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1.
During the latter stages of the lethal H5N2 influenza eradication program in domestic poultry in Pennsylvania in 1983-84, surveillance of waterfowl was done to determine if these birds harbored influenza viruses that might subsequently appear in poultry. From late June to November 1984, 182 hemagglutinating viruses were isolated from 2043 wild birds, primarily ducks, in the same geographical area as the earlier lethal H5N2 avian influenza outbreak. The virus isolates from waterfowl included paramyxoviruses (PMV-1, -4, and -6) and influenza viruses of 13 antigenic combinations. There was only one H5N2 isolate from a duck. Although this virus was antigenically related to the lethal H5N2 virus, genetic and antigenic analysis indicated that it could be discriminated from the virulent family of H5N2 viruses, and it did not originate from chickens. Many of the influenza viruses obtained from wild ducks were capable of replicating in chickens after experimental inoculation but did not cause disease. These studies show that many influenza A virus strains circulating in waterfowl in the vicinity of domestic poultry in Pennsylvania did not originate from domestic poultry. These influenza viruses from wild ducks were capable of infecting poultry; however, transmission of these viruses to poultry apparently was avoided by good husbandry and control measures. 相似文献
2.
Wildlife surveillance associated with an outbreak of lethal H5N2 avian influenza in domestic poultry 总被引：2，自引：0，他引：2
Wildlife surveillance was conducted for influenza viruses in conjunction with the 1983-84 lethal H5N2 avian influenza epizootic in domestic poultry in Pennsylvania, New Jersey, Maryland, and Virginia. Virus-isolation attempts made on cloacal and tracheal swabs from 4,466 birds and small rodents within the quarantined areas and 1,511 waterfowl in nearby Maryland yielded only a single H5N2 isolate from a pen-raised chukar in Pennsylvania. Antibodies against hemagglutinin type 5 and/or neuraminidase type 2 were found in 33% of the aquatic birds tested; however, this finding could not be used to confirm previous H5N2 avian influenza virus activity because of the possibility of prior infections with multiple influenza subtypes. The low prevalence of lethal H5N2 avian influenza virus in wild birds and small rodents strongly indicated that these animals were not responsible for dissemination of the disease among poultry farms during the outbreak. 相似文献
3.
The H5N1 type A influenza viruses classified as Qinghai-like virus (clade 2.2) are a unique lineage of type A influenza viruses with the capacity to produce significant disease and mortality in gallinaceous and anseriform birds, including domestic and wild ducks. The objective of this study was to determine the susceptibility and pathogenesis of chickens and domestic ducks to A/Whooper Swan/Mongolia/224/05 (H5N1) high pathogenicity avian influenza (HPAI) virus when administered through respiratory or alimentary routes of exposure. The chickens and ducks were more susceptible to the H5N1 HPAI virus, as evidenced by low infectious and lethal viral doses, when exposed by intranasal as compared to alimentary routes of inoculation (intragastric or oral-fed infected chicken meat). In the alimentary exposure pathogenesis study, pathologic changes included hemorrhage, necrosis, and inflammation in association with virus detection. These changes were generally observed in most of the visceral organs of chickens, between 2 and 4 days postinoculation (DPI), and are similar to lesions and virus localization seen in birds in natural cases or in experimental studies using the intranasal route. Alimentary exposure to the virus caused systemic infection in the ducks, characterized by moderate lymphocytic encephalitis, necrotized hepatitis, and pancreatitis with a corresponding demonstration of virus within the lesions. In both chickens and ducks with alimentary exposure, lesions, virus, or both were first demonstrated in the upper alimentary tract on 1 DPI, suggesting that the alimentary tract was the initial site affected upon consumption of infected meat or on gavage of virus in liquid medium. However, as demonstrated in the infectivity study in chickens, alimentary infection required higher exposure doses to produce infection as compared to intranasal exposure in chickens. These data suggest that upper respiratory exposure to H5N1 HPAI virus in birds is more likely to result in virus infection and transmission than will consumption of infected meat, unless the latter contains high doses of virus, as found in cannibalized infected carcasses. 相似文献
4.
