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1.
All 4 sheep inoculated via the respiratory tract with 7×106 TCID50 af maedi M88 strain developed complement fixing (CF) antibodies within 3 months after inoculation, and a gradual rise in CF titers was found during the first year. The antibody titers have been maintained, though with some fluctation, through the following year, and the titers vary from 64 to 256. Virus neutralizing activity against maedi M88 strain was detected in the sera of all intrapulmonarily inoculated sheep within 8 months after inoculation. Titers have been maintained or have slightly increased. The level of titers, ranging from 8 to 256, was clearly different between individual sheep.One of the 4 sheep inoculated intracerebrally with 5×105 TCID50 of maedi M88 strain developed CF antibodies 1 month after inoculation, but no neutralizing antibodies until death 11 months after inoculation. The rest of the intracerebrally inoculated sheep displayed no evidence of CF or neutralizing antibodies within 18 months after inoculation in spite of numerous virus isolations from peripheral blood leukocytes. The absence of antibodies might perhaps be attributed to phenomena such as differences in tropism, provirus state, immunological tolerance and size of inoculum.One sheep hyperimmunized with repeated s.c. and i.v. injections of maedi M88 strain developed high CF antibody titers but lower neutralizing antibody titers.The 2 uninoculated control sheep developed no CF or neutralizing antibodies within 18 months after inoculation.  相似文献   

2.
Eight sheep were inoculated with Icelandic maedi strain M 88; 2 sheep served as control sheep and were in close contact with the inoculated ones. Four of the sheep were inoculated via the respiratory tract with 7×106 TGID50 of strain M88 and the other 4 intracerebrally with 5×105 TGID50 of the same strain.Maedi M88 strain was isolated from peripheral blood leukocytes of all inoculated sheep. There was a striking difference between the 2 groups in the appearance of demonstrable viremia after inoculation. Viremia could be demonstrated in the intrapulmonarily inoculated sheep within 2–6 months but not until 8–11 months after inoculation in the intracerebrally inoculated ones. This finding is thought most probably to reflect a weak neurotropism of the strain used. After the first demonstration of viremia, maedi virus has been recovered quite reqularly in peripheral leukocytes of all intrapulmonarily inoculated sheep, but less regularly in the intracerebrally inoculated ones. Maedi virus was isolated from 1 of the uninoculated control sheep 15 months after inoculation.The first clinical case with a clinical appearance suggesting combined involvement of maedi and visna was found among the intrapulmonarily inoculated sheep, 8% months after inoculation. Histopathological examination and virus isolation confirmed maedi. The cause of paraplegia could not be confirmed. No histopathological changes were found and no virus isolation was made from the central nervous system of this animal.One of the intracerebrally inoculated sheep died suddenly without any observed clinical signs 11 months after inoculation. Histopathological examination revealed pulmonary lesions of maedi, but no visna lesions in the central nervous system, although maedi virus was isolated from various parts of brain.None of the other experimental sheep displayed clinical signs of maedi or visna during the observation period of 18 months.  相似文献   

3.
The early immune response (19 weeks) in sheep inoculated parenterally with maedi virus was studied, using the lymphocyte transformation test, immunodiffusion test, complement-fixation test, and neutralization test. Cellular immune responses were detected between 3 and 7 weeks after the sheep were inoculated. Antibodies were detected by immunodiffusion test in 3 of 5 animals in weeks 7 to 11 and by complement-fixation test in weeks 15 to 19. Neutralizing antibodies were not detected. There was no sign of virus-induced immunosuppression as determined by lymphocyte responsiveness to mitogens or by in vivo and in vitro immune responses following BCG vaccination.  相似文献   

