Persistence and vertical transmission of chicken anaemia agent in experimentally infected laying hens

Effects of garlic, onion, and apple cider vinegar as a herbal mixture on performance and blood traits of broilers inoculated with chicken infectious anemia virus

This study assessed the effects of a herbal mixture (HM) to protect poultry against chicken infectious anemia (CIA) and to modulate the adverse effects of this virus on performance, mortality, blood profile, white blood cells (WBCs) count, liver enzymes, liver histopathology, and intestinal morphology. Therefore, 240 one-day-old male broiler chicks (Ross 308) were divided into four experimental groups, with six replicates and ten chicks per group. The experimental groups consisted of a control group and groups with 2.5%, 5%, and 7.5% HM, all based on corn-soybean meal. All chicks were inoculated with the CIA virus (CIAV) on day 7. The results showed that supplementation of 2.5% of HM to broiler diet increased feed intake (FI) (P < 0.05) and also increased body weight (BW) and weight gain (WG) slightly (P > 0.05). Adding 7.5% HM caused a reversible decrease in FI, BW, and WG and increased FCR. Compared with the control group, mortality rates declined with an additional dose of HM in CIAV-infected chickens. HM supplementation in the diet of CIAV-infected chickens increased hematocrit (HCT), hemoglobin (Hb), and mean corpuscular volume (MCV) and decreased mean corpuscular hemoglobin concentration (MCHC) compared to the control (P < 0.05). Lymphocyte percentage and lymphocyte/heterophile ratio increased in HM-supplemented groups, especially at 2.5% (P < 0.05), and heterophile and granulocyte percentages were reduced (P < 0.05). Liver enzyme alkaline phosphatase (ALP) and liver steatosis declined in the 2.5% HM-treated group compared to the control (P < 0.05). It was concluded that adding 2.5% of the HM to the CIAV-infected broiler's diet did not negatively affect chicken performance. In addition to its hypolipidemic effects, it could prevent HCT and Hb from decreasing in chicks infected with CIAV and positively affect leukocyte types and liver enzymes. Interestingly, an additional dose of HM in the diet of the CIAV-infected broilers reduced mortality. Therefore, adding 2.5% of HM could prevent the adverse effects of CIA on hematological traits in broiler chicken flocks without adverse effects on performance.

Genomic Characterization of CIAV Detected in Contaminated Attenuated NDV Vaccine: Epidemiological Evidence of Source and Vertical Transmission From SPF Chicken Embryos in China

Live attenuated vaccines have been extensively used to prevent infectious disease in poultry flocks. Freedom from exogenous virus is a high priority for any veterinary vaccines. Recently, attenuated Newcastle disease virus (NDV) vaccines were detected to be contaminated with chicken infectious anemia virus (CIAV) in a routine screening for exogenous viruses. To investigate the possible source of the contamination, we conducted virological tests on a specific-pathogen-free (SPF) layer breeder flock that provide the raw materials for vaccines in this manufacturer. Firstly, CIAV antibodies in serum and egg yolks samples of the SPF laying hens were detected by ELISA assays. The results showed that CIAV antibodies in serum and egg yolks were 62% positive and 57% positive, respectively. Then, DNA was extracted from the NDV vaccines and SPF chicken embryonated eggs, and detected by molecular virology assays. The results showed that three assays for pathogens in embryonated eggs had similar positive rates (35.8%). And the sequences of CIAV from SPF embryos and NDV vaccines consisted of 2,298 nucleotides (nt) with 100% homology. The new full-length genome of CIAV was designated SDSPF2020 (Genbank accession number: MW660821). Data showed SDSPF2020 had the sequence similarities of 95.8–99.6% with reference strains, and shared the highest homology with the Chinese strain HLJ15125. These results strongly suggested that exogenous CIAV contamination is most likely caused by wild virus infection in SPF flocks and vertical transmission to chicken embryos. Collectively, this study illustrated that vertical transmission of CIAV from a SPF layer breeder flock to embryos was a non-neglible way for exogenous virus contamination in vaccine production.

Genomic Sequence and Pathogenicity of the Chicken Anemia Virus Isolated From Chicken in Yunnan Province, China

Chicken anemia virus (CAV), which has been reported in many countries, causes severe anemia and immunosuppression in chickens. In this study, a CAV strain YN04 belonging to genotype A was first identified from infected chickens in Yunnan province, China. Moreover, the animal infection experiments further confirmed that the strain YN04 is a highly pathogenic strain, which can cause 86.67% mortality in chickens in the infection group. The mean death time of infected chickens was 13.1 days post infection (dpi). CAV infection induced severe anemia with significant decrease in packed cell volume (PCV), and serious atrophy and lesion of thymus and bursa with high viral load at 14 dpi. Besides, CAV infection caused a sharp decrease in chicken body weight and immune organ indices including the ratio of thymus or bursa to body weight at 21 dpi, which displayed the potential immunosuppression state at this stage. These findings enrich the epidemiological data on CAV and may provide information for preventing its further spread in Yunnan province, China.

Establishment of an In Vitro Model of Persistent Chicken Anemia Virus Infection

Persistent infection of chicken anemia virus (CAV) in chickens has been suspected to result in immunosuppression and exogenous virus contamination within vaccine production. However, no direct evidence for persistent CAV infection has thus far been obtained. In this study, we aimed to establish an in vitro model of persistent CAV infection. CAV-infected MDCC-MSB1 (MSB1) cells, a Marek’s disease virus-transformed continuous cell line, were cultured in the presence of both CAV and CAV neutralizing antibody (NA). Cell viability, expression of viral antigens, viral DNA, and recovery of CAV were examined by acridine orange/propidium iodide staining, immunofluorescence measurement, real-time PCR, and viral isolation, respectively. The results indicated that CAV was maintained and possibly replicated in CAV-infected cells cultured in the presence of NA, without affecting host cell viability. It was also shown that persistently infectious CAV induced cell death again after removing NA. The persistent infection of CAV in MSB1 cells was not related to viral gene mutation. In summary, we have herein established a novel model of persistent CAV infection in MSB1 cells cultured in the presence of NA.

