上海地区野鸟中伯氏疏螺旋体和西尼罗病毒感染的血清学调查

于2005年从飞抵上海的12种候鸟和4种留鸟中采集208份血清样品,采用酶联荧光测定(ELFA)法和酶联免疫吸附试验(ELISA),分别对伯氏疏螺旋体和西尼罗病毒的感染状况进行了血清抗体调查,结果受检野鸟样品的检测结果均为阴性。     

Pathogenicity of two recent Western Mediterranean West Nile virus isolates in a wild bird species indigenous to Southern Europe: the red-legged partridge

ABSTRACT: West Nile virus (WNV) is an emerging zoonotic pathogen whose geographic spread and incidence in humans, horses and birds has increased significantly in recent years. WNV has long been considered a mild pathogen causing self-limiting outbreaks. This notion has changed as WNV is causing large epidemics with a high impact on human and animal health. This has been particularly noteworthy since its introduction into North America in 1999. There, native bird species have been shown to be highly susceptible to WNV infection and disease with high mortalities. For this reason, the effect of WNV infection in North American bird species has been thoroughly studied by means of experimental inoculations in controlled trials. To a lesser extent, European wild birds have been shown to be affected clinically by WNV infection. Yet experimental studies on European wild bird species are lacking. The red-legged partridge (Alectoris rufa) is a gallinaceous bird indigenous to the Iberian Peninsula, widely distributed in South Western Europe. It plays a key role in the Mediterranean ecosystem and constitutes an economically important game species. As such it is raised intensively in outdoor facilities. In this work, red-legged partridges were experimentally infected with two recent WNV isolates from the Western Mediterranean area: Morocco/2003 and Spain/2007. All inoculated birds became viremic and showed clinical disease, with mortality rates of 70% and 30%, respectively. These results show that Western Mediterranean WNV variants can be pathogenic for some European bird species, such as the red-legged partridge.     

野鸟传播的重要传染病研究进展

野鸟在迁徙和飞行过程中,因能携带和散播多种病原体,在公共卫生学方面具有重要的意义.通过野鸟能潜在性传播人和动物的重要传染病,包括禽类疫病(禽流感、新城疫、禽痘、禽肺病毒感染、禽分支杆菌感染和鸭瘟)和其他重要疫病(口蹄疫、衣原体病、日本脑炎、莱姆病、西尼罗病毒感染、博尔纳病、Q热、东方马脑炎及致病菌感染),由此应对野鸟传播的疫病予以必要的重视和警惕,并提出有效的防范措施.     

Evidence of West Nile virus seropositivity in wild birds on the island of Cyprus

West Nile Virus (WNV)¹ is an emerging pathogen in Cyprus, with the first human case of infection reported in 2016, and another documented in 2018. A cluster of cases in humans was then reported in 2019. However, little is known regarding which avian species might bring WNV to Cyprus. Here, we investigated seroprevalence of WNV antibodies in migratory and resident birds, captured across Cyprus to assess to what extent human populations might be exposed to WNV. We used Enzyme-Linked Immunosorbent Assay (ELISA)² to test for the presence of WNV antibodies in 836 avian blood samples of 44 species captured between 2015 and 2020. A seropositivity rate of 1.3 % was found. The majority of seropositive wild birds belonged to the migratory species Sylvia atricapilla, a common and widespread migrant, implying a high risk of WNV being introduced throughout Cyprus.     

Pathogenesis of West Nile virus lineage 1 and 2 in experimentally infected large falcons

