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Salmonella enteritidis: clinical epidemiological approaches for prevention and control of S. enteritidis in poultry production.

Salmonella enteritidis infections in poultry appear to be of major public concern. Prevalence levels in veal calves and pigs are rather low. Because of the complex of socio-psychological, welfare, economic and public health aspects great emphasis should be put on prevention and control. This paper deals with some clinical epidemiological approaches for prevention and control of S. enteritidis. Emphasis is set on multifactorial background of infection occurrence, epidemiological methods and features of monitoring and surveillance for evaluation of measures taken during a follow-up period. Finally, it is stated that the application of Risk Assessment & Analysis principles in this problem area, integrating the concepts previously addressed, might prove to be a valuable perspective.

Animals↗

Phenotypic characterisation of Pasteurella multocida isolates from Australian poultry.

A phenotypic characterisation of 110 isolates of bacteria previously identified as Pasteurella multocida was performed. Reference strains of many of the currently recognised species within the genus Pasteurella were included in the study. All the isolates had been obtained from Australian poultry-67 from chickens, 42 from turkeys and one from a duck. Ten different biochemical biovars were recognised amongst the isolates. Four of these biovars, representing 91 isolates, were identified as P. multocida subsp. multocida. One biovar, consisting of one isolate, was identified as P. multocida subsp. septica and another biovar, consisting of five isolates, as P. multocida subsp. gallicida. Two further biovars were tentatively identified as ornithine decarboxylase negative P. multocida subsp. multocida (five isolates) and maltose positive P. multocida subsp. septica (one isolate). The final two biovars, consisting of five and two isolates each, could not be assigned to any of the currently recognised subspecies of P. multocida.

Animals↗

Detection of a chloramphenicol efflux system in Escherichia coli isolated from poultry carcass.

An active chloramphenicol efflux system was demonstrated in a multiresistant E. coli isolated from poultry carcass. The effect of different concentrations of chloramphenicol on the original strain and on the plasmid-cured strain was determined in the presence and in the absence of CCCP, an uncoupler of the proton-motive force. Minimal inhibitory concentration (MIC) was lower in the presence of CCCP in the original strain. The plasmid-cured strain displayed lower resistance for chloramphenicol than the wild type, but the MIC was not affected by CCCP. The combined results indicate a plasmid encoded energy dependent resistance mechanism. 3H-chloramphenicol accumulation within the cells was measured by scintillation counting. The uptake or the efflux of 3H-chloramphenicol was influenced by CCCP in the original strain, but not in the plasmid-cured strain. More than one chloramphenicol resistance mechanism may exist in this strain. E. coli is an important commensal or pathogen that inhabits the gastrointestinal tracts of humans and animals, so a plasmid encoded active drug resistance mechanism can be a potential source of horizontal transfer of resistance.

Animals↗

Avian influenza viruses in Korean live poultry markets and their pathogenic potential.

We surveyed live-poultry markets in Korea in 2003 and isolated 9 H9N2, 6 H3N2, and 1 H6N1 influenza viruses. Antigenic and phylogenetic analyses showed that all 9 H9N2 isolates were of A/Chicken/Korea/25232-96006/96-like lineage (which caused disease in chickens in Korea in 1996) but were different from H9N2 viruses of southeastern China. They had at least 4 genotypes and replicated in chickens but not in mice. The H3N2 and H6N1 viruses were new to Korea and were probably reassortants of avian influenza viruses from southeastern China and recent Korean H9N2 viruses. All 8 segments of the H3N2 viruses formed a single phylogenetic cluster with 99.1 to 100% homology. The H3N2 viruses replicated in chickens and mice without preadaptation, but the H6N1 virus did not. Our results show an increasingly diverse pool of avian influenza viruses in Korea that are potential pandemic influenza agents.

Amino Acid Sequence↗

Evolution of H9N2 influenza viruses from domestic poultry in Mainland China.

