Research Note: Molecular and pathologic characterization of avian adenovirus isolated from the oviducts of laying hens in eastern Japan.

Cases of poor egg production were investigated in 2 layer farms from Ibaraki Prefecture in eastern Japan. To identify any microbial agents that may have caused the problem, necropsy, bacterial isolation, histopathology, and virus detection were performed. Members of the avian adenoviruses was detected by PCR in oviduct samples from both farms; chicken anemia virus coinfection was also confirmed in one of the farms. Avian adenovirus was isolated from the oviducts of the affected chickens on each farm. Inoculation into chick embryos showed tropism for the chorio-allantoic membrane. Stunting and hemorrhaging was observed in all infected embryos, as well as death in a few. Inoculation of 1-day-old specific pathogen-free chicks, and 400-day-old commercial hens, did not result in any significant findings. The isolated viruses were analyzed by sequencing of the hexon gene and were confirmed as fowl adenovirus type-c serotype-4 (FAdV-4). The 2 virus strains were found to be 99.29% similar to each other. One of the strains, Japan/Ibaraki/Y-H6/2016, was 99.15% similar to the KR5 strain. The other, Japan/Ibaraki/M-HB2/2016, was 99.57% similar to the KR5 strain. Fiber-2 gene analysis confirmed the identity as FAdV-4 that is closely related to nonpathogenic strains. Although nonpathogenic to chicks and laying hens, this infection can possibly cause economic damage. Perhaps the bigger concern is the effect on infected breeder operations. Because the virus is fatal to 9.09% of infected embryos, this could translate to a considerable loss in chick production owing to embryonic death. This is the first report of detection and isolation of FAdV-4 from the chicken oviduct; however, further studies are needed to elucidate its impact on both layer and breeder flocks. Indeed, FAdV-4 has negative effects on the avian reproductive tract as well.

Epidemiology, molecular characterization, and recombination analysis of chicken anemia virus in Guangdong province, China.

Chicken anemia virus (CAV) causes severe anemia and immunosuppression in young chickens and a compromised immune response in older birds, resulting in great economic losses to the poultry industry worldwide. Here, we report the molecular epidemiology and characterization of CAV circulating in poultry in Guangdong province, China. Ninety-one of 277 chickens collected from 2016 to 2017 were CAV positive. Full-genome sequencing revealed the presence of eight separate strains. Phylogenetic analysis based on the genome sequences obtained in this study and related sequences available in the GenBank database showed that all of the CAV isolates exhibit a close relationship to each other and belong to the same genotypic group. Putative recombination events were also detected in the genomes of the newly isolated CAVs. Collectively, our findings underscore the importance of CAV surveillance and provide information that will lead to a better understanding of the evolution of CAV.

The diseases suspected of the involvement of chicken anemia virus infection in 11 to 14-weeks old replacement pullets from eastern Japan: a case report.

Three strains of chicken anemia virus (CAV) were detected in 11 to 14-weeks old chickens, showing depression, wasting, and increased mortality, from three farms in eastern Japan. Another strain was detected in 12-weeks old chickens from one farm without clinical signs. Bacterial infections were suggested in three farms with clinical signs and its involvement in the occurrence of the diseases might be suspected. Sequence analysis of the VP1, VP2, and VP3 genes of four CAV strains revealed that the three from farms with clinical signs belonged to genotype A2, whereas that from the apparently-normal farm belonged to A3. This may be a rare case report about the diseases suspected of the involvement of the CAV infection in older birds.

Pathological and virological analysis of concurrent disease of chicken anemia virus infection and infectious bronchitis in Japanese native chicks.

