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The purpose of the study was a preliminary evaluation of the usefulness of Wrocław-2 EAV strain modified in cell culture lines as a live-virus vaccine used in prophylaxis against EVA. In four one year old horses vaccinated intravenously with Wrocław-2 strain was observed apathy lasting for several days, a moderate ocular conjunctiva congestion, and in 1 out of 4 horses postvaccination fever occurred on the day 5th. The virus was reisolated only from conjunctival swabs in 2 horses on the 2nd day after immunization. The peak titre of virus neutralizing antibodies — from 1/512 to 1/1024 — was noted after 2—3 weeks since the vaccination. After exposure of vaccinated horses to a virulent Bocyrus EAV strain clinical signs of disease were not observed, virus was not recovered from any of swabs and the secondary humoral immune response was characterized by a very sharp and rapid increase of titres of neutralizing antibodies. However in the unvaccinated control horse, acute arteritis occurred and viral shedding was intensive and longlasting. The virus was reisolated from conjunctival, nasal, oral, rectal and preputial swabs.
В проведенных исследованиях предприняли попытку адаптации синцитиального критерия для обнаружиивания естественных инфекций коров BLV в местных условиях по собственным техническим предпосылкам. Синтициальный критерий выполняли в пробирках Лейтона со стеклами-покрышками площадью ок. 3 см². 24—48-часовую культуру СС81 инфицировали 0,3 мл, 0,15 мл и 0,05 мл суспензии лимфоцитов периферической крови с концентрацией 5X10⁶/мл, 2,5X10⁶/мл, 1,25Х10⁶/мл и 0,625X10⁶/мл. Стекла-покрышки вынимали из пробирок через 3,5 и 7 дней. Лучше всего сформированные синцитии наблюдали на 5 и 7 дни после инфекции при 0,15 мл инокулум лимфоцитов с концентрацией 5Х10⁶/мл. В проводимых исследованиях 8 коров с положительными результатами гематологических и серологических исследований, а также 4 коров лишь с положительным серологическим результатом получили положительные результаты в синцитиальном критерии при сходстве результатов отрицательного контроля.
The objective of the study was to establish a percent of infections caused by equine arteritis virus (EAV) in chosen studs of breeding horses in Poland. A total of 711 samples of sera of clinically normal mares and stallions were examined in 1989—1990. Six hundred were obtained from arabian horses (302 from the stud J, 74 K and 224 M) and 111 samples were obtained from the stud S of thoroughbred horses. Serological examinations showed the presence of infection caused by EAV. In the stud J 5.3%, K 6.8%, M 48.7% and S 72.1% of sera reacted positively.
The purpose of the work was to determine the percentage of infections with arteritis virus and the analysis of epizootiological state in the stud of horses in the Upper Silesia. In the first period of studies the percentage of mares with specific antibodies was 58.3 per cent and after 6 months it increased by 79 per cent. It was lowest in young mares aged 3—4 years. The SN titres against EAV ranged between 4—512. In most cases they fluctuated between 32—256. The titre in one stallion was 128—256 while in another one no antibodies were found at all. Sera of mares without antibodies at day of mating showed the presence of the antibodies after three weeks following mating by a stallion serologically positive; that was not observed in case of mating by a stallion serologically negative. The findings indicated that in the horses under study equine arteritis virus was transmitted through the genital system during mating and the stallion’s semen was the source of infection.
Intervention vaccinations were undertaken after 2.5 weeks since the first cases of abortions, i.e. when the percentage of abortions was 23. There were used the following vaccines: Equivac RP, Prevaccinol and RPK. Immunizations were performed on 3 groups of mares: group A comprised 19 animals vaccinated once with Equivac at months 8—9 or 9—10 of pragnancy. Group В containing 29 pregnant mares was immunized 3 times: at first (9 animals) in the 2—3 month, 10 animals in the 4—5th month and 9 animals in the 5—6th month, then for the second time in the months 4—5, 6—7 and 7—8, and for the third time in months 6—7, 8—9 and 9—10. The third group (C) was immunized for the first time when the mares were not pregnant, then in the 3—4 and 7—8th month of pregnancy. The percentage of abortion was 94.7% (group A), 10.3% (group B) and 0% (group C). Only three fold vaccinations protected mares from abortions in the infected environment.
The examinations comprised all the mares and stallions of the stud K in the period from January 1989 to February 1991. Mares aged 6—12 months to 12 years were divided into 13 groups (from A to M). Serological tests were performed three times (I, II, III) at intervals of 1 years. The percentage of mares with neutralizing antibodies against EAV was 53.3, 67.5 and 48.5 (consecutive years). The titers of the antibodies ranged from 4 to ≥ 512. In the course of examinations the titers were 64—128, 32—64 and 16—32. In 24 of 27 fresh cases of infections between the first and second examination the appearance of specific antibodies was observed at week 3 after covering by a stallion with antibodies against EAV. In the same period there was noticed also a significant per cent of infections in 6—12 old mares of the group A (50%) and L (27.7%) being in contact with the mares covered by an infected stallion. After elimination of that stallion from the stud the number of new infections decreased markedly and only two cases were found in that time (between the second and third examination). The findings indicate that the primary transmission of EAV in the stud K took place through the genital tract due to infection by the infected stallion, and the secondary — by the respiratory tract.
Исследования SIA и AGID выполнили у 108 телят и телок нч-п породы от коров из стада, в котором процент инфекций BLV составлял свыше 80%. Животных разделили на 6 возрастных групп. В тесте AGID у всех 3—5-дневных и 7—14-дневных телят отметили положительные результаты (молозивные противотела). У 6—8-недельных телят противотела анти-BLV отметили у 40% животных, а у 5—6-месячньтх — 15.6%. Первые положительные результаты в тесте SIA отметили у 6—8-недельных телят (40%), затем в группе 5—6-месячных телят (34,4%), у 16—18-месячных телок (40,9%) и в группе 22—24-месячных телок (25%). У серологически положительных телят в тесте AGID, отрицательные результаты в тесе SIA получили у 20% 5—6-месячных животных, у 9,1% 16—18-месячных телок и 30% 22—24-месячных телок. С другой стороны, у серологически отрицательных животных наличие BLV обнаружили у 18,8% в группе 5—6-месячных телят, у 4,5% в группе 16—18-месячных телок и у 5% в группе 22—24-месячных телок. Кроме того, у избранных 6 5—6-месячных телят с положительным результатом теста SIA отметили наличие BLV в ультраструктурном исследовании.
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