West Nile virus (WNV) is a zoonotic flavivirus that is transmitted by blood-suckling mosquitoes with birds serving as the primary vertebrate reservoir hosts (enzootic cycle). Some bird species like ravens, raptors and jays are highly susceptible and develop deadly encephalitis while others are infected subclinically only. Birds of prey are highly susceptible and show substantial mortality rates following infection. To investigate the WNV pathogenesis in falcons we inoculated twelve large falcons, 6 birds per group, subcutaneously with viruses belonging to two different lineages (lineage 1 strain NY 99 and lineage 2 strain Austria). Three different infection doses were utilized: low (approx. 500 TCID50), intermediate (approx. 4 log10 TCID50) and high (approx. 6 log10 TCID50). Clinical signs were monitored during the course of the experiments lasting 14 and 21 days. All falcons developed viremia for two weeks and shed virus for almost the same period of time. Using quantitative real-time RT-PCR WNV was detected in blood, in cloacal and oropharyngeal swabs and following euthanasia and necropsy of the animals in a variety of neuronal and extraneuronal organs. Antibodies to WNV were first time detected by ELISA and neutralization assay after 6 days post infection (dpi). Pathological findings consistently included splenomegaly, non-suppurative myocarditis, meningoencephalitis and vasculitis. By immunohistochemistry WNV-antigens were demonstrated intralesionally. These results impressively illustrate the devastating and possibly deadly effects of WNV infection in falcons, independent of the genetic lineage and dose of the challenge virus used. Due to the relatively high virus load and long duration of viremia falcons may also be considered competent WNV amplifying hosts, and thus may play a role in the transmission cycle of this zoonotic virus.     

Salmonella enterica subspecies enterica serotype Typhimurium and Escherichia coli O86 in wild birds at two garden sites in south-west Scotland

Salmonella enterica subspecies enterica serotype Typhimurium and Escherchia coli O86:K61:NM are two bacteria that can cause outbreaks of mortality in garden birds visiting bird tables and other feeding stations. Two sites in south-west Scotland were monitored for the two organisms for 12 months. At site A, large numbers of birds fed throughout the year, and at site B smaller numbers of birds fed only in the winter months. Samples of composite faeces were collected from the feeding stations and screened for the organisms, and any dead birds were also screened. S Typhimurium definitive type (DT) 56 (variant) was found to be endemic at site A, and was recovered from 48 per cent of samples of composite faeces collected from the bird table, from 42 per cent of composite faeces from underneath a hanging feeder, and from 33 per cent of composite faeces from below a roost used by house sparrows; the organism was also isolated from the carcases of six wild birds found dead at the site. In contrast, S Typhimurium (DT41) was recovered only once at site B, from 2 per cent of the composite faeces from below a hanging feeder, and no dead birds were recovered from the site. E coli O86 was not recovered from the faeces collected from either site, but was isolated from a bird that died from trauma at site A.     

West Nile virus--causative agent of a zoonosis with increasing significance?

The epidemic West Nile Virus (WNV) infections observed in the last years, particularly those in the USA in 1999 and the following years, have led to an increasing interest in this zoonotic infection. Here, the most prominent aspects of WNV biology and epidemiology are presented. Clinical signs observed in men and horses are described, as well as the current state of diagnostics and immunoprophylaxis. Preliminary results of investigations on the prevalence of WNV in Germany show that migrating birds have been in contact with WNV; there is however no indication for the presence of this virus. While WNV is endemic in many parts of the "Old World", thus inducing "natural immunity" in (migrating) birds and vertebrates, a susceptible bird population with no existing immunity against this virus was exposed in the "New World".     

Serological evidence of West Nile virus infection in human populations and domestic birds in the Northwest of Morocco

West Nile virus (WNV) was recently detected in Culex pipiens mosquitoes in Morocco. The aim of this study was to evaluate the seroprevalence of WNV in humans and in domestic birds in two regions of Morocco by the detection of IgG antibodies. Blood samples were obtained from 91 human patients and 92 domestic birds from September to December 2019. All study samples were tested using competitive enzyme-linked immunosorbent assay (cELISA) and WNV neutralization tests (VNT) were performed on positive sera. Of all samples, 4 (4.39 %) humans and 4 (4.34 %) birds were found to be seropositive for flaviviruses by the cELISA test. The VNT revealed that three of the four human samples detected positive by cELISA contained neutralizing antibodies against WNV. Two bird samples were confirmed positive by VNT. These results show a significant seroprevalence of anti-WNV antibodies and therefore suggest the active circulation and exposure of human and bird populations in the northwest of Morocco.     