H9N2 viruses have circulated in domestic poultry in Mainland China since 1994, and an inactivated vaccine has been used in chickens to control the disease since 1998. The present study analyzed 27 H9N2 avian influenza viruses that were isolated from chickens and ducks from 1996 to 2002. Infection studies indicated that most of the viruses replicate efficiently but none of them is lethal for SPF chickens. However, these viruses exhibit different phenotypes of replication in a mouse model. Five viruses, including 4 early isolates and one 2000 isolate, are not able to replicate in mice; 14 viruses replicate to moderate titers in mouse lungs and cause less than 5% weight loss, while other 8 viruses could replicate to high titers in the lungs and 7 of them induce 10-20% weight loss of the mice on day 5 after inoculation. Most of the viruses isolated after 1996 are antigenically different from the vaccine strain that is currently used in China. Three viruses isolated in central China in 1998 are resistant to adamantanes. Phylogenetic analysis revealed that all of the viruses originated from CK/BJ/1/94-like virus and formed multiple genotypes through complicated reassortment with QA/HK/G1/97-, CK/HK/G9/97-, CK/SH/F/98-, and TY/WI/66-like viruses. This study is a description of the previously uncharacterized H9N2 avian influenza viruses recently circulating in chickens and ducks in Mainland China. Our findings suggest that urgent attention should be paid to the control of H9N2 influenza viruses in animals and to the human's influenza pandemic preparedness.

Animals↗

Introduction to poultry vaccines and immunity.

The poultry industry constitutes a significant sector of world agriculture. In the United States, more than 8 billion birds are produced yearly with a value exceeding $20 billion. Broiler chickens are the largest segment of the industry. Birds raised under commercial conditions are vulnerable to environmental exposure to a number of pathogens. Therefore, disease prevention by vaccination is an integral part of flock health management protocols. Active immunization using live vaccines is the current industry standard. Routinely used vaccines in chickens include MDV, NDV, IBV, and IBDV, and in turkeys NDV and HEV. Newer vaccines, including molecular recombinants in which genes of immunogenic proteins from infectious agents are inserted into a live viral vector, are also being examined for commercial use. Efforts are under way to enhance vaccine efficacy by the use of adjuvants, particularly cytokines. The vaccine delivery systems include in ovo injection, aerosol, spray, drinking water, eye drop, and wing web injection. The in ovo vaccination procedure is relatively new and at the present time it is used primarily to vaccinate broiler chickens against MDV. Birds respond to vaccines by developing humoral and cellular immune responses. Bursa of Fabricius and the thymus serve as the primary lymphoid organs of the immune system. B cells use surface immunoglobulins as antigen receptors and differentiate into plasma cells to secrete antibodies. Three classes of antibodies are produced: IgM, IgG (also called IgY), and IgA. Successful vaccinal response in a flock is often monitored by demonstrating a rise in antibody titer within a few days of vaccination. ELISA is used most commonly for serologic monitoring. T cells are the principal effector cells of specific cellular immunity. T cells differentiate into alpha beta and gamma delta cells. In adult birds, gamma delta cells may constitute up to 50% of the circulating T cells. Functionally, CD4+ cells serve as helper cells and CD8+ cells as cytotoxic/suppressor cells.

Animal Husbandry↗

Heterocyclic amines in poultry products: a literature review.

Health risks associated with heterocyclic amines in cooked foods have been discussed and analysed since the presence of these food mutagens was first detected. Intake, metabolism, carcinogenicity and epidemiology are important parameters in the risk assessment of heterocyclic amines. It is very difficult to determine the human intake of heterocyclic amines, as the content in cooked meat is highly dependent on the type of meat and how it has been prepared. This review summarises data on estimates of the content of heterocyclic amines in heat-treated poultry products.

Amines↗

Detection and identification of salmonellas from poultry-related samples by PCR.

