A survey of specific pathogen‐free chicken flocks for antibodies to chicken anaemia agent, avian nephritis virus and group a rotavirus

Whole genome analysis and molecular characterization of chicken infectious anemia virus from an outbreak in a layer flock reveals circulation of genogroup IIIb in South India

The complete genome (2298 nucleotides) of the economically important and immunosuppressive, chicken infectious anemia virus (CAV), from a disease outbreak in a layer flock is discussed. This is the first report of a complete genome sequence of CAV from India. The phylogenetic analyses grouped this isolate with CAV genogroup IIIb based on both complete genome and capsid protein (VP1) sequences. The analyses further revealed the presence of CAV genogroups II, IIIa and IIIb in India. The VP1 sequence identity ranged between 84.4 to 99.3% with that of the Indian isolates and carried a unique substitution at position 447 (serine instead of threonine). Two novel amino acid substitutions were observed at position 52 of VP1 (serine instead of proline) and at position 26 of VP2 (asparagine instead of serine). Sequence analyses of VP1, VP2 and VP3 suggested that the isolate could be attenuated. Comparison with CAV variants, isolated from mammalian species, showed similarities in the numbers of certain transcription factor binding sites in the non-coding regions. Recombination analysis detected no recombination events in this isolate. Further investigations are needed to understand the implications of the unique features of this isolate on viral virulence.

Spectrophotometric microplate assay for titration and neutralization of avian nephritis virus based on the virus cytopathicity

INTRODUCTION

Plaque assay (PA) is a gold standard for virus titration and neutralization of various cytopathic viruses, including avian nephritis virus (ANV), the etiological agent associated with kidney disorders in chickens. In this study, as an alternative to the labor-intensive PA, we developed a spectrophotometric microplate assay (MA) for ANV titration and neutralization based on the virus cytopathicity to primary chicken kidney (CK) cells.

METHODS

CK cells were infected with ANV in the presence or absence of chicken serum in a 96-well microplate, and the virus-induced cytolysis was quantified by measurement of neutral red uptake using a spectrophotometer. The absorbance values obtained were subjected to a sigmoidal four-parameter logistic regression analysis for the virus titer determination and serum neutralization assessment. Accuracy and reliability of the serum neutralization MA in comparison to the standard PA was statistically evaluated.

RESULTS

The ANV-MA was capable of quantifying infectious virus titers based on a virus dose-dependent cytolysis of CK cells, and serum neutralization could be assessed as an inhibition of the virus-induced cytolysis accordingly. Statistical evaluation using a 2 × 2 contingency table and receiver-operating characteristic analyses showed 82 % sensitivity, 99 % specificity and 0.97 area under the curve, supporting an overall diagnostic accuracy of the neutralization MA.

CONCLUSION

The newly developed MA using simplified experimental procedures in the microplate format and direct spectophotometric data readout is readily applicable to general laboratories for high-throughput screening of serum neutralization of ANV.

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.

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.

Seroprevalence of antibodies to astrovirus in chickens in Grenada, West Indies

Aim:

Chicken astroviruses (CAstV) are known to cause mild gastroenteritis, growth depression, and even mortality in poultry, especially in chickens, turkeys, and ducks. To the best our knowledge, there is no published information on CAstV in Grenada. This study was conducted to determine the prevalence of astrovirus in chickens in Grenada.

Materials and Methods:

Blood samples from 366 indigenous chickens and 92 commercial chicken layers were collected from all parishes of the island and tested for antibodies against CAstV using commercial enzyme-linked immunosorbent assay.

Results:

The seroprevalence of antibodies against astrovirus was 57.6% (95%, Confidence interval [CI]: 47.4-67.2) in commercial layers and 61.5% (95%, CI: 56.4-66.3) in indigenous chickens. The results show the presence of infection throughout the island.