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 infectious anaemia virus infections in chickens in northern Vietnam: epidemiological features and genetic characterization of the causative agent

Since the first report of chicken infectious anaemia virus (CIAV) in Vietnam in 2013, there have not been many studies focused on the detection of CIAV or the molecular characteristics of the virus. This study attempted to investigate the presence of CIAV in northern Vietnam by molecular-based methods. Regarding the spatial distribution of CIAV, the PCR-based results showed that CIAV was detected in 47 out of 64 farms (73.4%) and in all 10 investigated provinces. Of the 119 samples assayed by PCR, 74 (62.2%) tested positive for CIAV DNA. By arranging the samples into different categories, it was found that CIAV was detected at high rates (above 50%) based on all 4 evaluated criteria as follows: production type of chicken, housing system, flock size and age group. Different housing systems were significantly associated with the detection rates of CIAV (P = 0.003). By genetic analyses, all of the Vietnamese CIAVs were found to (i) lack substitutions related to attenuation substitutions, (ii) group separately from vaccine-like CIAVs and (iii) belong to genogroups G2 and G3 of CIAV. Because of the wide distribution of CIAV and because the virus was confirmed not to be vaccine-like viruses, it is suggested that further studies be conducted on the clinical form of chicken infectious anaemia, as well as the immunosuppressive effect of CIAV on chickens in Vietnam.RESEARCH HIGHLIGHTS Wide distribution of chicken infectious anaemia virus (CIAV) in northern Vietnam.Vietnamese CIAVs belong to genogroups G2 and G3 of CIAV.

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.

Synergetic pathogenicity of Newcastle disease vaccines LaSota strain and contaminated chicken infectious anemia virus

Newcastle disease virus (NDV)-attenuated vaccine has been widely used to prevent ND in poultry flocks, while many reports also mentioned the exogenous virus contamination in attenuated vaccines, which might be the reason for the widespread of some contagious diseases. Recently, the chicken infectious anemia virus (CIAV) contamination in the NDV-attenuated vaccine was also found in China, though no systemic study has studied the pathogenicity or infection mechanism of this special transmission route. Accordingly, simulation experiments were launched using CIAV isolated from a contaminated NDV-attenuated vaccine. Results showed that using NDV-attenuated vaccine contaminated with CIAV could cause CIA in chickens with obvious symptoms, including anemia, hemorrhage, lymphoatrophy, and growth retardation, while the synergistic reaction of CIAV and LaSota prompted their multiplication in vivo and disturbed the production of antibodies against each other. And CIAV could significantly reduce the NDV antibody titers and decrease the protective effectiveness. This study showed the synergetic pathogenicity of CIAV and LaSota strain after using contaminated NDV-attenuated vaccine, helping us to understand how the CIAV causes infection and induces severe diseases with a relatively low dose through the mouth, as well as reminding us that the damage of an attenuated vaccine contaminated with CIAV even in extremely low dose is not insignificant.

Efficacy of CpG-ODN and Freund's immune adjuvants on antibody responses induced by chicken infectious anemia virus VP1, VP2, and VP3 subunit proteins

Chicken infectious anemia virus is an important pathogen that causes severe anemia and immunosuppression in chickens, leading to serious economic losses worldwide in the poultry industry. However, no commercialized inactivated vaccine, subunit vaccine, or genetically engineered vaccine that is effective for controlling this virus is available. In this study, 3 recombinant plasmids were constructed to produce corresponding viral proteins in an Escherichia coli system. The immune effects of the subunit proteins accompanied by CpG-ODN or Freund's immune adjuvants were evaluated and analyzed in systemic animal experiments. The results showed that VP1 induced the highest antibody titers with the participation of VP2 protein, indicating better protection under combined treatment, and the CpG-ODN adjuvant induced higher antibody titers and smaller dispersion of antibody titers than Freund's adjuvants. This is the first study to demonstrate that VP1 protein formulated with VP2 and CpG-ODN adjuvant can induce highest antibody titers and markedly enhance the immune response, indicating its promise as a vaccine candidate.

Study of dynamic of chicken infectious anaemia virus infection: which sample is more reliable for viral detection?

Chicken infectious anaemia virus (CIAV) is a widely distributed immunosuppressive agent. SPF flocks and eggs used for vaccine production and diagnostics must be CIAV-free. Detection of CIAV infection in SPF flocks involves primarily serology or other invasive methods. In order to evaluate different types of samples for rapid detection of CIAV infection, a trial was conducted in serologically negative broiler breeder pullets vaccinated with a commercial live-attenuated CIAV vaccine. Controls and vaccinated groups were sampled before and after vaccination. Invasive and non-invasive samples were used for CIAV DNA detection by real-time PCR. Seroconversion occurred at 14 days post-inoculation (DPI) in the vaccinated group, whereas CIAV genome was detected by qPCR at 7 DPI in both invasive and non-invasive samples. Only invasive samples remained qPCR positive for CIAV DNA by 21 DPI despite seroconversion of the chickens.

