Chicken Anemia Virus Infection Research Articles

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.

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.

Correlation between cytokine profile,antibody titre and viral load during sub-clinical chicken anaemia virus infection

The present work was carried out to investigate the correlation between viral load and the cytokine profile and virus specific antibody levels at five day intervals up to 25 days post infection (dpi) in various tissues of chicks infected with chicken infectious anaemia virus (CIAV) at six weeks of age (sub-clinical infection) (dpi). For determining the viral load in the various tissues, recombinant plasmid vp2-pet32b was prepared and serially diluted tenfold for the generation of a standard curve using real time polymerase chain reaction (PCR). Cytokine fold changes in mRNA levels of IFN-&amp;gamma;, IL-1, IL-2, IL-12 in the spleen and IFN-&amp;gamma;, IL-12 in freshly collected whole blood were determined. The results showed that peak viral load occurs between 10&amp;ndash;20 days post infection in the lymphoid tissues viz., thymus, spleen, liver, bone marrow, bursa and also blood, being highest in blood followed by thymus. A varied response in the expression levels of individual cytokines was observed during all the intervals post infection. The IFN-&amp;gamma; increased two to five fold in blood and spleen while IL-2 decreased in the splenic tissue during the same period. Peak IFN-&amp;gamma; coincided with peak viral load in the spleen at 10 dpi while in blood it peaked earlier at five days post infection and remained high during the peak viral load at 10&amp;ndash;20 dpi. Virus specific antibodies were significantly higher at 15 dpi and were thereafter found to be strongly associated with viral load regression although higher concentrations of virus remained in the blood and thymic tissues until 25 dpi, indicating a role of other immune components in virus clearance. In conclusion, this study reports a negative correlation of viral load and the progression of the antibody response and IFN-&amp;gamma; cytokine expression in chicks infected with CIAV during their sub-clinical infectious stage. However, cytokine expression from the various individual immune cells like monocytes, heterophils, CD4&lt;sup&gt;+ &lt;/sup&gt;T, CD8&lt;sup&gt;+&lt;/sup&gt; T cells and others during the pathogenesis of this immunosuppressive poultry pathogen remains to be elucidated. &amp;nbsp;

The Development and Application of an Indirect ELISA Test for the Detection of Chicken Anaemia Virus (CAV) by VP1 in Chicken Flock Serum

Chicken anaemia virus (CAV) causes a viral disease in chickens worldwide and thus has economic importance. The main aim of this study was to develop a rapid, sensitive and specific VP1-CAVI indirect ELISA for the detection of CAV infection. The CAV-VP1, was separately cloned and expressed in recombinant E. coli. The purified recombinant CAV-VP1 protein was then coated as an antigen on an ELISA plates to evaluate its reactivity against chicken sera. The resulting indirect ELISA was then compared with a commercial ELISA. The specificity and sensitivity of the indirect ELISA were measured as 93.3% and 100%, respectively. A t-test produced a t-value of 15.805 for the indirect ELISA and revealed a significant difference between CAV-positive serum and CAV-negative serum (p-value of 0.001). For the second variable (i.e., a commercial ELISA), the t-test yielded a t-value of 5.063, which revealed a significant difference between CAV-positive serum and CAV-negative serum (p-value of 0.015). This intervention produces statistically significant improvements in both variables (p-values r = 0.93. Therefore, this work can be considered as a new achievement in diagnosis for Chicken anaemia virus in chicken flocks.

Seromolecular study of chicken infectious anemia in chickens, ostriches, and turkeys in Iran

SUMMARY Until recently, the chicken has been considered the only natural host and the main host for chicken anemia virus (CAV). However, CAV infection has now been reported in other avian species, including Japanese quail, jackdaws, rooks, and rare avian breeds. In this study, we examined chickens, ostriches, and turkeys for seromolecular detection of CAV in Iran. For the study, 375 serum and thymus samples from chickens, 84 serum and blood samples from ostriches, and 100 serum and blood samples from turkeys were collected from various locations in Iran. Serum samples were examined using ELISA. Deoxyribonucleic acid was extracted from the thymus, and blood samples were analyzed for detection of the VP2 genome of CAV by PCR. According to these results, 69.07 and 58.4% of chickens were positive for the antibody to CAV and the VP2 genome of CAV, respectively. In addition, in ostriches 27.38 and 34.52% were positive for the CAV antibody and the CAV VP2 genome, respectively. In turkey flocks, all turkeys (100%) were negative with respect to detection of the VP2 CAV genome and CAV antibody. It was concluded that CAV is distributed in broiler chickens and ostriches throughout Iran. Furthermore, ostriches may be considered a reservoir of CAV, and turkeys appear not to be susceptible to CAV infection.

