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1.
A disease challenge experiment was conducted to determine if including 10% dried distillers grains with solubles (DDGS) in the diet, with or without antimicrobial supplementation, reduces the incidence or severity, or both, of intestinal lesions in growing pigs after an Lawsonia intracellularis challenge. One hundred 17-d-old weaned pigs were blocked by sex, ancestry, and BW and randomly allotted to 1 of 5 treatment groups: negative control, unchallenged, corn-soy diet; positive control, challenged, corn-soy diet; 10% DDGS diet, challenged; positive control with antimicrobial regimen, challenged; and 10% DDGS diet with antimicrobial regimen, challenged. For antimicrobial-supplemented treatments, diets contained 33 ppm bacitracin methylene disalicylate throughout the experiment, with chlortetracycline (Aureomycin) pulsed at 550 ppm from d 3 prechallenge to d 11 postchallenge. Challenged pigs were orally inoculated with 8.0 x 10(8) L. intracellularis organisms after a 4-wk prechallenge period. On d 21 postchallenge, pigs were euthanized, lesions of intestinal mucosa were evaluated, and ileal tissue samples were analyzed by immunohistochemistry to determine the presence and proliferation rate of L. intracellularis. Compared with other dietary treatments, feeding a diet containing 10% DDGS reduced ileum and colon lesion length and prevalence (P < 0.05) and reduced severity of lesions in the ileum (P < 0.05) and colon (P < 0.10) in challenged pigs. Compared with other challenged pigs, those fed the diet containing the antimicrobial regimen had a lower prevalence and severity of lesions in the jejunum (P < 0.05) and tended to have reduced total tract lesion length (P = 0.11). Compared with other challenged pigs, pigs on the 10% DDGS diet with antimicrobial regimen exhibited no differences in length, severity, or prevalence of lesions (P > 0.15), but fecal shedding of L. intracellularis was reduced on d 14 postchallenge (P < 0.05). No dietary effects on fecal shedding were observed by d 20 postchallenge (P > 0.10). The proportion of cells infected with L. intracellularis was reduced when DDGS (P = 0.05) or antimicrobial (P = 0.10) diets were fed. Under the conditions of this experiment, dietary inclusion of 10% DDGS appears to provide some benefit to growing pigs subjected to a moderate L. intracellularis challenge, similar to those of a currently approved antimicrobial regimen.  相似文献   

2.
In two separate trials pigs were experimentally infected with Lawsonia intracellularis at 5-6 weeks of age followed by antibiotic treatment and resolution of the primary infection and then re-inoculated at 12-13 weeks of age. A treatment-control group of pigs received the primary infection and antibiotic treatment only, and served as control for the antibiotic treatment of the primary infection. A challenge-control group of pigs received the second inoculation dose only at 12-13 weeks of age to control infectivity of the challenge-dose and susceptibility of pigs to L. intracellularis at this age. Pigs were monitored for shedding of L. intracellularis in faeces by PCR, and for the development of antibodies and responses of acute phase proteins in serum. The presence of L. intracellularis antigen in the intestinal mucosa was examined in post mortem samples by immunohistochemistry. In both trials primary infected pigs were protected from infection after challenge inoculation as evidenced by absence of faecal shedding of L. intracellularis, lack of changes in acute phase protein concentrations after challenge and with low levels of bacterial antigen in the intestinal mucosa of re-inoculated pigs comparable to that of the treatment-control pigs. In contrast, challenge-control pigs shed L. intracellularis in faeces, had L. intracellularis antigen extensively present within all layers of the intestinal mucosa and developed a significant acute phase protein response in serum after the experimental infection. The acute phase protein response to L. intracellularis infection was detected as an increased rise in the serum concentrations of C-reactive protein and haptoglobin from day-6 post infection, and increased serum concentrations of haptoglobin were generally seen 2-3 weeks after inoculation both at 5-6 and 12-13 weeks of age. In conclusion substantial protection against L. intracellularis infection was found in the re-inoculated pigs in contrast to the development of infection in age-matched control pigs. The acute phase protein responses reflected both the observed protection against L. intracellularis infection upon secondary challenge and that increased resistance to the infection develops with age.  相似文献   