Depression of Vaccinal Immunity to Marek's Disease by Infection with Chicken Infectious Anemia Virus

Marek’s disease (MD) has been occurring with increasing frequency in chickens in recent years. To our knowledge, however, there has been no report of the very virulent plus (vv+) MD virus (MDV) field isolate in China. Studies have shown that dual infection with immunosuppressive viruses such as chicken infectious anemia virus (CIAV) occurs frequently in chickens developing MD. In this study, we performed a designed set of in vivo experiments, which comprised five different groups of chickens, including the group of CVI988/Rispens-vaccinated chickens, the groups of CVI988/Rispens-vaccinated chickens infected with MDV or CIAV or both viruses (MDV and CIAV), and the group of MDV-challenged chickens. The effects of CIAV dual infection on the immunization of commercial MDV vaccine CVI988/Rispens were evaluated. The results show that infection of the SD15 strain of CIAV significantly reduced the weight and antibody titers to avian influenza virus (AIV)/Newcastle disease virus (NDV) inactivated vaccines of chickens immunized with the CVI988/Rispens, and resulted in the atrophy of thymus/bursa and the enlargement of spleen. The CVI988/Rispens vaccination conferred good immune protection for chickens challenged with 2000 PFU of the GX0101 strain of MDV. However, dual infection with SD15 significantly reduced the body weight, antibody titers induced by AIV/NDV inactivated vaccines and protective index of CVI988/Rispens, and resulted in the aggravation of the immunosuppression, mortality, and viremia of GX0101 in CVI988/Rispens-immunized/GX0101-challenged chickens. Overall, CIAV infection significantly reduced the protective effects of the CVI988/Rispens vaccine against MDV, implying that concurrent infection with CIAV may be a major contributor in the frequent attacks of MD in China in recent years.

Identification and evaluation of semiochemicals for the biological control of the beetle Omorgus suberosus (F.) (Coleoptera: Trogidae), a facultative predator of eggs of the sea turtle Lepidochelys olivacea (Eschscholtz)

The beetle Omorgus suberosus (F.) is a facultative predator of eggs of the olive ridley turtle Lepidochelys olivacea (Eschscholtz). Laboratory and field investigations were conducted in order to characterize volatile attractants of O. suberosus and to explore the potential for application of these volatiles in a selective mass trapping method. Headspace sorptive extraction (HSSE) coupled to thermo-desorption gas chromatography-mass spectrometry (TD-GC-MS) analysis of the volatile constituents from beetles or turtle nests revealed 24 potential compounds. However, electroantennographic (EAG) measurements revealed antennal sensitivity only to indole, linoleic acid, trimethylamine, dimethyl sulphide, dimethyl disulphide and ammonia. Behavioural tests showed that these compounds are highly attractive to O. suberosus. Field trapping experiments revealed that indole and ammonia were more attractive than the other volatile compounds and showed similar attractiveness to that produced by conventional baits (chicken feathers). The use of a combined bait of indole and NH3 would therefore be the most effective trap design. The data presented are the first to demonstrate effective massive capture of O. suberosus using an attractant-based trapping method. These findings have potential for the development of an efficient mass trapping method for control of this beetle as part of efforts towards conservation of L. olivacea at La Escobilla in Oaxaca, Mexico.

Transcriptomic Profiling of Virus-Host Cell Interactions following Chicken Anaemia Virus (CAV) Infection in an In Vivo Model

Chicken Anaemia Virus (CAV) is an economically important virus that targets lymphoid and erythroblastoid progenitor cells leading to immunosuppression. This study aimed to investigate the interplay between viral infection and the host's immune response to better understand the pathways that lead to CAV-induced immunosuppression. To mimic vertical transmission of CAV in the absence of maternally-derived antibody, day-old chicks were infected and their responses measured at various time-points post-infection by qRT-PCR and gene expression microarrays. The kinetics of mRNA expression levels of signature cytokines of innate and adaptive immune responses were determined by qRT-PCR. The global gene expression profiles of mock-infected (control) and CAV-infected chickens at 14 dpi were also compared using a chicken immune-related 5K microarray. Although in the thymus there was evidence of induction of an innate immune response following CAV infection, this was limited in magnitude. There was little evidence of a Th1 adaptive immune response in any lymphoid tissue, as would normally be expected in response to viral infection. Most cytokines associated with Th1, Th2 or Treg subsets were down-regulated, except IL-2, IL-13, IL-10 and IFNγ, which were all up-regulated in thymus and bone marrow. From the microarray studies, genes that exhibited significant (greater than 1.5-fold, false discovery rate <0.05) changes in expression in thymus and bone marrow on CAV infection were mainly associated with T-cell receptor signalling, immune response, transcriptional regulation, intracellular signalling and regulation of apoptosis. Expression levels of a number of adaptor proteins, such as src-like adaptor protein (SLA), a negative regulator of T-cell receptor signalling and the transcription factor Special AT-rich Binding Protein 1 (SATB1), were significantly down-regulated by CAV infection, suggesting potential roles for these genes as regulators of viral infection or cell defence. These results extend our understanding of CAV-induced immunosuppression and suggest a global immune dysregulation following CAV infection.

Experimental pathological studies of an Indian chicken anaemia virus isolate and its detection by PCR and FAT

Chicken Infectious Anaemia Virus (CIAV) is one of the potent immunosuppressive and economically important agents affecting poultry industry worldwide. Recent reports indicate the emergence of this virus in the poultry flocks of the country. The present study aimed to investigate the pathogenic potential of a recent isolate of CIAV obtained from poultry flock of Uttaranchal State, India. Twenty first day-old age Specific Pathogen Free (SPF) chicks were inoculated intramuscularly with 10(4.5) median tissue culture infective dose (TCID50) of CIAV passaged in the Marek's disease virus transformed chicken splenic T lymphocyte (MDCC-MSB 1) cell line while 15 chicks were kept as control. The CIAV isolate produced consistent clinical signs, loss in body weight gain, anaemia, low haematocrit values, bone marrow aplasia and generalized lymphoid atrophy. Mean Packed Cell Volume (PCV) value of the infected chicks was significantly low (18.22±2.22) compared to control group (34.12±4.72) at 14 day post infection (dpi). The establishment of virus infection in chicks was confirmed both at molecular and antigenic levels by Polymerase Chain Reaction (PCR) and Indirect Immunofluorescent Test (IIFT), respectively. Characteristic apoptotic pattern was also detected in the affected organs and the virus was re-isolated successfully in MDCC-MSB1 cell cultures. The present results revealed that the virus circulating in poultry flocks of Uttaranchal state is both pathogenic and immunosuppressive in nature. Extensive epidemiological studies are suggested in the poultry flocks of the country along with adaptation of appropriate diagnostic, prevention and control strategies so as to prevent economic losses caused by this important poultry pathogen.

