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1.
Five 5-month-old merino lambs were nasally inoculated with 10(5.0) TCID50 of Aujeszky's disease virus (ADV). The dynamics of virus excretion in the nasal discharges--in agreement with the histologic findings--indicated that ADV also replicates in extraneural sites, in the upper and lower parts of the respiratory tract. The virus was excreted continuously in the nasal discharges, even during the incubation period. The titres, with certain fluctuations, increased gradually up to the final stage of the fatal disease. Following the onset of the clinical disease, the titre of excreted virus (ranging from 10(4.0) to 10(6.0) TCID50/0.1 ml) was comparable with the ADV content found in the nasal discharge of naturally infected piglets. However, the horizontal transmission of ADV to contact lambs failed.  相似文献   

2.
The use of gl deleted live vaccines against Aujeszky's disease (AD) facilitates to differentiate vaccinated from field-virus infected animals. In this study different modes of vaccination were tried to find out how sheep can be protected from a lethal infection with ADV. It could clearly be demonstrated that Aujeszky disease virus (ADV) is spread by horizontal transmission from infected pigs to sheep. The nasal discharges of infected pigs contained a maximum of 10(8.75)TCID50/g mucus at days 3 and 4 p.i. and those of the contact-pigs 10(8.5)TCID50/g mucus at days 6 and 7 after contact. Non-vaccinated contact sheep were infected horizontally by the pigs. The highest titres ranged from 10(6.25) to 10(7.5)TCID50/g mucus. These animals were sacrificed at day 5 p.i. exhibiting acute symptoms of AD. The nasal discharge of vaccinated sheep contained much lower amounts of ADV (maximum: 10(4.25)TCID50/g mucus). All surviving animals had developed antibodies. Following challenge with the ADV-strain NIA3, no febrile response or virus-shedding was observed in sheep vaccinated 2x s.c. or 2x i.m. with a gl deleted live vaccine, whereas sheep, vaccinated only 1x i.m. (4 out of 4 animals) or 1x i.m. (3 out of 4 animals) or 1x i.n. and 1x i.m. (1 out of 4 animals) had to be sacrificed after showing acute symptoms of AD. In conclusion it can be stated that a double parental vaccination with a gl deleted live vaccine protects sheep against a field-virus AD infection.  相似文献   

3.
Both conventional and specific pathogen free pigs were inoculated intranasally with a strain of Aujeszky's disease virus (ADV). Nasal cells were collected daily by swab, aspiration or wash. The nasal cells were examined for ADV by isolation on cell culture, direct or indirect immunofluorescence and immunoperoxidase staining by monoclonal antibodies. The infected pigs were studied for nasal shedding of infected cells until 30 days after infection. The study was also extended to naturally infected farm pigs. Swabbing, washing and aspiration proved effective methods of collecting between 10(5) and 10(8) pavement or columnar epithelial cells and non-epithelial cells. Macrophages and polymorphonuclear leucocytes were also identified. Infected nasal cells were detected by immunofluorescence and immunoperoxidase from one to 21 days after infection. The viral antigen was detected in both epithelial and non-epithelial cells, the fluorescence was nuclear and, or, 'cytoplasmic', in the latter case only the cell membrane was stained. ADV antigens were detected in nasal cavity cells in pigs infected with a virulent and a hypovirulent strain. Nasal swabs proved effective in confirming infection both by virus isolation and immunological assay, and the latter was shown to be a useful experimental tool for the rapid diagnosis of Aujeszky's disease virus infection in fattening pigs suffering from acute respiratory distress.  相似文献   

4.
The transmission of mucosal disease virus (MDV) from infected ewes and their lambs to susceptible sheep was investigated. MDV was recovered from the amniotic fluid of an infected pregnant ewe and from the blood, nasal swabs and urine of hairy lambs. MDV infection was transmitted either at lambing, from infective foetal fluids or lambs, or later as a result of contact with a surviving with a hairy lamb and either aborted or gave birth to an infected hairy lamb. Adult sheep and 12-months-old sheep were less readily infected than were newborn lambs. Pregnant ewes were infected by contact with a hairy lamb and either aborted or gave birth to an infected hairy lamb. A method to minimise spread of the infection in the field is suggested.  相似文献   

