PCR for specific detection of haemorrhagic enteritis virus of turkeys, an avian adenovirus

Turkey adenovirus 3: ORF1 gene sequence comparison between vaccine-like and field strains

Haemorrhagic enteritis is an economically significant disease reported in the majority of the countries where turkeys are raised intensively; it is caused by Turkey adenovirus 3 (TAdV-3). The aim of this study was to analyse and compare the ORF1 gene 3' region from turkey haemorrhagic enteritis virus (THEV) vaccine-like and field strains in order to develop a molecular diagnostic method to differentiate the strains from each other. Eighty samples were analysed by sequencing and phylogenetic analyses using a new set of polymerase chain reaction (PCR) primers targeting a genomic region spanning the partial ORF1, hyd and partial IVa2 gene sequences. A commercial live vaccine was also included in the analysis. The results showed that 56 of the 80 sequences obtained in this study showed ≥99.8% nucleotide identity with the homologous vaccine strain sequence. Three non-synonymous mutations - ntA1274G (aaI425V), ntA1420C (aaQ473H) and ntG1485A (aaR495Q) - were detected in the THEV field strains but not in the vaccine strain. Phylogenetic analysis confirmed the clustering of the field and vaccine-like strains in different phylogenetic branches. In conclusion, the method employed in this study could be a useful tool towards making a correct diagnosis. The data could contribute to the knowledge of field distribution of THEV strains and increase the limited existing information available on native isolates around the world.

Poult Enteritis and Mortality Syndrome in Turkey Poults: Causes, Diagnosis and Preventive Measures

Simple Summary

The poult enteritis and mortality syndrome (PEMS) causes severe economic losses in turkeys. Several agents were described to be associated with the PEMS; however, a specific etiological agent(s) has not been identified. The diagnosis of PEMS is still a huge challenge for several reasons: (1) no specific clinical signs or pathognomonic lesions, (2) isolation of some enteric viruses still difficult, (3) the pathogenicity of several enteric viruses in turkeys is not fully understood, (4) PEMS is an interaction between several known and might be unknown agents and (5) opportunistic microorganisms also have a role in the pathogenesis of PEMS. Both electron microscopy and molecular techniques can be used for diagnosis of PEMS and might help to discover unknown causes. Until now, no specific vaccines against enteric viruses associated with PEMS. However, biosecurity, maintaining a healthy gut and strengthening the immune system of turkey poults using probiotics, prebiotics and/or phytogenic substances are crucial factors to prevent and/or reduce losses of PEMS in turkeys. This review is a call for scientists to perform further research to investigate the real cause(s) of PEMS and to develop a preventive strategy against it.

Abstract

Poult enteritis and mortality syndrome (PEMS) is one of the most significant problem affecting turkeys and continues to cause severe economic losses worldwide. Although the specific causes of PEMS remains unknown, this syndrome might involve an interaction between several causative agents such as enteropathogenic viruses (coronaviruses, rotavirus, astroviruses and adenoviruses) and bacteria and protozoa. Non-infectious causes such as feed and management are also interconnected factors. However, it is difficult to determine the specific cause of enteric disorders under field conditions. Additionally, similarities of clinical signs and lesions hamper the accurate diagnosis. The purpose of the present review is to discuss in detail the main viral possible causative agents of PEMS and challenges in diagnosis and control.

Health surveillance of a potential bridge host: Pathogen exposure risks posed to avian populations augmented with captive-bred pheasants

Augmentation of wild populations with captive‐bred individuals presents an inherent risk of co‐introducing novel pathogens to naïve species, but it can be an important tool for supplementing small or declining populations. Game species used for human enterprise and recreation such as the ring‐necked pheasant (Phasianus colchicus) are commonly raised in captivity and released onto public and private wildlands as a method of augmenting naturalized pheasant populations. This study presents findings on pathogen exposure from three sources of serological data collected in California during 2014–2017 including (a) 71 pen‐reared pheasants sampled across seven game bird breeding farms, (b) six previously released pen‐reared pheasants captured at two study sites where wild pheasants occurred and (c) 79 wild pheasants captured across six study sites. In both pen‐reared and wild pheasants, antibodies were detected against haemorrhagic enteritis virus (HEV), infectious laryngotracheitis (ILT), infectious bursal disease virus (IBDV), paramyxovirus type 1 (PMV‐1) and Pasteurella multocida (PM). Previously released pen‐reared pheasants were seropositive for HEV, ILT, and PM. Generalized linear mixed models accounting for intraclass correlation within groups indicated that pen‐reared pheasants were more than twice as likely to test positive for HEV antibodies. Necropsy and ancillary diagnostics were performed in addition to serological testing on 40 pen‐reared pheasants sampled from five of the seven farms. Pheasants from three of these farms tested positive by PCR for Siadenovirus, the causative agent of both haemorrhagic enteritis in turkeys and marble spleen disease of pheasants, which are serologically indistinguishable. Following necropsy, owners from the five farms were surveyed regarding husbandry and biosecurity practices. Farms ranged in size from 10,000 to more than 100,000 birds, two farms raised other game bird species on premises, and two farms used some form of vaccination. Biosecurity practices varied by farm, but the largest farm implemented the strictest practices.