A polymerase chain reaction (PCR) assay was developed for the generic detection of Salmonella sp. and the identification of S. Enteritidis (SE), S. Gallinarum (SG), S. Pullorum (SP) and S. Typhimurium (ST) in material collected in the field from poultry. The specificity and sensitivity of the assay combined with Rappaport-Vassiliadis selective enrichment broth (PCR-RV) were determined, and field samples were analyzed to verify the validity of the method application. Specificity of the assay was tested using 29 SE, 11 SG, 10 ST and 10 SP strains, along with 75 strains of 28 other Salmonella serovars and 21 strains of other bacterial genera. The assay was 100% specific for Salmonella detection and ST identification. The primer pair for SE, SG and SP also detected S. Berta. PCR detection limits for Salmonella at the genus level were 2 ST, 8 SE, 1.1x10(3) SG and 1.8x10(5) SP cells. At the serovar level, detection limits were 7 ST, 1.2x10(3) SE, 4.4x10(7) SG and 1.8x10(6) SP cells. At the genus level, PCR-RV detected approximately 128% more positive field samples than the standard microbiological techniques and results were ready in 48h instead of 7 days. PCR-RV method is diagnostic of Salmonella at the genus level and ST at the serovar level, although other tests are needed to identify SE, SG and SP to serovar level.

Animals↗

Occurrence of the vanA and vanC2/C3 genes in Enterococcus species isolated from poultry sources in Malaysia.

Enterococcus species isolated from poultry sources were characterized for their resistance to antibiotics, plasmid content, presence of van genes and their diversity by randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The results showed that all isolates were multi-resistance to the antibiotics tested. Ampicillin (15/70) followed by chloramphenicol (37/70) were the most active antibiotics tested against the Enterococcus spp. isolates, while the overall resistant rates against the other antibiotics were between 64.3% to 100%. All vancomycin-resistant E. faecalis, E. durans, E. hirae and E. faecium isolates tested by the disk diffusion assay were positive in PCR detection for presence of vanA gene. All E. casseliflavus isolates were positive for vanC2/C3 gene. However, none of the Enterococcus spp. isolates were positive for vanB and vanC1 genes. Plasmids ranging in sizes between 1.1 to ca. 35.8 MDa were detected in 38/70 of the Enterococcus isolates. When the genetic relationship among all isolates of the individual species were tested by RAPD-PCR, genetic differences detected suggested a high genetic polymorphisms of isolates in each individual species. Our results indicates that further epidemiological studies are necessary to elucidate the role of food animals as reservoir of VRE and the public health significance of infections caused by Enterococcus spp.

Animals↗

Necropsy of chickens, turkeys, and other poultry.

Necropsy of dead or terminally ill birds is a key approach to disease diagnosis. It is important that one establish an orderly, consistent necropsy procedure and evaluate gross lesions as to their likely cause and significance. A very high percentage of farm flock poultry maladies can be diagnosed by gross lesions plus a few simple laboratory procedures, such as direct microscopy, Gram's stain, fecal flotation, and aerobic bacteriology.

Animals↗

Vaccination and early protection against non-host-specific Salmonella serotypes in poultry: exploitation of innate immunity and microbial activity.

A recent European Union Directive required member states to put monitoring and control programmes in place, of which vaccination is a central component. Live Salmonella vaccines generally confer better protection than killed vaccines, because the former stimulate both cell-mediated and humoral immunity. Administering Salmonella bacteria orally to newly hatched chickens results in extensive gut colonization and a strong adaptive immune stimulus but broiler chickens are immunologically immature. However, colonization exerts a variety of rapid (within 24 h) protective effects. These include specific colonization-inhibition (competitive exclusion) in which the protective bacteria exert a profound resistance to establishment and colonization by other related bacteria. This is thought to be primarily a metabolic attribute of the vaccinating bacteria but may also involve competition for attachment sites. The presence of large numbers of bacteria originating from a live Salmonella vaccine in the intestine can also induce infiltration of polymorphonuclear cells into the intestinal wall, which confers resistance to invasion and systemic spread by virulent Salmonella strains. This opens new perspectives for vaccine usage in broilers, layers and breeding poultry but also in other animals which show increased susceptibility to infection because of their young age or for other reasons, such as oral chemoprophylaxis or chemotherapy, where the lack of established normal gut flora is an issue. We recommend that all live vaccines considered for oral administration should be tested for their ability to induce the two protective effects described above. Further developments in live Salmonella vaccines are, however, currently hindered by fears associated with the use and release of live vaccines which may be genetically modified.

