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1.
The fluorescent antibody technique was employed to detect hog cholera virus in tissue sections of various organs from experimentally infected swine. The method proved to be highly sensitive and infection could be detected in these animals as early as three days after inoculation with the virus. Best results were obtained when tissues were collected from young animals in advanced disease rather than from sows or from pigs in the early febrile phase. Tonsil, spleen and lymph node were the tissues of choice and were most satisfactory when removed from freshly killed animals rather than from those that had died.  相似文献   

2.
The pathogenicity of V. coli for conventional swine was studied by inoculating pigs with cultures of V. coli and V. coli infected gut of gnotobiotic pigs. Thus, six conventional pigs were inoculated with strains of V. coli freshly isolated from infected gnotobiotic pigs. The cultures were grown in simulated sows milk, and added to the feed. Two other groups, of three pigs each, were infected by administration of minced intestine from two gnotobiotic pigs, heavily infected with the organism. Vibrio was isolated from all pigs, including five of the six controls, but larger numbers were isolated from the inoculated groups, especially from those fed macerated gut. Clinical signs of disease were not observed.  相似文献   

3.
Severe clinical signs of swine infertility and respiratory syndrome (SIRS) of unknown cause were observed in several Minnesota swine farms between November 1990 and March 1991. Forty-five lung samples of weak pigs were collected from 13 swine farms, and virus isolation was attempted using swine alveolar macrophage (SAM) cultures. A cytopathic virus was isolated from 19 lung samples collected from 6 different farms. Four pregnant sows were infected intranasally with a tissue suspension from which virus was isolated, and 4 6-week-old pigs and 2 contact pigs were infected intranasally with 1 of the isolates. The 4 sows farrowed 12 stillborn and 32 normal pigs. Virus was recovered from 10 of 19 pigs examined. Infected 6-week-old pigs were clinically normal except for slightly elevated rectal temperatures and mild respiratory signs. No or mild interstitial pneumonic lesions were observed in inoculated pigs, but the lesion was obvious in the 2 contact pigs. Seroconversion was observed in sows and pigs as measured by indirect fluorescent antibody (IFA). Serologic identification of the isolates was carried out by IFA using reference serum prepared from an experimentally infected sow. A cytoplasmic fluorescence was observed on the SAM monolayers infected with each of the 19 different isolates. Fluorescence was also observed when the monolayers were tested with SIRS virus ATCC VR-2332-infected sow sera. Replication of the isolates was not affected in the medium containing 5-iodo-2'-deoxyuridine but was inhibited by treatment with ether. The isolates were relatively stable at 56 C and did not agglutinate with various erythrocytes tested.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
Light and electron microscopical studies were carried out after experimental induced and spontaneous infection with African swine fever virus. The experimental infection was performed in 18 pigs divided into two groups consisting of 9 animals. The pigs of group I were inoculated with virulent isolate E 70, those of group II with attenuated isolate E 75. Two infected pigs of group I and one control animal were killed on days 3, 5 or 7 p.i., two pigs of group II and one control animal were killed on days 9, 11 or 13 p.i. Additionally 19 spontaneous infected and seropositive animals and two seronegative pigs without clinical signs were examined. Infection with African swine fever virus resulted in slight morphological alterations of the intestine. The pathological findings showed a more intense involvement of the large intestine, especially the caecum and colon, than the small intestine, where the ileum was mostly affected. In all three groups edema and vacuolisation could be observed in endothelial cells. In spite of beginning degenerative signs, especially after spontaneous infection, the fenestrated structure of the endothelium was conserved in most of the cases. In animals infected with virulent isolate the vascular lumina contained aggregations of fibrin, which was severe pronounced in the pigs of the other groups. In the area of these alterations disturbance of permeability with extravasation could be found. In all groups single virions or virus aggregates could be identified in concave depressions of the erythrocyte membrane or free within the blood plasma, in some cases enveloped by a plasma-like material.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
To determine whether swine become naturally age resistant to group A rotavirus infection, colostrum-deprived, rotavirus-naive newborn pigs that were raised in isolation (n = 34) were studied. Neonatal pigs and pigs 1, 2, 4, 6, 8, 10, and 12 weeks of age were inoculated orally with group A porcine rotavirus or mock inoculum and euthanatized at 24, 31, or 48 hours post-infection. Nine sections of small intestine, cecum, and colon were harvested and immunohistochemically examined for evidence of rotavirus replication within enterocytes. Infectivity was semiquantified by intestinal segment, and a composite score was obtained for each animal. In pigs inoculated at 1 week of age, enterocyte infection was mild and scattered; all other pigs became infected regardless of age or region of intestine, and older animals that became infected had infectivity scores similar to those of younger animals. In a second more limited study, pigs raised in the same isolation environment (n = 11) but previously exposed to virus and demonstrating rotavirus serum antibody had a much lower degree of enterocyte infection at 8, 10, and 12 weeks of age (2, 4, and 6 weeks, respectively, after initial exposure to virus). Age resistance to clinical rotavirus disease in swine is due to factors other than an age-dependent development of resistance of enterocytes to infection, at least through 12 weeks of age.  相似文献   