Development of a blocking latex agglutination test for the detection of antibodies to chicken anemia virus

A blocking latex agglutination test (b-LAT) developed in this study was evaluated for the detection of antibodies against chicken anemia virus (CAV) in chickens. Polystyrene latex beads were coupled with a neutralizing monoclonal antibody (mAb) to CAV (mAb-beads). When mAb-beads were mixed with antigens prepared from the lysate of MDCC-MSB1 cells infected with CAV, agglutination occurred. A short pre-incubation of CAV antigens with CAV-specific antiserum inhibited the agglutination of mAb-beads. The test results were obtained within 5min. The specificity of b-LAT was evaluated using sera from specific pathogen-free chickens and sera containing antibodies to avian influenza virus, Newcastle disease virus, infectious bursal disease virus, and Marek's disease virus; nonspecific agglutination and cross-reactivity with antibodies to unrelated viruses were not observed. The examination of 94 serum samples collected from commercial breeder chickens of various ages (17-63 weeks) revealed good agreement (93.6%, Kappa value=0.82) between b-LAT and a virus neutralization test, known to be most sensitive and specific in the detection of antibodies to CAV. These results indicate that b-LAT, a simple and rapid test, is a useful and reliable tool in CAV serology.

Interactions ofPlasmodium juxtanucleareand chicken anaemia virus: establishing a model

The pathogensPlasmodium juxtanucleareand chicken anaemia virus (CAV) are easily transmitted and potentially harmful to chickens. In this study, we established an experimental model to investigate the effects of avian malaria caused byP. juxtanuclearein white leghorn specific-pathogen-free (SPF) chicks previously immunosuppressed with CAV. Parasitaemia, haematological variables and clinical and pathological parameters were determined in four different experimental groups: chicks coinfected by CAV andP. juxtanuclearestrain (Coinfected group), chicks exclusively infected by CAV (CAV group) orP. juxtanucleare(Malaria group) and uninfected chicks (Control group). Our data demonstrated thatP. juxtanucleareparasitaemia was significantly higher in the Coinfected group. Furthermore, haematological parameters, including the RBC, haematocrit and haemoglobin concentration were significantly reduced in coinfected chicks. In agreement with the changes observed in haematological features, the mortality among coinfected chicks was higher compared with animals with single infections. Clinical analysis indicated moderate changes related to different organs size (bursa of Fabricius, heart and liver) in coinfected birds. The experimental coinfection of SPF chickens withP. juxtanucleareand CAV may represent a research tool for the study of avian malaria after CAV immunosuppression, enabling measurement of the impacts caused by different pathogens during malarial infection.

Epidemiology of chicken anemia virus in Central African Republic and Cameroon

Background

Although chicken anemia virus (CAV) has been detected on all continents, little is known about this virus in sub-Saharan Africa. This study aimed to detect and characterize CAV for the first time in Central African Republic and in Cameroon.

Results

An overall flock seroprevalence of 36.7% was found in Central African Republic during the 2008–2010 period. Virus prevalences were 34.2% (2008), 14.3% (2009) and 10.4% (2010) in Central African Republic and 39% (2007) and 34.9% (2009) in Cameroon. CAV DNA was found in cloacal swabs of 76.9% of seropositive chickens, suggesting that these animals excreted the virus despite antibodies. On the basis of VP1 sequences, most of the strains in Central African Republic and Cameroon belonged to 9 distinct phylogenetic clusters at the nucleotide level and were not intermixed with strains from other continent. Several cases of mixed infections in flocks and individual chickens were identified.

Conclusions

Our results suggest multiple introductions of CAV in each country that later spread and diverged locally. Mixed genotype infections together with the observation of CAV DNA in cloacal samples despite antibodies suggest a suboptimal protection by antibodies or virus persistence.

Chicken anemia virus

Chicken anemia virus (CAV), the only member of the genus Gyrovirus of the Circoviridae, is a ubiquitous pathogen of chickens and has a worldwide distribution. CAV shares some similarities with Torque teno virus (TTV) and Torque teno mini virus (TTMV) such as coding for a protein inducing apoptosis and a protein with a dual-specificity phosphatase. In contrast to TTV, the genome of CAV is highly conserved. Another important difference is that CAV can be isolated in cell culture. CAV produces a single polycistronic messenger RNA (mRNA), which is translated into three proteins. The promoter-enhancer region has four direct repeats resembling estrogen response elements. Transcription is enhanced by estrogen and repressed by at least two other transcription factors, one of which is COUP-TF1. A remarkable feature of CAV is that the virus can remain latent in gonadal tissues in the presence or absence of virus-neutralizing antibodies. In contrast to TTV, CAV can cause clinical disease and subclinical immunosuppression especially affecting CD8+ T lymphocytes. Clinical disease is associated with infection in newly hatched chicks lacking maternal antibodies or older chickens with a compromised humoral immune response.

Unraveling the puzzle of human anellovirus infections by comparison with avian infections with the chicken anemia virus

Current clinical studies on human annelloviruses infections are directed towards finding an associated disease. In this review we have emphasized the many similarities between human anellovirus and avian circoviruses and the cell and tissue types infected by these pathogens. We have done this in order to explore whether knowledge acquired from natural and experimental avian infections could reflect and be extrapolated to the less well-characterized human annellovirus infections. The knowledge gained from the avian system may provide suggestions for decoding the enigmatic human anellovirus infections, and finding the specific disease or diseases caused by these human anellovirus infections. Each additional parallelism between chicken anemia virus (CAV) and Torque teno virus (TTV) further strengthens this premise. As we have seen information from human infections can also be used to better understand avian infections as well. Increased attention must be focused on the "hidden" or unrecognized, seemingly asymptomatic effects of circovirus and anellovirus infections. Understanding the facilitating effect of these infections on disease progression caused by other pathogens may help to explain differences in outcome of complicated poultry and human diseases. The final course of a pathogenic infection is determined by variations in the state of health of the host before, during and after contact with a pathogen, in addition to the phenotype of the pathogen and host. The health burden of circoviridae and anellovirus infections may be underestimated, due to lack of awareness of the need to search past the predominant clinical effect of identified pathogens and look for modulation of cellular-based immunity caused by co-infecting circoviruses, and by analogy, human anneloviruses.