The chicken TH1 response: Potential therapeutic applications of ChIFN-γ

The outcomes of viral infections are costly in terms of human and animal health and welfare worldwide. The observed increase in the virulence of some viruses and failure of many vaccines to stop these infections has lead to the apparent need to develop new anti-viral strategies. One approach to dealing with viral infection may be to employ the therapeutic administration of recombinant cytokines to act as ‘immune boosters’ to assist in augmenting the host response to virus. With this in mind, a greater understanding of the immune response, particularly cell mediated T-helper-1 (TH1) type responses, is imperative to the development of new anti-viral and vaccination strategies. Following the release of the chicken genome, a number of TH1-type cytokines have been identified, including chicken interleukin-12 (ChIL-12), ChIL-18 and interferon-γ ChIFN-γ), highlighting the nature of the TH1-type response in this non-mammalian vertebrate. To date a detailed analysis of the in vivo biological function of these cytokines has been somewhat hampered by access to large scale production techniques. This review describes the role of TH-1 cytokines in immune responses to viruses and explores their potential use in enhancing anti-viral treatment strategies in chickens. Furthermore, this review focuses on the example of ChIFN-γ treatment of Chicken Anemia Virus (CAV) infection. CAV causes amongst other things thymocyte depletion and thymus atrophy, as well as immunosuppression in chickens. However, due to vaccination, clinical disease appears less often, nevertheless, the subclinical form of the disease is often associated with secondary complicating infections due to an immunocompromised state. Since CAV-induced immunosuppression can cause a marked decrease in the immune response against other pathogens, understanding this aspect of the disease is critically important, as well as providing insights into developing new control approaches. With increasing emphasis on developing alternative control programs for poultry diseases, novel therapeutic strategies provide one approach. We show here that the in ovo administration of ChIFN-γ impacts the depletion of T-cell precursors during CAV infection. Therefore, it appears that ChIFN-γ may have the potential to be used as a novel therapeutic reagent to impact virus infection and alter immunosuppression caused by CAV and potentially other pathogens.

Chicken anemia virus infection in broiler chickens vaccinated and not vaccinated for avian influenza in Iran

SUMMARY To study the role of influenza vaccination in inducing chicken anemia infection in broiler chickens in Iran, 25 flocks vaccinated for avian influenza (AI) and 25 nonvaccinated flocks were randomly selected. In this study, we attempted to select flocks with similar mortality and growing conditions. At the end of the rearing period, 15 thymus samples were taken, and after DNA extraction, a 713-bp viral protein 2 (VP2) gene of the chicken anemia virus (CAV) was amplified by specific primers. In addition, 20 batches belonging to 10 different commercial chicken vaccines were examined for evidence of CAV contamination. A total of 105 out of 375 chickens were vaccinated for AI (28%) and 135 out of 375 nonvaccinated chickens (36%) were infected with CAV. The frequency of CAV infection in the 750 studied chickens was 32% at slaughter age. The CAV VP2 gene was not detected in any commercial chicken vaccines. On the basis of statistical analyses, there were no significant correlations between vaccination for AI and CAV infection. Furthermore, comparison of the infection rate for CAV in AI-vaccinated and nonvaccinated chickens revealed no significant differences between these 2 groups. Vaccination against AI seems to play no role in increasing or reducing the prevalence of CAV.