3.
Little is known about the humoral and, especially, cell-mediated immune response in pigs exposed to Lawsonia intracellularis. The objectives of this study were to investigate the onset and duration of fecal shedding, cell-mediated and humoral immune responses in pigs after challenge with a pathogenic isolate or a commercial live vaccine strain of L. intracellularis. Twenty-four 5-week-old pigs were exposed to 4.4x10(9) organisms of a pathogenic L. intracellularis isolate PHE/MN1-00 (10 pigs), a L. intracellularis live attenuated vaccine strain (10 pigs) or sham inoculum (4 pigs). Fecal, serum and whole blood samples were collected from all animals before exposure and weekly up to 13 weeks post inoculation and tested by PCR, immunoperoxidase monolayer assay serology and an interferon-gamma assay, respectively. One animal from each group was euthanized on day 22 post exposure to confirm infection. Humoral and cell-mediated immune responses were initially detected 2 weeks after exposure in pigs challenged with the pathogenic isolate, and 5 and 4 weeks, respectively, in pigs exposed to the modified-live vaccine group. Humoral and cell-mediated immune responses were still detected in some pigs from both L. intracellularis exposed groups 13 weeks after exposure. Fecal shedding was initially detected 1 week and lasted, intermittently, 12 weeks post exposure in pigs challenged with the pathogenic isolate, while fecal shedding was first detected 2 weeks and lasted, also intermittently, 9 weeks after exposure to the vaccine. In summary, both pathogenic isolate challenged and vaccine exposed pigs demonstrated long-term shedding of and immune responses to L. intracellularis.  相似文献   

4.
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   

5.
ABSTRACT: To investigate immune responses upon re-infection with Lawsonia intracellularis, local and peripheral humoral and cell-mediated immune responses to primary and challenge inoculations were studied in 22 pigs. Pigs were orally inoculated with virulent L. intracellularis at the age of 5-6 weeks, treated with antibiotics and challenged with a re-inoculation (RE) at the age of 12 weeks. Treatment control (TC) pigs received only the primary inoculation and challenge control (CC) pigs received only the secondary inoculation at 12 weeks of age. Following this regimen, all RE pigs were protected against the re-infection as defined by reduced colonisation and pathology of intestinal mucosa, absence of bacterial shedding and without increase in serum acute phase protein response. In the protected RE pigs, serum IgG responses were variable with both high and low responders. Serum IgA responses were not boosted by the re-inoculation, since identical intestinal IgA responses developed in response to the inoculation in both the susceptible CC pigs and the protected RE pigs. A memory recall cell-mediated immune response developed in RE pigs which was significantly stronger compared to the primary response in age-matched CC pigs as assessed by whole blood IFN-γ assay and by calculation of IFN-γ integrated median fluorescence intensity (iMFI) after flow cytometry. The major IFN-γ producing cells were identified as CD8+ and CD4+CD8+ double positive lymphocytes. The results indicate that cell-mediated immune responses are likely mediators of protective immunity against L. intracellularis, with CD8+ effector cells and CD4+CD8+ double positive memory T cells as main contributors to the antigen-specific IFN-γ production.  相似文献   