A concurrent infection of chicken anemia virus (CAV) and infectious bronchitis virus (IBV) was detected in Japanese native chicks in 2017, in which a high mortality rate (97.7%) was recorded in a small flock of 130 chicks exhibiting poor growth. Histological examination revealed that the affected chicks exhibited two different pathological entities: one was severe hematopoietic and lymphocytic depletion with abnormally large cells containing intranuclear inclusion bodies of CAV, whereas the other was renal tubular necrosis due to IBV infection. Immunohistochemistry detected CAV antigens in the bone marrow, liver, and spleen as well as IBV antigens in the kidneys, trachea, and air sacs. CAV was isolated from the liver sample of the chicks, and the isolated strain was designated as CAV/Japan/HS1/17. A phylogenetic analysis of the CAV VP1 gene revealed that CAV/Japan/HS1/17 is genetically similar to Chinese strains collected from 2014 to 2016. An experimental infection was performed using CAV/Japan/HS1/17 and specific-pathogen-free chicks to determine the pathogenicity of CAV/Japan/HS1/17. The isolate caused 100% anemia and 70% mortality to chicks inoculated at one day old, 80% of chicks inoculated at seven days old also developed anemia, and 10% died from CAV infection. These results suggest that the unusually high mortality in Japanese native chicks can be attributed to dual infection with both CAV and IBV. The results of the experimental infection suggest that CAV/Japan/HS1/17 has a pathogenic potential to specific-pathogen-free chicks and a relatively higher pathogenicity than previous Japanese CAV strains.

Chicken anemia virus in northern Vietnam: molecular characterization reveals multiple genotypes and evidence of recombination.

Chicken anemia virus (CAV) has a ubiquitous and worldwide distribution in the chicken production industry. Our group previously reported a high seroprevalence of CAV in chickens from northern Vietnam. In the present study, tissue samples collected from a total of 330 broiler and breeder commercial chickens in eleven provinces of northern Vietnam were tested for CAV infection. All samples were collected from clinically suspected flocks and diseased birds. The CAV genome was detected in 157 out of 330 (47.58%) chicken samples by real-time PCR. The rate of CAV genome detection in young chickens at 2-3 weeks of age (61.43%), which had not been previously reported in Vietnam, was significantly higher than that in older chickens at 4-11 (44.83%) and 12-28 (35.71%) weeks of age. For nine representative CAV strains from broiler chickens, analysis of the entire protein-coding region of the viral genome was conducted. Phylogenetic analysis of the VP1 gene indicated that the CAVs circulating in northern Vietnam were divided into three distinct genotypes: II, III, and V. Only one of the nine Vietnamese CAV strains clustered with a vaccine strain (Del-Ros), whereas the other eight strains did not cluster with any vaccine strains. Among the three genotypes, genotype III was most widely found in northern Vietnam and this included three sub-genotypes (IIIa, IIIb, and IIIc). The Vietnamese CAV strains were closely related to the Chinese, Taiwanese, and USA strains. One strain was defined to be of genotype V, which is a newly reported CAV genotype. Moreover, recombination analysis suggests that this novel genotype V was generated by recombination between genotype II and sub-genotype IIIc.

Cross-species transmission of poultry pathogens in backyard farms: ducks as carriers of chicken viruses.

In backyard farms of Lao People's Democratic Republic, mixed-species rearing of poultry is a breeding-ground for cross-species transmission. Here, the epidemiology of viruses circulating among backyard poultry in Vientiane Province was assessed to guide future control strategies. Oral/tracheal and cloacal swabs, collected from 605 poultry (308 ducks, 297 chickens) between 2011 and 2015, were screened by PCR for Newcastle disease virus (NDV), coronavirus (CoV) and chicken anaemia virus (CAV). Chicken sera were screened for anti-NDV antibodies by ELISA. Statistical and phylogenetic analyses revealed transmission patterns and relationships. Closely related strains co-circulated in chickens and ducks. While CoV RNA was detected in oral/tracheal swabs of 9.3% of the chickens and 2.4% of the ducks, rates were higher in faecal swabs of both species (27.3% and 48.2%). RNA of infectious bronchitis virus (IBV) and duck CoV was found in faecal swabs of chickens (19.7% and 7.1%) and ducks (4.1% and 44.1%). Moreover, DNA of the generally chicken-specific CAV was detected in oral/tracheal swabs of chickens (18.1%) and, sporadically, of ducks (2.4%). Despite serological evidence of NDV circulation or vaccination (86.9%), NDV RNA was not detected. We found a high prevalence and indication for cross-species transmission of different CoV strains in backyard poultry. Interestingly, ducks served as biological, or at least mechanical, carriers of viral strains closely related not only to IBV, but also to CAV. Bird containment and poultry species separation could be first steps to avoid cross-species transmission and emergence of novel strains with broad host range and enhanced pathogenicity. RESEARCH HIGHLIGHTS High rates of avian viruses were detected by PCR in backyard poultry from Lao PDR. Diverse coronavirus and chicken anemia virus strains co-circulated. Phylogenetic analyses suggested virus transmission between chickens and ducks. Serological evidence of Newcastle disease was found, but viral RNA was not detected.

