A survey of Newcastle disease in Swiss laying-hen flocks using serological testing and simulation modelling

Newcastle disease (ND) is a highly contagious viral disease of birds particularly domestic poultry. Switzerland is currently declared free from ND; since vaccination is prohibited, the detection of antibodies against ND virus (NDV) results in the destruction of the respective flock (stamping-out policy). However, in 1995 and 1996, antibody-positive flocks were detected and sporadic ND outbreaks even occurred in Switzerland. Therefore, a serosurvey was done to look for evidence of NDV infections in Swiss laying-hen flocks. The survey was designed to provide 95% confidence of detecting at least one seropositive flock if the flock prevalence were 1%. Thirty blood samples from each of 260 commercial laying-hen flocks were collected during 1996 in a central poultry slaughterhouse. Sera were screened for NDV antibodies with a commercial blocking enzyme-linked immunosorbent assay (ELISA). Samples with a questionable or positive test result were retested with the same ELISA. A stochastic computer model was applied to define a cut-off number of test-positive samples to help to differentiate between true- and false-positive flocks and to estimate the true flock prevalence of infection. Four flocks were identified as NDV-seropositive and the NDV true seroprevalence among commercial laying-hen flocks in Switzerland was most likely between 1.35 and 1.55%. This indicates that Swiss laying-hen and parental flocks with more than 150 animals have been in contact with strains of NDV that cause subclinical infection in chicken, because no clinical symptoms have been observed. In this context, computer simulation was a useful technique to interpret survey results.     

Questionnaire study and postmortem findings in backyard chicken flocks in Finland

Background

Although modern commercial poultry production today is based on large farms and intensive husbandry, keeping backyard poultry has regained popularity in industrialized countries. However, the health status of backyard flocks is still relatively poorly documented. A questionnaire was sent to the owners of 376 backyard poultry flocks (<500 birds) in order to study health management procedures and characterize backyard poultry populations in Finland. Information was also collected on the postmortem findings from non-commercial flocks using necropsy data from the Finnish Food Safety Authority (Evira).

Results

Backyard flocks in Finland are small in size (<50 birds), comprising mainly chickens. Based on the results of the questionnaire, the health of such flocks is good, mortality low and vaccinations are not commonly used. Most of the flocks were registered in the national poultry register. The standard biosecurity practices are not generally applied and contact with wild birds, pets and farm animals is frequent, which can make the flocks more prone to infectious diseases. We conducted an 11-year retrospective study of the postmortem necropsy findings of the Evira in order to document the diseases, which caused mortality in backyard chickens in Finland. Necropsy was performed on a total of 132 non-commercial laying hens during 2000 – 2011. The most common postmortem findings were Marek’s disease (27%) and colibacillosis (17%).

Conclusions

This study is the first to report data on characteristics of and management practices for backyard chicken flocks in Finland. Close connections with commercial flocks are rare and farms are usually distantly located suggesting that the risk that these backyard flocks pose to commercial poultry is low.     

Epidemiologic characterization of Colorado backyard bird flocks

Backyard gallinaceous bird flocks may play an important role in the spread of infectious diseases within poultry populations as well as the transmission of zoonotic diseases to humans. An epidemiologic characterization was conducted of Colorado backyard flocks to gather information on general flock characteristics, human movement of birds, human-bird interaction, biosecurity practices, and flock health. Our results suggest that backyard poultry flocks in Colorado are small-sized flocks (68.6% of flocks had < 50 birds); consist primarily of layer chickens (85.49% of flocks), show chickens (32.18% of flocks), and waterfowl (34.07% of flocks); and are primarily owned for food (meat or egg) production for the family (86.44%) or as pet or hobby birds (42.27%). The backyard flock environment may promote bird-to-bird transmission as well as bird-to-human transmission of infectious disease. Birds are primarily housed with free access to the outside (96.85%), and many are moved from the home premises (46.06% within 1 yr). Human contact with backyard flocks is high, biosecurity practices are minimal, and bird health is negatively impacted by increased movement events. Increased knowledge of backyard bird characteristics and associated management practices can provide guidelines for the development of measures to decrease disease transmission between bird populations, decrease disease transmission from birds to humans, and increase the overall health of backyard birds.     

The role of indigenous wild, semidomestic, and exotic birds in the epizootiology of velogenic viscerotropic Newcastle disease in southern California, 1972-1973.