6.
The fluorescent-antibody technique was employed for the detection of bluetongue virus in bovine foetal kidney cell cultures inoculated with tissues and blood from experimentally infected animals.

In the first series, a total number of 79 inoculated suckling-mouse brains were examined, 36 as frozen sections alone and 43 as impression slides in conjunction with tissue culture inoculation of the same material. With the combined tissue culture immunofluorescent methods, 36 suspicious were detected by impression smears and 37 positives by the tissue culture out of 43 brains examined. Twenty-two were suspicious out of the 36 examined as frozen sections.

Results obtained with the second series, using sheep tissues, showed that the combined tissue culture-fluorescent antibody method was satisfactory for demonstrating the virus in blood of infected animals 1 to 9 days postinfection, and in some organs after death. No false positive reactions were obtained.

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7.
Two strains of the agent of virus pneumonia, were tested for the ability to propagate in 12 types of cell cultures and in chicken embryos. The 5 primary cell cultures used were: swine kidney, lung, bone marrow, testicle, and chicken embryo kidney; and the 7 serial passage cell cultures were: swine kidney, kidney-tumor, testicle, bone-marrow, bovine kidney, and human cervical carcinoma (HeLa). The agent of virus pneumonia was propagated in primary swine kidney and in HeLa cell cultures as shown by the production of typical gross and microscopic lesions in pigs inoculated with cell future fluids. Third passage cell culture fluids, produced typical gross lesions in pigs, but fourth passage cell culture fluids produced only microscopic lesions, and no lesions were produced by sixth and eleventh passage fluids. Control pigs receiving fluids from uninoculated cell cultures remained free of gross or microscopic lesions, as did uninoculated controls. Cytopathic effects were not detected in any of the inoculated cell cultures and no cellular changes were detected by staining with Giemsa stain or acridine orange.

Neither lesions nor deaths occurred in chicken embryos inoculated with both strains of virus pneumonia virus. Pneumonia was not produced in pigs inoculated with suspensions from second chicken embryo passage of the 2 strains inoculated by the chorioallantioic sac, the amniotic sac, and the yolk sac routes.

Identical gross and microscopic lesions were produced in pigs inoculated with either pneumonic lung suspensions or with virulent cell culture fluids. Gross lesions consisted of areas of light to reddish-purple consolidation usually limited to the anterior, cardiac, and intermediate lobes of the lungs. Pleuritis and pericarditis were never present in experimentally produced virus pneumonia. The microscopic lesions were characterized by: 1. perivascular and peribronchiolar lymphoid infiltration and hyperplasia, 2. alveolar interstitial thickening and infiltration, and 3. alveolar exudates consisting of alveolar cells, lymphocytes, plasma cells, and neutrophiles.

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8.
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9.
Pseudorabies virus (PRV) antibodies, detectable by indirect radioimmunoassay (IRIA), serum-virus neutralization test (NT), or microimmunodiffusion test (MIDT) were developed within 8 days after pigs were inoculated with virulent PRV or attenuated PRV vaccine. Indirect radioimmunoassay and NT titers in pigs inoculated with virulent PRV were developed at the same rate, with IRIA titers being higher than NT titers. Pigs inoculated with attenuated or inactivated PRV vaccine developed peak mean prechallenge NT antibody titers of 4 and 1 (reciprocals of serum dilutions), respectively. Pigs inoculated with attenuated PRV vaccine had peak mean prechallenge IRIA antibody titers of 6, whereas pigs inoculated with inactivated PRV vaccine had mean IRIA antibody titers of 64. Challenge exposure of swine inoculated with attenuated or inactivated PRV vaccine elicited quantitatively equivalent responses, as measured by IRIA or NT, which were higher than prechallenge titers. There were no false-positive IRIA, NT, or MIDT results obtained when sera from nonvaccinated, nonchallenge-exposed pigs were tested. It appears that the PRV infection status of a seropositive swine herd could be ascertained by serologically monitoring several representative animals from a herd, using the NT. If 2 or more tests of representative animals at 14-day intervals were done and the mean NT titer was 4 or less, it could be concluded that the herd was vaccinated against, but not infected with, virulent virus.  相似文献   