6.
An avirulent mutant strain of Salmonella cholerae-suis was cloned for resistance to streptomycin and nalidixic acid. The mutant strain 33-13 also was used because of its avirulence and immunogenicity in mice. Weaned pigs were vaccinated with live strain 33-13; 5 pigs were vaccinated by conjunctivally administered 5.5 X 10(7) organisms (low dose), 5 were conjunctivally administered 5.5 X 10(9) organisms (high dose), and 5 pigs were administered 5.5 X 10(9) organisms (high dose) IM. Transient fever and transient fecal shedding of the vaccine strain developed in pigs vaccinated IM, but not in 2 groups of pigs vaccinated conjunctivally. After intratracheal administration of virulent strain 38-9, nonvaccinated control pigs (n = 9) developed persistent high fever, anorexia, bacteremia, diarrhea, and fecal shedding of strain 38-9, whereas vaccinated pigs remained afebrile and clinically normal. Nonvaccinated and uninfected sentinel pigs (n = 8) were kept in units of 2 pigs with each group of experimental pigs, and remained healthy throughout the experiment. Thirteen vaccinated and 7 nonvaccinated control pigs were killed 42 days after vaccination, and 2 vaccinated, 2 nonvaccinated, and 8 sentinel control pigs were killed 58 days after vaccination. Ten organs were evaluated by quantitative bacteriology on necropsy of all pigs for the presence of vaccine strain 33-13, and for virulent strain 38-9. Strain 33-13 was not found. Lung and liver, lesions were found in most of the nonvaccinated control pigs, with a high frequency of recovery of large numbers of strain 38-9 from the mesenteric lymph nodes, lungs, liver, and ileum.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
The course of naturally acquired Lawsonia intracellularis infection was studied in 41 pigs by testing blood and faeces samples collected four to seven times from before weaning to slaughter 5 months old. At slaughter, a sample of ileum was taken for histopathology. In the first sampling when the pigs were 2-4 weeks old maternally derived IgG against L. intracellularis was demonstrated by immunofluorescence antibody test in nine pigs whereas the bacterium was detected by PCR in faeces from six pigs. The maternally derived antibodies did not prevent pigs from becoming infected as seven pigs later on shed and/or were seropositive for L. intracellularis. The lowest prevalence of L. intracellularis was observed in 6-13 weeks old pigs and it seemed as though L. intracellularis in early infected pigs only activates a minor antibody response. At slaughter 66% of the pigs were found positive by immunofluorescence antibody test compared to 24% by immunohistochemistry on ileal samples. Thus, applied at the time of slaughter the antibody test appeared to be a highly sensitive ante-mortem diagnostic tool for identifying L. intracellularis exposed pigs with or without current proliferative enteropathy.  相似文献   

8.
An experiment was conducted to determine if dietary inclusion of distillers dried grains with solubles (DDGS), soybean hulls, or soybean hulls sprayed with an egg-based, polyclonal antibody product would reduce the incidence or severity of infection, or both, in growing pigs after a Lawsonia intracellularis challenge. One hundred 17-d-old weaned pigs were blocked by sex, ancestry, and BW, and randomly allotted to 1 of 5 treatment groups: negative control, unchallenged, corn-soy diet; positive control, challenged, corn-soy diet; 20% DDGS diet (D), challenged; 5% soybean hulls diet (SH), challenged; and SH sprayed with a polyclonal antibody product diet, challenged. Challenged pigs were orally inoculated with 6.4 x 10(8) L. intracellularis organisms after a 4-wk prechallenge feeding period. On d 21 postchallenge, pigs were euthanized, lesions of intestinal mucosa were evaluated, and ileal tissue samples were analyzed by immunohistochemistry to determine the presence and proliferation rate of L. intracellularis. Challenging pigs with L. intracellularis reduced growth rate, feed intake, and efficiency of gain (P < 0.02) and increased the proportion of internal organ weights relative to BW (P < 0.01). Dietary treatment did not affect growth performance pre- or postchallenge (P > 0.10). Heart, empty stomach, and liver weights were similar among dietary treatments (P > 0.10). Weight of the large intestine as a percentage of BW was increased in D and SH pigs compared with positive control pigs (P < 0.05). Lesion length, prevalence, and severity, and fecal shedding of L. intracellularis were primarily unaffected by dietary treatment (P > 0.10), although ileal lesion length and severity observed tended to be greater in the SH sprayed with polyclonal antibody product diet vs. the D pigs (P < 0.10). Results from a previous study indicated that diet composition may affect length, severity, and prevalence of lesions caused by L. intracellularis in growing pigs subjected to a moderate challenge. However, beneficial results were not observed by feeding the dietary treatments used in this study.  相似文献   