5.
Hysterectomy-produced colostrum-deprived 5- and 27-day-old pigs were inoculated intramuscularly (IM) or intranasally (IN) with the temperature-sensitive and thymidine kinase-deficient ZHtsTK- strain of Aujeszky's disease virus (ADV), and the nasal swabs and organs of the pigs were periodically collected for virus isolation. No abnormal clinical signs were observed in these pigs, except for a mild febrile response. Viral shedding in the nasal swabs with low titers was detected in the pigs inoculated IN between postinoculation day (PID) 1 and 5, but not in those of the pigs inoculated IM. No contact infection, however, occurred in the cohabiting pigs. Viruses with low titers were isolated only from the muscles and lymph nodes at the site of inoculation in the pigs inoculated IM on PID 2 and 4, but not from any organs of the pigs inoculated IN. To investigate the ability of the ZHtsTK- strain to establish a latent infection in pigs, the pigs inoculated IM or IN with the ZHtsTK- strain were treated with prednisolone. No virus was detected in the trigeminal ganglia or the nasal swabs collected after prednisolone treatment by the cocultivation method. The immunological evaluation demonstrated that immunization of pigs with this strain was effective in preventing clinical signs caused by ADV infection. The duration of virus shedding was markedly shortened in immunized pigs, particularly in those immunized twice and the total quantity of virus recovered from immunized pigs was reduced in comparison with unimmunized pigs.  相似文献   

6.
The safety of an Aujeszky's disease virus vaccine based on strain 783, a deletion mutant which does not express glycoprotein I and thymidine kinase, was assessed in pigs, calves and sheep. Four-day-old piglets which were inoculated intranasally and intramuscularly with 10(7) plaque forming units (PFU) developed only slight depression and fever. The virus was transmitted to a sentinel piglet. Six weeks after inoculation, the pigs were injected with high doses of corticosteroids in an attempt to reactivate the vaccine virus. The pigs did not shed Aujeszky's disease virus, did not develop a rise in virus neutralising antibody titres and sentinel pigs remained seronegative to Aujeszky's disease virus. Strain 783 was passaged in two series of three- to five-day old piglets, but after the third and fourth passages virus could no longer be recovered. Pregnant sows were inoculated with 10(7) PFU of virus strain 783 around day 35 or on day 85 of pregnancy, and their fetuses and piglets were assayed for Aujeszky's disease virus and antibodies against Aujeszky's disease virus. No evidence was found for transplacental transmission of the virus. Calves and sheep were given 10(7) PFU of virus strain 783 intranasally or intramuscularly; they survived and did not develop clinical signs of Aujeszky's disease. All the sheep and the calves inoculated intramuscularly developed neutralising antibodies to Aujeszky's disease virus.  相似文献   

7.
In pigs inoculated with Aujeszky's disease virus (ADV), recrudescence of herpesvirus infection was induced by daily administration of 1,000 mg of prednisolone for 5 days at 2 (group A) or 5 (group B) months after the primary infection. At necropsy in group A pigs, ADV was recovered from nasal secretions 3 to 9 days after prednisolone treatment initiation and from the brain cortex 10 days after treatment initiation; ADV was not recovered from group B pigs. In pigs of both groups killed 10 days after treatment initiation, 2 types of characteristic lesions were found. One type was a nonsuppurative encephalitis that consisted of neuronal necrosis, neuronophagia, and formation of eosinophilic intranuclear inclusion bodies. The 2nd type had basophilic intranuclear inclusion bodies in the enlarged endothelial cells of the kidneys, liver, lungs, adrenal glands, and lymph node sinusoids. Cells containing intranuclear inclusion bodies had immature and mature herpesvirus particles. Therefore, the brain lesions containing the eosinophilic inclusion bodies were considered to be due to ADV. Basophilic inclusion bodies in the endothelial cells were due to porcine cytomegalovirus. These observations indicated that prednisolone treatment resulted in recrudescence of ADV and porcine cytomegalovirus infections.  相似文献   

8.
Two commercial Aujeszky's disease vaccines, a modified killed vaccine and a sub-unit vaccine, both carrying a deletion of glycoprotein-I, were evaluated in pigs. Each vaccine was administered to two groups of four pigs, twice at 4-week intervals, with two pigs held as unvaccinated controls. All pigs were challenged with a New Zealand field isolate of Aujeszky's disease virus 3 weeks after the second vaccination. The results indicate that the sub-unit vaccine was able to protect pigs against clinical Aujeszky's disease much better than the pigs vaccinated with the modified killed vaccine when challenged with a virulent virus. However, the amount and the duration of virulent virus excretion following challenge was greater with the sub-unit vaccine than the modified killed vaccine. Pigs vaccinated with the sub-unit vaccine were shown to be latently infected following challenge. Latent infection was demonstrated by excretion of Aujeszky's disease virus from the nasal cavity after dexamethasone treatment and seroconversion of a sentinel in contact pigs to Aujeszky's disease virus.  相似文献   