Conclusion:

The results show the infection with CAstV in approximately half of the chicken population in Grenada. This is the first report on the prevalence of CAstV in chickens in Grenada and the Caribbean region.

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.

Avian Astroviruses

Avian astroviruses comprise a diverse group of viruses affecting many avian species and causing enteritis, hepatitis, and nephritis. To date, six different astroviruses have been identified in avian species based on the species of origin and viral genome characteristics: two turkey-origin astroviruses [Turkey Astrovirus type 1 (TAstV-1) and type 2 (TAstV-2)]; two chicken-origin astroviruses [Avian Nephritis Virus (ANV) and Chicken Astrovirus (CAstV)]; and two duck-origin astrovirus [Duck Astrovirus type 1 (DAstV-1) and type 2 (DAstV-2)]. ANV has also been detected in turkeys, ducklings, pigeons, and guinea fowl; and TAstrovirus-2-like viruses have also been found in guinea fowl. Astroviruses are commonly associated with enteric disease syndromes in poultry including runting-stunting syndrome of broilers (RSS), poult enteritis complex or syndrome (PEC or PES), poult enteritis mortality syndrome (PEMS), and enteritis in guinea fowl. The molecular characterization of the different avian astroviruses shows great genetic variability among each type, and this variability influences the ability to detect these viruses by molecular and serological techniques. In this chapter, we review the different aspects related to avian astroviruses, including molecular biology, pathogenesis, diagnosis, and control.

Detection of astrovirus infection in pigeons (Columbia livia) during an outbreak of diarrhoea

Avian astrovirus infections are widespread in many countries, and infections have been linked to enteritis and increased mortality in young poultry. Although pigeons are treated as an important poultry product in some countries, their diseases are often poorly understood and astrovirus infection in pigeons has not been reported. In the present study, faecal samples were collected during an outbreak of gastrointestinal illness in a population of Shanghai pigeons. The samples were examined for astroviruses by reverse transcription-polymerase chain reaction. Eighty-nine per cent (40/45) and 4% (2/45) were found to be positive for avian nephritis virus (ANV) and chicken astrovirus, respectively. One positive sample indicated a co-infection with both ANV and chicken astrovirus. Phylogenetic analysis based on the partial polymerase gene sequence and full-length capsid protein from published avian astrovirus sequences in GenBank revealed that the pigeon viruses detected in this study were evolutionarily closely related to chicken ANV. The present study provided evidence for the presence of astrovirus in pigeons and suggests that cross-infection between pigeons and commercial chickens was likely. Whether the astroviruses in pigeons were responsible for the diarrhoea remains to be determined.

Astrovirus infections in humans and animals - molecular biology, genetic diversity, and interspecies transmissions

Astroviruses are small, non-enveloped, positive sense, single-stranded RNA viruses first identified in 1975 in children suffering from diarrhea and then described in a wide variety of animals. To date, the list of animal species susceptible to astrovirus infection has expanded to 22 animal species or families, including domestic, synantropic and wild animals, avian, and mammalian species in the terrestrial and aquatic environments. Astrovirus infections are considered among the most common cause of gastroenteritis in children, second only to rotavirus infections, but in animals their association with enteric diseases is not well documented, with the exception of turkey and mink astrovirus infection. Genetic variability has been described in almost all astrovirus species sufficiently examined infecting mammals and birds; however, antigenic variability has been demonstrated for human astroviruses but is far less investigated in animal viruses. Interestingly, there is an increasing evidence of recombination events occurring in astroviruses, which contributes to increase the genetic variability of this group of viruses. A wide variety of species infected, the evident virus genetic diversity and the occurrence of recombination events indicate or imply either cross-species transmission and subsequent virus adaptation to new hosts or the co-infection of the same host with different astroviruses. This can also favor the emergence of novel astroviruses infecting animals or with a zoonotic potential. After more than 30 years from their first description in humans, there are many exciting streams of research to be explored and intriguing questions that remain to be answered about the relatively under-studied Astroviridae family. In the present work, we will review the existing knowledge concerning astrovirus infections in humans and animals, with particular focus on the molecular biology, interspecies transmission and zoonotic potential of this group of viruses.