Runyu Yuan Jin Cui Shuo Zhang Lan Cao Xiaoke Liu Yinfeng Kang Yafen Song Lang Gong Peirong Jiao Ming Liao 《Veterinary microbiology》2014
In this study, we selected three H5N1 highly pathogenic avian influenza viruses (HPAIVs), A/Goose/Guangdong/1/1996 (clades 0), A/Duck/Guangdong/E35/2012 (clade 2.3.2.1) and A/Chicken/Henan/B30/2012 (clade 7.2) isolated from different birds in China, to investigate the pathogenicity and transmission of the viruses in terrestrial birds and waterfowl. To observe the replication and shedding of the H5N1 HPAIVs in birds, the chickens were inoculated intranasally with 106 EID50 of GSGD/1/96, 103 EID50 of DkE35 and CkB30, and the ducks and geese were inoculated intranasally with 106 EID50 of each virus. Meanwhile, the naive contact groups were set up to detect the transmission of the viruses in tested birds. Our results showed that DkE35 was highly pathogenic to chickens and geese, but not fatal to ducks. It could be detected from all the tested organs, oropharyngeal and cloacal swabs, and could transmit to the naive contact birds. GSGD/1/96 could infect chickens, ducks and geese, but only caused death in chickens. It could transmit to the chickens and ducks, but was not transmittable to geese. CkB30 was highly pathogenic to chickens, low pathogenic to ducks and not pathogenic to geese. It could be transmitted to the naive contact chickens, but not to the ducks or geese. Our findings suggested that H5N1 HPAIVs from different birds show different host ranges and tissue tropisms. Therefore, we should enhance serological and virological surveillance of H5N1 HPAIVs, and pay more attention to the pathogenic and antigenic evolution of these viruses. 相似文献
5.
The prototype mildly pathogenic A/chicken/Pennsylvania/21525/83 (H5N2) avian influenza virus, which was isolated more than 5 months before the emergence of highly pathogenic virus in the major 1983 Pennsylvania outbreak, was examined for the presence of minority subpopulations of highly pathogenic virus. Selective serial passage of the parental mildly pathogenic virus in leghorn hens did not lead to recovery of highly pathogenic virus. However, several highly pathogenic reisolates were recovered from hens inoculated with either of two mildly pathogenic virus clones selected for their ability to efficiently produce plaques in trypsin-free chicken embryo fibroblasts. Unlike the parental virus, these reisolates caused high mortality in chickens and produced postmortem lesions typical of highly pathogenic avian influenza. Electrophoretic mobilities of the hemagglutinin glycoproteins of the highly pathogenic derivatives resembled those of the prototype highly pathogenic A/chicken/Pennsylvania/1370/83 (H5N2) virus isolated in October 1983. These results suggest that unrecognized subpopulations of highly pathogenic virus may have infected Pennsylvania chickens for several months before emerging as the clinically manifest component of the virus population. 相似文献
6.
Choi JG Kang HM Kim MC Paek MR Kim HR Kim BS Kwon JH Kim JH Lee YJ 《Veterinary microbiology》2012,155(2-4):147-157
The H3 subtype avian influenza virus (AIV) is one of the most frequently isolated subtypes in domestic ducks, live poultry markets, and wild birds in Korea. In 2002-2009, a total of 45 H3 subtype AIVs were isolated from the feces of clinically normal domestic ducks (n=28) and wild birds (n=17). The most prevalent subtypes in domestic ducks were H3N2 (35.7%), H3N6 (35.7%), H3N8 (25.0%), and H3N1 (3.6%, novel subtype in domestic duck in Korea). In contrast, H3N8 (70.6%) is the most prevalent subtype in wild birds in Korea. In the phylogenetic analysis, HA genes of the Korean H3 AIVs were divided into 3 groups (Korean duck, wild bird 1, and wild bird 2) and all viruses of duck origin except one were clustered in a single group. However, other genes showed extensive diversity and at least 17 genotypes were circulating in domestic ducks in Korea. When the analysis expanded to viruses of wild bird origin, the genetic diversity of Korean H3 AIVs became more complicated. Extensive reassortments may have occurred in H3 subtype influenza viruses in Korea. When we inoculated chickens and ducks with six selected viruses, some of the viruses replicated efficiently without pre-adaptation and shed a significant amount of viruses through oropharyngeal and cloacal routes. This raised concerns that H3 subtype AIV could be a new subtype in chickens in Korea. Continuous surveillance is needed to prepare the advent of a novel subtype AIV in Korea. 相似文献
7.