9.
Aujeszky's disease virus (ADV) envelope glycoprotein gVI (gp50) was purified from virus-infected Vero cells by ion-exchange and immunoaffinity chromatography and its usefulness as a subunit vaccine was evaluated in active and passive immunization studies. Four-week-old piglets were immunized intramuscularly (IM) with purified gVI twice two weeks apart and challenged intranasally (IN) 10 days after the second immunization with 30 LD50 (10(8)PFU) of a virulent strain of ADV. Pigs, vaccinated with 100 micrograms of purified gVI, produced virus neutralizing antibodies and did not develop clinical signs after challenge exposure. The challenge virus was not isolated from nasal swabs and tonsils of gVI-vaccinated pigs, whereas non-vaccinated control pigs developed illness after challenge exposure with the same virulent ADV strain which was later recovered from their nasal swabs and tonsils. Pregnant sows vaccinated twice with purified gVI (IM) at a three week interval produced virus neutralizing antibodies in colostrum. Four-day-old sucking piglets born of vaccinated sows were passively protected by colostral antibodies against intranasal challenge with a lethal dose of virulent ADV. Sera from gVI-vaccinated pigs were distinguished from experimentally infected swine sera by their differential reactivity in enzyme-linked immunosorbent assay (ELISA) using four major viral glycoproteins (excluding gVI) as antigen purified by the use of lentil-lectin.  相似文献   

10.
Peste des petits ruminants virus (PPRV) recently caused a serious outbreak of disease in Moroccan sheep and goats. Alpine goats were highly susceptible to PPRV with mortality rates approaching 100%, as opposed to local breeds of sheep which were less susceptible to the disease. The relative susceptibility of alpine goats was investigated through an experimental infection study with the Moroccan strain of PPRV. Severe clinical signs were observed in the alpine goats with virus being excreted through ocular, nasal and oral routes. No difference in the severity of the disease in goats was observed with different inoculation routes and transmission of the virus by direct contact was confirmed. This study confirmed the susceptibility of the alpine goat to PPRV infection and describes a challenge protocol that effectively and consistently reproduced severe clinical signs of PPR in experimentally infected goats.  相似文献   

11.
This study was carried out in nine unvaccinated Swedish weaner pig-producing herds, ranging in size from 20 to 134 breeding animals, which had experienced a previous outbreak of Aujeszky's disease (AD) and in which seropositive sows were still present. The objective was to quantify the seroconversion rate to Aujeszky's disease virus (ADV) in breeding animals and to find out whether unvaccinated herds could become free from ADV by using only seronegative animals for replacement. Serum samples were initially obtained from all adult pigs in the herds. Animals testing negative, as well as replacement animals, were subsequently tested every second or third month and the herds were followed for 10-28 months. The herd owners were advised to keep seropositive and seronegative animals separate whenever possible and to implement sanitary measures against the reintroduction of the virus into the herds. All herds experienced long consecutive periods (> or = 4 months, median 9 months) without seroconversion. Three herds became free from ADV during the serological study; in two of these herds no seroconversion was observed. In those seven herds where seroconversion occurred, between 9 and 86% of the susceptible pigs became infected. The reinfection was indicative of the reactivation of latent virus in all herds but two, where the reintroduction of the virus was most likely. The pattern of seroconversion was either sporadic, involving not more than three animals at a time, or epidemic, involving a large proportion of the susceptible animals in the herd. Severe clinical outbreaks hit the two largest herds and these only became ADV-free after the conclusion of the study when vaccine was used, which reduced the incidence of seroconversion to zero. The results from the present study show that it is possible for smaller herds to achieve freedom from ADV without any radical control methods, provided that only ADV-free replacement animals are used and the virus is not reintroduced. Moreover, the finding that long periods can elapse without transmission suggests that when infection is discovered in a herd, the risk of massive spread is not necessarily imminent.  相似文献   