Prevalence of Salmonella spp in selected birds captured on California dairies

OBJECTIVE: To determine the prevalence of Salmonella spp in wild birds commonly found on California dairies. DESIGN: Prospective study. ANIMALS: 7 selected species of birds were captured on 9 dairies in Kings and Tulare counties, California. PROCEDURE: Birds were captured (using traps and nets) and euthanatized, and the entire gastrointestinal tract was removed. Contents of the gastrointestinal tract were subjected to culture for Salmonella spp. RESULTS: 892 birds were captured, and Salmonella spp were isolated from 22 birds. The prevalence by dairy ranged from 0.7 to 16.7%, whereas the prevalence by bird species ranged from 1.2 to 3.2%. Cowbirds and English sparrows had the highest prevalence of Salmonella organisms. Five serotypes of Salmonella organisms were isolated, including Meleagridis, Montevideo, Muenster, Typhimurium, and an untyped serotype. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of our findings, birds that commonly inhabit California dairies harbor Salmonella organisms. However, because of the low prevalence of Salmonella organisms in birds and the Salmonella serotypes isolated, birds are not important reservoirs of Salmonella organisms on California dairies.     

Cytokine gene expression in chicken cecal tonsils following treatment with probiotics and Salmonella infection

Probiotics are currently employed for control of pathogens and enhancement of immune response in chickens. In this study, we investigated the underlying immunological mechanisms of the action of probiotics against colonization of the chicken intestine by Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella serovar Typhimurium). Birds received probiotics by oral gavage on day 1 of age and, subsequently, received Salmonella serovar Typhimurium on day 2 of age. Cecal tonsils were removed on days 1, 3 and 5 post-infection (p.i.), RNA was extracted and subjected to real-time quantitative RT-PCR for measurement of interleukin (IL)-6, IL-10, IL-12 and interferon (IFN)-gamma gene expression. There was no significant difference in IL-6 and IL-10 gene expression in cecal tonsils of chickens belonging to various treatment groups. Salmonella serovar Typhimurium infection resulted in a significant increase in IL-12 expression in cecal tonsils on days 1 and 5p.i. However, when chickens were treated with probiotics prior to experimental infection with Salmonella, the level of IL-12 expression was similar to that observed in uninfected control chickens. Treatment of birds with probiotics resulted in a significant decrease in IFN-gamma gene expression in cecal tonsils of chickens infected with Salmonella compared to the Salmonella-infected birds not treated with probiotics. These findings reveal that repression of IL-12 and IFN-gamma expression is associated with probiotic-mediated reduction in intestinal colonization with Salmonella serovar Typhimurium.     

The effect of exogenous corticosterone on West Nile virus infection in Northern Cardinals (Cardinalis cardinalis)

ABSTRACT: The relationship between stress and disease is thought to be unambiguous: chronic stress induces immunosuppression, which likely increases the risk of infection. However, this link has not been firmly established in wild animals, particularly whether stress hormones affect host responses to zoonotic pathogens, which can be transmitted to domesticated animal, wildlife and human populations. Due to the dynamic effects of stress hormones on immune functions, stress hormones may make hosts better or poorer amplifying hosts for a pathogen contingent on context and the host species evaluated. Using an important zoonotic pathogen, West Nile virus (WNV) and a competent host, the Northern Cardinal (Cardinalis cardinalis), we tested the effects of exogenous corticosterone on response to WNV infection. Corticosterone was administered at levels that individuals enduring chronic stressors (i.e., long-term inclement weather, food shortage, anthropogenic pollution) might experience in the wild. Corticosterone greatly impacted mortality: half of the corticosterone-implanted cardinals died between five - 11 days post-inoculation whereas only one of nine empty-implanted (control) birds died. No differences were found in viral titer between corticosterone- and empty-implanted birds. However, cardinals that survived infections had significantly higher average body temperatures during peak infection than individuals that died. In sum, this study indicates that elevated corticosterone could affect the survival of WNV-infected wild birds, suggesting that populations may be disproportionately at-risk to disease in stressful environments.     