Prevalence of Fowl Adenovirus Serotype 4 and Co-Infection by Immunosuppressive Viruses in Fowl with Hydropericardium Hepatitis Syndrome in Shandong Province, China.

Fowl adenovirus serotype 4 (FAdV-4) is the pathogenic agent of hydropericardium hepatitis syndrome (HHS) in chickens and ducks, which has caused huge economic losses for the Chinese poultry industry since 2015. In order to objectively determine the prevalence and co-infection status of the virus in Shandong province in China, we analyzed a total of 679 clinical cases of chickens and ducks from 36 farms in the province. The results showed that the FAdV-4 infection rate was 65.2% (443/679), and the rate in breeder ducks was almost two-fold higher than that in breeder chickens (68.57% vs. 34.30%). Notably, co-infection by H9N2 avian influenza virus, infectious bursal disease virus, and/or chicken infectious anemia virus was very common in the 443 FAdV-4-positive cases. Furthermore, phylogenetic analysis of the hexon genes of four Shandong FAdV-4 isolates revealed that these strains clustered into Indian reference strains, indicating that the Shandong FAdV-4 strains might have originated in India. These findings provide the first data on the prevalence and co-infection status of FAdV-4 in Shandong province, which may serve as a foundation for the prevention of FAdV-4 in the field.

Identification of four serotypes of fowl adenovirus in clinically affected commercial poultry co-infected with chicken infectious anaemia virus in Trinidad and Tobago.

Fowl adenovirus (FAdV), which causes the high-impact diseases such as inclusion body hepatitis and hepatitis-hydropericardium syndrome, is of major concern to the poultry industry internationally. This study was carried out in direct response to mortality rates of up to 75% in commercial broiler flocks in Trinidad, West Indies. Symptoms in 3- to 8-week-old broilers and 13- to 18-week-old pullets pointed to infection with an immunosuppressive viral pathogen. The objectives of the study were to determine whether the infectious agent FAdV, along with other viral pathogens, was responsible for the clinical disease, and to obtain information on the serotypes of FAdV that were infecting the birds. Tissue samples from clinically affected birds from eight different farms were tested for chicken infectious anaemia virus (CIAV) and infectious bursal disease virus (IBDV) by real-time reverse transcription polymerase chain reaction (PCR) and for FAdV by conventional PCR. The birds tested positive for FAdV and CIAV, but negative for IBDV. The gene corresponding to the L1 loop of the hexon protein for FAdV was amplified and sequenced. Phylogenetic analysis of seven FAdV strains inferred that four serotypes were likely to be circulating in the chickens. Well supported genetic relatedness was observed for serotype 8a (97.8%), 8b (97.8%), 9 (95.8%) and 11 (98.8%-99.5%). This is the first published report from Trinidad and Tobago on the presence and circulation of pathogenic FAdV strains, in combination with CIAV, in poultry. The data demonstrate a possible need for the introduction of serotype-specific vaccines against FAdV, as well as vaccines against CIAV, in broilers in the region and emphasize the importance of maintaining high levels of biosecurity on farms to prevent the spread of these potentially devastating viruses between farms.

Development of real-time PCR assays for single and simultaneous detection of infectious bursal disease virus and chicken anemia virus.

