Newcastle disease--seroepidemiologic study of a highly contagious epizootic in poultry and in wild birds in Switzerland

Newcastle disease (ND) is a highly contagious viral disease particularly of domestic poultry. Switzerland is currently declared free from ND. A serosurvey using an ELISA was performed to investigate infections with ND-Virus (NDV) in 260 Swiss laying hen flocks, 169 backyard poultry flocks and 1576 wild birds. For laying hen flocks, a stochastic model was applied to analyse the results from serological testing. Four laying hen flocks were identified as NDV-seropositive, and the true NDV seroprevalence in this population was most likely between 1.3 and 1.5%. NDV antibodies were also detected in five of the 169 backyard poultry-flocks. ND-antibody positive birds were found in 10% of all wild birds examined, with the highest proportions among cormorants, grebes, birds of prey, owls, and swifts. The study indicated that positive flocks must have been in contact with NDV strains causing sub-clinical infection, since no clinical signs had been observed. Moreover, trade of poultry or poultry eggs was considered to be an important factor associated with seropositivity in backyard poultry flocks. Contact to wild birds did not seem to be of major importance.     

Cases of swollen head syndrome in broiler chickens in Greece

From 50 commercial broiler flocks included in a study concerning respiratory disease, signs of swollen head syndrome (SHS) were shown in eight. Postmortem examination was performed in eight birds showing signs of SHS from each flock. The trachea and head from each bird were collected for laboratory investigation. An enzyme-linked immunosorbent assay (ELISA) was used for the detection of viral and avian mycoplasma antigens in the trachea, and bacteriologic examinations were performed from the infraorbital sinuses of the infected birds. According to the ELISA results, the most frequently detected antigen in the trachea was Mycoplasma synoviae (six flocks, 75%), followed by infectious bronchitis virus (IBV) (five flocks, 62.5%), avian adenovirus (four flocks, 50%), avian reovirus (three flocks, 37.5%), Mycoplasma gallisepticum (one flock, 12.5%), and Newcastle disease virus (NDV) (one flock, 12.5%). Turkey rhinotracheitis (TRT), infectious laryngotracheitis, and avian influenza viral antigens were not detected. Experimental assays for characterization of NDV and IBV isolates showed that they were strains of low virulence (evidently vaccine strains). Bacteriologic examinations from the infraorbital sinuses of the affected birds resulted in the isolation of Escherichia coli (seven cases, 87.5%) and Staphylococcus spp. (one case, 12.5%). It is evident that TRT virus did not play a causal role in SHS in commercial broiler flocks in Greece, but in this condition, other viruses (IBV, NDV), mycoplasmas, or bacteria may be involved, and environmental conditions seem to be essential to the occurrence and severity of the disease.     

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.     

Strategies of newcastle disease vaccination for commercial ostrich farms in Japan

Strategies of Newcastle disease (ND) vaccination were demonstrated in a commercial ostrich farm in Japan. Three of 13 seven-month-old ostriches kept in a pen were vaccinated with a live ND vaccine by eye dropping for the 1st and 2nd vaccinations and spraying for the 3rd to 5th vaccinations. Antibodies against ND virus (NDV) were detected in all of the unvaccinated ostriches by virus neutralization test. At 2.5 months post final vaccination, 2 ostriches introduced into the pen raised antibodies against NDV. These data indicate that NDV may be transmitted from vaccinated to unvaccinated ostriches in the flock and that the virus may be sustained for a certain period in the flock. These data may be helpful for ND vaccination management in ostrich farms.     

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.     

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.     

Immune responses of breeding chickens to trivalent oil emulsion vaccines: responses to infectious bronchitis

Three similar flocks of broiler breeder parent chickens that had been given live infections bronchitis (IB) vaccines during rearing were injected at 20 weeks of age with three different oil emulsion vaccines: a commercial monovalent Newcastle disease (ND) vaccine (flock A); an experimental bivalent vaccine containing ND and infectious bursal disease (IBD) components (flock B); and an experimental trivalent vaccine containing ND, IBD and IB components (flock C). One week after vaccination 40 hens from flock A and 40 from flock C were taken to the laboratory and their egg yields individually recorded. At 37 weeks of age they were challenged by aerosol exposure to virulent IB virus. The egg production dropped significantly in the hens from flock A but not in the hens from flock C. On the farm, flock C showed a higher mean IB virus antibody titre four weeks after vaccination but titres rose in all three flocks indicating the presence of active IB virus infection. No differences in egg yields were found between the three farm flocks.     

Seroprevalences for ovine enzootic abortion in Switzerland

Our aim was to assess the seroprevalence of Chlamydophila (Cd) abortus (Chlamydia psittaci serotype 1), denoted ovine enzootic abortion (OEA), in the Swiss sheep population. A competitive enzyme-linked immunosorbent assay (cELISA) was adapted for the investigation of pooled serum samples (pool approach) and receiver-operator characteristic (ROC) analysis was applied to define the cut-off of the pool approach. At a cut-off value of 30% inhibition, the flock-level pooled sensitivity and specificity were 92.9% and 97.6% when compared to classifying the flock based on individual-animal samples.