Serological and molecular identification of subclinical chicken anaemia virus infection in broiler chickens in Iran

Chicken anaemia virus (CAV) can occur in immunosuppressive syndrome in broiler chickens. CAV infection in presence of maternal antibody appears sub-clinically. In this study subclinical infection of CAV was studied in broiler chickens in four provinces of Iran, by ELISA and PCR. For this, total of 375 serum samples and 375 thymus samples were collected from 25 broiler chicken flocks. Results showed all flocks to be positive by ELISA and PCR (in which at least one chicken was detected as positive). The positivity rate of CAV infection in broiler chickens, following PCR assay, was 58.4%. The results indicate high prevalence of subclinical CAV infection in Iran. Therefore, a proper vaccination strategy in broiler breeder and even broiler chickens, without interfering with maternal antibodies, must be investigated. Key words: Chicken anaemia virus, subclinical, Iran

Development and characterization of a potential diagnostic monoclonal antibody against capsid protein VP1 of the chicken anemia virus

Chicken anemia virus (CAV) is an important viral pathogen that causes anemia and severe immunodeficiency syndrome in chickens worldwide. In this study, a potential diagnostic monoclonal antibody against the CAV VP1 protein was developed which can precisely recognize the CAV antigen for diagnostic and virus recovery purposes. The VP1 gene of CAV encoding the N-terminus-deleted VP1 protein, VP1Nd129, was cloned into an Escherichia (E.) coli expression vector. After isopropyl-β-D-thiogalactopyronoside induction, VP1Nd129 protein was shown to be successfully expressed in the E. coli. By performing an enzyme-linked immunoabsorbent assay using two coating antigens, purified VP1Nd129 and CAV-infected liver tissue lysate, E3 monoclonal antibody (mAb) was found to have higher reactivity against VP1 protein than the other positive clones according to the result of limiting dilution method from 64 clones. Using immunohistochemistry, the presence of the VP1-specific mAb, E3, was confirmed using CAV-infected liver and thymus tissues as positive-infected samples. Additionally, CAV particle purification was also performed using an immunoaffinity column containing E3 mAb. The monoclonal E3 mAb developed in this study will not only be very useful for detecting CAV infection and performing histopathology studies of infected chickens, but may also be used to purify CAV particles in the future.

Chicken Anemia Virus: An Understanding of theIn-VitroHost Response Over Time

Chicken anemia virus (CAV) is an economically important virus affecting the chicken meat and egg industry. CAV is characterized by anemia, lymphoid depletion, and immunosuppression. Microarrays were used to investigate the response of MDCC-MSB1 cells (MSB1) to infection with CAV at 24 and 48 h post-infection (hpi). The major genes responding to CAV infection include genes involved in inflammation, apoptosis, and antiviral activity. Several cytokines were differentially regulated at either 24 or 48 hpi, including interleukin 2 (IL-2), interleukin receptors IL-1R, IL-22R, IL-18R, and IL-7R, and interferon-α (IFN-α). While there were many genes differentially regulated in this experiment, only two genes were common to both time points, suggesting a dramatic change in gene expression over the two time points studied. The present study is the first microarray experiment to investigate CAV, and we identified a number of key pathways involved in viral infection. Overall, there were more genes upregulated at 24 hpi than at 48 hpi, including genes involved in cytokine signaling, apoptosis, and antiviral activity. The two time points were vastly different in their gene expression patterns, in that at 24 hpi there were many genes involved in the response to infection, whereas at 48 hpi there were many genes associated with apoptosis and immunosuppression.

Production and Diagnostic Application of a Purified, E. coli-Expressed, Serological-Specific Chicken Anaemia Virus Antigen VP3

The aim of this study was to evaluate the production of chicken anaemia virus VP3 protein in different Escherichia coli strains and to address the diagnostic application of purified E. coli-expressed VP3 protein for the detection of chicken anaemia virus (CAV) infection and the development of an ELISA kit. Three E. coli strains, BL21, BL21 codonplus RP and BL21 pLysS, each harbouring a VP3 protein expressing plasmid, were investigated after induction to produce recombinant VP3 protein. After isopropyl-β-D-thiogalactoside (IPTG) induction, VP3 protein was successfully expressed in all three E. coli strains. The BL21 pLysS strain gave the best performance in terms of protein productivity and growth profile. In addition, the optimal culture temperature and IPTG concentration were found to be 0.25 mM and 20 °C, respectively. Using Ni-NTA-purified VP3 protein as an ELISA coating antigen, the purified VP3 was shown to be highly antigenic and able to discriminate sera from chickens infected with CAV from those that were uninfected during an evaluation of CAV infection serodiagnosis. A VP3-based ELISA demonstrated 100% (6/6 x 100%) specificity and sensitivities of 91.3% (21/23 x 100%) and 82.6% (19/23 x 100%) using cut-off values of the mean plus 2 SD and the mean plus 3 SD, respectively.