Animals↗

Frequency of occurrence of Campylobacter spp. in red meats and poultry in Northern Ireland and their subsequent subtyping using polymerase chain reaction-restriction fragment length polymorphism and the random amplified polymorphic DNA method.

Sampling of lamb (n = 100) and beef (n = 100) carcasses in abattoirs in Northern Ireland produced no evidence of Campylobacter spp. contamination and when retail packs of beef (n = 50) and pork (n = 50) were sampled these were also apparently free of Campylobacter spp. However, 38% of retail packs of chicken pieces (n = 120), yielded Campylobacter spp. These packs were purchased over a period of 1 year and came from a single local producer. After the species of the isolates had been determined (Campylobacter jejuni and Camp. coli were found in approximately equal numbers) they were subtyped using both polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and the random amplified polymorphic DNA (RAPD) method of typing. All of the poultry isolates were successfully typed by these methods, in contrast to the results obtained with serotyping where several isolates were found to be untypable. PCR-RFLP typing showed that specific subtypes were isolated repeatedly over a period of 1 year in the output of the producer studied. The more discriminating RAPD confirmed this observation, but with fewer isolates. This appears to indicate recurrent infection of broilers whose source can now be investigated using the methodologies developed.

Animals↗

Antigen quantification as in vitro alternative for potency testing of inactivated viral poultry vaccines.

Routine batch control of licensed inactivated viral vaccines for poultry usually includes a potency assay as a measure of vaccine efficacy. Potency assays often consist of vaccination-challenge experiments in the target species or in laboratory animals. Instead of measuring the protection of vaccinated animals against virulent pathogens, the serological response after vaccination can be quantified for some vaccines. In vitro antigen quantification assays would be attractive alternatives for the current potency assays because the time and costs involved could be greatly reduced and animal use could be avoided. Such in vitro assays will only be acceptable when the correlation between results and efficacy or potency has been demonstrated convincingly. The results of our studies on antigen quantification assays indicate that, in principle, quantification of viral antigens from inactivated oil-adjuvanted vaccines is feasible and reproducible using specially developed antigen capture ELISAs in combination with specific software for statistical analysis of the ELISA data. We have developed methods to quantify the haemagglutination-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV), the viral protein 3 (VP3) of the infectious bursal disease virus (IBDV), and the spike-1 (S1) protein of the infectious bronchitis virus (IBV). Vaccination experiments with inactivated ND vaccines indicate that the in vitro quantified HN- or F-proteins of NDV are reliable indicators of the serological response after vaccination.

Animals↗

The World Veterinary Poultry Association: the beginnings and first 25 years.

The World Veterinary Poultry Association (WVPA) was formed in 1959, the honour of being the first President of the Association going to Professor de Blieck and that of Secretary to Dr R.F. Gordon, who had both championed its formation. The First WVPA Conference (the name "Congress" was not applied until the third meeting) took place in Utrecht in 1960. The second Conference (1962) and the third Congress (1965) were in Cambridge and Paris, respectively. The fourth Congress, in Belgrade (1969), was a landmark one for two reasons: firstly, submitted papers were introduced, and secondly, the notion of a WVPA journal, later to be called Avian Pathology, was first discussed. A year later (1970) the journal came into being, Professor Klimes (Czhechoslovakia), the driving force behind its creation, being the first Editor-in-Chief, with Professor Kosic (Yugoslavia) as production Editor. Due to the ill health of Professor Klimes, Peter Biggs was confirmed as Editor-in-Chief in 1973. A charitable company, Avian Pathology Ltd, was formed in 1980, under which Avian Pathology was published. Dr L.N. (Jim) Payne succeeded Dr Biggs as Editor-in-Chief in 1988. The fifth and six Congresses were in Munich (1973) and Atlanta, Georgia, USA (1977), respectively. Four years later, at the Oslo Congress, it was agreed that the rather crude logo adopted at the fourth Congress should improved. This was done and is the current logo. On the 25th anniversary (1985) of the first WVPA Congress, the eighth Congress was held in Jerusalem. Membership had increased to almost 1000, with members in 39 countries, 22 of which had branches of WVPA. In 4 years it will be time to publish an account of the second 25 years in the history of the WVPA.

