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1.
Since the ban on growth-promoting antibiotics in animal feed in the European Union, necrotic enteritis has become a major cause of mortality in broiler chickens. Despite the importance of the disease, the pathogenesis is still not completely understood. In the current study, Clostridium perfringens strains isolated from healthy flocks and isolates from outbreaks of necrotic enteritis were evaluated for the ability to cause gut necrosis in an intestinal loop model in laying hens and in an experimental infection model in broilers. High, intermediate and low alpha toxin producing strains were chosen from each isolation source. Only the isolates from field outbreaks induced necrotic gut lesions, independent of the amount of alpha toxin produced in vitro. It was also shown that alpha toxin producing isolates from calf hemorrhagic enteritis cases were not able to induce necrotic enteritis in poultry. These results suggest the presence of host specific virulence factors in C. perfringens strains, isolated from chickens with intestinal necrotic enteritis lesions.  相似文献   

2.
A novel toxin, NetB, has recently been identified in virulent avian Clostridium perfringens isolates and shown to be an essential virulence factor in a clinical necrotic enteritis isolate. To assess whether NetB is more generally associated with avian necrotic enteritis isolates we have screened a range of C. perfringens strains from geographically diverse locations for both the presence and expression of the netB gene. Forty-four isolates were derived from necrotic enteritis disease cases from Australia, Belgium, Denmark and Canada and 55 isolates from healthy chickens from Australia and Belgium. The majority of strains isolated from necrotic enteritis-affected birds were netB positive (70%) and there was an absolute correlation between the presence of netB and in vitro expression of the NetB protein. Only two of the C. perfringens isolates from healthy chickens carried netB. Sequencing of the netB gene from 23 positive isolates showed that NetB is highly conserved, with only one predicted amino acid (A168T) difference, in six isolates, compared to the published sequence. This change did not alter the in vitro activity of the NetB toxin. The gene encoding the recently discovered TpeL toxin was also screened using PCR and only found in a small proportion of NetB-positive isolates from diseased birds. A selection of NetB-negative isolates, originating from diseased birds, was unable to cause disease in a necrotic enteritis induction model. This study provides further evidence that NetB is important in pathogenesis and advances our current understanding of C. perfringens virulence factors in avian necrotic enteritis.  相似文献   

3.
The intestines from 124 dead, sick and normal broiler chickens from 24 cases of necrotic enteritis were subjected to histological examination. Tissue sections from the duodenum, jejunum, ileum and ceca from each broiler were examined histologically for lesions of necrotic enteritis and the presence of coccidia. Lesions of necrotic enteritis were present in one or more areas of the intestine in all but six of 94 dead or sick birds and they were most common and severe in the jejunum. Coccidia were found in only small numbers in both diseased and normal birds.

Brown and Brenn stained sections showed Gram-positive bacilli intimately associated with early necrotic lesions on the tips of villi. Tissue sections from the intestines of sick birds permitted a proposed pathogenesis for this disease with the lesion starting at the tips of villi.

The similarity in pathogenesis and pathological lesions in this disease of broilers and Clostridium perfringens type C enteritis in baby pigs is discussed.

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4.
Currently, the factors/toxins responsible for Clostridium perfringens-associated avian enteritis are not well understood. To assess whether specific C. perfringens' toxinotypes are associated with avian enteritis, the isolates of C. perfringens from 31 cases of avian necrotic or ulcerative enteritis submitted between 1997 and 2005 were selected for retrospective analysis using multiplex PCR. C. perfringens was isolated from chickens, turkeys, quail, and psittacines. The toxinotypes of isolates from diseased birds were compared against the toxinotype of 19 C. perfringens isolates from avian cases with no evidence of clostridial enteritis. All C. perfringens isolates were classified as type A regardless of species or disease history. Although many isolates (from all avian groups) had the gene encoding the C. perfirngens beta2 toxin, only 54% produced the toxin in vitro when measured using Western blot analysis. Surprisingly, a large number of healthy birds (90%) carried CPB2-producing isolates, whereas over half of the cpb2-positive isolates from diseased birds failed to produce CPB2. These data from this investigation do not suggest a causal relationship between beta2 toxin and necrotic enteritis in birds.  相似文献   