Infectious bursal disease virus (IBDV) and chicken anemia virus (CAV) cause relevant immunosuppressive diseases in poultry. Clinical diagnosis of these viruses is challenging given the different disease presentations and the frequent occurrence of co-infections with other pathogens. Here, we standardized and validated simplex and duplex RT-qPCR assays for the straightforward detection of IBDV and CAV. The qPCR assays are based on primers and hydrolysis probes that target highly conserved regions of IBDV and CAV genomes. Analytical sensitivity tests on 10-fold serial dilutions containing 100-108 viral genomes indicated that the simplex assays have good determination coefficients and efficiency and detect a wide range of virus doses (102 to 108 molecules copies/reactions). The relatively small values of intra- and inter-assay variability ensure the repeatability and support its reproducibility in different diagnostic and research facilities. The assays are also efficient tools for absolute quantification as indicated by the analytical performance analysis. The assays have an excellent specificity and absence of cross-reactivity with negative samples, or with other common avian viruses. The simplex IBDV and CAV assays use probes labelled with different dyes (FAM and HEX) and can be multiplexed for the simultaneous detection of both viruses. The determination coefficients, PCR efficiencies, and relatively small intra- and inter-assay variability were comparable to the simplex assays. This duplex assay is the first to simultaneously detect IBDV and CAV using the same RNA extraction from the bursa of Fabricius in a single and straightforward step. Therefore, this method is time saving, provides quantitative results for both targets without any cross-reaction, and reduces the risk of carrying-over contaminations. The qPCR assays here developed can be used in simplex and duplex formats for detection and quantification of large number of samples with reliable sensitivity and specificity. These tools are expected to improve surveillance and control of these ubiquitous viruses.

Development of a loop-mediated isothermal amplification assay for the detection of chicken anemia virus.

Chicken anemia virus (CAV) infection has been reported in various poultry industries worldwide. Since CAV infection is becoming increasingly prevalent, especially in local chickens of China, rapid CAV detection has become essential. The conventional diagnostic methods are time consuming and need special expertise. Therefore, in this study, we developed a specific and sensitive loop-mediated isothermal amplification (LAMP) assay for CAV detection by using multiple sequence alignment of VP2. This assay was performed at 61°C for 1 h, and there was no non-specific reaction to common avian disease viruses. The detection limit was 65 copies of viral DNA; thus, this assay showed similar sensitivity to quantitative polymerase chain reaction (qPCR) but it was more sensitive than conventional PCR. Moreover, this assay was performed using clinical samples. The LAMP assay results were 83.6% correlated to the PCR results of the clinical samples, indicating that this method is an effective tool for the rapid detection of CAV.

Characterization of full genome sequences of chicken anemia viruses circulating in Egypt reveals distinct genetic diversity and evidence of recombination.

Chicken anemia virus (CAV) is one of the commercially important diseases of poultry worldwide. In Egypt, CAV has been reported to be a potential threat to the commercial poultry sectors. Hence, this study was aimed at isolation and full genomic analysis of CAVs circulating in chicken populations in different geographical location in Egypt. A total of 42 samples were collected from broiler chicken flocks in 9 governorates in Egypt from 12 to 42 days of age. The mortality rate observed among chickens was ranging from 3% to 22%. Nineteen out of 42 farms were found positive for the CAV genome by polymerase chain reaction (PCR). Full genome sequencing was conducted for 18 positive samples. Genetic analysis revealed a high similarity of >99% in 11 viruses with the vaccine strain Del-Ros; while the other seven samples shared close similarity to CAV field strains isolated from China, Taiwan, and Brazil. The data also indicated Q139 and Q144 amino acids substitutions among the VP1 of Egyptian field strains, which are known to be important in virus replication and spread. Phylogenetic analysis of the sequenced viruses (n = 18) based on either the full gene nucleotide sequence or VP1 coding sequence, suggested the circulation of four distinct genotypes in Egypt designated as group A, B, C and D. Moreover, evidence of recombination was detected among four Egyptian CAVs located within group A. The findings of this study succeeded to elucidate the epidemiological and genetic features of CAVs circulating in Egypt, and underscores the important of CAVs surveillance.