The effect of calcium stress was studied in an attempt to reproduce lethal infections in laying chickens with A/Chicken/Alabama/75 (H4N8) influenza virus and with two nonpathogenic H5N2 influenza viruses from the 1983-84 outbreak in the eastern United States. Hens were fed calcium-deficient or standard diets for 7 to 14 days; then the calcium-deficient feed was replaced with standard feed supplemented with ad libitum oyster shell, and both groups of hens were inoculated with virus. When hens were infected with the H4N8 virus, respective mortalities of those on the calcium-deficient and standard diets were 19% (27/141) and 5% (7/143). The H5N2 viruses did not kill hens fed either diet. In standard pathogenicity tests, Alabama H4N8 viruses reisolated from the hens that died generally were more lethal for 4-week-old chickens than the stock virus. These results argue for characterization of the Alabama H4N8 virus as pathogenic rather than nonpathogenic as originally determined. 相似文献
8.
Influenza viruses in birds of the Atlantic flyway. 总被引：2，自引：0，他引：2
I L Graves 《Avian diseases》1992,36(1):1-10
Isolation of type A influenza viruses from the feces of 5013 birds of 16 species was attempted during a 33-month study (1977-79). Seventy viruses were isolated from the feces of 3403 ring-billed gulls in Baltimore, Md., during 16 months of sampling. Six hemagglutinin (HA) subtypes and seven neuraminidase (NA) subtypes in 15 combinations were found. The H13N6 virus was the only subtype found each year and accounted for 40% of the isolates. The rate of isolation from gulls was 0.26% in the cold months and 3.0% in the warm months. Hemagglutination-inhibition (HI) and elution-inhibition antibody profiles reflected the presence of some but not all of the viruses isolated. In mute swans, the rates of seroconversions were 16% for HA antibody and 14% for NA antibody, whereas the viral isolation rate was 0.4% over a 3-year period. Both the H5 and the N2 subtypes, which were responsible for the lethal chicken outbreaks in 1983 in Pennsylvania, were isolated from gulls in 1978 in association with subtypes not found in the chicken virus. Also, seroconversions for the H5 HA occurred in mute swans in 1978. 相似文献
9.
The H7N2 subtype of avian influenza virus (AIV) field isolate (H7N2/chicken/PA/3779-2/97), which caused the 1997-98 AIV outbreak in Pennsylvania, was evaluated for its infectivity, length of infection, and immune response in specific-pathogen-free (SPF) chickens. The composite findings of three clinical trials with various concentrations of virus indicated that this H7N2 subtype contained minimal pathogenicity for chickens. The concentration of the virus in the inoculum proved critical in the establishment of a productive infection in a chicken. Seven-day-old SPF chickens were not infected when inoculated with 10(0.7-2.0) mean embryo lethal dose (ELD50) of the H7N2 virus per bird. At this dose level, the immune response to this virus was not detected by the hemagglutination-inhibition (HI) test. Nonetheless, chickens at ages of 5 and 23 wk old tested were successfully infected when exposed to 10(4.7-5.7) ELD50 of H7N2 infectious doses per bird by various routes of administration and also by direct contact. Infected birds started shedding virus as early as 2 days postinoculation, and the period of virus shedding occurred mostly within 1 or 2 wk postinoculation (WPI). This H7N2 subtype of AIV induced a measurable immune response in all birds within 2 wk after virus exposure. Antibody titers were associated with AIV infectious doses and age of exposure of birds. Challenge of these infected birds with the same H7N2 virus at 5 and 10 WPI indicated the infective virus was recoverable from cloacal swabs at 3 days postchallenge and disappeared thereafter. In these challenged birds, the antibody levels as measured by the HI test spiked within 1-2 wk. 相似文献
10.