A survey of jaagsiekte sheep retrovirus (JSRV) infection in sheep in the three northeastern provinces of China

Ovine pulmonary adenomatosis (OPA) is caused by jaagsiekte sheep retrovirus (JSRV) and is a chronic, progressive, and infectious neoplastic lung disease in sheep, which causes significant economic losses to the sheep industry. Neither a vaccine nor serological diagnostic methods to detect OPA are available. We performed a JSRV infection survey in sheep using blood samples (n = 1,372) collected in the three northeastern provinces of China (i.e., Inner Mongolia, Heilongjiang, and Jilin) to determine JSRV infection status in sheep herds using a real-time PCR assay targeting the gag gene of JSRV. The ovine endogenous retrovirus sequence was successfully amplified in all sheep samples tested (296 from the Inner Mongolia Autonomous Region, 255 from Jilin province, and 821 from Heilongjiang province). Subsequently, we attempted to distinguish exogenous JSRV (exJSRV) and endogenous JSRV (enJSRV) infections in these JSRV-positive samples using a combination assay that identifies a ScaI restriction site in an amplified 229-bp fragment of the gag gene of JSRV and a "LHMKYXXM" motif in the cytoplasmic tail region of the JSRV envelope protein. The ScaI restriction site is present in all known oncogenic JSRVs but absent in ovine endogenous retroviruses, while the "LHMKYXXM" motif is in all known exJSRVs but not in enJSRVs. Interestingly, one JSRV strain (HH13) from Heilongjiang province contained the "LHMKYXXM" motif but not the ScaI enzyme site. Phylogenetic analysis showed that strain HH13 was closely related to strain enJSRV-21 reported in the USA, indicating that HH13 could be an exogenous virus. Our results provide valuable information for further research on the genetic evolution and pathogenesis of JSRV.

Changes in the intestinal mucosal proteome of turkeys (Meleagris gallopavo) infected with haemorrhagic enteritis virus

Haemorrhagic enteritis (HE) is a viral disease affecting intestinal integrity and barrier function in turkey (Meleagris gallopavo) and resulting in a significant economic loss. Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS) was applied to identify crucial proteins involved in HE infection. A total of 938 proteins were identified and used to generate a reference library for SWATH-MS analysis. In total, 523 proteins were reliably quantified, and 64 proteins were found to be differentially expressed, including 49 up-regulated and 15 down-regulated proteins between healthy and HE-affected intestinal mucosa. Functional analysis suggested that these proteins were involved in the following categories of cellular pathways and metabolisms: 1) energy pathways; 2) intestine lipid and amino acid metabolism; 3) oxidative stress; 4) intestinal immune response. Major findings of this study demonstrated that natural HE infection is related to the changes in abundance of several proteins involved in cell-intrinsic immune defense against viral invasion, systemic inflammation, modulation of excessive inflammation, B and T cell development and function and antigen presentation. mRNA quantitative expression demonstrated that most of the proteins involved in innate immunity that were found to be differentially abundant were produced by intestinal mucosa, suggesting its direct involvement in immune defences against HE infection.

Gastrointestinal microbial population of turkey (Meleagris gallopavo) affected by hemorrhagic enteritis virus

Hemorrhagic enteritis (HE) is an acute viral disease that affects avian species, particularly turkeys, compromising their commercial production and having a negative effect on animal welfare. Turkey adenovirus 3 (TAdV-3), is the main causal agent of the disease. In this study, we considered 3 groups of turkeys to achieve 2 purposes: 1) A preliminary investigation on the microbiota content in the 4 parts of healthy turkey's intestine (group A), namely duodenum, jejunum, ileum, and ceca was done; 2) an investigation on the relationship between natural infections with TAdV-3 and the intestinal microbiota in the jejunum, where HE mostly develops, comparing group A with animals with molecular positivity for the virus and with clinical signs of HE (group B) and animals with molecular positivity for the virus but without clinical signs (group C). Massive sequencing of the hypervariable V1-V2 regions of 16S rRNA gene and QIIME 1.9.1 software analysis was performed, and operation taxonomic units (OTUs) were classified into 4 abundant phyla: Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The microbial population of small intestine was distributed almost homogeneously in the healthy turkeys, and Firmicutes was the prevalent phylum (79.85% in duodenum, 89.57% in jejunum and 99.28% in ileum). As compared with small intestine, ceca microbial community was much more heterogeneous: Firmicutes (48.03%), Bacteroidetes (33.60%) and Proteobacteria (12.32%). In the natural infections of HEV, the main bacterial families were Bacteroidaceae (Bacteroidetes) and Peptostreptococcaceae (Firmicutes), uniquely detected in group B and C. Also Clostridiaceae (Firmicutes) was detected, uniquely in group B.