9.
Proliferative enteropathy (PE; ileitis) is a common intestinal disease affecting susceptible pigs raised under various management systems around the world. Major developments in the understanding of PE and its causative agent, Lawsonia intracellularis, have occurred that have led to advances in the detection of this disease and methods to control and prevent it. Diagnostic tools that have improved overall detection and early onset of PE in pigs include various serological and molecular-based assays. Histological tests such as immunohistochemistry continue to be the gold standard in confirming Lawsonia-specific lesions in pigs post mortem. Despite extreme difficulties in isolating L. intracellularis, innovations in the cultivation and the development of pure culture challenge models, have opened doors to better characterization of the pathogenesis of PE through in vivo and in vitro L. intracellularis-host interactions. Advancements in molecular research such as the genetic sequencing of the entire Lawsonia genome have provided ways to identify various immunogens, metabolic pathways and methods for understanding the epidemiology of this organism. The determinations of immunological responsiveness in pigs to virulent and attenuated isolates of L. intracellularis and identification of various immunogens have led to progress in vaccine development.  相似文献   

10.
An experiment was conducted to determine if including distillers dried grains with solubles (DDGS) in the diet of growing pigs reduces the incidence or severity of infection after a Lawsonia intracellularis challenge. Eighty 17-d-old weaned pigs were blocked by sex, ancestry, and BW and randomly allotted to 1 of 4 treatment groups: negative control (NC), unchallenged, corn-soy diet; positive control (PC), challenged, corn-soy diet; 10% DDGS diet (10D), challenged; and 20% DDGS diet (20D), challenged. Challenged pigs were orally inoculated with 1.5 x 10(9) L. intracellularis organisms after a 4-wk prechallenge feeding period. On d 21 postchallenge, pigs were euthanized, lesions of intestinal mucosa were evaluated, and ileal tissue samples were analyzed by immunohistochemistry to determine the presence and proliferation rate of L. intracellularis. Compared with unchallenged pigs, challenging pigs with L. intracellularis reduced growth rate, feed intake, and efficiency of gain (P < 0.01) and increased gauntness (P < 0.05) and diarrhea (P < 0.01). Diet did not affect growth performance postchallenge (P > 0.40). Feeding 10 or 20% DDGS diets did not reduce lesion length, prevalence, proliferation of L. intracellularis, or severity of lesions (P > 0.10). Thus, dietary inclusion of DDGS did not reduce the incidence or severity of lesions under the conditions of a severe L. intracellularis challenge used in this study.  相似文献   

11.
Pigs with and without naturally occurring Lawsonia intracellularis infection were fed diets with different texture. In a previous study from 79 pig herds using a similar feeding on pelleted or non-pelleted form showed that the non-pelleted diet was associated with a reduced prevalence of L. intracellularis. In this study a mechanistic approach was taken for explaining and testing this observation by studying the microbiota and the occurrence of L. intracellularis in the distal ileum of 54 pigs by terminal restriction fragment length polymorphism (T-RFLP) analysis, Real-Time PCR and in situ hybridization. The texture of the diet influenced the microbiota, and from a quantitative discriminative analysis of the terminal restriction fragments (T-RFs) of ileum samples it was deduced that Clostridium spp. and Lactobacillus spp. were associated with the non-pelleted diet and Streptococcus spp. with the pelleted diet. In experimentally infected pigs it was verified that 89bp and 90bp sized T-RFs (HhaI) from ileum represented L. intracellularis. The non-pelleted diet seemed to reduce the relative amount of L. intracellularis in the total microbiota of the ileum, but the number of pigs detected positive with L. intracellularis by Real-Time PCR was not influenced. The five pigs with highest L. intracellularis content showed T-RFs that were not present in profiles from less or non-infected pigs, which may indicate that some bacterial species were associated with L. intracellularis infection.  相似文献   