Development and evaluation of a loop‐mediated isothermal amplification assay for rapid detection of chicken anaemia virus

Chicken anaemia virus (CAV) causes an economically important viral disease in chickens worldwide. The main aim of this study was to establish a rapid, sensitive and specific loop-mediated isothermal amplification (LAMP) assay for detecting CAV infection. A set of four specific LAMP primers were designed based on the nucleotide sequence of the CAV VP2 gene, which encodes a nonstructural protein. These were used for the amplification of a specific target region of the VP2 gene. LAMP amplicons were successfully amplified and detected by DNA electrophoresis and by direct naked eye SYBR Green I visualization. A sensitivity test systematically demonstrated that the LAMP assay was superior to a conventional PCR assay with a minimum concentration limit of 100 fg compared to 10 ng for the conventional PCR. The specificity of the LAMP assay for CAV detection is consistent with conventional PCR. Using this established LAMP assay, infected and uninfected clinical samples obtained from an experimental farm were fully verified. A novel nucleic acid-based approach of LAMP assay was successfully developed for detecting CAV infection. In this study, these results indicate that the developed LAMP assay herein for CAV detection is a time-effective, simple, sensitive and specific test that can be used as an alternative approach in the future for large-scaled diagnosis on the farm of CAV infection.

Pathological and immunohistochemical study of chickens with co-infection of Marek's disease virus and chicken anaemia virus

Chicken anaemia virus (CAV) is the most important confounding pathogen in Marek's disease virus (MDV) infection. The effect of CAV co-infection at 4 weeks of age after inoculation of virulent MDV (vMDV, KS strain) or very virulent MDV (vvMDV, Md/5 strain) in 1-day-old chicks was investigated by pathological and immunohistochemical studies. CAV increased the mortality rates induced by vMDV or vvMDV. The packed cell volume was reduced significantly in vMDV–CAV infection; however, no reduction or non-significant reduction was observed in vMDV infection. Bone marrow hypoplasia was related to CAV co-infection and none of the birds inoculated with vMDV or vvMDV had hypoplasia. Severe atrophy of the thymus and bursa of Fabricius was observed in the vvMDV–CAV and vvMDV groups. Complete regeneration of the thymus cortex and bursa of Fabricius in the vMDV group was noted and was in contrast to sequential lymphoid depletion after CAV inoculation in the vMDV–CAV group. The spleen was either regenerated, lymphoid depleted or had lymphoproliferative lesions. Lymphoid depletion in the spleen was not detected in the vMDV group; however, it was prominent in the vMDV–CAV and vvMDV–CAV groups during the first 2 weeks after CAV inoculation. CAV inclusions and antigens were detected in the thymus cortex and spleen of vMDV–CAV and vvMDV–CAV groups during the experiment. Severe depletion of CD8+ T cells was observed in depleted spleen and thymus. The neoplastic foci appeared around splenic arterioles and venules, and stained mainly by CD4 antibody; however, CD8+ T cells were singly dispersed or were present in clusters. It could be concluded that CAV was responsible for bone marrow hypoplasia, severe anaemia and hindrance of lymphoid organ regeneration in MDV–CAV co-infection.