Investigation into diseases in free-ranging ring-necked pheasants (Phasianus colchicus) in northwestern Germany during population decline with special reference to infectious pathogens

The population of ring-necked pheasants (Phasianus colchicus) is decreasing all over Germany since the years 2008/2009. Besides impacts of habitat changes caused by current rates of land conversion, climatic influences or predators, a contribution of infectious pathogens needs also to be considered. Infectious and non-infectious diseases in free-living populations of ring-necked pheasants have been scarcely investigated so far. In the present study, carcasses of 258 deceased free-ranging pheasants of different age groups, predominantly adult pheasants, collected over a period of 4 years in the states of Lower Saxony, North Rhine–Westphalia and Schleswig-Holstein, were examined pathomorphologically, parasitologically, virologically and bacteriologically, with a focus set on infectious pathogens. A periocular and perinasal dermatitis of unknown origin was present in 62.3% of the pheasants. Additional alterations included protozoal cysts in the skeletal musculature (19.0%), hepatitis (21.7%), enteritis (18.7%), gastritis (12.6%), and pneumonia (11.7%). In single cases, neoplasms (2.6%) and mycobacteriosis (1.7%) occurred. Further findings included identification of coronaviral DNA from trachea or caecal tonsils (16.8%), siadenoviral DNA (7.6%), avian metapneumoviral RNA (6.6%), and infectious bursal disease viral RNA (3.7%). Polymerase chain reaction (PCR) on herpesvirus, avian influenza virus (AIV), paramyxovirus type 1 (PMV-1), avian encephalomyelitis virus (AEV), and chlamydia were negative. Based on the present results, there is no indication of a specific pathogen as a sole cause for population decline in adult pheasants. However, an infectious disease can still not be completely excluded as it may only affect reproduction effectivity or a certain age group of pheasants (e.g., chicks) which were not presented in the study.

Haemorrhagic enteritis of turkeys - current knowledge

Haemorrhagic enteritis virus (HEV), an adenovirus associated with acute haemorrhagic gastro-intestinal disease of 6-11-week old turkeys predominantly hampers both humoral and cellular immunity. Affected birds are more prone to secondary complications (e.g. colibacillosis and clostridiosis) and failure to mount an effective vaccine-induced immune response. HEV belongs to the new genus Siadenovirus. Feco-oral transmission is the main route of entry of the virus and it mainly colonizes bursa, intestine and spleen. Both naturally occurring virulent and avirulent strains of HEVs are serologically indistinguishable. Recent findings revealed that ORF1, E3 and fib genes are the key factors affecting virulence. The adoption of suitable diagnostic tools, proper vaccination and biosecurity measures have restrained the occurrence of disease epidemics. For diagnostic purposes, the best source of HEV is either intestinal contents or samples from spleen. For rapid detection highly sensitive and specific tests such as quantitative real-time PCR based on Taq man probe has been designed. Avirulent strains of HEV or MSDV can be effectively used as live vaccines. Novel vaccines include recombinant hexon protein-based subunit vaccines or recombinant virus-vectored vaccines using fowl poxvirus (FPV) expressing the native hexon of HEV. Notably, subunit vaccines and recombinant virus vectored vaccines altogether offer high protection against challenge or field viruses. Herein, we converse a comprehensive analysis of the HEV genetics, disease pathobiology, advancements in diagnosis and vaccination along with appropriate prevention and control strategies.

Molecular Characterization of Hemorrhagic Enteritis Viruses (HEV) Detected in HEV-Vaccinated Commercial Turkey Flocks in Germany