Newcastle disease virus-attenuated vaccine co-contaminated with fowl adenovirus and chicken infectious anemia virus results in inclusion body hepatitis-hydropericardium syndrome in poultry.

Inclusion body hepatitis-hydropericardium syndrome (IBH-HPS) induced by fowl adenovirus type 4 (FAdV-4) has caused huge economic losses to the poultry industry of China, but the source of infection for different flocks, especially flocks with high biological safety conditions, has remained unclear. This study tested the pathogenicity of Newcastle disease virus (NDV)-attenuated vaccine from a large-scale poultry farm in China where IBH-HPS had appeared with high mortality. Analysis revealed that the NDV-attenuated vaccine in use from the abovementioned poultry farm was simultaneously contaminated with FAdV-4 and chicken infectious anemia virus (CIAV). The FAdV and CIAV isolated from the vaccine were purified for the artificial preparation of an NDV-attenuated vaccine singly contaminated with FAdV or CIAV, or simultaneously contaminated with both of them. Seven-day-old specific pathogen-free chicks were inoculated with the artificially prepared contaminated vaccines and tested for corresponding indices. The experiments showed that no hydropericardium syndrome (HPS) and corresponding death occurred after administering the NDV-attenuated vaccine singly contaminated with FAdV or CIAV, but a mortality of 75% with IBH-HPS was commonly found in birds after administering the NDV-attenuated vaccine co-contaminated with FAdV and CIAV. In conclusion, this study found the co-contamination of FAdV-4 and CIAV in the same attenuated vaccine and confirmed that such a contaminated attenuated vaccine was a significant source of infection for outbreaks of IBH-HPS in some flocks.

Co-infection of fowl adenovirus with different immunosuppressive viruses in a chicken flock.

In poultry, fowl adenovirus (FAdV) and immunosuppressive virus co-infection is likely to cause decreased egg production, inclusion body hepatitis, and pericardial effusion syndrome. In this study, fowl adenovirus infection was found in parental and descendent generations of chickens. We used quantitative polymerase chain reaction (PCR) and dot blot hybridization to detect the infection of reticuloendotheliosis (REV), avian leukosis virus (ALV), and chicken infectious anemia virus (CIAV) in 480 plasma samples. The test samples were 34.58% FADV-positive, 22.29% REV-positive, 7.5% CAV-positive, and 0.63% ALV-positive. Sequence analysis showed that FADV belonged to serotype 7, which can cause inclusion body hepatitis. The ALV strain was ALV-A, in which the homology of gp85 gene and SDAU09C1 was 97.3%. The positive rate was lower because of the purification of avian leukemia, whereas the phylogenetic tree analysis of REV showed that the highest homology was with IBD-C1605, which was derived from a vaccine isolate. Through pathogen detection in poultry we present, to our knowledge, the first discovery of fowl adenovirus type 7 infection in parental chickens and found that there was co-infection of FAdV and several immunosuppressive viruses, such as the purified ALV and CIAV. This indicates that multiple infection of different viruses is ever-present, and more attention should be given in the diagnosis process.

Viruses with Circular Single-Stranded DNA Genomes Are Everywhere!

Circular single-stranded DNA viruses infect archaea, bacteria, and eukaryotic organisms. The relatively recent emergence of single-stranded DNA viruses, such as chicken anemia virus (CAV) and porcine circovirus 2 (PCV2), as serious pathogens of eukaryotes is due more to growing awareness than to the appearance of new pathogens or alteration of existing pathogens. In the case of the ubiquitous human circular single-stranded DNA virus family Anelloviridae, there is still no convincing direct causal relation to any specific disease. However, infections may play a role in autoimmunity by changing the homeostatic balance of proinflammatory cytokines and the human immune system, indirectly affecting the severity of diseases caused by other pathogens. Infections with CAV (family Anelloviridae, genus Gyrovirus) and PCV2 (family Circoviridae, genus Circovirus) are presented here because they are immunosuppressive and affect health in domesticated animals. CAV shares genomic organization, genomic orientation, and common features of major proteins with human anelloviruses, and PCV2 DNA may be present in human food and vaccines.