12.
An outbreak of Aujeszky's disease occurred in a flock of sheep which had been housed together with pigs. After the death of five sheep with clinical signs of Aujeszky's disease, the remaining sheep were vaccinated with the Bartha vaccine strain, and the pigs were vaccinated with the 783 vaccine strain of Aujeszky's disease virus. Despite vaccination, however, more sheep died. Brain tissues from four sheep were collected for virus isolation and for immunobistological examinations. Only vaccine virus (gE-negative) was detected in the tissue. After DNA restriction enzyme analysis of the isolated virus, DNA of one or both of the vaccine strains was detected in all sheep. In one sheep field virus DNA was also detected. However, when the polymerase chain reaction was performed on samples prepared from paraffin-embedded tissues, DNA of field virus (gE-positive) was detected in all four sheep. It was probable that the sheep had not yet mounted a sufficient immune response to the vaccine virus, or were already infected with field virus at the time of vaccination. We concluded that the sheep died from field virus infection and not from vaccine virus infection and that only the polymerase chain reaction made it possible to specifically detect even very small amounts of field virus DNA among vaccine virus DNA in all investigated sheep.  相似文献   

13.
Ten-week-old pigs with high levels of maternally derived antibody (MDA) against Aujeszky's disease virus (ADV) were given either a single intranasal vaccination or one or two doses (with an interval of three weeks) of commercially available attenuated ADV vaccines intramuscularly. The pigs did not produce a clear neutralising antibody response to ADV. However, pigs vaccinated intranasally and pigs given two doses of attenuated ADV vaccines were protected against intranasal challenge with virulent ADV two months after the first vaccination. Pigs given one parenteral dose of attenuated ADV vaccine were insufficiently protected. Protection was shown by shorter periods of growth arrest and fever and a greater reduction of virulent virus shedding after challenge in vaccinated pigs than in unvaccinated control pigs. Although intranasal vaccination conferred protection comparable to two parenteral doses of attenuated vaccines, it reduced shedding of virulent virus much more effectively. These results, together with those of other studies, show that intranasal vaccination confers better protection against Aujeszky's disease in pigs with MDA than parenteral vaccination. However, the efficacy of intranasal vaccination also decreases with increasing levels of MDA at the time of vaccination.  相似文献   

14.
Previous studies have shown that during acute infection of the porcine trigeminal ganglia (TG), Aujeszky's disease virus (ADV)-infected neurons are protected from apoptosis induced by the virus itself and by cells of the immune system. However, TG neurons productively infected by ADV finally die and are phagocytosed by adjacent cells, a fact that leads us to speculate that the inhibition of neuronal apoptosis by ADV may be temporary rather than absolute. To address this issue we used TG and brain stem from pigs during acute infection by ADV. Infected cells were detected by immunohistochemical staining of viral antigens, whereas apoptotic cells were identified with an anti-active caspase-3 antibody, the TUNEL assay and by transmission electron microscopy. The results obtained in this study support the contention that the inhibition of neuronal apoptosis by ADV is temporary, since activation of caspase-3 could be detected in infected neurons at late stages in infection and because foci of advanced neuronophagia contained neurons exhibiting typical ultrastructural features of apoptosis.  相似文献   

15.
On three consecutive days, six pigs were exposed for 15 minutes to aerosols of Aujeszky's disease virus. The total estimated dose was 4·5 log10 50. Within each isolation room, a sentinel pig was placed on a deck two feet away from the infected pig. The breath of the pigs that had inhaled the aerosols was collected on days 3, 7 and 13. The respiratory and other clinical signs of the infected pigs resembled those in field cases of Aujeszky's disease. All the pigs infected with Aujeszky's disease virus seroconverted within seven to 10 days after infection. Among the sentinel pigs, clinical signs were minimal and only three seroconverted.  相似文献   

16.
Two outbreaks of border disease occurred on farms with sheep flocks and breeding cattle. The infection of the pregnant sheep was probably caused by transmission of virus from calves persistently infected with non-cytopathic bovine virus diarrhoea virus (BVDV) which were kept in close confinement with the ewes during mid-pregnancy. Border disease was also induced experimentally in eight lambs by exposing their dams at 38 to 78 days of gestation to a heifer persistently infected with BVDV. Both the natural and the experimental infections were characterised by typical signs such as 'hairy-shaker' lambs and high lamb mortality. The diagnosis was confirmed by virus isolations from live-born lambs, seroconversion and pathology. The study supports the assertion that cattle persistently infected with BVDV and in close contact with pregnant sheep, are an important source of strains of virus capable of causing border disease.  相似文献   