Ok-Mi Jeong Min-Chul Kim Min-Jeong Kim Hyun-Mi Kang Hye-Ryoung Kim Yong-Joo Kim Seong-Joon Joh Jun-Hun Kwon Youn-Jeong Lee 《Journal of veterinary science (Suw?n-si, Korea)》2009,10(1):53-60
Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype have spread since 2003 in poultry and wild birds in Asia, Europe and Africa. In Korea, the highly pathogenic H5N1 avian influenza outbreaks took place in 2003/2004, 2006/2007 and 2008. As the 2006/2007 isolates differ phylogenetically from the 2003/2004 isolates, we assessed the clinical responses of chickens, ducks and quails to intranasal inoculation of the 2006/2007 index case virus, A/chicken/Korea/IS/06. All the chickens and quails died on 3 days and 3-6 days post-inoculation (DPI), respectively, whilst the ducks only showed signs of mild depression. The uninoculated chickens and quails placed soon after with the inoculated flock died on 5.3 and 7.5 DPI, respectively. Both oropharyngeal and cloacal swabs were taken for all three species during various time intervals after inoculation. It was found that oropharyngeal swabs showed higher viral titers than in cloacal swabs applicable to all three avian species. The chickens and quails shed the virus until they died (up to 3 to 6 days after inoculation, respectively) whilst the ducks shed the virus on 2-4 DPI. The postmortem tissues collected from the chickens and quails on day 3 and days 4-5 and from clinically normal ducks that were euthanized on day 4 contained the virus. However, the ducks had significantly lower viral titers than the chickens or quails. Thus, the three avian species varied significantly in their clinical signs, mortality, tissue virus titers, and duration of virus shedding. Our observations suggest that duck and quail farms should be monitored particularly closely for the presence of HPAIV so that further virus transmission to other avian or mammalian hosts can be prevented. 相似文献
11.
Lu H Dunn PA Wallner-Pendleton EA Henzler DJ Kradel DC Liu J Shaw DP Miller P 《Avian diseases》2004,48(1):26-33
An avian influenza (AI) outbreak occurred in meat-type chickens in central Pennsylvania from December 2001 to January 2002. Two broiler breeder flocks were initially infected almost simultaneously in early December. Avian influenza virus (AIV), H7N2 subtype, was isolated from the two premises in our laboratory. The H7N2 isolates were characterized as a low pathogenic strain at the National Veterinary Services Laboratories based on molecular sequencing of the virus hemagglutinin cleavage site and virus challenge studies in specific-pathogen-free leghorn chickens. However, clinical observations and pathologic findings indicated that this H7N2 virus appeared to be significantly pathogenic in meat-type chickens under field conditions. Follow-up investigation indicated that this H7N2 virus spread rapidly within each flock. Within 7 days of the recognized start of the outbreak, over 90% seroconversion was observed in the birds by the hemagglutination inhibition test. A diagnosis of AI was made within 24 hr of bird submission during this outbreak using a combination of virus detection by a same-day dot-enzyme-linked immunosorbent assay and virus isolation in embryonating chicken eggs. Follow-up investigation revealed that heavy virus shedding (90%-100% of birds shedding AIV) occurred between 4 and 7 days after disease onset, and a few birds (15%) continued to shed virus at 13 days post-disease onset, as detected by virus isolation on tracheal and cloacal swabs. AIV was not detected in or on eggs laid by the breeders during the testing phase of the outbreak. The two flocks were depopulated at 14 days after disease onset, and AIV was not detected on the two premises 23 days after depopulation. 相似文献
12.