Genetic Analysis of Two Chicken Infectious Anemia Virus Variants-Related Gyrovirus in Stray Mice and Dogs: The First Report in China, 2015.

Chicken infectious anemia virus (CIAV) causes acute viral infection in chickens worldwide. It can infect chickens of all ages, but the disease is seen only in young chickens and is characterized by hemorrhagic lesions in the muscles, atrophic changes in the lymphoid organs, aplastic bone marrow, and immunosuppression causing increased mortality. Previous studies have demonstrated that CIAV can be isolated from blood specimens of humans and fecal samples of stray cats. In the present study, two variants of CIAV were isolated from fecal samples of mice (CIAV-Mouse) and stray dogs (CIAV-Dog), respectively. The genome of the two CIAV variants was sequenced and the results of the recombination detection program suggested that the CIAV-Dog strain could be a recombinant viral strain generated from parental CIAV strains, AB119448 and GD-1-12, with high confidence. Particularly, these findings were obtained from the comparison of genetic diversity and the relationship of CIAV between different hosts. This is the first report indicating that there is a significant difference in the number of transcription factor binding sites in CIAV noncoding regions from different hosts. Further studies are required to investigate the large geographic distribution of CIAV and monitor the variants, host range, and associated diseases.

A survey for selected avian viral pathogens in backyard chicken farms in Finland.

Backyard poultry are regaining popularity in Europe and increased interest in the health and management of non-commercial farms has resulted. Furthermore, commercial poultry farm owners have become concerned about the risk represented by contagious avian diseases that nearby backyard poultry could transmit. Fifty-one voluntary backyard chicken farms were visited between October 2012 and January 2013. Blood samples and individual cloacal swabs were collected from 457 chickens. In 44 farms (86%), one or more of the tested chickens had antibodies against avian encephalomyelitis and chicken infectious anaemia viruses, 24 farms (47%) had chickens seropositive for infectious bronchitis virus, 10 farms (20%) had chickens seropositive for infectious bursal disease virus, six farms (12%) had chickens seropositive for infectious laryngotracheitis virus and two farms (5.4%) had chickens seropositive for avian influenza virus. No farms had chickens seropositive for Newcastle disease virus. Of the 51 farms, five (10%) had chickens positive for coronavirus reverse transcription polymerase chain reaction. A phylogenetic analysis showed that all backyard chicken coronaviruses collected were QX type infectious bronchitis viruses. All chickens tested for avian influenza and Newcastle disease viruses using real time reverse transcription polymerase chain reaction were negative. To our knowledge, there is no evidence to date to suggest that these diseases would have been transmitted between commercial and non-commercial flocks.

Molecular characterization of chicken infectious anemia virus from contaminated live-virus vaccines.

The aim of this study was to investigate possible causes of the pervasiveness of chicken infectious anemia virus (CIAV) infection in chickens in recent years in China. A total of 14 batches of live-virus vaccines were examined using PCR to detect CIAV contamination, of which only 2 samples (a Newcastle disease vaccine and a fowl pox vaccine) tested positive for CIAV. These Newcastle and fowl pox vaccines were then inoculated into 1-day-old specific-pathogen-free chickens. Serum samples were collected from chickens infected with the PCR-positive vaccines, and these tested positive for CIAV-specific antibodies as tested using ELISA. In addition, DNA samples isolated from the serum samples also tested positive by PCR. The results indicated that the samples were contaminated with CIAV and identified 2 exogenous CIAV strains, designated CIAV-N22 and CIAV-F10, in the respective samples. The full genome sequences of these novel CIAV strains were sequenced and analyzed. Phylogenetic tree analysis indicated that the CIAV-F10 strain might represent a recombinant viral strain arising from the parental CIAV strains JQ690762 and KJ728816. Overall, the results suggested that vaccination with CIAV-contaminated vaccines contributed to the prevalence and spread of CIAV infection in chickens. Furthermore, the CIAV contaminant was likely subsequently transmitted to commercial chickens through congenital transmission. Our findings therefore highlight the need for more extensive screening of live-virus vaccines for poultry in China to reduce the threat of contamination with exogenous viruses.