4.
A long-term experiment in sheep inoculated intranasally with 2 strains of Norwegian maedi virus was carried out in 2 groups of Norwegian Dala sheep (7 sheep/group). Virus-specific cellular immune response was assayed in the lymphocyte transformation test sequentially during 3 years after sheep were inoculated in group 1 and 4 times in the 3rd year in group 2. Humoral immune response was assayed by immunodiffusion, complement-fixation, and neutralization tests on sequential serum samples collected from the 2 groups. Attempts to isolate virus were made. All group 1 sheep showed transient and irregularly recurring cellular immune responses. In group 2, 6 of the 7 sheep gave similar responses. The frequency of virus isolations was low compared with that reported by various research workers using other breeds for studying experimental maedi-visna infection. Precipitating antibodies were detected earlier, and in more animals, than were complement-fixing antibodies. Both were, however, detected later and less frequently than were reported by other research workers. There was a marked difference in the capability of the 2 maedi virus strains to induce neutralizing antibodies. The sequential sera usually showed distinct differences in neutralizing capacity of the virus strains, indicating that they are antigenically different.  相似文献   

5.
The final results of experimental infections with virus recovered from the lungs of sheep suffering from progressive interstitial pneumonia (=zwoegerziekte=maedi) are reported. The virus could be reisolated from blood samples of all experimentally infected sheep. Every animal produced antibodies against the virus. The neutralising, complement-fixing and precipitating antibodies remained present in the blood for six years. Fourteen out of 21 intrapulmonarily infected sheep developed clinical and/or histopathological lung lesions and in three a meningo-leucoencephalitis was detected in addition. One of these three developed the clinical and pathological signs of 'visna' 14 months after inoculation. Signs of visna were seen in eight of 10 sheep that had been inoculated intracerebrally. Furthermore, nine of these sheep suffered from progressive interstitial pneumonia. Hence the name maedi-visna virus is proposed for the agent which causes both disease entities. Three sheep that yielded virus after infection and in which antibodies were detected, did not develop histopathological lesions.  相似文献   

6.
Thirteen sheep were inoculated with maedi-visna virus by respiratory or intra-cerebral (i.c.) routes and were kept in close contact with 7 uninoculated control sheep. Immune responses and virological events were followed in all 20 sheep for periods up to 3 years post-inoculation.Three out of 7 i.c. infected sheep produced no complement fixing (CF) or serum neutralising (SN) antibody, whilst all 5 infected by the respiratory route and the hyperimmunised sheep developed CF and SN antibody which persisted with fluctuating titre over the period of study.Ten out of 11 sheep, which were followed from 3 months after experimental inoculation to 16–21 months (5 sheep) or 3 years (6 sheep) after inoculation, developed transient late virus-specific cell-mediated responses with intermittent virus isolation from peripheral blood leucocytes (PBL) over the period of study.In the contract control sheep, virus was isolated from PBL of 2 sheep during the 2nd year of contact, and transient virus-specific cell-mediated responses, but no antibody responses, were detected.  相似文献   

7.
Studies on transmission of maedi virus to lambs   总被引：4，自引：0，他引：4  
Lambs born to 5 ewes in 3 successive years were studied for presence of maedi virus and its antibodies. In the middle of the first-year pregnancies the ewes and the only ram of the colony were inoculated with maedi virus. No antibodies or viraemia could be detected in the lambs at birth. After sucking colostrum, antibodies appeared in the lambs of the ewes which themselves were seropositive, and reached their peak in a few days. Maternal antibodies disappeared within 12 weeks in all the lambs. Neutralizing antibodies were demonstrated in the colostrum and their content declined rapidly after lambing. Virus was isolated from the milk of 2 ewes in the third year of the studyIn the first year the spread of maedi virus was demonstrated to only 1 of the lambs, but in the other 2 years maedi virus was detected in tissues of half of the lambs sacrificed at 3–12 weeks of age. It was concluded that lambs born to chronically infected ewes are readily infected, indicating excretion of virus by ewes. The study yielded no information on the specific routes of transmission, except for the finding of the virus in milk of 2 ewes in the third year of the study. No evidence was obtained of transplacental transmission of maedi.  相似文献   