Sequence analyses of the representative Chinese-prevalent strain of avian nephritis virus in healthy chicken flocks

Avian nephritis virus (ANV), which belongs to the Astroviridae family, has been associated with acute nephritis in chickens. Cases of ANV infection have been recorded in Japan and in several European countries. However, related studies have never been performed in China. Thus, this study isolated ANV in Chinese chicken flocks. ANV RNA was detected by reverse transcription-PCR in stool samples collected from healthy layer chickens in the Sichuan Province of China in 2009. Of the 192 stool specimens collected, 32.3% (62/192) were positive for ANV infection. The whole genome of ANV-Sichuan54, the first representative Chinese strain, was 6941 nucleotides in length, including the 5' untranslated region, three open reading frames (ORFs), a 3' UTR, and a poly-(A) tail. Comparative and phylogenetic analyses based on partial RNA-dependent RNA polymerase (ORF1b) demonstrated that the majority of ANV investigations were more closely related to the U.S. ANV strain (DQ324827-324836) than to the G-4260 (AB033998).

Molecular characterization of avian astroviruses

Astroviruses are frequently associated with enteric diseases in poultry, being isolated from cases of runting-stunting syndrome (RSS) of broiler chickens, poult enteritis complex (PEC), and poult enteritis mortality syndrome (PEMS) of turkeys. Currently, five types of avian astrovirus have been identified: turkey astroviruses 1 and 2 (TAstV-1, TAstV-2), avian nephritis virus (ANV), chicken astrovirus (CAstV) and duck astrovirus (DAstV). The objective of this study was to molecularly characterize the different types of avian astroviruses circulating in commercial poultry. Sequence analysis of a region of ORF2, which encodes the capsid precursor protein associated with serotype and viral pathogenesis, revealed extensive variation in amino acid sequence within each subtype: TAstV-2 (81.5%-100%), ANV (69.9%-100%), and CAstV (85.3%-97.9%). However, this region was more conserved in TAstV-1's (96.2%-100%). Furthermore, a novel astrovirus was detected in chicken samples and found to be <64% similar to ANV and <30.6% similar to CAstV. The results of this study underline the great genetic variability of avian astroviruses and indicate that there are most likely multiple serotypes of each avian astrovirus circulating in commercial poultry.

Detection of avian nephritis virus in Australian chicken flocks

Avian nephritis virus (ANV) is thought to infect poultry flocks worldwide, but no confirmed case has been reported in Australia. The first such case is described in this study. Cases of young chickens with clinical signs of dehydration and diarrhea were submitted to our laboratory and histopathology detected interstitial nephritis. Vaccine strains of infectious bronchitis virus were detected in some of these cases but were not considered to be the causative agent. A total of seven fresh submissions from broiler chicken flocks were collected at 8-11 days of age. Degenerate PCR primers were designed based on published ANV polymerase gene sequences and used to analyze historic cases as well as the fresh submissions. Six of the seven fresh submissions, and one historic case, were positive for ANV with nucleotide sequencing confirming these results. These results establish ANV as an infectious pathogen circulating in Australian poultry.

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.

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

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

Isolation of non-cytopathic viruses implicated in the aetiology of nephritis and baby chick nephropathy and serologically related to avian nephritis virus

Three embryo-lethal agents were isolated from broiler chickens having either stunting syndrome or baby chick nephropathy. The agents replicated at low levels in chick kidney cells, but a cytopathic effect was not seen. Their presence was detected by embryo mortalities after yolk sac inoculations. All three agents caused nephritis and growth suppression when inoculated into 1-day-old chicks, and one agent caused increased incidence of baby chick nephropathy. This, and one other agent, were serologically closely related to avian nephritis virus G-4260. Picornavirus-like particles were present in the kidneys of infected birds. The histopathology of baby chick nephropathy was similar to, although more severe than, the nephritis seen in clinically normal birds. The strain of birds used to produce chick kidney cells influenced the ability of G-4260 to form a cytopathic effect and plaques. Strain of bird also influenced the lesions produced on chorio-allantoic membranes after inoculation of G-4260 and the above isolates.