Genomic Analysis of the Chicken Infectious Anemia Virus in a Specific Pathogen-Free Chicken Population in China.

The antibody to chicken infectious anemia virus (CIAV) was positive in a specific pathogen-free (SPF) chicken population by ELISA test in our previous inspection, indicating a possible infection with CIAV. In this study, blood samples collected from the SPF chickens were used to isolate CIAV by inoculating into MSB1 cells and PCR amplification. A CIAV strain (SD1403) was isolated and successfully identified. Three overlapping genomic fragments were obtained by PCR amplification and sequencing. The full genome sequence of the SD1403 strain was obtained by aligning the sequences. The genome of the SD1403 strain was 2293 bp with a nucleotide identity of 94.8% to 98.5% when compared with 30 referred CIAV strains. The viral proteins VP2 and VP3 were highly conserved, but VP1 was not relatively conserved. Both amino acids 139 and 144 of VP1 were glutamine, which was in accord with the low pathogenic characteristics. In this study, we first reported that CIAV exists in Chinese SPF chicken populations and may be an important reason why attenuated vaccine can be contaminated with CIAV.

Impact of virus load on immunocytological and histopathological parameters during clinical chicken anemia virus (CAV) infection in poultry.

Chicken anemia virus (CAV) is one the important pathogen affecting commercial poultry sector globally by causing mortality, production losses, immunosuppression, aggravating co-infections and vaccination failures. Here, we describe the effects of CAV load on hematological, histopathological and immunocytochemical alterations in 1-day old infected chicks. The effects of CAV on cytokine expression profiles and generation of virus specific antibody titer were also studied and compared with viral clearance in various tissues. The results clearly confirmed that peak viral load was achieved mainly in lymphoid tissues between 10 and 20 days post infection (dpi), being highest in the blood (log1010.63 ±0.87/ml) and thymus (log1010.29 ±0.94/g) followed by spleen, liver, bone marrow and bursa. The histopathology and immunoflowcytometric analysis indicated specific degeneration of T lymphoid cells in the thymus, spleen and blood at 15 dpi. While the transcript levels of interleukin (IL)-1, IL-2, IL-12 decreased at all dpi, interferon (IFN)-γ increased (3-15 fold) during early stages of infection and the appearance of virus specific antibodies were found to be strongly associated with virus clearance in all the tissues. Our findings support the immunosuppressive nature of CAV and provide the relation between the virus load in the various body tissues and the immunopathological changes during clinical CAV infections.

Serological and molecular detection of chicken anaemia virus in Iranian poultry flocks.

Despite chicken being the main natural host for chicken anaemia virus (CAV), other birds may be infected by this virus too. In this study we examined chickens, turkeys, and quails for serological and molecular detection of CAV in Iran. For this study, we used 375 sera and thymus samples from broiler chickens, 100 sera and blood samples from turkeys, and 250 thymus samples from quails. The sample were collected from all over Iran between 2009 and 2010. Serum samples were examined using ELISA. DNA was extracted from thymus and blood samples and was analysed for the presence of the VP2 gene of CAV by polymerase chain reaction. Results showed that 69.07% of chickens were positive for antibody to CAV. In chickens, 58.4% were positive for CAV VP2 gene. The prevalence of CAV infection in quails was 15%, based on CAV VP2 gene detection. In turkey flocks, all turkeys (100%) were negative with respect to detection of VP2 CAV gene and CAV antibodies. It was concluded that, for the span of the time considered in this study, CAV has circulated in broiler chickens and quails throughout Iran.