Lesions in the thymus and bone marrow in chicks with experimentally induced chicken infectious anemia disease

One-day-old SPF chicks were inoculated with the Cux-l strain of chicken infectious anemia virus (CIAV), and the clinical development of disease and its macroscopic and microscopic alterations in the thymus and bone marrow, were observed. Tissue sections of thymus and bone marrow were stained using the streptavidin-biotin peroxidase method and examined under light microscope for evaluation of antigenic intensities in tissues. Those findings were then compared with blood parameters and ELISA results obtained through collected sera during sacrifice procedures. We sought to determine: the localization of viral antigens in thymus and bone marrow tissues after inoculation, the correlation between antigen intensities and hematologic, serologic and histopathologic findings, definitive diagnostic criteria using histopathologic and immunoperoxidase methods, and the reliability of these methods in the diagnosis of CIAV infection. For this purpose, 83, one-day-old SPF chicks were used. The birds were divided into experimental (n = 52) and control (n = 26) groups. A virus dose of TCID50 of 100,000/ml was administered intramuscularly to every bird in the experimental group. Based on the results of this study, we have suggested that clinical examination, along with macroscopic and microscopic evaluation of the thymus and bone marrow, maybe undertaken starting from day 7 post-inoculation (PI). ELISA, might be of value, as it might give consistent results starting from day 14 PI. However, the most reliable results were obtained through examination of thymus and bone marrow sections from infected birds stained by immunoperoxidase technique, as early as day 4 PI.

The contribution of feathers in the spread of chicken anemia virus

Chicken anemia virus (CAV) spreads vertically and horizontally, however, the process is mostly still obscure. To further clarify the horizontal CAV spread, we examined the contribution of feathers. We demonstrated that CAV could be amplified from DNA purified from feather shafts of experimentally infected chicks, and the process efficacy was evaluated by comparing the amplification of DNA purified from feather shafts and lymphoid organs of CAV-experimentally infected chicks. DNA from feathers was found as an efficient source for CAV detection. Further, to substantiate whether CAV reaches the feather shafts passively via the blood, or intrinsically, causing histopathological changes, the feather follicle tissues were examined for CAV-induced lesions. Specific histological changes were found, however, immunohistochemistry failed to detect viral proteins. To determine whether the feather shafts are a source of infective virus, they were homogenized and used to infect 1-day-old chicks via the mucosal entries (eyes, nose and oropharynx). That infection mode simulates the natural route of horizontal infection in commercial poultry houses. We demonstrated the CAV-infection by serology, virology and pathology, showing that feather shafts carry infectious CAV either on their surface or within their feather pulp, and concluded that feathers contribute to the horizontal CAV dissemination.

Cloning and expression of chicken anemia virus VP3 protein in Escherichia coli

Purification of chicken anemia virus (CAV) VP3 protein, expressed in a prokaryotic expression system as histidine-tagged fusion protein is demonstrated in the present study. CAV particle was obtained from infected liver of chicken and DNA was extracted. The VP3 protein gene was amplified from the extracted DNA by polymerase chain reaction (PCR) and cloned. The recombinant expression construct (pTrc-VP3) was identified by PCR and sequencing analysis. Expression of VP3 protein with a molecular mass of approximately 21kDa was confirmed by Western blotting analysis with CAV-specific antibodies. The in vitro expressed VP3 protein was purified to near homogeneity by elution from the gel, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The purified VP3 protein was recognized by CAV antibodies in a Western blotting assay. This finding indicates that recombinant VP3 expressed in the pTrcHis2 vector system can be used as antigen to detect anti-CAV antibodies.

Characterization and Phylogenetic Analysis of Brazilian Chicken Anaemia Virus

Chicken anaemia virus (CAV) was detected by a Nested-PCR assay in field samples from different regions of Brazil. The 539 bp amplified fragments of vp1 gene from 44 field samples were sequenced and 10 new nucleotide sequences of CAV were observed. These sequences were phylogenetically analysed by Mega2 using neighbour joining distance methods with 1000 bootstrap replications. Phylogenetic analysis did not show correlation between CAV pathology pattern and genetic groups. The 10 nucleotide sequences of the Brazilian samples were also analysed together with 30 sequences of CAV strains previously described from other countries. The genetic variability observed was not related to the geographical distribution. Amino acid substitutions were detected at 9 positions of the Brazilian sequences and two of them had not been observed before, (65)R replacing the Q residue and (98)F replacing Y residue.

Development of a multiplex PCR for detection of avian adenovirus, avian reovirus, infectious bursal disease virus, and chicken anemia virus

A multiplex polymerase chain reaction (mPCR) was developed and optimized for the simultaneous detection and differentiation of avian reovirus (ARV), avian adenovirus group I (AAV-I), infectious bursal disease virus (IBDV), and chicken anemia virus (CAV). Four sets of specific oligonucleotide primers were used in this test for ARV, AAV-I, IBDV, and CAV. The mPCR DNA products were visualized by gel electrophoresis and consisted of fragments of 365 bp for IBDV, 421 bp for AAV-I, 532 bp for ARV, and 676 bp for CAV. The mPCR assay developed in this study was found to be sensitive and specific. Detection of PCR-amplified DNA products was 100 pg for both CAV and IBDV, and 10pg for both ARV and AAV-I and this mPCR did not amplify nucleic acids from the other avian pathogens tested. The mPCR demonstrated similar sensitivity in tests using experimental fecal cloacal swab specimens that were spiked with ARV, AAV-1, IBDV, and CAV, and taken from specific pathogen free (SPF) chickens. This mPCR detected and differentiated various combinations of RNA/DNA templates from ARV, AAV-I, CAV, and IBDV without reduction of amplification from feces.