12.
Escherichia coli O157:H7 remains a threat to humans via cattle-derived fecal contamination of food and water. Preharvest intervention strategies represent a means of reducing the pathogen burden before harvest. In this study, the efficacy of a commercially produced type III secreted protein (TTSP) vaccine was evaluated with the use of a commingled experimental calf infection model (30 placebo-treated animals and 30 vaccinates). The calves were vaccinated on days 0, 21, and 42 and infected with 10(9) colony-forming units (CFU) of E. coli O157 by oral-gastric intubation on day 56. Fecal shedding was monitored daily for 14 d. Serologic assessment revealed a robust immune response to vaccination; the serum titers of antibodies against EspA, Tir, and total TTSPs were significantly higher in the vaccinates than in the placebo-treated animals on days 21, 42, 56, and 70. Significantly less (P = 0.011) of the challenge organism was shed by the vaccinates than by the placebo-treated animals on days 3 to 10. Peak shedding occurred in both groups on days 3 to 6; during this period the vaccinates showed a mean log reduction of 1.4 (P = 0.002) and a mitigated fraction of 51%. The number of animals shedding was significantly lower among the vaccinates compared with the placebo group on days 3 to 6 (P ≤ 0.05), with a mean prevented fraction of 21%. No differences in the duration of shedding were observed. Owing to the low challenge shedding in both groups on days 11 to 14 (mean CFU/g < 10; median = 0), no significant differences were observed. These data indicate that TTSP vaccination had protective effects through significant reductions in the number of animals shedding and the number of challenge organisms shed per animal and provides evidence that TTSP vaccination is an effective preharvest intervention strategy against E. coli O157.  相似文献   

13.
Detection method of Lawsonia intracellularis was studied in formalin-fixed paraffin-embedded intestinal tissues from 5 naturally infected pigs by immunohistochemistry with a monoclonal antibody against outer membrane protein of L. intracellularis. Warthin-Starry silver stain revealed clusters of argyrophilic, slightly curved rod-shaped organisms in the apical cytoplasm of enterocytes. Immunohistochemical staining with a L. intracellularis-specific monoclonal antibody confirmed the presence of the organism in the apical cytoplasm of hyperplastic enterocytes. The presence of L. intracellularis in the ileum of pig with proliferative enteropathy was confirmed by polymerase chain reaction (PCR) further on the basis of amplification of 319 base pair products specific for porcine L. intracellularis chromosomal DNA. Immunohistochemistry and PCR may be a complementary method to confirm the diagnosis of L. intracellularis infection in pigs.  相似文献   

14.
The objective of this investigation was to study if different feeding strategies influence experimental infections of pigs with Lawsonia intracellularis, the causative agent of proliferative enteropathy. In three sequential trials, a total of 144 weaned pigs were fed five different diets all made from a standard diet based on wheat and barley as carbohydrate source and soybean as protein source. The five diets were: a standard diet (fine ground and pelleted), the standard diet fed as fermented liquid feed, the standard diet added 1.8% formic acid, the standard diet added 2.4% lactic acid and a diet similar to the standard diet (made from the same ingredients), but fed coarse ground. Twenty-four pigs on each diet were orally inoculated with L. intracellularis and growth performance and faecal excretion of bacteria were monitored. Twenty-four pigs fed the standard diet were included as not experimentally infected controls. Pigs in the first two trials were sacrificed 4 weeks post-inoculation, whereas animals in the third trial were sacrificed after 5 weeks. Pigs in all experimentally infected groups excreted L. intracellularis. The fermented liquid diet delayed the excretion of L. intracellularis and furthermore, pigs fed the standard diet supplemented with lactic acid had limited pathological lesions when the intestines were examined 4 weeks after inoculation. The growth performance was reduced in pigs experimentally challenged with L. intracellularis, however the prevalence and severity of diarrhea was limited.  相似文献   