Pathology and tissue tropism of natural West Nile virus infection in birds: a review

West Nile virus (WNV) is a globally distributed arthropod-borne flavivirus capable of infecting a wide variety of vertebrates, with birds as its natural reservoir. Although it had been considered a pathogen of little importance for birds, from the 1990’s, and especially after its introduction in the North American continent in 1999, thousands of birds have succumbed to West Nile infection. This review summarizes the pathogenesis and pathology of WNV infection in birds highlighting differences in lesion and antigen distribution and severity among bird orders and families. Despite significant species differences in susceptibility to infection, WNV associated lesions and viral antigen are present in the majority of organs of infected birds. The non-progressive, acute or more prolonged course of the disease accounts for part of the differences in lesion and viral antigen distribution and lesion severity. Most likely a combination of host variables and environmental factors in addition to the intrinsic virulence and pathogenicity of the infecting WNV strain influence the pathogenesis of the infection.     

Simulation of the seasonal cycles of bird, equine and human West Nile virus cases

The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health states for each of the 3 host species. It is the first WNV model that simulates the seasonal cycle by explicitly considering the environmental temperature. The latter determines model parameters responsible for the population dynamics of the mosquitoes and the extrinsic incubation period. Once initialized, our WNV model runs for the entire period 2002-2009, exclusively forced by environmental temperature. Simulated incidences are mainly determined by host and vector population dynamics, virus transmission and herd immunity, respectively. We adjusted our WNV model to fit monthly totals of reported bird, equine and human cases in the Minneapolis metropolitan area. From this process we estimated that the proportion of actually WNV-induced dead birds reported by the Centers for Disease Control and Prevention is about 0.8%, whereas 7.3% of equine and 10.7% of human cases were reported. This is consistent with referenced expert opinions whereby about 10% of equine and human cases are symptomatic (the other 90% of asymptomatic cases are usually not reported). Despite the restricted completeness of surveillance data and field observations, all major peaks in the observed time series were caught by the simulations. Correlation coefficients between observed and simulated time series were R=0.75 for dead birds, R=0.96 for symptomatic equine cases and R=0.86 for human neuroinvasive cases, respectively.     

Experimental infection of house sparrows (Passer domesticus) with West Nile virus isolates of Euro-Mediterranean and North American origins

West Nile virus (WNV) is a zoonotic arboviral pathogen transmitted by mosquitoes in a cycle involving wild birds as reservoir hosts. The virus has recently emerged in North America and re-emerged in Europe. North American WNV outbreaks are often accompanied by high mortality in wild birds, a feature that is uncommon in Europe. The reason for this difference is unknown, but the intrinsic virulence of the viruses circulating in each continent and/or the susceptibility to the disease of Palearctic as opposed to Nearctic wild bird species could play a role. To assess this question, experimental inoculations with four lineage 1 WNV strains, three from southern Europe (Italy/2008, Italy/2009 and Spain/2007) and one from North America (NY99) were performed on house sparrows (Passer domesticus), a wild passerine common in both continents. Non-significant differences which ranged from 0% to 25% were observed in mortality for the different WNV strains. Viremias lasted from 1 to 5–6 days post-inoculation (dpi) in all cases; individuals inoculated with NY99 had significantly higher titres than those inoculated with any of the Euro-Mediterranean strains. Remarkably, host competence was found to be higher for NY99 than for the other strains. Consequently, albeit being pathogenic for house sparrows, some Euro-Mediterranean strains had reduced capacity for replication in -and transmission from- this host, as compared to the NY99 strain. If applicable also to other wild bird host species, this relatively reduced transmission capacity of the Euro-Mediterranean strains could explain the lower incidence of this disease in wild birds in the Euro-Mediterranean area.     