Role of viral load in the pathogenesis of chicken anemia virus

The pathogenesis of strain 3711 of the chicken anemia virus (CAV), propagated in chickens, and two preparations of strain 3711 that had been adapted to grow to high titre in cells of the MDCC-MSB1 line were studied in chicken embryos and/or chickens. Highest viral loads in infected chickens, as measured by a microplate DNA-hybridization assay, were detected in the thymus, clotted blood and pancreas, and the lowest in the duodenum. The CAV DNA copy number in the organs of chicken embryos was significantly lower than in chickens. Route of infection was an important determinant of the course of disease in chickens, with clinical signs appearing earlier in birds infected by the intramuscular than those infected by the oral route; there was a direct relationship between viral load in particular organs and the extent of clinical signs. No reduction in the pathogenicity for chickens was noted for strain 3711 after 65 or 129 passages in the MDCC-MSB1 cell line.

Detection of chicken anemia virus in the gonads and in the progeny of broiler breeder hens with high neutralizing antibody titers

Previous evidence for the presence of chicken anemia virus (CAV) in the gonads of immune specific-pathogen-free chickens raised the question whether this occurs also in commercial breeders. The presence of CAV was investigated by nested PCR in the gonads and spleens of hens from two 55- and 59-week-old, CAV-vaccinated (flocks 2 and 3), and two 48- and 31-week-old non-vaccinated broiler breeder flocks (flocks 1 and 4). In addition, lymphoid tissues of 20-day-old embryos from these hens were also investigated for the presence of CAV. CAV was detected in the gonads and of 5/6 and 11/22 of the vaccinated hens and in some hens also in the spleen alone. Embryos from 7/8 and 5/18 of these hens were positive. In the non-vaccinated flocks, CAV was detected in the gonads of 11/34 and 10/10 hens in flocks 1 and 4, respectively. In addition, 11 birds in flock 1 had positive spleens. CAV DNA was detected in 3/11 and 2/10 of their embryos. CAV-positive gonads and embryos were detected in samples from hens with moderate as well as high VN antibody titers. Vaccinated chickens positive for CAV in the gonads and in their embryos had VN titers ranging from >1:512 to <1:2048. In non-vaccinated chickens, the VN titers of CAV positive chickens ranged from 1:128 to 1:4096. These results demonstrate that CAV genome can remain present in the gonads of hens in commercial broiler breeder flocks even in the presence of high neutralizing antibody titers that have been associated with protection against CAV vertical transmission. It also suggests that transmission to the progeny may occur irrespectively of the level of the humoral immune response in the hens.

Chicken Infectious Anemia Virus: An Example of the Ultimate Host–Parasite Relationship

Chicken infectious anemia virus (CIAV) is a resistant and ubiquitous virus of chickens causing disease in young chickens and immunosuppression in all birds. This paper reviews the current knowledge of CIAV with a focus on new findings indicating that immunosuppressive effects have not been fully appreciated, especially as they relate to the development of antigen-specific cytotoxic T cells. A more complete understanding of the immunosuppressive effects of CIAV emphasizes the need for better vaccines, especially for the broiler industry. In addition, a new model is proposed for the control of viral replication in the reproductive tract of specific-pathogen-free chickens, which may be latently infected. This model suggests that virus transcription is controlled by viral enhancer and repressor elements, which are regulated by different hormones. As a consequence, CIAV has a well-adapted relationship with its host, avoiding immune detection, ensuring passage of virus to the next generation, and eliciting limited pathology to the host.

Prevalence of antibodies against chicken anaemia virus (CAV) in broiler breeders in Southern Brazil

Chicks infected during the first two weeks of life with chicken anaemia virus (CAV) manifest clinical disease that can be avoided if the breeder hens transfer enough antibodies to their progeny. The objective of the present work was to establish the prevalence and titer of anti-CAV antibodies in some Brazilian broiler hen breeder flocks and verify in which phase of life the birds were infected. A total of 1,709 serum samples from 12 broiler hen flocks vaccinated against CAV and 64 unvaccinated flocks were analyzed for CAV antibodies with an enzyme-linked immunosorbent assay (ELISA). All non-vaccinated breeder flocks were found to be infected with CAV, with 89% of the hens tested presenting antibodies, 52% of these with titers considered high enough to protect their progeny against CAV infection. Likewise, all vaccinated hens had antibody titer to CAV capable of conferring protection to their progeny. Thus, vaccination of hens seems capable of conferring protection to chicks against clinically apparent CAV-associated disease.

Chicken anemia virus in broilers: dynamics of the infection in two commercial broiler flocks

Chicken anemia virus (CAV) can cause a disease syndrome characterized by severe anemia, bone marrow atrophy, and severe immunosuppression in young chicks. Maternal antibodies prevent these clinical signs but do not prevent infection, transmission of the virus, or immunosuppression. The clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease is ubiquitous. The dynamics of CAV infection, CAV antibody responses, relative lymphoid organ weights, and associated lesions were studied in two broiler flocks from a commercial producer. Both groups had detectable CAV antibodies at hatch, which waned over the first 3 wk of life. Both groups had detectable CAV DNA in both thymi and bursae over the same period. At 35 days of age, virus was detectable by polymerase chain reaction in 16 of 20 chickens, and 7 of 20 had detectable antibodies. By 42 days of age, virus was detectable in 18 of 20 chickens, and 18 of 20 had antibodies to CAV. We observed a decrease in relative thymic weights beginning at 35 days of age, coincidental withthe detection of CAV in the thymus. Bursal sizes began to decrease at 28 days of age, coincidental with a rise in antibody titers to infectious bursal disease virus. In this study, we demonstrated that under typical field conditions CAV infections in broilers have unique dynamics unlike those reported in egg laying strains of chickens managed under specific-pathogen-free conditions.