17.
The most effective method of containing an outbreak of foot-and-mouth disease (FMD) is by the culling of livestock. However, qualified people must diagnose the disease before the culling can begin, and they must avoid susceptible animals after having been in contact with infected premises, to prevent them from transmitting the virus. To test the effectiveness of biosecurity procedures in preventing the transmission of FMD virus (O/UK/35/2001) investigators contacted and sampled pigs inoculated with FMD virus for approximately 45 minutes and then contacted and sampled sentinel pigs and sheep after either using no biosecurity procedures, or washing their hands and donning clean outerwear, or showering and donning clean outerwear. The virus was detected in the nasal secretions of one investigator immediately after the postmortem investigation of the inoculated pigs but was not detected in samples collected between approximately 12 and 84 hours later. After the contaminated personnel had showered and changed into clean outerwear they did not transmit the strain of FMD virus to susceptible pigs and sheep.  相似文献   

18.
Aujeszky's disease is a worldwide problem in the pig industry. In this experiment, four pigs chosen to act as shedder pigs were intranasally infected with Aujeszky's disease virus. Next, on three consecutive days, eight recipient pigs were exposed to the breath of a pair of shedder pigs via a mask-to-mask module. Except for the virtual absence of CNS signs, shedder pigs expressed clinical signs that were similar to pigs infected naturally or experimentally. Only mild respiratory signs occurred in recipient pigs, but all were infected by aerosols of Aujeszky's disease virus as evidenced by seroconversion. The pig is a much more sensitive indicator of airborne virions than our aerosol collection methods. We conclude that the mild respiratory disease acquired by the aerogenous route in recipient pigs is an easily managed model for studying the transmission of airborne respiratory infections and the immune responses to this type of infection.  相似文献   

19.
African swine fever virus (ASFV) is a highly virulent swine pathogen that has spread across Eastern Europe since 2007 and for which there is no effective vaccine or treatment available. The dynamics of shedding and excretion is not well known for this currently circulating ASFV strain. Therefore, susceptible pigs were exposed to pigs intramuscularly infected with the Georgia 2007/1 ASFV strain to measure those dynamics through within- and between-pen transmission scenarios. Blood, oral, nasal and rectal fluid samples were tested for the presence of ASFV by virus titration (VT) and quantitative real-time polymerase chain reaction (qPCR). Serum was tested for the presence of ASFV-specific antibodies. Both intramuscular inoculation and contact transmission resulted in development of acute disease in all pigs although the experiments indicated that the pathogenesis of the disease might be different, depending on the route of infection. Infectious ASFV was first isolated in blood among the inoculated pigs by day 3, and then chronologically among the direct and indirect contact pigs, by day 10 and 13, respectively. Close to the onset of clinical signs, higher ASFV titres were found in blood compared with nasal and rectal fluid samples among all pigs. No infectious ASFV was isolated in oral fluid samples although ASFV genome copies were detected. Only one animal developed antibodies starting after 12 days post-inoculation. The results provide quantitative data on shedding and excretion of the Georgia 2007/1 ASFV strain among domestic pigs and suggest a limited potential of this isolate to cause persistent infection.  相似文献   

20.
It has recently been shown that the antibody response to glycoprotein I (gI) of Aujeszky's disease virus can be used to distinguish infected from vaccinated pigs. To examine whether pigs exposed to low doses of a mildly virulent strain of Aujeszky's disease virus produce antibody to gI four groups of four pigs were inoculated intranasally with 10, 10(2), 10(3) or 10(4) plaque forming units (PFU) of the Sterksel strain. Two unvaccinated pigs and two pigs vaccinated intranasally with Bartha's K strain, a gI-negative vaccine, were placed in contact with each group. The pigs given 10 PFU and the in-contact pigs in this group did not become infected. The inoculated and the unvaccinated in-contact pigs in the other groups developed mild signs of illness and produced antibody to gI. Four of six vaccinated in-contact pigs that became infected showed neither clinical signs nor virus shedding and still produced antibody to gI. The other two vaccinated pigs appeared to be resistant to contact-challenge. The antibody response to gI persisted for at least seven months. These results support the idea that Aujeszky's disease virus may be eradicated by a programme based on vaccination with gI-negative vaccines, in conjunction with the detection and subsequent removal of gI-antibody positive, infected, pigs.  相似文献   

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