15.
Little information is available on reproduction of proliferative enteropathy (PE) using a virulent pure culture of Lawsonia intracellularis. Reproduction of the disease using PE-diseased mucosa homogenates, however, is well-characterized. The aims of this study were to evaluate and compare clinical signs, growth performance and the severity of lesions in pigs inoculated with intestinal mucosa homogenate or pure culture of the homologous L. intracellularis isolate. Five-week-old pigs were inoculated with pure culture of L. intracellularis (isolate PHE/MN1-00; n=10), PE-diseased mucosa (n=10), or control media (n=4). The L. intracellularis isolate PHE/MN1-00 used in the pure culture inoculum was extracted from a fragment of the same intestine used to prepare the mucosa homogenate. Clinical signs and growth performance were evaluated throughout the study. Fecal shedding was evaluated in all animals weekly during the experiment. All animals were euthanized 22 days post-inoculation, the intestines were examined grossly and histologically. Results showed that both the infection procedures reproduced clinical disease, macroscopic and histologic lesions typical of PE. Fecal shedding was detected in animals in both challenge groups. In conclusion, the L. intracellularis isolate PHE/MN1-00 reproduces typical clinical signs and lesions of PE similar to the homologous infection with an intestinal mucosa homogenate.  相似文献   

16.
The aim of the present study was to develop an immunohistochemical method (IHC) for detection of Lawsonia intracellularis (L. intracellularis) in formalin-fixed, paraffin embedded sections of intestines from pigs and to implement this method in differential diagnosis of swine diseases with diarrhea in postweaning pigs. The study was conducted on 165 sections of intestines (ileum, caecum and colon) collected from 76 pigs, representing 42 Polish pig farms. The animals included in the analysis suffered from diarrhea, with bloody or grey to brown feces, and were suspected of porcine proliferative enteropathy (PPE). Sections of intestines were analyzed for the presence of L. intracellularis by polymerase chain reaction (PCR) and IHC. Among 165 intestinal samples from pigs with diarrhea, L. intracellularis DNA was detected by PCR in 33 (20.0%) samples. In this group, 30 samples (18.2% of all the samples tested) were also found positive in IHC, while only 3 (1.8%) were IHC-negative. One hundred thirty-two (80.0%) samples were negative in both tests. The PCR- and IHC-positive samples originated from 11 pigs, 4- to 20-week old, from 8 farms. L. intracellularis antigen was visualized by IHC mostly in intestinal crypts and/or in mononuclear cells of the lamina propria). The positive signal in epithelial cells was observed close to the luminal borders, creating typical specifically stained rims around the crypt lumina. The results of the present study further confirm the usefulness of IHC in the detection of L. intracellularis antigen in the intestinal tissues.  相似文献   

17.
These experiments tested the hypothesis that long-acting oxytetracycline (oxytetracycline-LA) was more effective than regular oxytetracycline in preventing porcine pleuropneumonia when administered either 24 or 48 h prior to experimental challenge with virulent strains of Actinobacillus pleuropneumoniae. Two experiments (1 and 2) were conducted using growing pigs (average weight 12-15 kg). Antibiotic treatments were administered once intramuscularly at 20 mg/kg body weight; controls received an equivalent volume of saline. Clinical signs were recorded over seven days, and mortality rates and pathological lesions were analyzed using analysis of variance. Serum oxytetracycline levels were compared 48 and 72 h postinjection. All pigs developed clinical disease following experimental infection. Actinobacillus pleuropneumoniae was recovered from 42% of experiment 1 pigs and all of experiment 2 pigs. The data showed that both oxytetracycline and oxytetracycline-LA given at the same dose protected pigs against experimental infection when given 24 h prior to challenge, and there was no difference between the efficacy of the two drugs in this experiment. When administered 48 h prior to challenge, only oxytetracycline-LA reduced the clinical signs and pathological changes following A. pleuropneumoniae challenge. Between 48 and 72 h postinjection, oxytetracycline-LA blood levels were significantly greater compared to oxytetracycline-treated pigs.  相似文献   