8.
Serological responses of Icelandic sheep experimentally infected with visna virus (vv) were contrasted with responses in American Targhee sheep naturally infected with progressive pneumonia virus (PPV). Precipitating antibodies assayed by immunodiffusion were compared with the neutralising and complementing fixing antibody response. In experimental infections with vv, complement fixing and neutralising antibodies appeared early after infection and rose to high levels in all sheep, while precipitating antibodies were detected only at minimal titre. In natural infections with PPV, immune responses were less consistent and precipitating antibodies were detected more frequently than complement fixing or neutralising antibodies against PPV. These results may suggest important biological differences between the lytic fibroblast-tropic virus strains used for experimental infection of Icelandic sheep and the nonlytic macrophage-tropic strains of PPV circulating in nature. Lytic strains evoke a brisk response against the viral glycoprotein with high titre neutralising antibody while nonlytic strains induce a less consistent response to the glycoprotein.  相似文献   

9.
Immunologic response of sheep to inactivated and virulent bluetongue virus   总被引：2，自引：0，他引：2  
Humoral and cellular immune responses of sheep to inactivated and virulent bluetongue virus (BTV) were studied. All sheep inoculated with inactivated BTV developed BTV group-specific nonneutralizing antibodies, as determined by agar-gel immunodiffusion. The development of group-specific, nonneutralizing, complement-fixing antibodies was variable and appeared to be dependent on immunizing BTV serotype, sheep breed, and individual variation. Virus-neutralizing antibodies were never detected after inoculation with the inactivated BTV. In vitro lymphocyte stimulation to BTV soluble antigen was observed with cells from all inoculated Warhill sheep and with cells from 1 of 3 inoculated Suffolk cross sheep. Complement-fixation titers did not appear to correlate with the degree of protection observed, ie, duration of postchallenge-exposure viremia. The development of postchallenge-exposure neutralizing antibody titer was inversely correlated to protective immunity. The development of a response to BTV antigen in the lymphocyte-stimulation test associated most closely with protection. Warhill sheep were afforded better protection, by inoculation with inactivated BTV, to live virus challenge exposure than were the Suffolk cross sheep. Approximately 30% of the inoculated Suffolk cross sheep responded to challenge exposure with intensified clinical signs of blue-tongue, compared with the challenge-exposed control sheep of the same breed.  相似文献   

10.
A successful attempt was made to mechanically transmit bovine leukosis virus (BLV) from a BLV-infected cow with a normal lymphocyte count to sheep by inoculation with horse fly (Tabanus abactor) mouthparts. After interrupted natural feeding, horse flies were anesthetized with CO2. Mouthparts were severed and pooled into a tissue grinder containing medium. Five inocula containing the mouthparts of 10 flies each, and 5 inocula containing the mouthparts of 20 flies each, were prepared and inoculated SC in the right axilla of 10 BLV antibody-negative sheep. Five additional sheep served as controls. Serum samples were collected at 2-week intervals and tested by agar gel immunodiffusion for BLV antibodies. One sheep injected with 20 mouthparts developed antibodies to BLV at 10 weeks after inoculation. Six months after inoculation with fly mouthparts, 1 BLV antibody-negative sheep was randomly selected from each treatment group and injected, in the left axilla, with 3 ml of blood from the donor cow to confirm susceptibility of the sheep. All 3 sheep developed antibodies to BLV within 4 weeks.  相似文献   