Chicken anemia virus infection in broiler chickens in Shahrekord, Iran: serological, hematological, and histopathological findings

Chicken infectious anemia caused by a single-strand DNA circovirus is a disease in young chickens that is characterized by aplastic anemia, generalized lymphoid atrophy, and immunosuppression. In the present study, the presence of chicken anemia virus (CAV) infection and the hematologic and histopathologic changes in CAV seropositive broiler chickens in Shahrekord region, center of Iran, were investigated. Blood and lymphoid tissue samples were obtained from 271, 2–6-week-old chicks of 23 commercial broiler chicken flocks. Measurement of CAV antibody titers by enzyme-linked immunosorbent assay (ELISA) and differential leukocyte counts were carried out on serum and whole blood, respectively. The results of ELISA showed that all flocks of different ages were positive for anti CAV antibodies. Histological examination of lymphoid organs revealed lymphocytic depletion in 72 chicks, of which 66 cases were seropositive in ELISA. Twenty chicks had lymphocytic depletion in both thymus and bursa of Fabricius and 46 cases had only bursal lymphoid depletion. Macroscopic appearance of bone marrows and spleen were normal. The mean antibody titers, packed cell volumes (PCVs), and number of lymphocytes and heterophils of the chickens with both thymic and bursal lymphoid depletion were significantly different than antibody titers and PCVs of the other group. These results have demonstrated CAV infection and immunosuppressive effect of this virus in broiler chickens and the need for vaccination of breeder flocks in center of Iran.

Rapid identification of chicken anemia virus in Nigerian backyard chickens by polymerase chain reaction combined with restriction endonuclease analysis

Chicken infectious anemia (CIA) has not been routinely diagnosed in other avian species apart from commercial chickens. A sensitive polymerase chain reaction (PCR) combined with restriction endonuclease (RE) analysis was used for the detection and characterization of chicken anemia virus (CAV) in backyard chickens (Gallus gallus domesticus) in Nigeria. Using a pair of primers designed to amplify a 733 bp fragment in the VP1 (capsid protein) gene of CAV, the PCR assay detected CAV DNA in 9 of 12 serum samples from apparently healthy backyard chickens. RE digestion of the purified PCR products of commercial and backyard chickens with CfoI yielded two separate restriction endonuclease patterns, suggesting that Nigerian backyard chicken CAVs differed from the commercial chicken isolates at the nucleotide sequence level. Results of RE analysis also suggested that the backyard chickens contained a mixed population of CAV strains. These findings confirm that backyard chickens are susceptible to CAV infection and could also harbor the virus.

Rapid identification of chicken anemia virus in Nigerian backyard chickens by polymerase chain reaction combined with restriction endonuclease analysis

Chicken infectious anemia (CIA) has not been routinely diagnosed in other avian species apart from commercial chickens. A sensitive polymerase chain reaction (PCR) combined with restriction endonuclease (RE) analysis was used for the detection and characterization of chicken anemia virus (CAV) in backyard chickens (Gallus gallus domesticus) in Nigeria. Using a pair of primers designed to amplify a 733 bp fragment in the VP1 (capsid protein) gene of CAV, the PCR assay detected CAV DNA in 9 of 12 serum samples from apparently healthy backyard chickens. RE digestion of the purified PCR products of commercial and backyard chickens with CfoI yielded two separate restriction endonuclease patterns, suggesting that Nigerian backyard chicken CAVs differed from the commercial chicken isolates at the nucleotide sequence level. Results of RE analysis also suggested that the backyard chickens contained a mixed population of CAV strains. These findings confirm that backyard chickens are susceptible to CAV infection and could also harbor the virus.

Attenuation of chicken anemia virus by site-directed mutagenesis of VP2

Chicken anemia virus (CAV) is a significant immunosuppressive pathogen of chickens, but relatively little is known about the effect of specific mutations on its virulence. In order to study the virulence of CAV, an infection model was developed in embryos. Significant growth depression, measured as a reduction in mean body weight, was found for wild-type CAV infection. Infection with wild-type CAV resulted in a significant reduction in thymic and splenic weights and consistently produced severe lesions in the thymus, spleen and bone marrow, as well as haemorrhages. CAVs mutated in the VP2 gene were infectious for embryos, but were highly attenuated with respect to growth depression and CAV-specific pathology. Relative to wild-type infection, viruses Mut C86R, Mut R101G, Mut H103Y, Mut R129G, Mut Q131P, Mut R/K/K150/151/152G/A/A, Mut D/E161/162G/G and Mut E186G were highly attenuated, and viruses Mut L163P and Mut D169G were moderately attenuated. Attenuation of the ability to produce lesions was found consistently for the thymus, spleen and bone marrow, thymic and splenic weights, and for CAV-induced haemorrhage. There was no growth depression associated with infection by the group of highly attenuated mutant viruses and a moderate reduction in mean body weight was only found for virus Mut L163P. These findings show that mutations in the VP2 gene can reduce the virulence of CAV and these mutant viruses may have value as vaccine candidates.