Detection of chicken anemia virus DNA in embryonal tissues and eggshell membranes

Chicken infectious anemia virus (CIAV) is a ubiquitous and highly resistant virus of chickens that causes anemia and death in chicks less than 3 wk of age and immunosuppression in chickens older than 3 wk of age. The production of specific-pathogen-free eggs free of CIAV is essential for research and vaccine production. Currently, flocks are screened for CIAV by antibody tests to ensure freedom from CIAV infection. Recent evidence, however, indicates that chickens may carry and vertically transmit CIAV DNA independently of their antibody status. In this study, we tested embryos and eggshell membrane residues by nested polymerase chain reaction (PCR) as a sensitive method of detecting CIAV DNA. CIAV DNA could be detected in the blastodisks and semen obtained from antibody-positive and -negative chickens. Examination of different tissues between 18 and 20 days of incubation indicated that many but not all organs of individual embryos were positive. The lymphoid organs and gonads had the highest incidence of CIAV DNA, which was significantly different (P < 0.05) from the incidence in the liver. Eggshell membrane samples from embryos or newly hatched chicks were an excellent noninvasive source for the detection of CIAV DNA, identifying significantly more positive embryos than did pooled lymphoid organs. The use of dexamethasone injections as a method to improve the detection of carrier birds did not result in an increase of vertical transmission or cause seroconversion in the treated hens. A combination of testing eggshell membrane residues at hatch and periodic testing of blood DNA by nested PCR can be used to identify chickens carrying CIAV DNA and may be used to eradicate carrier birds.

Detection of circovirus with a polymerase chain reaction in the ostrich (Struthio camelus) on a farm in The Netherlands

This study describes for the first time the presence of circoviruses in ostrich tissue including embryos. A polymerase chain reaction (PCR) was used for the detection of the virus in liver samples. The use of a polymerase for low copy detection significantly increased the sensitivity of the test as well as a Southern blot. Viral DNA could be detected in chicks and eggs that did not hatch. For localisation of the virus in the liver in situ hybridisation was performed on a selection of positive liver tissues.

Infection with chicken anaemia virus impairs the generation of pathogen-specific cytotoxic T lymphocytes

Infection with chicken anaemia virus (CAV), a circovirus, can result in immunosuppression and subsequent increased susceptibility to secondary infections. This is the first report of impairment of pathogen-specific cytotoxic T lymphocytes (CTL) after natural and experimental infection of chickens with CAV and Marek's disease virus (MDV) or reticuloendotheliosis virus (REV). MDV- and REV-specific CTL were generated at 7 days post infection by 9-30-day-old-chickens that were positive for maternal antibodies to CAV at 9-17 days of age. Replication of CAV could not be demonstrated in these chickens using quantitative real-time polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR assays. In contrast, REV-specific CTL failed to develop when chickens negative for maternal antibodies at 9-17 days of age were infected. Infection with CAV at 45 days of age after CAV maternal antibodies had waned also caused a decreased REV-specific CTL response. In these chickens increased levels of CAV DNA of up to 107 copy numbers per micro g DNA and increased relative transcript levels of CAV by up to a factor of 106 were detected by quantitative real-time PCR and RT-PCR. Interleukin (IL)-1beta and IL-2 mRNA levels were not significantly affected by CAV infection at 7 or 14 days p.i. Similar assays for interferon-gamma (IFN-gamma) transcripts demonstrated a 10-fold increase in IFN-gamma mRNA levels at 7 days post infection following REV or REV + CAV infection, while CAV alone caused a two- to fourfold increase. These results show a strong link between CAV antibody status, CAV replication, and the ability to generate REV-specific CTL. It is likely that the immunosuppressive effects of subclinical infection have previously been underestimated.

Identification of a genetic determinant of pathogenicity in chicken anaemia virus

The molecular basis of pathogenicity of the chicken anaemia virus (CAV) needs to be clarified in order to develop a safe, live virus vaccine. In this study, several high- and low-pathogenic infectious DNA clones were obtained from field virus samples after 12 or 38 passages in MDCC-MSB1 cells. The high-pathogenic clones induced a low haematocrit, low weight gain and high mortality. Nucleotide sequence analyses identified one amino acid, at residue 394 of the VP1 capsid protein, as a major determinant of pathogenicity. To determine the role of this amino acid in pathogenicity, chimeric infectious DNA clones and point-mutated clones were used for chicken pathogenicity tests. These analyses clearly demonstrated that residue 394 of VP1 was crucial for the pathogenicity of CAV; all of the cloned viruses with glutamine at this position were highly pathogenic, whereas those with histidine had low pathogenicity. Low-pathogenic CAV, based on an infectious DNA clone, is a candidate for a genetically homogeneous and stable CAV live vaccine.

Distribution of chicken anaemia virus in the reproductive tissues of specific-pathogen-free chickens

The specific-pathogen-free (SPF) flocks of chickens maintained by the Department of Microbiology and Immunology at Cornell University became infected, inadvertently, with chicken anaemia virus (CAV), as demonstrated by seroconversion. Chickens from five flocks representing three different strains were examined for the presence of CAV using nested PCR. Virus was detected in ovaries, infundibula, vas deferentia, testes and spleens. Ovaries were positive in 38 to 72% of the hens in four flocks with 13 to 56 birds examined per flock. Interestingly, the ovaries were often the only positive tissues, while a few hens had only positive spleens. In roosters, the vas deferens was positive in 30 to 79% of the birds with 5 to 19 birds examined per flock; the vas deferens was the only positive tissue in 20 to 37%. Individual cells in the theca externa and rare epithelial cells in the infundibular epithelium were positive for CAV by in situ PCR. Positive cells were not detected in testes or vas deferentia. The SH-1 strain of CAV was isolated from these tissues and partially sequenced. Only minor sequence differences were found compared to CIA-1 and Cux-1. Embryos from matings between persistently infected dams and sire had CAV-positive cells in mesenchyme near the developing vertebral column. The data show that CAV persists in the reproductive tissues far longer than previously thought, and that it can be vertically transmitted from persistently infected birds.