Despite the application of live hemorrhagic enteritis virus (HEV) vaccines, HEV field outbreaks are suspected to still occur in turkey flocks in Germany. Increasing secondary bacterial infections in HEV-vaccinated flocks suggest that vaccines may be losing efficacy or, possibly, that vaccine strains are causing disease. Thus, the goal of the current study was to investigate the diversity of HEV isolates from fattening turkey flocks between 2008 and 2012 by characterizing the open reading frame (ORF)1 gene at its 5' and 3' ends. Analyses of ORF1 sequences of field isolates and comparison with sequences present in databases revealed that in many cases (13 out of 16 samples), vaccine (avirulent) strains were present. In addition, data indicated the circulation of suspected virulent field isolates and these isolates (3 out of 16) cluster with an early isolate from Germany in the 1980s, but show some mutations in the predicted amino acid (aa) sequences of ORF1 compared to the early isolate. These virulent isolates clearly differ from the spleen-derived avirulent Domermuth vaccine strain used in Germany. In this study, a unique isolate was identified and showed unusual nucleotide mutations that resulted in aa exchanges at the 5' end of ORF1 between aa positions 34 and 174. This genetic drift suggests evolution of HEV including virulent and vaccine-derived strains in the field. This may lead to evasion of vaccinal immunity by drifted viruses and/or an increase in the virulence of field strains.

Expression and serological reactivity of hemorrhagic enteritis virus hexon protein

The aim of this work was to express the recombinant hexon protein of the hemorrhagic enteritis virus, to establish the diagnostic value of this protein for serological detection of antibodies in turkey serum samples and to assess seroprevalence of the infection in the Czech Republic. The N' terminal part of the hexon protein was expressed in a bacterial expression system and used as an antigen in an ELISA test for the detection of hemorrhagic enteritis virus specific antibodies in turkey sera. Validation of the test was performed by comparison with a commercially available ELISA test. Serological reactivity was assessed on a panel of 126 turkey sera by a newly developed ELISA test. Serum samples were taken from turkey farms with the history of hemorrhagic enteritis virus infection, from farms with animals free of infection, and from turkey farms following vaccination. Both ELISA kits gave identical results (100 %) with the tested sera. ELISA based on the recombinant hexon protein thus proved useful and cheaper for detection of antibodies in turkey flocks infected with the hemorrhagic enteritis virus.

Application of cross-priming amplification (CPA) for detection of fowl adenovirus (FAdV) strains

Fowl adenoviruses (FAdVs) are widely distributed among chickens. Detection of FAdVs is mainly accomplished by virus isolation, serological assays, various polymerase chain reaction (PCR) assays, and loop-mediated isothermal amplification (LAMP). To increase the diagnostic capacity of currently applied techniques, cross-priming amplification (CPA) for the detection of the FAdV hexon gene was developed. The single CPA assay was optimised to detect all serotypes 1-8a-8b-11 representing the species Fowl aviadenovirus A-E. The optimal temperature and incubation time were determined to be 68 °C for 2 h. Using different incubation temperatures, it was possible to differentiate some FAdV serotypes. The results were recorded after addition of SYBR Green I(®) dye, which produced a greenish fluorescence under UV light. The CPA products separated by gel electrophoresis showed different "ladder-like" patterns for the different serotypes. The assay was specific for all serotypes of FAdV, and no cross-reactivity was observed with members of the genus Atadenovirus, duck atadenovirus A (egg drop syndrome virus EDS-76 [EDSV]) or control samples containing Marek's disease virus (MDV), infectious laryngotracheitis virus (ILTV) or chicken anaemia virus (CAV). The results of the newly developed FAdV-CPA were compared with those of real-time PCR. The sensitivity of CPA was equal to that of real-time PCR and reached 10(-2.0) TCID50, but the CPA method was more rapid and cheaper than the PCR systems. CPA is a highly specific, sensitive, efficient, and rapid tool for detection of all FAdV serotypes. This is the first report on the application of CPA for detection of FAdV strains.

Detection of enteric pathogens in Turkey flocks affected with severe enteritis, in Brazil

Twenty-two flocks of turkeys affected by enteric problems, with ages between 10 and 104 days and located in the Southern region of Brazil, were surveyed for turkey by PCR for turkey astrovirus type 2 (TAstV-2), turkey coronavirus (TCoV), hemorrhagic enteritis virus (HEV), rotavirus, reovirus, Salmonella spp., and Lawsonia intracellularis (Li) infections. Eleven profiles of pathogen combination were observed. The most frequently encountered pathogen combinations were TCoV-Li, followed by TCoV-TAstV-2-Li, TCoV-TastV-2. Only TCoV was detected as the sole pathogen in three flocks. Eight and 19 flocks of the 22 were positive for TAstV-2 and TCoV, respectively. Six were positive for Salmonella spp. and L. intracellularis was detected in 12 turkey flocks. Reovirus and HEV were not detected in this survey. These results throw new light on the multiple etiology of enteritis in turkeys. The implications of these findings and their correlation with the clinical signs are comprehensively discussed, illustrating the complexity of the enteric diseases.