During an epornitic of velogenic viscerotropic Newcastle disease (VVND) in southern California, free-flying wild birds, captive and free-ranging semidomestic birds, and exotic birds were collected from the quarantine area to determine their role in the epizootiology of the disease. The VVND virus was isolated from 0.04% of 9,446 free-flying wild birds, 0.76% of 4,367 semidomestic birds, and 1.01% of 3,780 exotic birds examined. Three house sparrows and 1 crow directly associated with infected poultry flocks were the only free-flying wild birds from which VVND virus was isolated. Among semidomestic species, ducks, quail, chukars, pheasants, peafowl, pigeons, and doves were found to be infected. Psttacines, pittas, and toucans accounted for 92% of the VVND virus isolations from exotic birds. In addition, domestic Newcastle disease virus (NDV) was isolated from 0.29% of the free-flying wild birds, from 1.65% of the semidomestic birds, and from 0.19% of the exotic birds collected. Hemagglutination-inhibition against domestic NDV was demonstrated in 0.24% of 3,796 wild bird serums, 8.28% of 2,004 semidomestic bird serums, and 3.90% of 231 exotic bird serums tested. Although few free-flying wild birds were infected with VVND virus in this epornitic, the isolation of domestic NDV strains from free-flying wild ducks and mourning doves suggests the potential for transportation of NDV over long distances by migratory birds.     

A Serological Survey for Avian Infectious Bronchitis Virus and Newcastle Disease Virus Antibodies in Backyard (Free-range) Village Chickens in Mexico

The commercial flocks in Yucatan, Mexico are free of Newcastle disease virus (NDV) in its velogenic viscerotropic form, but little is known about the disease status of backyard poultry. A seroprevalence survey in 30 villages using haemagglutination inhibition (HI) tests for infectious bronchitis virus (IBV) and NDV antibodies was carried out from December 1997 to June 1998. The seroprevalences were 56.5% (95% CI 50–63%) for IBV and 2.2% (95% CI 0.5–3.8%) for NDV. All the villages had chickens that were positive for antibodies to IBV and nine of the villages had chickens that were positive for antibodies to NDV. This suggests that IBV may be responsible for a large proportion of the respiratory disease observed in backyard chickens in Yucatan. The implications of these findings are discussed, including the highly susceptible status of the backyard chickens in Yucatan to NDV and the possibility of this virus being one cause of the syndrome known as mortandad by the local people.     

Antibody prevalence of low-pathogenicity avian influenza and evaluation of management practices in Minnesota backyard poultry flocks

Low‐pathogenicity avian influenza (LPAI) viruses have caused illness in poultry and humans with poultry contact. To determine whether there is evidence of exposure to avian influenza viruses (AIV) among backyard poultry in Minnesota and their human caretakers, 150 flocks of backyard birds were sampled for antibodies to AIV from August 2007 through December 2008. One hundred flocks were tested through routine slaughter surveillance by the Minnesota Board of Animal Health and an additional 50 flocks were contacted and sampled by study investigators. Blood was collected from 10 to 13 birds from each flock and a survey of biosecurity and management practices was administered to the flock owner. Blood samples were tested by agar gel immunodiffusion (AGID) for influenza A antibodies. Tested flocks had a median flock size of 100 birds (range: 12–800 birds), and were most commonly owned for meat for personal use (81% of respondents), fun or hobby (58%) and eggs for personal use (56%). Although 7% of flock owners reported that their birds had shown respiratory signs in the previous 3 months, only 1 of 150 flocks tested positive for influenza by AGID. Antibodies to LPAI H6N1 were detected in the positive flock. The owner of the positive flock did not have antibodies to H6 or other common AIV. Based on the findings of this study, the risk of transmission of LPAI viruses from backyard poultry to owners in Minnesota appears to be low under current conditions and management practices.     

Non-commercial poultry industries: surveys of backyard and gamefowl breeder flocks in the United States

The National Animal Health Monitoring System (NAHMS) Poultry '04 study was conducted to better describe non-commercial United States poultry populations, in particular, backyard and gamefowl breeder flocks. To estimate the density of backyard flocks in close proximity to commercial operations, a sample of 350 commercial poultry operations in 18 top poultry producing states was selected from the National Agricultural Statistics Service (NASS) list of poultry operations. A 1 mile radius circle was drawn around each operation, and door-to-door canvassing was conducted within these circles to enumerate premises with all species of birds. Premises with backyard poultry flocks completed a questionnaire focusing on bird health, bird movement, and biosecurity practices. A similar questionnaire, provided in both English and Spanish, was mailed to all members of State affiliates of the United Gamefowl Breeders Association (UGBA) as well as to members of State associations not affiliated with UGBA. An average of 29.4 residences was found within a 1 mile radius of commercial operations, of which 1.9 residences per circle had backyard poultry flocks. Gamefowl breeder flocks were larger, used more health care and biosecurity practices, and moved birds more frequently compared to backyard flocks.     