Early immune dynamics following infection with Salmonella enterica serovars Enteritidis, Infantis, Pullorum and Gallinarum: cytokine and chemokine gene expression profile and cellular changes of chicken cecal tonsils

Salmonella enterica subspecies enterica infection remains a serious problem in a wide range of animals and in man. Poultry-derived food is the main source of human infection with the non-host-adapted serovars while fowl typhoid and pullorum disease are important diseases of poultry. We have assessed cecal colonization and immune responses of newly hatched and older chickens to Salmonella serotypes Enteritidis, Infantis, Gallinarum and Pullorum. S. Enteritidis and S. Infantis colonized the ceca more efficiently than S. Gallinarum and S. Pullorum. Salmonella infection was also associated with increased staining for B-lymphocytes and macrophages in the cecal tonsils of infected birds. S. Enteritidis infection in newly hatched birds stimulated the expression of CXCLi1 and CXCLi2 chemokines in the cecal tonsils, while S. Gallinarum up-regulated the expression of LITAF. In older chickens, S. Enteritidis infection resulted in a significantly higher expression of CXCLi2, iNOS, LITAF and IL-10 while S. Pullorum appeared to down-regulate CXCLi1 expression in the cecal tonsils. Data from spleens showed either no expression or down-regulation of the tested genes.     

Serosurveillance for Japanese encephalitis virus in wild birds captured in Korea

Climate change induced by recent global warming may have a significant impact on vector-borne and zoonotic diseases. For example, the distribution of Japanese encephalitis virus (JEV) has expanded into new regions. We surveyed the levels of hemagglutination-inhibition (HI) antibodies against JEV (Family Flaviviridae, genus Flavivirus) in wild birds captured in Korea. Blood samples were collected from 1,316 wild birds including the following migratory birds: Oceanodroma castro (n = 4), Anas formosa (n = 7), Anas penelope (n = 20), Fulica atra (n = 30), Anas acuta (n = 89), Anas crecca (n = 154), Anas platyrhynchos (n = 214), Aix galericulata (n = 310), and Anas poecilorhyncha (n = 488). All were captured in 16 locations in several Korea provinces between April 2007 and December 2009. Out of the 1,316 serum samples tested, 1,141 (86.7%) were positive for JEV. Wild birds captured in 2009 had a higher seroprevalence of ant-JEV antibodies than those captured in 2007. Wild birds with an HI antibody titer of 1 : 1,280 or higher accounted for 21.2% (280/1,316) of the animals tested. These findings indicated that wild birds from the region examined in our study have been exposed to JEV and may pose a high risk for introducing a new JEV genotype into Korea.     

Ecological Surveillance for West Nile in Catalonia (Spain), Learning from a Five‐Year Period of Follow‐up

To enhance early detection of West Nile virus (WNV) transmission, an integrated ecological surveillance system was implemented in Catalonia (north‐eastern Spain) from 2007 to 2011. This system incorporated passive and active equine surveillance, periodical testing of chicken sentinels in wetland areas, serosurveillance wild birds and testing of adult mosquitoes. Samples from 298 equines, 100 sentinel chickens, 1086 wild birds and 39 599 mosquitoes were analysed. During these 5 years, no acute WNV infection was detected in humans or domestic animal populations in Catalonia. WNV was not detected in mosquitoes either. Nevertheless, several seroconversions in resident and migrant wild birds indicate that local WNV or other closely related flaviviruses transmission was occurring among bird populations. These data indicate that bird and mosquito surveillance can detect otherwise silent transmission of flaviviruses and give some insights regarding possible avian hosts and vectors in a European setting.     

A virological survey in migrating waders and other waterfowl in one of the most important resting sites of Germany

Wild birds are considered a potential reservoir or a carrier of viral diseases and may therefore play a role in the epidemiology of economically important or zoonotic diseases. In 2001 and 2002, a survey with special emphasis on virus isolation in migrating waders and some other birds were conducted. In one of the most important inland resting sites for migratory waterfowl, tracheal and cloacal swabs were collected from 465 waders representing 19 different species, and 165 other birds that were not captured on purpose. A total of 42 avian viruses were isolated, 34 of these were identified as paramyxoviruses (PMVs). The majority of isolates came from waders and wild ducks, and were characterized as PMV-1. In contrast, PMV-4 was found in wild ducks only, PMV-6 was mainly detected in wader species. Four avian influenza viruses (AIVs), belonging to H4 and H3 haemagglutinin subtype, were isolated from wild duck species. Furthermore, four reo-like viruses were isolated from one particular wader species for the first time. The majority of virus positive birds were <1 year old and did not show any clinical symptoms. There was no evidence for the presence of West Nile virus in these birds. These results confirm that the restricted resting sites in Western Europe must be considered as important locations for the intra- and interspecies transmission of avian viruses.     