Marina A. Gulyaeva Kirill A. Sharshov Anna V. Zaykovskaia Lidia V. Shestopalova Aleksander M. Shestopalov 《Journal of veterinary science (Suw?n-si, Korea)》2016,17(2):179-188
During 2006, H5N1 HPAI caused an epizootic in wild birds, resulting in a die-off of Laridae in the Novosibirsk region at Chany Lake. In the present study, we infected common gulls (Larus canus) with a high dose of the H5N1 HPAI virus isolated from a common gull to determine if severe disease could be induced over the 28 day experimental period. Moderate clinical signs including diarrhea, conjunctivitis, respiratory distress and neurological signs were observed in virus-inoculated birds, and 50% died. The most common microscopic lesions observed were necrosis of the pancreas, mild encephalitis, mild myocarditis, liver parenchymal hemorrhages, lymphocytic hepatitis, parabronchi lumen hemorrhages and interstitial pneumonia. High viral titers were shed from the oropharyngeal route and virus was still detected in one bird at 25 days after infection. In the cloaca, the virus was detected sporadically in lower titers. The virus was transmitted to direct contact gulls. Thus, infected gulls can pose a significant risk of H5N1 HPAIV transmission to other wild migratory waterfowl and pose a risk to more susceptible poultry species. These findings have important implications regarding the mode of transmission and potential risks of H5N1 HPAI spread by gulls. 相似文献
13.
The last highly pathogenic outbreak of avian influenza in the United States was caused by an H5N2 influenza virus in Pennsylvania and New Jersey in 1983-84. Through a combined federal and state eradication effort, the outbreak was controlled. However, in 1986-89, multiple H5N2 viruses were isolated from poultry farms and the live bird markets (LBMs) in the United States. To determine the epidemiologic relationships of these viruses, the complete coding sequence of the nonstructural gene and the hemagglutinin protein subunit 1 of the hemagglutinin gene was determined for 11 H5N2 viruses and compared with previously available influenza sequences. The H5N2 isolates from 1986-89 were all closely related to the isolates from the 1983-84 Pennsylvania outbreak by nucleotide and amino acid sequence analysis for both genes, providing additional evidence that the Pennsylvania/83 (PA/83) virus lineage was not completely eradicated. The PA/83 lineage also had a large number of unique amino acid changes not found in other avian influenza viruses, which was suggestive that this lineage of virus had been circulating in poultry for an extended period of time before the first isolation of virus in 1983. High substitution and evolutionary rates were measured by examining the number of nucleotide or amino acid substitutions over time as compared with the index case, CK/PA/21525/83. These rates, however, were similar to other outbreaks of avian influenza in poultry. This study provides another example of the long-term maintenance and evolution of influenza viruses in the U.S. LBMs and provides further evidence of the connection of the LBMs and the Pennsylvania 1983 H5N2 outbreak. 相似文献
14.
Anna Germundsson Knut I Madslien Monika Jankowska Hjortaas Kjell Handeland Christine Monceyron Jonassen 《Acta veterinaria Scandinavica》2010,52(1):28
The prevalence of influenza A virus infection, and the distribution of different subtypes of the virus, were studied in 1529 ducks and 1213 gulls shot during ordinary hunting from August to December in two consecutive years, 2006 and 2007, in Norway. The study was based on molecular screening of cloacal and tracheal swabs, using a pan-influenza A RT-PCR. Samples found to be positive for influenza A virus were screened for the H5 subtype, using a H5 specific RT-PCR, and, if negative, further subtyped by a RT-PCR for the 3''-part of the hemagglutinin (HA) gene, encompassing almost the entire HA2, and the full-length of the neuraminidase (NA) gene, followed by sequencing and characterization. The highest prevalence (12.8%) of infection was found in dabbling ducks (Eurasian Wigeon, Common Teal and Mallard). Diving ducks (Common Goldeneye, Common Merganser, Red-breasted Merganser, Common Scoter, Common Eider and Tufted Duck) showed a lower prevalence (4.1%). In gulls (Common Gull, Herring Gull, Black-headed Gull, Lesser Black-headed Gull, Great Black-backed Gull and Kittiwake) the prevalence of influenza A virus was 6.1%. The infection prevalence peaked during October for ducks, and October/November for gulls. From the 16 hemagglutinin subtypes known to infect wild birds, 13 were detected in this study. Low pathogenic H5 was found in 17 dabbling ducks and one gull. 相似文献
15.