Molecular characterization and typing of chicken and turkey astroviruses circulating in the United States: implications for diagnostics

Avian astroviruses were detected by reverse transcriptase and polymerase chain reaction in intestinal contents collected from commercial chickens and turkeys from throughout the United States from 2003 through 2005. Astroviruses were detected in birds from both healthy and poorly performing flocks with or without enteric disease. Phylogenetic analysis was performed with sequence data from the polymerase (ORF-1b) genes of 41 turkey-origin astroviruses and 23 chicken-origin astroviruses. All currently available avian astrovirus sequence data and selected mammalian astrovirus sequence data were included in the analysis. Four groups of avian astroviruses were observed by phylogenetic analysis: turkey astrovirus type 1 (TAstV-1)-like viruses, turkey astrovirus type 2 (TAstV-2)-like viruses, both detected in turkeys; avian nephritis virus (ANV)-like viruses, detected in both chickens and turkeys; and a novel group of chicken-origin astroviruses (CAstV). Among these four groups, amino acid identity was between 50.1% and 73.8%, and was a maximum of 49.4% for all avian isolates when compared with the mammalian astroviruses. There were multiple phylogenetic subgroups within the TAstV-2, ANV, and CAstV groups based on 9% nucleotide sequence divergence. Phylogenetic analysis revealed no clear assortment by geographic region or isolation date. Furthermore, no correlation was observed between the detection of a particular astrovirus and the presence of enteric disease or poor performance. Based on these data, a revision of the present taxonomic classification for avian astroviruses within the genus Avastrovirus is warranted.

Immunopathologic Investigations with an Attenuated Chicken Anemia Virus in Day-Old Chickens

The immunopathologic effects induced by two attenuated chicken anemia virus (CAV) isolates, known as cloned isolate 34 (CI 34) and cloned revertant isolate 18 (CRI 18), that were derived from highly passaged pools of Cux-1 CAV isolate, were compared with those induced by a pathogenic, molecularly cloned, low-passage Cux-1 isolate (CI Cux). This comparison involved the intramuscular inoculation of 1-day-old specific-pathogen-free chicks with each of the viruses and investigation of birds at selected days postinoculation for gross pathology and depletions in the thymic T-cell populations as determined by flow cytometry. Whereas infection with the pathogenic CI Cux produced severe anemia and pronounced bone marrow and thymus lesions, infections with the attenuated CRI 18 and CI 34 isolates produced no anemia, no or mild lesions, respectively, and moderate T-cell depletion. The results suggest that, with CAV, reduced pathogenicity for 1-day-old chicks correlates with reduced depletion of T-cell populations in the thymus and with reduced severity of lesions in the thymus and bone marrow.

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.

A comparison of three serological methods to detect chicken and turkey antibodies to avian nephritis virus and the use of virus-specific monoclonal antibodies

Avian nephritis virus (ANV) strain G-4260 was inoculated orally in to 1-day-old and 3-week-old chickens and the sequential antibody response to the virus was monitored by serum neutralization, ELISA and immunofluorescence tests. The order of sensitivity of the serological tests was in the sequence given above, with the neutralization test being by far the most sensitive. There was no obvious difference in the antibody titres produced by either age group. Virus was recovered from kidney tissue, the highest titres being obtained 3 to 5 days post-inoculation. Histological examination revealed mainly lymphocytic infiltration of the interstitium and degenerative changes in the tubular epithelium of the kidney. The G-4260 strain of ANV was given orally to 1-day-old turkey poults, but no serological response was induced. Virus was not recovered from the kidneys and no histological lesions were produced in this organ. Monoclonal antibodies were produced which neutralized the infectivity of ANV. An antigen trap ELISA was developed using a monoclonal antibody and infected chicken kidney tissue cultures. However, this assay did not detect ANV in kidney samples taken directly from infected chickens, with the exception of one sample which was shown to contain the highest concentration of infectious virus.