Anticorpos Para o Vírus da Anemia das Galinhas (CAV) em Matrizes de Corte no Brasil

Apesar do diagnóstico da anemia infecciosa e mais evidências recentes de infecção em campo (Brentano & Ottati, 1999), não havia até hoje dados disponíveis da prevalência do vírus da anemia das galinhas (CAV) no Brasil. Uma vez que o conhecimento da prevalência do vírus e da distribuição de anticorpos nos lotes de matrizes é essencial para o delineamento de estratégias de controle da doença, realizamos um levantamento em 5 Estados com produção comercial intensiva de linhas de corte, abrangendo lotes de aves com diferentes idades. De 2.355 soros testados por ELISA, 89% foram positivos, indicando a alta prevalência do CAV no Brasil, em todos os Estados testados. A análise do soro de aves das 6 até as 70 semanas de idade demonstrou que lotes de 6 a 18 semanas apresentam desuniformidade na imunidade ao CAV, caracterizada por títulos de anticorpos abaixo dos níveis considerados protetores e aves ainda negativas para o CAV. A desuniformidade nos títulos de anticorpos e a ausência dos mesmos são evidentes ainda, mas em menor proporção também até as 24 semanas, enquanto que apenas partir das 25 semanas há 100% de soroconversão, acompanhada de significativa redução da desuniformidade no título de anticorpos das matrizes para menos de 2,5% das aves. Esses resultados fornecem evidência de uma progressiva disseminação do vírus em matrizes de corte, mas com riscos da presença de aves ainda susceptíveis à transmissão vertical e inadequada transferência de imunidade passiva no início do período de postura, que podem culminar em surtos da doença na progênie.

Persistent infection with chicken anaemia virus and some effects of highly virulent infectious bursal disease virus infection on its persistency

Chicken anaemia virus (CAV) infectivity and the effect of highly virulent infectious bursal disease virus (hv IBDV) infection on CAV's infectivity were examined in chickens inoculated with CAV or inoculated dually with CAV and hv IBDV. Five chickens inoculated dually with hv IBDV at 35 days old and then with CAV at 40 days old exhibited no clinical signs of disease, but showed atrophic bursae of Fabricius when necropsied 4 weeks later. Upon examining the chickens at 7 days postinoculation (dpi) with CAV, it was found that hv IBDV infection had inhibited production of virus neutralising (VN) antibody to CAV, and that it was possible to recover CAV from plasma of these chickens. Although VN antibody to CAV appeared after 14 dpi, CAV was recovered from blood cells (BC s) at high titres ranging from 10(2.5)to 10(5.5)TCID(50)/0.1 ml, 7 to 28 dpi in IBDV -induced immunosuppressed chickens. In addition, CAV was sporadically recovered, using rectal swabs, from the dually inoculated chickens at low titers, ranging from 10(1.0)to 10(2. 0)TCID(50)/0.1 ml). In contrast, although CAV was recovered from BC s in most of the chickens inoculated with CAV alone, the titers were lower (10(1.0)to 10(2.5)TCID(50)/0.1 ml). No CAV was detected from the rectal swabs of these chickens. The results of virus recovery were confirmed by polymerase chain reaction. This study first examined the persistency of CAV in BC s and the effective enhancement of primary CAV infection as a result of immunosuppression caused by hv IBDV infection.

Serological survey on the prevalence of chicken anaemia virus infection in Hungarian chicken flocks

A serological survey on the prevalence of chicken anaemia virus (CAV) infection was performed by using the indirect immunofluorescence (IF) and the virus neutralization (VN) tests in commercial Hungarian chicken populations. By the indirect IF test, a total of 846 serum samples from 13 meat-type parent flocks of two breeds were investigated between 10 and 62 weeks of age. All flocks were found to be positive for anti-CAV antibodies, and the rates of antibody-positive birds among flocks ranged from 40 to 93.3% and with an average of 73.3%. From nine 1-day- to 9-week-old progeny broiler flocks, 96 serum samples were tested. In the 3 flocks, sampled at the hatchery, 75 to 100% (average 86.4%) of the 22 tested birds were antibody positive. From the 6 flocks, tested between 4 to 9 weeks of age, 3 were antibody negative at 4 and 5 weeks of age, whereas in the 3 remaining 6- to 9-week-old flocks 10 to 20% (average 13.5%) of the birds were antibody positive. In egg-laying parent flocks of 14 and 35 weeks old, 54.4 and 71.7% of the tested 79 and 46 birds had antibodies to CAV, respectively. By the VN test, a total of 670 serum samples from 9 meat-type parent flocks aged between 11 and 37 weeks were investigated. The rate of antibody positivity in flocks was always over 80% and averaged 90.9%. From 7 progeny broiler flocks, 261 serum samples were tested between one day and 7 weeks of age, and the rates of seropositivity in flocks were between 93.3 to 100% and averaged 96.9%. In an egg-laying parent flock, 89.2% of the tested 102 birds had neutralizing antibodies to CAV at 35 weeks old. It was concluded that CAV is widespread in Hungarian commercial chicken populations. Though, according to simultaneous examination of 195 flock sera, the VN test revealed 11.3% more antibody-positive birds, the indirect IF test was found suitable for serological surveys at flock(s) level, provided that sufficient numbers of individual chicks were tested.