16.
Siengsanan-Lamont J Robertson I Blacksell SD Ellis T Fenwick S Saengchoowong S Suwanpukdee S Yongyuttawichai P Sariya L Prompiram P Chaichoun K Wiriyarat W Pothieng D Ratanakorn P 《Veterinary microbiology》2011,148(2-4):213-218
A serological and virological surveillance program to investigate the HPAI H5N1 virus in wild bird populations was undertaken from February 2007 to October 2008. The purpose of the survey was to investigate the infection status in free ranging wild birds in Banglane district, Nakhon Pathom province, central Thailand. Samples from wild birds were collected every two months. Choanal and cloacal swabs, serum and tissue samples were collected from 421 birds comprising 44 species. Sero-prevalence of the virus tested by H5N1 serum neutralization test (using a H5N1 virus clade 1; A/chicken/Thailand/vsmu-3-BKK/2004) was 2.1% (8 out of 385 samples; 95% CI 0.7, 3.5). Species that were antibody positive included rock pigeons (Columba livia), Asian pied starling (Gracupica contra), spotted dove (Streptopelia chinensis), oriental magpie robin (Copsychus saularis), blue-tailed bee-eater (Merops philippinus), myna (Acridotheres spp.), and pond heron (Ardeola spp.). Prevalence by H5N1 virus isolation was 0.5% (2 out of 421 samples; 95% CI 0.0, 1.1); the two H5N1 virus-positive samples were from Asian pied starling (Gracupica contra) and white vented myna (Acridotheres grandis). Positive virological samples were collected in June 2007 while all positive serology samples were collected between May and August except for one sample collected in December 2007. No positive samples were collected in 2008. Molecular studies revealed that the wild bird H5N1 viruses were closely related to poultry viruses isolated in other parts of Thailand. However, there was no poultry H5N1 prevalence study performed in the study site during the time of this wild bird survey. Interpretation of source of virus isolates would include spill-over of H5N1 viruses from contaminated sources due to movement of domestic poultry and/or fomites from other areas; or infection of wild birds within the outbreak locations and then translocation by wild bird movement and interaction with wild birds inhabiting distant locations. 相似文献
17.
In this study, two highly pathogenic avian influenza (HPAI) H5N8 viruses were isolated from chicken and geese in 2018 and 2019 (Chicken/ME-2018 and Geese/Egypt/MG4/2019). The hemagglutinin and neuraminidase gene analyses revealed their close relatedness to the clade-2.3.4.4b H5N8 viruses isolated from Egypt and Eurasian countries. A monovalent inactivated oil-emulsion vaccine containing a reassortant virus with HA gene of the Chicken/ME-2018/H5N8 strain and a bivalent vaccine containing same reassortant virus plus a previously generated reassortant H5N1 strain (CK/Eg/RG-173CAL/17). The safety of both vaccines was evaluated in specific-pathogen-free (SPF) chickens. To evaluate the efficacy of the prepared vaccines, 2-week-old SPF chickens were vaccinated with 0.5 mL of a vaccine formula containing 108/EID50 /dose from each strain via the subcutaneous route. Vaccinated birds were challenged with either wild-type HPAI-H5N8 or H5N1 viruses separately at 3 weeks post-vaccine. Results revealed that both vaccines induced protective hemagglutination-inhibiting (HI) antibody titers as early as 2 weeks PV (≥5.0 log2). Vaccinated birds were protected clinically against both subtypes (100 % protection). HPAI-H5N1 virus shedding was significantly reduced in birds that were vaccinated with the bivalent vaccine; meanwhile, HPAI-H5N8 virus shedding was completely neutralized in both tracheal and cloacal swabs after 3 days post-infection in birds that had been vaccinated with either vaccine. In conclusion, the developed bivalent vaccine proved to be efficient in protecting chickens clinically and reduced virus shedding via the respiratory and digestive tracts. The applicability of the multivalent avian influenza vaccines further supported their value to facilitate vaccination programs in endemic countries. 相似文献
18.