鸡新城疫HI抗体水平及带毒状况调查

对2007年3月～2008年5月泰安及周边地区鸡群新城疫抗体水平检测结果进行了统计分析,统计结果显示:抗体效价超过正常免疫水平且离散度较大,疑似新城疫野毒感染的鸡群较多.其中肉仔鸡(或麻鸡)群、育成蛋鸡群分别为12.3%、21.5%,而产蛋鸡群高达51.2%.采用接种鸡胚分离病毒和间接免疫荧光试验验证HI试验检测结果的判定,探讨鸡群的带毒状况.调查结果表明,目前鲁中地区各种鸡群的新城疫感染带毒状况较为严重,高比例带毒鸡群的存在是我国控制新城疫的最大难题.     

A preliminary investigation of New Zealand isolates of Pasteurella multocida

Abstract

AIMS: To determine the proportion of residential land parcels with backyard poultry in an urban and urban-rural fringe area of provincial New Zealand. To document key husbandry and biosecurity practices of owners of backyard poultry, and to identify factors that might assist animal health authorities in locating backyard poultry flocks in the event of an infectious disease emergency.

METHODS: A cross-sectional survey was undertaken, in which residents of 449 land parcels in an urban and urban-rural fringe area within and adjacent to the city of Palmerston North, respectively, were visited between February and November 2006. Residents were asked if backyard poultry were kept on the premises. Details recorded for those that kept poultry included the type and number of birds kept, and details of management and biosecurity practices. The geographical distribution of poultry-positive land parcels was assessed for evidence of spatial clustering.

RESULTS: Backyard poultry were kept on 3.5 (95% CI=2.15.0)% of land parcels; 1.6 (95% CI=0.7-3.4)% in the urban area and 18.9 (95% CI= 11.6–29.3)% in the urban-rural fringe area. There were no significant clusters of poultry-positive land parcels in either area. On all poultry-positive parcels birds were allowed, for at least a portion of the day, to range freely over the property. Three poultry-positive land parcels were within a distance of 1 km of a commercial poultry enterprise in the urban-rural fringe area. Most owners of backyard poultry used feed prepared commercially.

CONCLUSIONS: The prevalence of ownership of backyard poultry in this area of New Zealand was low, and varied according to classification of the land, viz urban, or urban-rural fringe. The close proximity of backyard flocks to the single commercial enterprise in the urban-rural fringe area reiterates the importance of strict biosecurity measures on commercial farms. In the event of an infectious disease emergency, it is proposed that a sampling frame of owners of backyard poultry might be rapidly obtained by contacting suppliers of commercial feed.     

Molecular characterization and phylogenetic analysis of Newcastle disease virus isolates from healthy wild birds

Wild waterfowl is considered a natural reservoir of potentially infectious agents and a source of pathogenic viruses like avian paramyxoviruses type 1 (APMV 1). In 1997, commercial poultry in Argentina had reached the status of being free from virulent Newcastle disease virus (NDV) infections. Vaccination and biosecurity measures are actively performed to maintain this preferential sanitary condition. However, the risk of reintroduction of pathogenic viruses is always present. In this context, we conducted a study to describe the status of wild healthy birds in a geographic region relevant for the poultry industry. The presence of anti-NDV antibodies was determined in different species in all areas sampled suggesting previous contact with NDV. Seven ND viruses were isolated and characterized as apathogenic strains by biological and molecular methods. The phylogenetic analysis revealed that the majority of the Argentinian isolates form a subgroup related to viruses of genotype II. The results presented here highlight the importance of maintaining strict biosecurity measures and vaccination programs in poultry industries in order to preserve the virulent NDV-free status for commercial flocks in the country.     

Isolation of avian paramyxovirus-2 from domestic and wild birds in Costa Rica

A survey for Newcastle disease virus (NDV) in wild birds of Costa Rica was conducted by swabbing wild-caught pet birds, backyard chickens, and wild birds captured in Japanese mist nets in tropical rain forests and agricultural areas. Cloacal swabs were collected from 876 birds of approximately 132 species representing 24 taxonomic families. Hemagglutinating agents were isolated from 18.7% of the birds. Paramyxovirus type 2(PMV-2) (Yucaipa-like), unreported in free-flying passerines in the Americas, was recovered from a finch, wren, and chicken, each from a different location. Pathogenicity trials with infected turkey poults and newly hatched chicks did not result in growth impairment or significant clinical signs of disease. Attempts to isolate NDV were negative.     