18.
Lawsonia intracellularis is the causative agent of proliferative enteritis in pigs (PPE). This bacterium is difficult to culture from clinical samples and antemortem demonstration is therefore usually performed by PCR on faecal samples. The aim of this study was to elucidate the frequency of L. intracellularis infection in pig herds in Estonia using PCR, histopathological methods and electronmicroscopical studies. The frequency of demonstration of L. intracellularis was highest in 9-12 weeks old pigs (68.1%). It was more frequent in growing pigs with enteritis on small farms where the system of "all-in all-out" was not practiced and where standards of hygiene were poor. Gross and histopathological studies demonstrated that characteristic macroscopic changes associated with PPE were localised to the distal jejunum and ileum.Thickened longitudinal and circumferential folds occurred in the mucosa of the affected regions of the bowel. Samples from pigs aged 4 to 20 weeks exhibited the most intensive inflammatory changes. The distal part of the jejunum, ileum and the upper third of proximal colon and cecum wall were visibly thickened with reduced luminal diameter. Hyperplasia of lymphoid tissue and, in many cases, pseudomembranous or fibrinous inflammation was found. L. intracellularis was detected in 56 young pigs using histopathological methods. Additionally, in 8 of these pigs intracellular bacteria were demonstrated in ilial epithelial cells by transmission electronmicroscopical (TEM) investigation. On the basis of these TEM investigations it was concluded that L. intracellularis causes disturbances of normal growth, differentiation and apoptosis of the epithelial cells of ileum.  相似文献   

19.
Twenty-eight cesarean derived, colostrum deprived (CDCD) piglets were used to evaluate the efficacy of killed and modified live rotavirus (MLV) vaccines against challenge with virulent A-1 and A-2 rotaviruses. Two killed rotavirus vaccines were evaluated: an experimental vaccine and a commercially available vaccine. Efficacy parameters included: average daily weight gains, rotavirus shedding in feces, morbidity incidence and duration, and rotavirus serum antibody conversion post-vaccination and post-challenge. Piglets vaccinated orally/intramuscularly with the modified live vaccine were completely protected from A-1 and A-2 virulent rotavirus challenge. Nonvaccinated control piglets and piglets receiving killed rotavirus vaccines developed diarrhea, shed virus and exhibited reduced weight gains post-challenge. Only the MLV rotavirus vaccine was able to prevent virus shedding in feces after virulent challenge. Both controls and pigs which received killed vaccines intraperitoneally, orally or intramuscularly shed virus in the feces for 7 days post-challenge and virus peak titers approached 10(7) fluorescent antibody infectious dose (FAID)50/g feces. These studies clearly reflected the inability of killed rotavirus vaccines to induce active local immunity to rotaviral diarrhea in piglets.  相似文献   

20.
An inactivated virus vaccine was developed for prevention of FeLV infection in domestic cats. When given in 2 doses, 3 weeks apart, to cats that were greater than or equal to 9 weeks old at the time of first vaccination, the vaccine prevented persistent viremia from developing in 132 of 144 (92%) vaccinates after oronasal challenge exposure with virulent FeLV. In contrast, persistent viremia developed after oronasal challenge exposure with FeLV in 39 of 45 (87%) age-matched nonvaccinated control cats. Transient viremia, indicated by early detection of p27 by ELISA in serum of cats protected from persistent viremia at 12 weeks after challenge exposure, was found in 10 of 132 (8%) vaccinates. Cats that were aviremic 12 to 16 weeks after challenge exposure were examined for reactivation of latent FeLV infection; 4 weekly doses of methylprednisolone were administered, followed by in vitro culture of bone marrow cells. Latent infection was readily reactivated in 6 of 8 (75%) nonvaccinated control cats that had been transiently viremic after challenge exposure. However, latent infection was reactivated in only 5 of 48 (10%) protected vaccinates, and in none of 38 vaccinates in which transient viremia had not been detected. In a safety field trial, only 34 mild reactions of short duration were observed after administration of 2,379 doses of vaccine to cats of various ages, breeds, and vaccination history, for a 1.43% reaction rate. Results indicate that the aforementioned inactivated virus vaccine is safe and efficacious for the prevention of infection with FeLV.  相似文献   

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