Viral load in 1-day-old and 6-week-old chickens infected with chicken anaemia virus by the intraocular route

Although the effects of chicken anaemia virus (CAV) infection have frequently been investigated in young chickens, there have been few studies of the pathogenesis of CAV infection in older birds. The aim of the work reported here was to study viral loads in 6-week-old chickens and to compare these with those seen in younger birds. Specific pathogen free chickens were inoculated at 1 day or at 6 weeks of age with 10(4) median tissue culture infective doses of CAV by the intraocular route. Chicks infected when 1 day old were euthanized at day 14, 18 or 22 post inoculation (p.i.), and those infected when 6 weeks old at day 16, 18 or 20 p.i. Their body and thymus weights were determined and samples were collected from their spleen, liver and thymus. A quantitative polymerase chain reaction assay was developed and used to determine the number of viral genome copies in the tissue samples. In both age groups, viral genome concentrations increased in all organs up to day 18 p.i. and reached a peak in the spleen and liver at day 18 p.i. The peak viral concentrations in the thymus were detected at day 18 in the younger birds and at day 20 p.i. in older chickens. These studies have shown that exposure to CAV in older birds leads to similar levels of active viral replication to those seen in younger birds, and may result in subclinical infections in older birds with the potential to increase susceptibility to other infectious agents.

Oral Infection with Chicken Anemia Virus in 4-Wk Broiler Breeders: Lack of Effect of Major HistocompatibilityBComplex Genotype

The pathologic consequences of chicken anemia virus (CAV) oral inoculation in 4-wk-old broiler breeders of different major histocompatibility B complex (MHC) genotypes were evaluated. MHC B complex was determined by hemagglutination and sequence-based typing. Clinical signs, serology, gross lesions, histopathologic analysis, and CAV genome quantification were used to evaluate disease progression. Clinical disease was not apparent in the inoculated broilers throughout the experimental period. At 14 days postinoculation, antibodies against CAV were detected in 26.4% (29/110) of the inoculated birds. The distribution of percent positive was 34.6% (9/26) and 32.3% (10/31) of the chickens with B A9/A9 and B A9/A4 MHC genotypes, respectively, and seroconversion in six other genotypes was 19% (10/53). These differences among MHC genotypes for specific seroconversion rate were not statistically significant. CAV genomes were detected in the thymus of 87.7% (93/110) of the inoculated birds with no statistically significant differences between MHC genotypes. Mild thymic lymphocytolysis, lymphedema, and medullary hemorrhage were observed in the inoculated chickens. Histomorphometric analysis showed that cortical lymphocyte-to-parenchyma ratios did not differ between inoculated and uninoculated groups or among MHC genotypes. Similar findings have been reported previously in white-leghorn chickens of similar age, suggesting that broilers show a similar resistance to the effects of CAV infection at this age. The absence of significant clinical and pathological changes in the orally inoculated broilers at this age contrasts with CAV-associated thymus damage seen frequently in condemned commercial broilers at harvest.

Serological evidence of chicken anaemia virus infection in Nigerian indigenous chickens : research communication

Serum samples from 20 out of 180 (11.1%) apparently healthy Nigerian indigenous chickens were negative for antibodies against chicken anaemia virus using the enzyme-linked immunosorbent assay (ELISA). Of the 160 positive sera (88.9%), 12 (7.5%) had titres ranging from 1500-3000, 46 (28.8%) had titres from 3000-5000 while 102 (63.8%) had titres between 5000-11000. The overall mean titre value was 5845 +/- 2402. This appears to be evidence of a natural outbreak of the infection since the chickens had no history of vaccination against any poultry disease.