ClassⅠ新城疫病毒概述

新城疫病毒是影响养禽业健康发展的主要病原之一。新城疫病毒只有一个血清型,但根据亲源关系可以划分为ClassⅠ和ClassⅡ两大类。ClassⅠ新城疫病毒于2006年被证实存在,当前可被细分为9个基因型(1～9)。ClassⅠ所有自然分离株均为无毒株或弱毒株,但有经人工传代返强的报道,由于其分布广泛,数量庞大,对养禽业有巨大的潜在威胁。为了更好的了解ClassⅠ新城疫毒株的生物学特性,为研究ClassⅠ新城疫病毒提供参考,现将其基因组结构、分子流行病学及检测方法等综述如下。     

Investigation of the concurrent colonization with Campylobacter and Salmonella in poultry flocks and assessment of the sampling site for status determination at slaughter

Fifty six broiler flocks and 20 laying hen and breeder flocks were sampled in six slaughterhouses for the presence of Campylobacter and Salmonella. Samples were taken from three different sites of the gastrointestinal tract, namely from the crop, the duodenum and the ceca. The prevalence of flocks colonized with Campylobacter and Salmonella was determined and an association between the concurrent colonization with these two pathogens was investigated. Furthermore, the best sampling site for status determination at the slaughterhouse level was evaluated. Of the broiler flocks, 73% were colonized with Campylobacter, whereas 13% were Salmonella-positive at slaughter. Concerning the laying hen and breeder flocks, all flocks were colonized with Campylobacter and 65% of the flocks were Salmonella-positive. No association was found between Campylobacter and Salmonella occurrence in broiler flocks. Since all laying hen and breeder flocks were colonized with Campylobacter, no association between the concurrent colonization with the two pathogens could be determined. At the slaughterhouse level, sampling only the duodena was sufficient to determine the Campylobacter status of poultry flocks, whereas the three sampling sites had to be analyzed to detect all flocks colonized with Salmonella.     

Biosecurity and bird movement practices in upland game bird facilities in the United States

Since 1996, the emergence of Asian-origin highly pathogenic avian influenza subtype H5N1 has spurred great concern for the global poultry industry. In the United States, there is concern over the potential of a foreign avian disease incursion into the country. Noncommercial poultry operations, such as upland game bird facilities in the United States, may serve as a potential source of avian disease introduction to other bird populations including the commercial poultry industry, backyard flocks, or wildlife. In order to evaluate how to prevent disease transmission from these facilities to other populations, we examined biosecurity practices and bird movement within the upland game bird industry in the United States. Persons that held a current permit to keep, breed, or release upland game birds were surveyed for information on biosecurity practices, flock and release environments, and bird movement parameters. Biosecurity practices vary greatly among permit holders. Many facilities allow for interaction between wild birds and pen-reared birds, and there is regular long-distance movement of live adult birds among facilities. Results suggest that upland game bird facilities should be targeted for biosecurity education and disease surveillance efforts.     

Development of a virosome vaccine for Newcastle disease virus

In an effort to protect chickens against Newcastle disease (ND), a nonreplicating virosome vaccine was produced by solubilization of Newcastle disease virus (NDV) with Triton X-100 followed by detergent removal with SM2 Bio-Beads. Biochemical analysis indicated that the NDV virosomes had similar characteristics as the parent virus and contained both the fusion and hemagglutinin-neuraminidase proteins. To target the respiratory tract, specific-pathogen-free chickens were immunized intranasally and intratracheally with the NDV virosome vaccine. This vaccine was compared with a standard NDV (LaSota) live-virus vaccine for commercial poultry. Seroconversion (> or = four fold increase in hemagglutination inhibition [HI] antibody titers) was achieved in all birds vaccinated with the virosome vaccine. Upon lethal challenge with a velogenic NDV strain (Texas GB), all birds receiving either vaccination method were protected against death. Antibody levels against NDV, as determined by enzyme-linked immunosorbent assay and HI titer, were comparable with either vaccine and increased after virus challenge. These results demonstrate the potential of virosomes as an effective tool for ND vaccination.     

陕北地区鸡新城疫免疫监测及分析

以神木县为例,介绍了陕北地区鸡新城疫的防疫情况,揭示新城疫防疫的薄弱环节。本研究从神木县多家种鸡场、商品蛋鸡场及活禽交易市场采集血清样本346份,用血凝抑制试验测定新城疫抗体滴度,结果显示商品蛋鸡场免疫效果较差,合格率只有69.6%;同时发现种鸡场也存在免疫问题。在今后新城疫防控过程应与重视。