5.
This study investigated the effects of necrotic enteritis challenge or a necrotic enteritis challenge with an additional challenge from dietary aflatoxin B1 compared to broilers that were unchallenged. Also tested were products designed to help alleviate those effects. Lesion scores were higher in broilers challenged to induce necrotic enteritis, but this did not increase with added aflatoxin. The presence of dietary aflatoxin during a necrotic enteritis challenge significantly increased the negative effects of the necrotic enteritis challenge. During the necrotic enteritis challenge virginiamycin, Calibrin-Z, or a blend of Calibrin-Z, an organic acid, and yucca, helped to decrease the effects of the challenge. When birds are challenged with necrotic enteritis and dietary aflatoxin is present, Calibrin-Z had an advantage over all other tested products.  相似文献   

6.
Lesions typical of necrotic enteritis could be produced experimentally in from 11-26% of broiler chickens consuming feed containing approximately 10(7) Clostridium perfringens per gram. Highest mortality was produced using isolates from field cases of necrotic enteritis which were reisolated from experimental cases in the laboratory. Penicillin in the drinking water at 100,000 I.U./litre completely prevented mortality whereas chloramphenicol at 110 mg/litre delayed the onset and reduced the number of deaths compared to controls.  相似文献   

7.
The available literature on necrotic enteritis in broiler chickens is reviewed.

The records of three poultry diagnostic laboratories in Ontario were examined for the years 1969, 1970 and 1971. During this period 855 (7.7%) of 11,076 consignments of broiler chickens examined were diagnosed as necrotic enteritis. The condition was most common in broilers at three weeks of age, with 66% of all cases occurring in chickens between two and four and one half weeks. The disease occurred throughout the year but it was most common during July, August, September and October. Necrotic enteritis often occurred more than once per year on a farm.

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8.
C Riddell  X M Kong 《Avian diseases》1992,36(3):499-503
Necrotic enteritis was reproduced in broiler chickens by mixing cultures of Clostridium perfringens in the feed. Mortality due to necrotic enteritis was higher among chickens fed rations based on wheat, rye, barley, and oat groats than among chickens fed corn-based rations. Addition of pentosanase to a wheat-based diet did not affect the level of mortality due to necrotic enteritis. Addition of pectin and guar gum to different rations severely reduced growth rate and eliminated necrotic enteritis from test birds. Addition of glucose to a corn-based diet caused a small increase in mortality due to necrotic enteritis.  相似文献   

9.
Tropical Animal Health and Production - A total of 464 samples comprising of cloacal swabs from necrotic enteritis suspected live birds (191), intestinal scrapings from dead birds with symptoms of...  相似文献   

10.
Necrotic enteritis is an acute gastrointestinal infectious disease with high morbidity and mortality which caused by Clostridium perfringens. The disease not only harms the livestock health and animal welfare,but also has been an emerging threat for breeding industry and human health. Antibacterial drugs played a positive role on preventing this disease,however,drug-resistant strains were increasing with irrational use of antibiotics,the incidence of necrotic enteritis has drastically increased, prevention and treatment of it faced severe challenges. The author reviewed the characteristics of necrotic enteritis include the etiology,physicochemical properties, epidemiology and clinical signs,at the same time, the control measures and common drugs were summarized,and the new development trend and direction for prevention and treatment necrotic enteritis was objective analyzed, aiming to establish a comprehensive understanding of the disease,provide references for prevention and treatment of the disease.  相似文献   

11.
One hundred and fourteen strains of Clostridium perfringens, isolated from the intestinal contents of cattle, sheep, and chickens with enteritis or other disease conditions were studied for their ability to produce enterotoxin. Reversed passive hemagglutination, fluorescent antibody and immunodiffusion tests were used. On the basis of the reversed passive hemagglutination titres, supported by the other two tests, enterotoxigenicity of the strains was arbitrarily classified into two categories: highly enterotoxigenic and potentially enterotoxigenic, with 12% falling into each category. All the highly enterotoxigenic strains originated from cases of enteritis and included all three animal species. Apart from enterotoxigenicity, one C. perfringens strain produced beta toxin (type C) and 21 strains produced large amounts of alpha-toxin. The latter strains were predominantly associated with necrotic enteritis in chickens.  相似文献   