Development and application of quantitative real-time PCR for the rapid detection of hemorrhagic enteritis virus in tissue samples

Hemorrhagic enteritis virus (HEV) is a type II avian adenovirus that causes intestinal hemorrhages accompanied with immunosuppression in 4-to-12-wk-old turkeys. In the present study, a hexon gene-based, quantitative real-time PCR with TaqMan probe was developed and applied to tissue samples from poultry farms to detect and quantify HEV genome copy numbers. The method was confirmed to be rapid, specific, and sensitive for the detection of HEV. This method is an excellent research and diagnostic tool that can be used to study pathogenesis and to gain insights into different phases of infection on poultry farms and for high-throughput epidemiologic investigations.

Interactions between Marek's disease virus Rispens/CVI988 vaccine strain and adenovirus field strain in chicken embryo fibroblast (CEF) cultures

The aim of the study was to determine the influence of adenovirus infection on the replication of Marek's disease virus vaccine strain Rispens/CVI988 during in vitro co-infection studies. Adenovirus field strain JN-5/10j was isolated from sick chickens. The study was conducted in chicken embryo fibroblast cultures (CEF). Monolayers of CEFs were infected with Rispens strain and field adenovirus strain JN-5/10j with different doses (10(1.0)-10(3.0) TCID50) in the following manner: a) simultaneously, b) first, infection with Rispens strain and after 24 h infection with adenovirus strain JN-5/10j and c) infection with adenovirus strain JN-5/10j 24 h before infection with Rispens strain. After 18, 24, 48, 72, and 96 h of incubation, the copy number of the pp38 gene of Rispens strain was determined using Real-time PCR. The results indicated that the Adenovirus infection before the infection with Rispens strain reduced the replication of the pp38 gene after 48 h by 2 log10.

Longitudinal field studies of avian metapneumovirus and turkey hemorrhagic enteritis virus in turkeys suffering from colibacillosis associated mortality

The aim of this study was to evaluate if the exposure to Avian metapneumovirus (aMPV) and/or to Turkey hemorrhagic enteritis virus (THEV) was significant for the induction of episodes of colibacillosis in aMPV and THEV vaccinated turkeys. Colibacillosis-associated mortality was recorded and longitudinal virological studies performed in three consecutive turkey flocks reared in the same farm. aMPV and THEV diagnostic swabs and blood samples were made once a week up to 14 weeks of age. Swabs were processed by molecular techniques for viruses detection and antibody titres were evaluated. Field subtype B aMPVs were detected in all flocks at different ages of life always associated with respiratory signs and increase of colibacillosis-associated mortality. THEV has been consistently detected in all flocks since the 9th week of age. Vaccination with a single dose of the THEV commercial inactivated vaccine available in Italy seems does not protect the birds from the infection. Sequence comparison of the hexon protein of one of the THEV strains detected, and strains isolated worldwide, revealed high similarity between them. These results are consistent with the notion that the hexon protein, being the major antigenic component of the virus, is highly conserved between the strains. Results showed that field aMPV infection is directly correlated to colibacillosis-associated mortality. Less clear appears the role of THEV because the endemicity of aMPV makes difficult to evaluate its role in predisposing colibacillosis in absence of aMPV. It would be interesting to further investigate this issue through experimental trials in secure isolation conditions.

Real-time fluorescence loop-mediated isothermal amplification for the diagnosis of hemorrhagic enteritis virus

Suspected cases of hemorrhagic enteritis associated with hemorrhagic enteritis virus (HEV) are becoming more frequent among yellow chickens in the Guangdong Province of China. In this study, we have developed a one-step, ecumenical, real-time fluorescence loop-mediated isothermal amplification (RealAmp) assay for the rapid diagnosis of HEV. The RealAmp assay was performed at 63°C and reduced the assay time to 15min, using a simple and portable device, the ESE-Quant Tube Scanner. The detection limit of DNA was 1fg/μl, and the detection was specific only to HEV. We also used nested PCR to evaluate the application of the RealAmp assay. The coincidence rate of the two methods was 100%. Our data indicated that the RealAmp assay provides a sensitive, specific, and user-friendly diagnostic tool for the identification and quantification of HEV for field diagnosis and in laboratory research.

Enteric viruses in Brazilian turkey flocks: single and multiple virus infection frequency according to age and clinical signs of intestinal disease