An influenza virus (H7N7) isolated from an outbreak of disease in chickens in Victoria, was examined for its ability to cause disease in inoculated chickens, turkeys and ducks. The virus was highly pathogenic in chickens and turkeys but produced no clinical disease in ducks. Transmission of infection occurred from inoculated chickens to those in direct contact but other chickens separated by a distance of 3m directly downwind developed neither clinical disease nor antibody to the virus. 相似文献
19.
Thomas J. DELIBERTO Seth R. SWAFFORD Dale L. NOLTE Kerri PEDERSEN Mark W. LUTMAN Brandon B. SCHMIT John A. BAROCH Dennis J. KOHLER Alan FRANKLIN 《Integrative zoology》2009,4(4):426-439
As part of the USA's National Strategy for Pandemic Influenza, an Interagency Strategic Plan for the Early Detection of Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds was developed and implemented. From 1 April 2006 through 31 March 2009, 261 946 samples from wild birds and 101 457 wild bird fecal samples were collected in the USA; no highly pathogenic avian influenza was detected. The United States Department of Agriculture, and state and tribal cooperators accounted for 213 115 (81%) of the wild bird samples collected; 31, 27, 21 and 21% of the samples were collected from the Atlantic, Pacific, Central and Mississippi flyways, respectively. More than 250 species of wild birds in all 50 states were sampled. The majority of wild birds (86%) were dabbling ducks, geese, swans and shorebirds. The apparent prevalence of low pathogenic avian influenza viruses during biological years 2007 and 2008 was 9.7 and 11.0%, respectively. The apparent prevalence of H5 and H7 subtypes across all species sampled were 0.5 and 0.06%, respectively. The pooled fecal samples (n= 101 539) positive for low pathogenic avian influenza were 4.0, 6.7 and 4.7% for biological years 2006, 2007 and 2008, respectively. The highly pathogenic early detection system for wild birds developed and implemented in the USA represents the largest coordinated wildlife disease surveillance system ever conducted. This effort provided evidence that wild birds in the USA were free of highly pathogenic avian influenza virus (given the expected minimum prevalence of 0.001%) at the 99.9% confidence level during the surveillance period. 相似文献
20.
Davison S Galligan D Eckert TE Ziegler AF Eckroade RJ 《Journal of the American Veterinary Medical Association》1999,214(8):1164-1167
OBJECTIVE: To determine economic losses associated with an outbreak of avian influenza in flocks in Pennsylvania during 1997 and 1998. SAMPLE POPULATION: 5 premises containing avian influenza-infected layer, pullet, and turkey flocks. PROCEDURE: Losses incurred before depopulation, those incurred at the time of depopulation, and those that were attributable to depopulation (unrealized loss of income) were evaluated. Results were extrapolated to provide values for all infected flocks. RESULTS: Extrapolating the costs determined on the basis of age and number of birds from the 5 sample flocks to all other flocks infected with nonpathogenic avian influenza H7N2 yielded an estimated total cost to the Pennsylvania poultry industry of $3.5 million. CLINICAL IMPLICATIONS: The H7N2 virus is not highly pathogenic. If the pathogenicity of the virus does not change, then the poultry industry and state and federal governments will not have severe economic losses for the 1997-1998 outbreak similar to those for the 1983-1984 avian influenza outbreak in Pennsylvania. To decrease the potential for financial losses that could result from future outbreaks of avian influenza, it is essential that the commercial industry and livebird market system be separated via increased use of biosecurity measures. 相似文献