Protection of laying hens against Salmonella Enteritidis by immunization with type 1 fimbriae

Eighteen chickens were immunized subcutaneously with purified type 1 fimbriae from Salmonella enterica serotype Enteritidis at 18 and 21 weeks of age. Evidence of IgG and IgA responses was found in the eggs and in the sera of the immunized hens. Three weeks later, immunized and non-immunized chickens (n=18) were challenged intravenously with 2x10(7) live Salmonella enterica serotype Enteritidis. There was no significant difference in the numbers of eggs laid by immunized and non-immunized birds. The percentage of Salmonella contaminated eggs was significantly higher in the non-immunized group than in the immunized group due to a higher percentage of contamination of the externally disinfected egg shells. There were no statistical differences in the percentages of contaminated yolks and egg whites between control and immunized birds. No differences in the number of colonizing bacteria could be found in the spleen nor in the liver between the immunized and the control groups throughout the experiment. Salmonella was cleared from the ovary of the immunized birds in the second week p.i., in contrast to the control birds where Salmonella was isolated till the third week after infection. Oviducts were significantly more infected in the control group than in the immunized group. Salmonella was cleared from the oviducts at 3 weeks p.i. in the immunized hens but not in the control hens. In conclusion, we demonstrated that the immunization of laying hens with type 1 fimbriae reduced the number of contaminated eggs and reduced the colonization of the reproductive organs.     

城市化对杭州市繁殖鸟类物种多样性与功能多样性格局的影响

2007年3月至2007年8月,在杭州地区的城区、城乡结合区、农田区、农林交错区和自然林区等不同城市化程度的栖息地内各设置了90条100 m×3000 m调查样线,采用样线法对鸟类种类及其数量进行调查,采用实地调查与查阅文献相结合的方法确定每种鸟类的营巢类型和功能团,采用Shannon-Wiener指数计算鸟类群落的物种多样性和功能多样性.同时,对栖息地的人为干扰、植被盖度、人工设施指数等3项参数进行测定,并以此计算出各样线的城市化综合指数.调查结果显示,研究区内共记录有繁殖鸟类96种,分属于林冠枝干营巢功能团、灌草丛营巢功能团、林冠枝干/灌草丛营巢功能团、自然洞穴营巢功能团、人工建筑营巢功能团、自然洞穴/人工建筑营巢功能团、地面营巢功能团、水面营巢功能团和寄生功能团等9种功能团.对鸟类群落的物种数、物种多样性、功能团丰富度、功能多样性与城市化综合指数进行回归分析发现,城市化对鸟类群落的物种数、物种多样性、功能团丰富度和功能多样性均有着极显著性的影响,并且随着城市化程度的提高这些参数值均明显下降.不过,物种数和物种多样性与功能团丰富度和功能多样性间的下降模式存在明显差异.其中,物种数和物种多样性基本旱线性下降模式,即随着城市化程度的提高,物种丰富度及多样性基本为匀速下降;而功能团丰富度和功能多样性则呈二次函数下降模式,即在城市化初期,功能团丰富度和功能多样性下降不明显,但随着城市化程度的继续提高,功能团丰富度和功能多样性呈现加速下降的趋势.可见,鸟类群落的物种多样性和功能多样性对城市化的响应存在差异.虽然适度城市化可使物种多样性下降,但对功能多样性的影响却不明显;而群落的功能多样性则对高度城市化更为敏感.进一步对鸟类群落功能多样性与物种多样性的回归分析显示,功能多样性与物种多样性亦呈二次函数曲线关系,即在低多样性水平时,功能多样性与物种多样性基本呈线性关系,但随着多样性水平的逐渐升高,功能多样性的增长速度则明显慢于物种多样性的增长速度.由此可见,当群落物种多样性达到一定水平时,物种的增加不会明显地提高群落的功能多样性.