10.
Inoculation experiments were performed with two German strains of swine fever virus. In Experiment I, ten pigs of Danish Landrace were inoculated with a strongly virulent strain, while in Experiment II ten pigs were inoculated with weakly virulent virus.The animals were killed at varying times after inoculation and organs taken out for examination by means of fluorescent antibodies (FA), by the complement fixation test (CFT), and by the agar gel diffusion test (AGT). Cryostat sections of tonsils, spleen and lymph nodes were examined by FA staining. Tissue suspensions from the same organs were inoculated into primary pig kidney tissue cultures, which were also stained with FA. Antigen produced from spleen tissue was used in the CFT and pieces of pancreas tissue in the AGT.The strongly virulent virus could be demonstrated easily by FA in all the inoculated pigs, both by direct staining of cryostat sections and by staining of inoculated tissue cultures. The CFT and AGT were positive when the tested organs originated from animals killed at a more advanced stage of the disease.While the weakly virulent virus could be demonstrated by FA staining of tissues from eight of the ten pigs in Experiment II, virus was found in none of these animals by the FA tissue culture method. The CFT was positive in one case and the AGT in three cases.In both experiments it was found that FA staining of cryostat sections of tonsils was a particularly suitable method for the demonstration of virus.The results are discussed and compared with recent German and American studies.  相似文献   

11.
Swine dysentery: pathogenicity of Treponema hyodysenteriae.   总被引：6，自引：0，他引：6  
When pure cultures of Treponema hyodysenteriae were orally inoculated into pigs, severe disease characteristic of swine dysentery developed. Less severe lesions were produced by oral inoculation of infective minced colon. Noninoculated pigs were used as controls. Inoculations of surgically isolated porcine colonic loops with either pure cultures or infective minced colon produced lesions only in the injected loop; the adjacent noninjected colon remained normal. Pigs and other experimental animals, including rabbits, guinea pigs, and mice, inoculated with washed cultures by various parenteral routes remained normal.  相似文献   

12.
Fifteen 6-week-old crossbred weaners weighing about 12 kg each were randomly divided into three groups of five animals each. One group of pigs was inoculated first with porcine reproductive and respiratory syndrome (PRRS) virus and then 3 days later with CSF virus. The second group received classical swine fever (CSF) virus, while the third group was inoculated with PRRS virus only. The aim of the experiment was to determine whether a primary PRRS virus infection influences the clinical outcome of experimentally induced CSF in young pigs. The PRRS virus infected weaners developed mild respiratory symptoms and recovered completely. All five weaners which were inoculated with CSF virus only showed severe clinical signs typical of the acute form of CSF. One pig had to be killed 15 days post-inoculation (p.i.); the remaining four died between the 18th and 22nd day p.i. The clinical course of the animals inoculated with both viruses was slightly different from that of the pigs that received only CSF virus. Four out of five pigs from the PRRS/CSF group became febrile and viraemic earlier than the animals which received CSF virus only. These pigs had to be killed 15–17 days post CSF virus inoculation. One animal in this group survived the acute phase of CSF and recovered completely. It was concluded that the observed divergences of the clinical courses would not have been noticed under field conditions. Therefore these findings cast doubt on the relevance of PRRS virus infection potentiating significantly the clinical outcome of CSF in young pigs.  相似文献   