Subsequently, sera from 775 randomly selected flocks out of 11 cantons of Switzerland were investigated using the pool approach. The cantons included in the study represented 72% of the Swiss sheep flocks and 76% of Swiss sheep population. Antibodies against Cd. abortus were found in almost 19% (144) of the 775 examined sheep flocks. Test prevalences were adjusted for the imperfect test characteristics using the Rogan–Gladen estimator and Bayesian inference. Seroprevalence was highest (43%) in the canton Graubünden. In the remaining 10 cantons the seroprevalence ranged from 2 to 29%. The cELISA in combination with testing pooled sera and statistical methods for true prevalence estimation provided a good survey tool at lower costs and time when compared to other approaches.     

Ovine enzootic abortion: seroprevalence in Switzerland using a competitive enzyme-linked immunosorbent assay (cELISA)

The present study gives an overview over the seroprevalence of ovine enzootic abortion in Switzerland. 639 sheep flocks out of eight cantons in Switzerland were examined by a competitive enzyme linked immunosorbent assay (cELISA) for antibodies against Chlamydophila abortus (Chlamydia psittaci serotype 1), the agent causing ovine enzootic abortion. The eight cantons included Aargau, Bern, Zürich, Appenzell-Ausserrhoden, Appenzell-Innerrhoden and Fribourg, the Vallais and the Graubünden. They were representative for 57% of the Swiss sheep flocks and for 60% of Swiss sheep population. In total, almost 19% (118) of the examined flocks were seropositive. Seroprevalence was the highest in Graubünden with 41%; this requires further examination and the evaluation of the need for a monitoring and controlling program. The examination of pooled sera made it possible to test a large number of samples with a reasonable amount of work. Higher sensitivity (92.9%) and specificity (97.6%) than the complement fixation test (CFT) in combination with testing of pooled sera makes the cELISA to be an usuable tool for serological screening on flock level.     

Efficacy of ELISA for detection of antibodies against several Ornithobacterium rhinotracheale serotypes

The present investigation were carried out to compare self-made ELISA based on SDS-Antigen extraction of serotype B and one commercial ELISA-kit (Biocheck, Gouda, The Netherlands) for their ability to detect antibodies against 12 ORT serotypes (A-L). Using both ELISA systems, antibodies against all serotypes were detected. Examination of serum samples collected from commercial flocks showed similar results on flock bases. However, some minor variations on sample basis could be demonstrated. In conclusion using both ELISA system antibodies against different serotypes could be detected.     

新城疫单抗ELISA试剂盒监测免疫鸡群中新城疫强毒

应用新城疫（ND）单抗ELISA试剂盒对2个免疫鸡群中ND强毒感染情况及个体感染强毒后排毒动态跟踪监测，并平等测定其HI抗体效价。共采集泄殖腔棉拭子和血液对应样品2317份。结果表明：HI效价2－14之间的个体均可检出强毒，其中HI效价在6以下和11以上的个体强毒检出率都较高。HI效价在6以上的个体仍角感染强毒，强毒感染导致HI抗体水平上升，且感染前低者上升速度较快，幅度亦较大；并且发现排毒个体的高水平抗体是强毒感染所致。个体感染强毒后排毒过程可长达3周，而且感染前抗体水平低者排毒时间相对较长。强毒一旦侵入鸡群便可在群内巡回传播，长期维持下来。     

江西省宜春地区鸡新城疫流行情况调查

为了解江西省宜春地区鸡新城疫（ND）流行情况,在2016年3月—2017年3月对宜春地区樟树、丰城、高安、宜春、万载5个重点养鸡县（市）的31个鸡场的疑似患有ND的鸡群进行现场问询、跟踪调查。结果发现,鸡新城疫在宜春地区一年四季均有流行,其中冬季发生该病的频率相对高些,其次为春季,夏、秋季发生该病的频率相对低些;发病鸡只的日龄无差异性,各阶段的鸡只均可发生;整体发病率为20.1%-30.8%,死亡率为9.0%-25.4%,产蛋下降率为15.3%-38.8%。同时,利用SPF鸡胚对来自宜春地区5个县（市）的31个鸡场的214份病料进行新城疫病毒（NDV）分离,共分离到27株具有血凝性的病毒,经过血凝试验（HA）、血凝抑制试验（HI）及血清中和试验,最终确定23株为NDV。其中,除了2株毒力不能确定之外,其余21株均为NDV强毒株。将21株病毒用30日龄非免疫鸡进行攻毒试验,发病率为80%~100%,死亡率为60%~100%,发病鸡只均出现鸡新城疫感染的典型症状及病变。     