12.
Two cases of peracute haemorrhagic enteritis in the dog are reported. Gram-positive bacilli, which were shown in one case to be Clostridium welchii were found adhering to the necrotic epithelial surfaces in parts of the gastrointestinal tract in both cases. Large numbers of C welchii were recovered from the intestines of both dogs.  相似文献   

13.
畜禽坏死性肠炎主要是由产气荚膜梭菌引起的一种急性消化道传染病,具有较高的发病率和死亡率。该病不仅损害畜禽健康,影响动物福利,而且对养殖业发展及人类健康造成了严重威胁。抗菌药的出现对该病起到了积极限制的作用,然而随着抗菌药的不合理使用,耐药菌株不断增加,坏死性肠炎的发病率呈现升高的趋势,防制坏死性肠炎面临严峻挑战。作者从坏死性肠炎的特征入手,综述了坏死性肠炎的病原学、理化特性、流行病学、临床症状等,与此同时对坏死性肠炎的防制措施及目前常用药物进行了总结,客观分析了防制坏死性肠炎的趋势与发展方向,旨在健全对该病的认识,为坏死性肠炎的防制研究提供参考。  相似文献   

14.
An acute disease with high mortality occurred in the ostrich farm and characterized by depression, severe diarrhea and sternal recumbency. Four dead ostriches of the farm were submitted to the National Veterinary Research & Quarantine Service, and diagnosed as necrotic enteritis. In the gross and histopathological examination, extensive diffuse fibrinonecrotic enteritis was found in the small intestine, especially jejunum. Clostridium perfringens was isolated from a pure culture from the duodenum and jejunum of these birds. Based on our current knowledge, this is the first report of an outbreak of necrotic enteritis in the ostrich in Korea.  相似文献   

15.
Coccidial oocysts and/or vegetative germs, spores, and toxins of Cl. perfringens Type A were used in mono-infection and poly-infection experiments on SPF chicken aged seven and 56 days and kept under different conditions. Necrotic enteritis was regularly reproduced in all experimental groups with polyinfections. In chicken aged seven days necrotic enteritis was reproduced even after repeated mono-infections with 4 X 10(9) gerus and toxin of Cl. perfringens. The loss figures recorded from ground-kept infected groups were higher than those established from the cage-kept animals. The pathologica-anatomic findings recorded from the dead chicken included necrotic, ulcerative, and catarrhal to haemorrhagic intestinal inflammations, with necrotic enteritis being most strongly pronounced in the ileum and jejunum. All infected groups lost not only animals but weight as well. Their average weight on the 21 st day from the onset of infection was up to 26.4 per cent lower than that of the control groups.  相似文献   

16.
Necrotic enteritis in cage-reared commercial layer pullets   总被引：1，自引：0，他引：1  
Necropsy of five 12-week-old pullets from a flock of 99,300 suffering from an increased mortality rate revealed enlarged, gas-filled intestines, the mucosal surfaces of which had the "dirty turkish towel" appearance typical of necrotic enteritis. Although the pullets had been raised entirely in cages, intestinal scrapings revealed the presence of Eimeria maxima. Histopathological findings were compatible with necrotic enteritis. Clostridium perfringens was isolated by anaerobic culture from the intestines. Mortality returned to normal after bacitracin and amprolium were added to the feed.  相似文献   

17.
Necrotic enteritis is an enteric disease of avian species caused by the anaerobic bacterium Clostridium perfringens. The disease is regularly controlled in the broiler chicken industry with antimicrobials in feed but is reemerging in areas such as Europe where there is a ban on antimicrobials as growth promoters. To study prospective therapies, researchers must be able to reproduce this disease in a controlled environment, but this is not always possible because of differences in the pathogenicity of C. perfringens strains. Our objective was to test the potential of five isolates (SNECP43, 44, 47, 49, and 50), taken from field cases of necrotic enteritis, at recreating the disease in a controlled challenge experiment. SNECP43 and 50 were derived from a common clone, with SNECP50 passed in vivo and SNECP43 subcultured in vitro. Four hundred birds were divided into 16 pens, with three pens each receiving one of five treatments, with one control pen. Day-old birds were raised on a high wheat-based diet to promote necrotic enteritis development and were challenged with between 3.4 x 10(9) and 3.2 x 10(11) colony-forming units (cfu) of C. perfringens in feed for a period of 24 hr starting on day 13 of the challenge experiment. Lesion scores were assessed on two birds per pen sacrificed on day 17 and on any dead birds during the 25-day study. Growth performance was assessed up to 25 days, and mortality recorded throughout. Only SNECP50 produced necrotic enteritis mortalities significantly different (P < or = 0.05) from the control. The five isolates were also typed using pulsed-field gel electrophoresis to assess their genetic relatedness. All epidemiologically unrelated isolates were deemed genetically unrelated, whereas SNECP43 and 50 differed by only a single minor band. Toxin type was assessed using polymerase chain reaction (PCR), which was also used for the detection of the gene encoding the beta2-toxin.  相似文献   