13.
Fifteen 6-week-old crossbred weaners weighing about 12 kg each were randomly divided into three groups of five animals each. One group of pigs was inoculated first with porcine reproductive and respiratory syndrome (PRRS) virus and then 3 days later with CSF virus. The second group received classical swine fever (CSF) virus, while the third group was inoculated with PRRS virus only. The aim of the experiment was to determine whether a primary PRRS virus infection influences the clinical outcome of experimentally induced CSF in young pigs. The PRRS virus infected weaners developed mild respiratory symptoms and recovered completely. All five weaners which were inoculated with CSF virus only showed severe clinical signs typical of the acute form of CSF. One pig had to be killed 15 days post-inoculation (p.i.); the remaining four died between the 18th and 22nd day p.i. The clinical course of the animals inoculated with both viruses was slightly different from that of the pigs that received only CSF virus. Four out of five pigs from the PRRS/CSF group became febrile and viraemic earlier than the animals which received CSF virus only. These pigs had to be killed 15-17 days post CSF virus inoculation. One animal in this group survived the acute phase of CSF and recovered completely. It was concluded that the observed divergences of the clinical courses would not have been noticed under field conditions. Therefore these findings cast doubt on the relevance of PRRS virus infection potentiating significantly the clinical outcome of CSF in young pigs.  相似文献   

14.
It has been demonstrated that pigs that have been double vaccinated with an E2 sub-unit marker vaccine and that are infected with classical swine fever virus (CSFV) through a natural contact infection may react positive in a CSFV detecting RT-nPCR test, whereas no virus could be isolated by using the conventional virus isolation (VI) technique. To evaluate whether these vaccinated and infected pigs may spread the virus, three experiments were set up. In the first, susceptible pigs were inoculated with serum originating from vaccinated RT-nPCR positive pigs. In the second, vaccinated RT-nPCR positive pigs were brought into contact with sentinel animals. In the third, vertical transmission was evaluated in RT-nPCR positive vaccinated pregnant gilts. In the first two experiments, no proof of virus transmission was found, whereas in the third vertical transmission was observed. The conclusion is that in vaccinated pigs that are positive in RT-nPCR but negative in VI, the level of circulating virus is probably not high enough for horizontal transmission, whereas vertical transmission of the virus is possible.  相似文献   

15.
The potential of porcine parvovirus (PPV) to persistently infect swine exposed in utero was studied. Forty eight 80- to 95-day-old fetuses from 5 PPV seropositive sows were inoculated intramusculary with a virulent strain of PPV or with cell culture medium (controls). Blood samples were collected at birth prior to nursing and at monthly intervals thereafter and tested for antibodies to PPV. Virus-inoculated and control pigs were euthanized at either 1 week before birth (-1), at birth (0) and at weeks 2, 4, 6, 8, 10, 22, and 28 after birth. Presence of viral DNA and antigen was evaluated using slot blot DNA hybridization and indirect FA techniques, respectively. All inoculated fetuses (n = 26) and 7 control fetuses (n = 22) seroconverted in utero, and these pigs maintained antibody titers greater than log10 2 for the period of testing (0-38 weeks after birth). After passive antibody titers had reached subdetectable levels in control animals, animals remained seronegative through an additional 14 weeks of testing in spite of close contact with infected pigs. Virus antigen was not detected in any tissues examined from pigs euthanized at term. In contrast, PPV DNA was detected consistently from pigs at birth from various tissues, and from the lung of one pig at 6 weeks of age and from the lymph nodes of one pig euthanized at 28 weeks of age. The results indicate that pigs infected with PPV in utero may be persistently infected, however the likelihood of shedding to contact animals is minimal.  相似文献   

16.
Pathogens causing significant respiratory disease in growing pigs include Porcine reproductive and respiratory syndrome virus, Porcine circovirus 2, swine influenza virus, porcine respiratory coronavirus, Mycoplasma hyopneumoniae, and Bordetella bronchiseptica. The objective of this research was to characterize the respiratory excretion of these pathogens by acutely infected pigs. Pigs were inoculated under experimental conditions with 1 pathogen. Samples were collected from the upper respiratory tract and exhaled air. All pathogens were detected in swabs of the upper respiratory tract, but only M. hyopneumoniae and B. bronchiseptica were detected in expired air from individually sampled, acutely infected pigs. These findings suggest either that the acutely infected pigs did not aerosolize the viruses or that the quantity of virus excreted was below the detection threshold of current sampling or assay systems, or both, at the individual-pig level.  相似文献   