11.
A double blind field trial was carried out with a live attenuated bovine respiratory syncytial virus vaccine. The trial involved 530 calves, two to 10 months old, on 27 dairy farms, where respiratory problems due to bovine respiratory syncytial virus infections had been observed during the preceding year. In 17 herds either all calves were vaccinated (nine groups) or all calves received a placebo (eight groups). In 10 herds half the number of calves were vaccinated and the other half kept as non-vaccinated controls. Calves were vaccinated intramuscularly twice with an interval of four to five weeks. These groups were under regular clinical observation and animals were tested periodically for antibodies to bovine respiratory syncytial virus and parainfluenza type 3 virus. Serological examination indicated that no bovine respiratory syncytial virus infection had occurred prior to the first vaccination in August. Vaccination did not cause adverse reactions. Low concentrations of neutralising and complement fixing antibodies were induced by vaccination and a sharp increase of antibody titres was observed after natural infection of vaccinated animals. Infections with bovine respiratory syncytial virus occurred in six out of eight non-vaccinated groups, in nine out of 10 partly vaccinated groups and in only two out of nine completely vaccinated groups. Virus infection in completely vaccinated groups was significantly reduced compared with partly vaccinated and non-vaccinated groups. The incidence of bovine respiratory syncytial virus lower respiratory disease was significantly reduced in completely vaccinated groups compared to non-vaccinated groups. Generally only mild signs of upper respiratory disease were present in completely vaccinated groups after bovine respiratory syncytial virus infection.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
The inoculation of eight five- to seven-month-old sheep by the respiratory route with a culture of Mycoplasma arginini, administered simultaneously with or two days before a culture of Pasteurella haemolytica A2, did not lead to the pulmonary establishment of either organism. Minor lung changes found at slaughter seven days later were therefore considered not to have been induced by the inocula. Two other groups of seven sheep each were initially inoculated intratracheally with an ampicillin-treated lung lesion homogenate in which only M ovipneumoniae was detectable. After seven days one group was inoculated intranasally and intratracheally with mixed cultures of M arginini and P haemolytica A2, and one with P haemolytica A2 alone. In the M arginini-treated group pyrexia peaked earlier and one animal died, but no macroscopic or microscopic differences were apparent between the two groups at necropsy 10 to 11 days later; six sheep from each group had lung lesions indistinguishable from ovine atypical pneumonia. M arginini was isolated in high titre from the respiratory tract of two animals in the M arginini-treated group, including the sole fatality. However, an adventitious parainfluenza type 3 virus infection, identified in four animals from the M arginini-treated group and one from the other, may have been responsible for the inter-group clinical differences. It was concluded that the strain of M arginini used was capable neither of predisposing the lung to secondary invasion by P haemolytica A2, nor of exacerbating the pneumonia and effects elicited with M ovipneumoniae and P haemolytica.  相似文献   

13.
A serological survey was conducted in an attempt to detect antibodies against bovine respiratory viruses in sheep and goats from seven geographical areas of Quebec. Sera from 10% of the animals in 182 sheep flocks and 40 goat flocks were collected and specific antibodies against parainfluenza-3, reovirus type 3, respiratory syncytial and infectious bovine rhinotracheitis viruses were detected by hemagglutination-inhibition tests for the former viruses and complement fixation and seroneutralization assays for the latter viruses. Results showed prevalence rates of serological reaction to parainfluenza-3, reovirus type 3 and respiratory syncytial viruses of 28, 72 and 35% in sheep and 26, 64 and 36% in goats, respectively. No antibodies in infectious bovine rhinotracheitis virus were detected in sheep or goats tested. Prevalence rates varied according to the geographical area. No relationships were detected between age, sex, breed, size of flock and prevalence rates of different antibodies except that parainfluenza-3 antibodies were more common in large goat flocks and in sheep flocks with total confinement housing. A relationship between presence of clinical signs in the flocks and prevalence rates of antibodies was only demonstrated for parainfluenza-3 infection in goat flocks.  相似文献   

14.
Haematological parameters and reactivity of lymphocyte antigens to monoclonal antibodies were studied over a 10-month period in sheep experimentally infected with bovine leukaemia virus (BLV). BLV-inoculated animals seroconverted within 1 month and showed a significant lymphocytosis 2-6 weeks after infection. Control animals inoculated with BLV-free lymphocytes showed a stronger and more immediate neutrophil response than those inoculated with BLV-positive lymphocytes. One month after infection, BLV-inoculated sheep showed a relative increase of cells bearing antigens T4, T6, T8 and T19, and 10 months into the trial, MHC II lymphocytes increased, T6 remained elevated, but T4 helper cells were significantly decreased in number. Lymphoma tissue showed the presence of T8 cells, and lymph nodes from seroconverted sheep had areas of concentrated T4 staining cells. These results demonstrate responses in cellular immune mechanisms to infection with BLV.  相似文献   

