production after four years under restrictive measures. Selective culling and repeated testing was attempted with the other six flocks, three of which attained MV-free status. One flock finished sheep production after two years in the control programme, the other two dropped out of the programme when the restrictive measures were withdrawn. It was concluded that the control programme was salient in eradicating MV from Finland and that serological monitoring of the situation must be continuous.
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In connection with a case of epidemic disease with high morbidity and mortality in a flock of sheep, a pestivirus infection could be diagnosed. Pathological-anatomical abnormalities were very similar to the character of BVD/MD. Scientific findings on pestivirus infections in sheep are discussed.
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