17.
The target cells of classical swine fever (CSF) virus in the peripheral blood of pigs infected with recent field isolates from Germany were studied. Eight weaned pigs were inoculated oronasally with the CSF virus field isolate Visbek/Han 95 and three weaners were inoculated with the isolate Losten/Freese 98. All pigs showed severe clinical signs typical of CSF and died or had to be euthanized between 9 and 24 days post‐infection (dpi). The first cells in the peripheral blood which became infected with CSF virus were mixed granulocytes (a combination of low‐ and high‐density granulocytes). These cells yielded the highest infectivity for PK 15 cell cultures. On day 7 post‐infection, the peripheral blood mononuclear cell (PBMC) fraction was virus positive, while the peripheral blood leucocyte (PBL), peripheral blood T lymphocyte (PBT) and high‐density granulocyte fractions were either negative or their infectivity was lower than the infectivity of the PBMC fraction. These results indicate that PBMC contain more virus‐positive cells than other fractions of leucocytes. These findings may also have diagnostic implications for the detection of CSF virus in blood samples. Because PBMC showed the highest infectivity in the early stages of CSF, it should be the sample of choice for CSF virus isolation.  相似文献   

18.
The purpose of the present study was to explore the most likely natural route of infection of swine hepatitis E virus (HEV) by oral inoculation of pigs and to investigate the potential infection by direct contact exposure. A preliminary experiment was performed to assess the infectiousness of the bile used as source of virus. Once confirmed, 16 pigs were inoculated via oral drop with an HEV positive bile suspension containing 2 × 105 genome equivalents per pig. Nine animals were kept as contact sentinels and 12 more pigs were used as negative controls. A number of pigs from the three groups were euthanized at 16, 32 and 64 days post-inoculation. From the HEV inoculated group, three pigs shed virus in faeces, two had virus RNA in bile at necropsy and two seroconverted. In the contact group, two animals showed presence of HEV RNA in bile. This study demonstrates that pigs orally inoculated with a single HEV dose got infection, although few animals had evidence of infection. Moreover, the virus was successfully transmitted to direct contact exposed pigs.  相似文献   

19.
Immunohistochemical, viral and bacterial isolation techniques were used to study the distribution and localization of porcine reproductive and respiratory syndrome virus (PRRSV) and Haemophilus (H.) parasuis in experimentally infected pigs. Thirty pigs seronegative to PRRSV and H. parasuis were divided into four groups. Group A pigs (10 animals) were inoculated with both virus and bacteria; group B pigs (10 animals) were inoculated with bacteria, group C pigs (five animals) were inoculated with virus and group D pigs (five animals) were kept as negative controls. All pigs of groups A and C became infected with PRRSV, according to virological techniques used (immunohistochemistry, virus isolation and virus serology). Lung, heart and tonsils were the most frequently immunolabeled tissues, and monocyte/macrophage lineage cells were the target for PRRSV in all tissues. All pigs in groups A and B also became infected with H. parasuis based on immunohistochemical and bacterial isolation results. Serosal surfaces, lung and tonsils were the most frequently immunolabeled tissues, and bacteria were found in monocyte/macrophage lineage cells as well as within neutrophil cytoplasm. No differences in terms of bacterial distribution or localization in tissues of pigs of groups A and B were detected. These results suggest that there is no influence of the previous infection with PRRSV in the occurrence of H. parasuis infection.  相似文献   

20.
Pigs exposed to swine vesicular disease virus developed vesicular lesions by postinoculation day 2. Lesions first appeared on the coronary band and then on the dewclaw, tongue, snout, lips, and bulbs of the heels. The onset of viremia coincided with febrile response and the appearance of vesicles. Virus was isolated from the nasal discharge, esophageal-pharyngeal fluid, and feces as early as postinoculation day 1. Greater amounts of virus were isolated from samples collected during the first week of infection, and lesser amounts from samples collected during the second week. The appearance and the distribution of specific fluorescence in various tissues indicated that during the development of swine vesicular disease virus infection, the epithelial tissues were initially involved, followed by a generalized infection of lymph tissues, and subsequently, a primary viremia. Seroconversion was detectable as early as postinoculation day 4. A mild nonsuppurative meningoencephalomyelitis throughout the CNS was observed in both inoculated and contact-exposed pigs. The olfactory bulbs were most severely and were frequently affected, particularly in contact pigs. The most severe brain lesions were found in pigs 3 to 4 days after the onset of viremia; contact pigs showed more severe brain lesions than inoculated pigs. Microscopic changes were also found in the coronary band, snout, tongue, and heart.  相似文献   

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