Salmonella contamination of poultry flocks in The Netherlands

The contamination of poultry in the Netherlands with Salmonella enteritidis was tested. For this, different methods (detection of S. enteritidis in faecal samples of 25 g; detection of S. enteritidis in cloacal swabs; detection of S. enteritidis by serological testing of antibodies in serum) were compared for their efficiency to detect S. enteritidis in flocks of poultry. Testing of faecal samples clearly yielded the best results. This method was used in a transmission study, in which 14 flocks descending from a contaminated primary mother flock were screened for the presence of S. enteritidis. The method was also used for screening 49 flocks of laying hens and 52 flocks of broiler chickens throughout the Netherlands. From the transmission study it became clear that S. enteritidis, phage type 2 (Dutch phage set) was isolated both from the mother flock and from five of the descendent flocks. Screening of poultry flocks for the presence of salmonella revealed that salmonella was present in 47% of the layer flocks and in 94% of the broiler flocks. S. enteritidis was isolated from 15% of the flocks screened.     

Newcastle disease virus outbreaks: Vaccine mismatch or inadequate application?

Newcastle disease (ND) is one of the most important diseases of poultry, and may cause devastating losses in the poultry industry worldwide. Its causative agent is Newcastle disease virus (NDV), also known as avian paramyxovirus type 1. Many countries maintain a stringent vaccination policy against ND, but there are indications that ND outbreaks can still occur despite intensive vaccination. It has been argued that this may be due to antigenic divergence between the vaccine strains and circulating field strains. Here we present the complete genome sequence of a highly virulent genotype VII virus (NL/93) obtained from vaccinated poultry during an outbreak of ND in the Netherlands in 1992-1993. Using this strain, we investigated whether the identified genetic evolution of NDV is accompanied by antigenic evolution. In this study we show that a live vaccine that is antigenically adapted to match the genotype VII NL/93 outbreak strain does not provide increased protection compared to a classic genotype II live vaccine. When challenged with the NL/93 strain, chickens vaccinated with a classic vaccine were completely protected against clinical disease and mortality and virus shedding was significantly reduced, even with a supposedly suboptimal vaccine dose. These results suggest that it is not antigenic variation but rather poor flock immunity due to inadequate vaccination practices that may be responsible for outbreaks and spreading of virulent NDV field strains.     

An investigation of the disease status of village poultry in Mauritania

Three contagious poultry diseases in Mauritania were studied. Serum samples and tracheal swabs were taken from 80 chickens in village poultry flocks in each of three different regions. Antibodies against Newcastle disease virus (NDV) were detected in 4.8% of chickens, antibodies against Gumboro disease virus in 15.8% of chickens and antibodies against Salmonella pullorum in 6.2% of chickens. Six isolates of NDV were made, of which four formed plaques on chicken embryo fibroblast monolayers. Seropositivity was highest in the Trarza region, bordering the River Senegal, and four out of six of the NDV isolates were made from chickens in this region.     

Newcastle disease in pheasants (Phasianus colchicus): a review

Newcastle disease (ND) is regarded throughout the world as one of the most important diseases of poultry, not only due to the serious disease and high flock mortality that may result from some ND virus (NDV) infections, but also through the economic impact that may ensue due to trading restrictions and embargoes placed on areas and countries where outbreaks have occurred. All ages of pheasants are purported to be highly susceptible to infection with NDV, but clinical signs and mortality levels in infected birds vary considerably. This article reviews the available literature relating to infections in pheasants, describing the clinical presentation of the disease and the epidemiological role these hosts may have in the spread of ND.     

Serological detection of chicken flocks naturally infected with salmonella enteritidis,using an enzyme‐linked immunosorbent assay based on monoclonal antibodies against the flagellar antigen

Summary

The Dutch Salmonella enteritidis monitoring and eradication programme for poultry prescribes a periodic examination of all breeding flocks for the presence of S. enteritidis. For the first years of the programme this was done by bacteriological examination of 50 faecal samples per visit per flock.

In this study we compare the results of bacteriological examination of faecal samples taken at 1580 visits from 545 flocks with those of a S. enteritidis enzyme‐linked immunosorbent assay (ELISA) applied on 24 serum samples per visit per flock. Two flocks were found positive for S. enteritidis by bacteriological examination; both flocks were also detected by ELISA. Ten flocks, bacteriologically negative for S. enteritidis were found positive by ELISA. S. enteritidis was isolated from three of these flocks by repeated and extensive bacteriological examination for verification. Verification was not possible in the fourth EL1SA positive flock. S. enteritidis infections were likely in three other flocks because of the farm histories.

On the basis of the results of this study it was decided to use this ELISA, starting from April 1992, as screening technique in the Dutch S. enteritidis programme instead of bacteriological examination of faecal samples. The ELISA is regarded as a flock test; an extensive, confirmatory bacteriological investigation for S. enteritidis is carried out in ELISA positive flocks to decide whether the flocks are truly infected.