Poult enteritis complex has been associated with enteritis and reduction in growth rates in commercial turkeys worldwide. Intestinal samples from 76 turkey flocks from different Brazilian states affected or not with intestinal disorders were evaluated for the presence of adenovirus groups 1 and 2 (TAV), astrovirus types 1 and 2 (TAstV-1 and TAstV-2), turkey coronavirus (TCoV), reovirus, rotavirus, and avian nephritis virus (ANV) using PCR. The percentage of positive samples was categorized according to the geographic origin, age of the flocks, and presence of clinical signs of intestinal disease. The percentage of samples that were positive for at least one virus was 93.4%, whereas the percentage of samples that were positive for more than one virus was 69.7%. An average of 3.20 viruses per sample was detected in turkeys in the growing phase of the production cycle (1 to 4 wk of age). The TAstV-1 and TCoV were the most frequently observed viruses in growing phase turkeys and occurred simultaneously in 85% of these samples. In turkeys in the finishing phase of development (5 to 18 wk), a lower average number of viruses was observed (2.41), and the most frequent viruses isolated in these turkeys were TAstV-1 (57.1%) and rotavirus (51.8%). Overall, every virus was detected more frequently in growing phase turkeys than in finishing phase turkeys with the exception of TAV. Samples from flocks exhibiting clinical signs of intestinal disease showed a higher rate of positivity, and TAstV-1, TAstV-2, and TCoV were the most frequently occurring viruses in this cohort. Birds without clinical signs most frequently harbored TAstV-1 and rotavirus. Future studies should focus on the description and elucidation of the role of each virus, as well as the pathogenic and immunological implications of the different combinations of viruses in turkeys.

Simultaneous detection of astrovirus, rotavirus, reovirus and adenovirus type I in broiler chicken flocks

Enteric diseases cause substantial economic losses to the poultry industry. Astroviruses, rotaviruses, reoviruses, and adenovirus type 1 have been reported as a significant cause of intestinal symptoms in poultry. In the present study, intestinal samples from 70 commercial broiler chicken flocks were examined for the presence of astroviruses, rotavirus, and reovirus by reverse transcription-polymerase chain reaction, and for the presence of group I adenovirus by polymerase chain reaction. Astroviruses were identified in 38.6% of samples tested. Both avian nephritis virus and chicken astrovirus were identified in the astrovirus positive flocks, where 74.1% of these flocks were positive for only one type of astrovirus, whereas, 25.9% of these flocks were positive for both types of astrovirus. Reoviruses, rotaviruses, and adenoviruses were identified in 21.4, 18.6, and 14.3% of these flocks, respectively. Concomitant infection with two or more viruses in the same flock were also prominent, where 5.7, 5.7, 2.9, 2.9, 1.4, and 1.4% of these flocks were positive with both astrovirus and rotavirus; astrovirus and adenovirus; astrovirus and reovirus; rotavirus and adenovirus; rotavirus and reovirus; and reovirus and adenovirus respectively. Moreover, 4.3 and 2.7% of these flocks were positive for astrovirus, reovirus, and adenovirus; and astrovirus, reovirus, and rotavirus, respectively. Further studies will focus on identifying specific viral factors or subtypes/subgroups associated with disease through pathogenesis studies, economic losses caused by infections and co-infections of these pathogens, and the costs and benefits of countermeasures.

Effect of infection of turkeys with haemorrhagic enteritis adenovirus isolate on the selected parameters of cellular immunity and the course of colibacillosis

The aim of the study was to determine the effect of a Polish low-virulence isolate of haemorrhagic enteritis adenovirus (HEV) on the immune system in turkeys and on the course of colibacillosis in birds infected under laboratory conditions. Turkeys were infected per os with HEV at the dose of 10(4.3)EID50/mL and with E. coli (APEC) (serotypes 078:K80:H9) at the dose of 4x10(9)CFU/mL by injection to the thoracic air sac. The birds infected with the HEV were infected with the APEC either simultaneously or after 5 days. Five days after HEV infection, the percentages of subpopulations of the CD3+CD4+ and CD3+CD8alpha+ T cells and the IgM+ B cells were determined in blood and spleens of the HEV-infected turkeys and in the control (uninfected) birds. The course of colibacillosis was more severe in turkeys infected with the APEC 5 days after infection with the HEV than in those infected with the HEV and APEC simultaneously and than in those infected only with APEC. Five turkeys out of the 18 infected with the APEC 5 days after infection with HEV, died. Their body weights were statistically significantly lower with higher FCR values 41 days after the infection in comparison to turkeys in the other groups. A considerable decrease in the percentage of the T and B cells subpopulations in the blood were found in turkeys infected with the HEV and while the percentage of CD3+CD4+ T cells subpopulation in the spleen increased significantly, the contribution of the CD3+CD8alpha+ T cells and IgM+ B cells subpopulations were decreased. These changes in the immune system of turkeys, occurring 5 days after infection with the HEV, made them more susceptible to infection with the APEC.