Animals↗

Evaluation of the use of amino acid composition data in assessing the protein quality of meat and poultry products.

A detailed analysis of the amino acid composition data of meat and poultry products, in relation to PER, clearly reveals high correlations between amino acid data expressed in various forms and results of protein quality estimations obtained with the PER assay. The significance of these observations in reference to protein quality evaluation for regulatory purposes will be considered in Background Paper 5.

Amino Acids↗

Commercial approaches to genetic selection for growth and feed conversion in domestic poultry.

Tremendous genetic progress has been observed historically for growth and feed conversion through the efforts of the primary breeding companies. However, significant between-strain variation still exists due to differences in selection emphasis and selection techniques practiced by these organizations. This paper provides an overview of methods currently employed in commercial poultry breeding with reference to factors complicating program design and future challenges facing the industry. Mass selection for body weight has resulted in a significant reduction in the number of days required to grow bird to market weight with indirect improvements in feed conversion. Direct selection for feed conversion is accomplished through part record testing of males that have been preselected for body weight, conformation, and defect traits. Data are commonly subjected to complex statistical analysis both to correct feed conversion for variation in body weight and to improve the accuracy of breeding value estimates. Feed conversion breeding values of male sibs are sometimes used for the selection of female candidates as well. Selection for growth rate and efficiency has resulted in negative complications, such as ascites, reduced reproductive performance, skeletal abnormalities, and increased carcass fatness. Some of these factors may be partially ameliorated through modified selection practices. If not addressed by the breeding industry, the disruption of physiological homeostasis might ultimately represent economic and genetic barriers to further progress in improving growth and efficiency. Modern techniques in molecular genetics, utilized in conjunction with traditional quantitative genetic approaches, will provide additional opportunities to circumvent these physiological complications associated with genetic selection for growth and feed efficiency.

Animals↗

Transcriptional analysis of the response of poultry species to respiratory pathogens.

Respiratory tract diseases are the single most important cause of economic loss due to infections among poultry populations worldwide. However, the molecular mechanisms of the host response to infections remain unknown. Here, we review the literature and describe the adoption of a conceptually simple approach to understand the genetic and biochemical responses of host cells during infection with respiratory pathogens, such as avian pneumovirus (APV). The strategy that we have adopted integrates the powerful techniques of cDNA subtraction hybridization and microarray analysis for global transcriptional profiling. The results of our investigations identify the specific transcriptional alterations in host-cell gene expression that result from an attempt by the host to combat and limit the spread of the pathogen or by the pathogen to enhance its own survival and ability to reproduce. Our studies suggest that a molecular description of host-pathogen interactions in terms of differential gene expression will provide key insights on the molecular basis of disease pathogenesis, pathogen virulence, and host immunity. In addition, the results suggest that the identification of genes and pathways with a role in host response to infection has considerable practical implications for the future design and development of effective immunomodulators and vaccines.

Animals↗

Brevibacterium avium sp. nov., isolated from poultry.

Two strains of a Brevibacterium-like bacterium originating from bumble-foot lesions of domestic fowls were subjected to a polyphasic taxonomic study. The phenotypic characteristics of the bacterium were consistent with its assignment to the genus Brevibacterium although comparative 16S rRNA gene sequencing showed that the organism represents a distinct subline within the genus. Chromosomal DNA-DNA pairing studies confirmed that the unidentified bacterium was genomically distinct and worthy of separate species status. Based on the phenotypic and genotypic distinctiveness of the bacterium from poultry, a new species, Brevibacterium avium, is proposed. The type strain of Brevibacterium avium is NCIMB 703055T.

Animals↗