Pandemic threat posed by avian influenza A viruses.
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Influenza pandemics, defined as global outbreaks of the disease due to viruses with new antigenic subtypes, have exacted high death tolls from human populations. The last two pandemics were caused by hybrid viruses, or reassortants, that harbored a combination of avian and human viral genes. Avian influenza viruses are therefore key contributors to the emergence of human influenza pandemics. In 1997, an H5N1 influenza virus was directly transmitted from birds in live poultry markets in Hong Kong to humans. Eighteen people were infected in this outbreak, six of whom died. This avian virus exhibited high virulence in both avian and mammalian species, causing systemic infection in both chickens and mice. Subsequently, another avian virus with the H9N2 subtype was directly transmitted from birds to humans in Hong Kong. Interestingly, the genes encoding the internal proteins of the H9N2 virus are genetically highly related to those of the H5N1 virus, suggesting a unique property of these gene products. The identification of avian viruses in humans underscores the potential of these and similar strains to produce devastating influenza outbreaks in major population centers. Although highly pathogenic avian influenza viruses had been identified before the 1997 outbreak in Hong Kong, their devastating effects had been confined to poultry. With the Hong Kong outbreak, it became clear that the virulence potential of these viruses extended to humans. (+info)
Fowlpox virus encodes a novel DNA repair enzyme, CPD-photolyase, that restores infectivity of UV light-damaged virus.
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Fowlpox virus (FPV), a pathogen of poultry, can persist in desiccated scabs shed from infected hosts. Although the mechanisms which ensure virus survival are unknown, it is likely that some type of remedial action against environmentally induced damage is required. In this regard, we have identified an open reading frame (ORF) coding for a putative class II cyclobutane pyrimidine dimer (CPD)-photolyase in the genome of FPV. This enzyme repairs the UV light-induced formation of CPDs in DNA by using blue light as an energy source and thus could enhance the viability of FPV during its exposure to sunlight. Based on transcriptional analyses, the photolyase gene was found to be expressed late during the FPV replicative cycle. That the resultant protein retained DNA repair activity was demonstrated by the ability of the corresponding FPV ORF to complement functionally a photolyase-deficient Escherichia coli strain. Interestingly, insertional inactivation of the FPV photolyase gene did not impair the replication of such a genetically altered virus in cultured cells. However, greater sensitivity of this mutant than of the parental virus to UV light irradiation was evident when both were subsequently photoreactivated in the absence of host participation. Therefore, FPV appears to incorporate its photolyase into mature virions where the enzyme can promote their survival in the environment. Although expression of a homologous protein has been predicted for some chordopoxviruses, this report is the first to demonstrate that a poxvirus can utilize light to repair damage to its genome. (+info)
Characterization of H5N2 influenza viruses from Italian poultry.
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From October 1997 to January 1998, highly pathogenic H5N2 avian influenza viruses caused eight outbreaks of avian influenza in northern Italy. A nonpathogenic H5N9 influenza virus was also isolated during the outbreaks as a result of virological and epidemiological surveillance to control the spread of avian influenza to neighbouring regions. Antigenic analysis showed that the Italian H5N2 isolates were antigenically similar to, although distinguishable from, A/HK/156/97, a human influenza H5N1 virus isolated in Hong Kong in 1997. Phylogenetic analysis of the haemagglutinin (HA) genes showed that the highly pathogenic Italian viruses clustered with the Hong Kong strains, whereas the nonpathogenic H5N9 virus, despite its epidemiological association with the highly pathogenic Italian isolates, was most closely related to the highly pathogenic A/Turkey/England/91 (H5N1) strain. Like the HA phylogenetic tree, the nonstructural (NS) phylogenetic tree showed that the H5N2 Italian virus genes are clearly separate from those of the H5N9 strain. In contrast, results of the phylogenetic analysis of nucleoprotein (NP) genes indicated a closer genetic relationship between the two Italian virus groups, a finding suggesting a common progenitor. Comparison of the HA, NS and NP genes of the Italian H5 strains with those of the H5N1 viruses simultaneously circulating in Hong Kong revealed that the two groups of viruses do not share a recent common ancestor. No virological and serological evidence of bird-to-human transmission of the Italian H5N2 influenza viruses was found. (+info)
Sporadic Campylobacter jejuni infections in Hawaii: associations with prior antibiotic use and commercially prepared chicken.