15.
The bovine lymphoblastoid BL 20 cell line derived from a case of sporadic bovine leukosis when inoculated into sheep did not induce an antibody response directed against bovine leukosis virus (BLV) structural proteins. Sheep were inoculated twice with the BL 20 cell line and then challenged with BLV infected lymphocytes. Three out of four sheep challenged four weeks after BL 20 inoculation did not develop BLV antibodies. Of the 12 sheep challenged later, three sheep did not develop BLV antibodies. BLV was isolated from all the seropositive animals and from none of the seronegative animals.  相似文献   

16.
The complement fixation test (CFT) and the virus neutralisation test (VNT), performed as a plaque reduction test, were employed to measure antibodies to bovine respiratory syncytial virus. The CFT with bovine sera was performed with supplementation of the complement factors in fresh guinea pig serum by an adequate amount of Clq-factor of the bovine species. Kinetics of maternally derived antibodies and the antibody response after spontaneous and experimental infections and after intramuscular vaccination were studied by both tests. Patterns of development of complement fixing and virus neutralising antibodies were generally similar and titres equalled each other in the test systems that are described. However a VNT detected antibodies a few days earlier after an infection than a CFT and peak-levels reached after a naturally acquired infection decreased faster in a CFT than in a VNT: a mean decrease of 3.1 and 1.4 log2 units was found in 13 weeks respectively. Mean half-life of passive antibodies was 25 days in a VNT. An infection with bovine respiratory syncytial virus could be diagnosed by serology, using a CFT on acute and convalescent serum samples of a number of animals in a group. Serology is preferable to virus isolation for routine diagnosis of bovine respiratory syncytial virus infections. Paired sera, collected at 14-day intervals and examined by CFT, are recommended for the diagnosis of the cause of respiratory disease. A VNT is preferable if low antibody levels are to be detected because non-specific reactions occur in a CFT at low serum dilutions.  相似文献   

17.
West African dwarf sheep were inoculated by the subcutaneous route with epizootic haemorrhagic disease of deer (EHD) virus or bluetongue (BT) virus. No clinical disease was observed following primary EHD or BT infection, or subsequent challenge with either homologous or heterologous virus. However, viraemia was detected in non-immune sheep exposed to BT virus, but not in BT- or EHD-immune sheep challenged with either virus, or in non-immune sheep exposed to primary EHD virus infection. Complement fixing antibodies developed against both EHD and BT viruses following the primary infection with either virus, or subsequent challenge with homologous or heterologous virus. Following a primary infection, virus-neutralising (VN) antibodies developed only against the inoculated virus, while the detection of VN antibodied to both viruses followed the challenge of an EHD- or BT-immuned sheep with either the homologous or heterologous virus. These findings further support previous reports of a relationship between EHD and BT viruses. between EHD and BT viruses.  相似文献   

18.
Summary

A small scale serological survey for antibodies to maedi‐visna virus among 15 flocks of sheep in Morocco revealed the infection in one flock. Infection appeared to be related with imported sheep. In addition, two abattoir surveys yielded, 0.1% lungs with gross and histological lesions suggestive of maedi.  相似文献   

19.
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20.
The clinical, virological and serological responses of sheep infected with an Australian bluetongue virus (BTV) isolate (serotype 20) were compared to responses in sheep inoculated with an American bluetongue isolate (serotype 17) with which it had shown cross-reactions in serum neutralization tests. In sheep inoculated with BTV 20, clinical signs were very mild and viremia was first detected by day 5; virus was isolated intermittently for a further 2 to 3 days. Neutralizing and precipitating antibodies were first detected in the serum of the sheep between 2 to 3 weeks following inoculation. In contrast, sheep inoculated with BTV 17 showed pyrexia and severe hyperemia of the nasolabial area and oral mucosa from day 7 to 17. Viremia was first detected on day 3 and extended to day 20, while the appearance and titers of serum antibodies was similar in both groups.After challenge with BTV 17 the sheep in both groups remained clinically normal, and virus was not detected in the blood; however, serum neutralizing antibody titers to both viruses increased 2 weeks after challenge and the mean titer of the two groups ranged from 1:250 to 1:640.  相似文献   

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