Partial sequence of the DNA-dependent DNA polymerase gene of fowl adenoviruses: a reference panel for a general diagnostic PCR in poultry

Adenoviruses are frequent infectious agents in different poultry species. The traditional, serological typing of new isolates by virus neutralisation tests is now in transition to be replaced by PCR and sequencing. The first PCRs, recommended for the detection of adenoviruses, had been designed to target the gene of the major capsid protein, the hexon. In birds, members of three different genera of the family Adenoviridae may occur. Accordingly, three specific hexon PCRs had to be elaborated for the detection of adenoviruses in poultry. A significantly more sensitive PCR, targeting the viral DNA-dependent DNA polymerase gene, has been described recently. This method proved to be an efficient alternative for the general detection of adenoviruses irrespective of their genus affiliation. Fowl adenoviruses (FAdVs), isolated from chicken to date, comprise twelve serotypes classified into five virus species (FAdV-A to E). The polymerase gene sequence has been determined yet only from three FAdV types representing three species. In the present work, the panel of polymerase gene sequences was completed with those of the rest of FAdVs. The newly determined sequences will facilitate the identification of new FAdV isolates as an existing species or as a putative new FAdV. Once the polymerase sequence is known, more specific PCRs for the amplification of the hexon and other genes can be designed and performed according to the preliminary species classification.

Viral Agents Associated with Poult Enteritis in Croatian Commercial Turkey Flocks

From 2003 to 2006, samples of intestinal content and spleens from 10-day-old to 6-week-old fattening turkeys showing clinical signs of enteritis were analyzed by specific PCR and RT-PCRs for detection of haemorrhagic enteritis virus (HEV), avian reovirus (ARV), turkey astrovirus-2 (TastV-2), and turkey coronavirus (TCV). A total of 23 flocks from 6 farms were included in the study. Specific sequence for HEV hexon gene was present in 6 samples from turkeys younger than and in one turkey at 6 weeks of age. A product of TastV-2 capsid gene was detected in 17/23 intestinal content samples. A 626-bp band of sigma A (S2) encoding gene segment from avian reovirus was present in three samples, all from the same farm. Sequence analysis of 450 bp fragment of avian reovirus sigma A encoding gene sequence showed that our strain had the identity of 91.3% with the strains 138, 2408, 1733, 919, T6, and Os161. No TCV specific PCR band was found in any sample. Four flocks were positive simultaneously for HEV and TastV-2, and three flocks on TastV-2 and ARV. Severity of poult enteritis described in our study is caused by immunosuppressive TastV-2 in combination with HEV or ARV.

Confirmation of a novel siadenovirus species detected in raptors: partial sequence and phylogenetic analysis

Partial genome characterisation of a novel adenovirus, found recently in organ samples of multiple species of dead birds of prey, was carried out by sequence analysis of PCR-amplified DNA fragments. The virus, named as raptor adenovirus 1 (RAdV-1), has originally been detected by a nested PCR method with consensus primers targeting the adenoviral DNA polymerase gene. Phylogenetic analysis with the deduced amino acid sequence of the small PCR product has implied a new siadenovirus type present in the samples. Since virus isolation attempts remained unsuccessful, further characterisation of this putative novel siadenovirus was carried out with the use of PCR on the infected organ samples. The DNA sequence of the central genome part of RAdV-1, encompassing nine full (pTP, 52K, pIIIa, III, pVII, pX, pVI, hexon, protease) and two partial (DNA polymerase and DBP) genes and exceeding 12 kb pairs in size, was determined. Phylogenetic tree reconstructions, based on several genes, unambiguously confirmed the preliminary classification of RAdV-1 as a new species within the genus Siadenovirus. Further study of RAdV-1 is of interest since it represents a rare adenovirus genus of yet undetermined host origin.

Enteric viruses detected by molecular methods in commercial chicken and turkey flocks in the United States between 2005 and 2006

Intestinal samples collected from 43 commercial broiler and 33 commercial turkey flocks from all regions of the United States during 2005 and 2006 were examined for the presence of astrovirus, rotavirus, reovirus, and coronavirus by reverse transcription-polymerase chain reaction (PCR), and for the presence of groups 1 and 2 adenovirus by PCR. Phylogenetic analysis was performed to further characterize the viruses and to evaluate species association and geographic patterns. Astroviruses were identified in samples from 86% of the chicken flocks and from 100% of the turkey flocks. Both chicken astrovirus and avian nephritis virus (ANV) were identified in chicken samples, and often both viruses were detected in the same flock. Turkey astrovirus type-2 and turkey astrovirus type-1 were found in 100% and 15.4% of the turkey flocks, respectively. In addition, 12.5% of turkey flocks were positive for ANV. Rotaviruses were present in 46.5% of the chicken flocks tested and in 69.7% of the turkey flocks tested. Based upon the rotavirus NSP4 gene sequence, the chicken and turkey origin rotaviruses assorted in a species-specific manner. The turkey origin rotaviruses also assorted based upon geographical location. Reoviruses were identified in 62.8% and 45.5% of chicken and turkey flocks, respectively. Based on the reovirus S4 gene segment, the chicken and turkey origin viruses assorted separately, and they were distinct from all previously reported avian reoviruses. Coronaviruses were detected in the intestinal contents of chickens, but not turkeys. Adenoviruses were not detected in any chicken or turkeys flocks. Of the 76 total chicken and turkey flocks tested, only three chicken flocks were negative for all viruses targeted by this study. Most flocks were positive for two or more of the viruses, and overall no clear pattern of virus geographic distribution was evident. This study provides updated enteric virus prevalence data for the United States using molecular methods, and it reinforces that enteric viruses are widespread in poultry throughout the United States, although the clinical importance of most of these viruses remains unclear.