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Campylobacter is the most common cause of bacterial foodborne illness in the United States, and Hawaii has the highest rate of Campylobacter jejuni infections in the nation. A case-control study was conducted to determine indigenous exposures that contribute to the high incidence of sporadic C. jejuni infection in Hawaii. A total of 211 case patients with diarrhea and confirmed Campylobacter infection was enrolled, along with 1 age- and telephone exchange-matched control subject for each patient. Participants were interviewed about illness, medicines, food consumption, food-handling practices, and exposure to animals. In matched logistic regression analyses, eating chicken prepared by a commercial food establishment in the 7 days before case illness onset (adjusted odds ratio [AOR], 1.8; P=.03) and consuming antibiotics during the 28 days before illness onset (AOR, 3.3; P=.03) were significant independent predictors of illness. Further study of the association of Campylobacter illness with commercially prepared chicken and prior antibiotic use is needed. (+info)
H9N2 influenza A viruses from poultry in Asia have human virus-like receptor specificity.
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H9N2 influenza A viruses are currently widespread in chickens, quail, and other poultry in Asia and have caused a few cases of influenza in humans. In this study, we found that H9N2 viruses from Hong Kong live bird markets have receptor specificity similar to that of human H3N2 viruses. In addition, the neuraminidase of poultry H9N2 viruses has mutations in its hemadsorbing site, a characteristic resembling that of human H2N2 and H3N2 viruses but differing from that of other avian viruses. Peculiar features of surface glycoproteins of H9N2 viruses from Hong Kong suggest an enhanced propensity for introduction into humans and emphasize the importance of poultry in the zoonotic transmission of influenza viruses. (+info)
Genotypic analysis of Escherichia coli strains from poultry carcasses and their susceptibilities to antimicrobial agents.
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Plasmid profiling and amplified fragment length polymorphism (AFLP) analysis were used to genotype 50 Escherichia coli strains from poultry carcasses. Thirty different plasmid profiles were evident, and clustering of the AFLP data showed that they were a distinctly heterogeneous group of strains. Susceptibility testing against five antimicrobial agents used in the South African poultry industry showed all strains to be susceptible to danofloxacin and colistin, while the majority (96%) were resistant to two tetracyclines. (+info)
Factors influencing consumer demand for U.S. pork exported to the Republic of Korea (South Korea).
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The potential market for single-ribbed bellies and Boston butts in South Korea was characterized and quantitative selection criteria were identified for use by U.S. packers when selecting pork for export. South Korean retail meat market managers and traders/wholesalers in Seoul and Pusan were interviewed and asked to identify the quality attributes that are considered when making pork-purchasing decisions. In addition, pork labeling characteristics and meat display case measurements and space allocations were recorded in each retail store. Data from box labels were recorded in retail storage coolers to characterize pork products currently being merchandized in South Korea. Sample retail packages of belly and butt slices were collected and sent to a commercial laboratory for analysis of iodine values, ether-extractable fat content, total aerobic plate count (APC), total coliform count (TCC), and generic Escherichia coli count (ECC). No quality attributes of U.S. products exceeded the expectations of retailers. Quality attributes of U.S. pork products that exceeded the expectations of traders included presence of foreign material, marbling, tenderness, juiciness, flavor, and overall eating satisfaction. Traders/wholesalers assigned negative ratings for overall workmanship and adherence to purchase criteria for U.S. pork products. Retail APC for South Korean belly samples were higher (P < 0.05) than APC for U.S. belly samples. Retail TCC and ECC for butts and belly samples and APC for butt samples did not differ by country of origin. Retail prices for South Korean bellies were higher (P < 0.05) than prices for retail U.S. and Danish bellies. Pork butt prices did not differ (P > 0.05) by country of origin. Beef, pork, and poultry products comprised 66.8, 27.8, and 5.4%, respectively, of the total meat display case frontage. U.S. beef products occupied, on average, 18% of the total beef display area, whereas U.S. pork products comprised 2.6% of the total pork display case area. (+info)
Exposure assessment and lung function in pig and poultry farmers.
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OBJECTIVES: To describe the relation between spirometric findings and farming characteristics and variables of exposure to organic dust measured during work in animal buildings. Farmers have traditionally been described as having one of the most dangerous occupations, so a large scale study on European farmers was carried out. This is the report of the second part of that study. METHODS: 40 pig farmers in Denmark and 36 poultry farmers in Switzerland were chosen randomly and were assessed over 1 working day. RESULTS: Mean (SD) baseline spirometric results in pig farmers were higher than in poultry farmers (forced expiratory volume in 1 second (FEV(1)) (% of reference value) 108.3 (16.7) v 100.2 (14.2); p=0.04). Baseline lung function results were significantly associated with ventilation of the animal houses. Furthermore, temperature was related to spirometric findings in pig farmers. CONCLUSIONS: Ventilation of the animal house and temperature might influence respiratory morbidity in farmers. (+info)