18.
Necrotic enteritis is a disease of considerable economic importance to the global poultry industry. Clostridium perfringens has long been recognised as the etiological agent of the disease. However, disease initiation and progression is complex and appears to be precipitated by a range of predisposing factors. The present study investigated microbial interactions in the caecum of birds challenged with C. perfringens that developed necrotic enteritis. Bacterial populations of healthy and diseased birds, across two independent animal trials, were characterised by pyrosequencing of the V1-V3 region of 16S rRNA genes. Significant changes in the microbiota of infected birds were detected. Most of the affected bacterial species, including a number of butyrate producers, were reduced in abundance in infected birds compared to uninfected controls and a number of phylotypes, classified as Weissella species, were also more abundant in healthy birds. Conversely, some bacterial groups were more abundant in the C. perfringens-infected birds, for example, members of an unclassified order of Mollicutes showed a 3.7-fold increase in abundance in infected birds. Representative sequences from this novel order shared 99% identity with sequences previously detected in intestinal microbiota of chickens and humans, and have previously been shown to be represented in a number of samples originating from irritable bowel syndrome disease patients. We speculate that these newly identified perturbations in the composition of caecal microflora may play a role in the development and manifestation of necrotic enteritis.  相似文献   

19.
An evaluation of histologic findings in full-thickness biopsies from the gastrointestinal tract (GIT) from 64 dogs with chronic GIT disease symptoms was performed. In the majority of cases (38/64; 59%), intestinal lymphangiectasia and mucosal edema of unknown etiology were present. In 10 dogs (16%) an eosinophilic colitis, either alone or together with gastritis and/or enteritis, was found. In 5 dogs (8%) lymphocytic-plasmacytic enteritis or enterocolitis was diagnosed. Five dogs (8%) had an intestinal T-cell lymphoma. Samples from the remaining cases were histologically normal or did not allow for a final diagnosis. In contrast to reports about findings in endoscopic biopsies (which often are of varying quality or inadequate for diagnosis), in the majority of cases of this study, examination of full-thickness biopsies from the GIT allowed us to make a definitive histopathologic diagnosis. Furthermore, the study revealed that transmural biopsies are very helpful for diagnosing lymphoma.  相似文献   

20.
Avian necrotic enteritis is a major economic and welfare issue throughout the global poultry industry and is caused by isolates of Clostridium perfringens that produce NetB toxin. Previously we have shown that birds directly vaccinated with inactivated C. perfringens type A culture supernatant (toxoid) combined with recombinant NetB (rNetB) protein were significantly protected from homologous and heterologous challenge. In the present study the protective effect of maternal immunization was examined. Broiler breeder hens were injected subcutaneously with genetically toxoided rNetB(S254L) alone, C. perfringens type A toxoid and toxoid combined with rNetB(S254L). Vaccination resulted in a strong serum immunoglobulin Y response to NetB in hens immunized with rNetB(S254L) formulations. Anti-NetB antibodies were transferred to the eggs and on into the hatched progeny. Subclinical necrotic enteritis was induced experimentally in the progeny and the occurrence of specific necrotic enteritis lesions evaluated. Birds derived from hens immunized with rNetB(S254L) combined with toxoid and challenged with a homologous strain (EHE-NE18) at either 14 or 21 days post-hatch had significantly lower levels of disease compared to birds from adjuvant only vaccinated hens. In addition, birds from hens immunized with rNetB(S254L) alone were significantly protected when challenged at 14 days post-hatch. These results demonstrate that maternal immunization with a NetB-enhanced toxoid vaccine is a promising method for the control of necrotic enteritis in young broiler chickens.  相似文献   

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