Periodic monitoring of commercial turkeys for enteric viruses indicates continuous presence of astrovirus and rotavirus on the farms

A longitudinal survey to detect enteric viruses in intestinal contents collected from turkeys in eight commercial operations and one research facility was performed using molecular detection methods. Intestinal contents were collected from turkeys prior to placement, with each flock resampled at 2, 4, 6, 8, 10, and 12 wk of age. The samples were screened for astrovirus, rotavirus, reovirus, and turkey coronavirus (TCoV) by a reverse transcriptase and polymerase chain reaction (RT-PCR), and for groups 1 and 2 adenovirus by PCR. Rotavirus was the only virus detected prior to placement (7 of 16 samples examined). All of the commercial flocks were positive for rotavirus and astrovirus from 2 until 6 wk of age, and most were intermittently positive until 12 wk of age, when the birds were processed. Of the 96 samples collected from birds on the farms, 89.5% were positive for astrovirus, and 67.7% were positive for rotavirus. All flocks were negative for TCoV, reovirus, and group 1 adenovirus at all time points, and positive for group 2 adenovirus (hemorrhagic enteritis virus) at 6 wk of age. All the flocks monitored were considered healthy or normal by field personnel. Turkeys placed on research facilities that had been empty for months and thoroughly cleaned had higher body weights and lower feed conversion rates at 5 wk of age when compared to turkeys placed on commercial farms. Intestinal samples collected at 1, 2, and 3 wk of age from these turkeys were free of enteric viruses. This report demonstrates that astroviruses and rotaviruses may be present within a turkey flock through the life of the flock. Comparison of infected birds with one group of turkeys that were negative for enteric viruses by the methods used here suggests that astrovirus and/or rotavirus may affect production. The full impact on flock performance needs to be further determined.

Enteric viruses of humans and animals in aquatic environments: health risks, detection, and potential water quality assessment tools

Waterborne enteric viruses threaten both human and animal health. These pathogens are host specific and cause a wide range of diseases and symptoms in humans or other animals. While considerable research has documented the risk of enteric viruses to human health from contact with contaminated water, the current bacterial indicator-based methods for evaluation of water quality are often ineffectual proxies for pathogenic viruses. Additionally, relatively little work has specifically investigated the risk of waterborne viruses to animal health, and this risk currently is not addressed by routine water quality assessments. Nonetheless, because of their host specificity, enteric viruses can fulfill a unique role both for assessing health risks and as measures of contamination source in a watershed, yet the use of animal, as well as human, host-specific viruses in determining sources of fecal pollution has received little attention. With improved molecular detection assays, viruses from key host groups can be targeted directly using PCR amplification or hybridization with a high level of sensitivity and specificity. A multispecies viral analysis would provide needed information for controlling pollution by source, determining human health risks based on assessments of human virus loading and exposure, and determining potential risks to production animal health and could indicate the potential for the presence of other zoonotic pathogens. While there is a need to better understand the prevalence and environmental distribution of nonhuman enteric viruses, the development of improved methods for specific and sensitive detection will facilitate the use of these microbes for library-independent source tracking and water quality assessment tools.

Application of RT-PCR for the detection of avian reovirus contamination in avian viral vaccines

An efficient procedure for the detection of avian reovirus (ARV)-specific RNA sequences in veterinary immunological medicinal products using reverse transcriptase polymerase chain reaction (RT-PCR) is described. Four ARV vaccine strains (1133, 1733, 2408 and Olson WVU2937), two ATCC strains (VR826 and VR856) as well as several ARV field isolates obtained from domestic, wild and pet birds could be easily detected with S2- and S4-specific primers. The identity of the amplified fragments was confirmed by restriction endonuclease analysis and sequence analysis. Furthermore, not only the starting substrates used for the production of a vaccine, but also additives and the manufacturing process (matrix effects) can influence the results. These RT-PCRs have been useful for screening poultry vaccines for extraneous ARV in the quality control of biologicals used in veterinary medicine.