Detection and differentiation of chicken anemia virus isolates by using the polymerase chain reaction

Complementary oligonucleotide primers which flank a 675-bp DNA fragment encompassing part of the putative gene for the capsid protein of chicken anemia virus (CAV) were used for the enzymatic amplification of CAV DNA by the polymerase chain reaction (PCR). Application of a dot blot hybridization assay by using a 32P-labeled cloned CAV DNA probe allowed PCR product amplified from as little as 0.1 fg of the target DNA sequence to be detected. When it was used for PCR amplification, DNA extracted from thymus tissue by a guanidine isothiocyanate-based method proved to be more efficient than that extracted by methods involving phenol or boiling. DNAs specified by 14 CAV isolates originating in the United Kingdom, Ireland, Germany, Sweden, the United States, Japan, and Australia were amplified. Restriction endonuclease analysis of the PCR-amplified DNAs with the enzymes HaeIII, HinfI, and HpaII indicated that the 14 CAV isolates can be assigned to seven groups, with isolates from different countries usually exhibiting the greatest number of restriction site differences.

Biological characterisation of Australian isolates of chicken anaemia agent

Three Australian isolates of chicken anaemia agent (CAA) resisted treatment at 70 degrees C for 5 min and chloroform treatment. Although minor antigenic differences were detected using monoclonal antibodies to CAA, the Australian isolates were indistinguishable from the reference Cux-1 and Gifu-1 isolates in cross-immunofluorescence and cross-neutralisation tests employing polyclonal chicken antiserums. The Australian viruses were pathogenic for intramuscularly inoculated 1-day-old SPF chicks, but were less pathogenic for 7-day-old chicks. Thus the Australian isolates of CAA did not differ significantly in these properties from previously characterised CAA isolates from other continents.

Dot blot hybridization assay for chicken anemia agent using a cloned DNA probe

A dot blot hybridization assay capable of detecting chicken anemia agent (CAA)-specific DNA in tissues from infected birds has been developed. The assay uses a 32P-labeled DNA probe prepared from cloned CAA-specific fragments representing the entire virus genome and has a sensitivity limit of between and 1 and 10 pg. DNAs from CAA isolates originating in the Federal Republic of Germany, Japan, the United States, the United Kingdom, and Australia were detected. Investigation of specimens from experimentally infected chicks indicated that virus-specific DNA was detected in the tissues of birds from 5 through 42 days after infection and that greater amounts were usually detected in the thymus than in the spleen, liver, feces, or blood. Tissues from specific-pathogen-free and broiler chicks which had become infected at an older age through contact with experimentally infected anemic chicks also contained CAA-specific DNA detectable by the assay. Thymuses from 1- to 2-week-old chicks from eight commercial broiler flocks which had been showing clinical signs characteristic of anemia-dermatitis syndrome were found positive by the hybridization technique, but thymuses from chicks obtained from broiler flocks which did not show such signs were found negative. Of the 35 positive samples (from 46 samples tested), 19 (54%) contained virus-specific DNA in sufficiently great amounts to permit 4-h autoradiography exposures and sample throughput times of 2 days. When compared with virus isolation, the CAA dot blot hybridization assay is time- and labor-saving.

Comparison of three animal viruses with circular single-stranded DNA genomes

No common antigenic determinants and no DNA sequence homologies were detected when three animal viruses, chicken anaemia agent (CAA), porcine circovirus (PCV), and psittacine beak and feather disease virus (PBFDV), all of which possess circular single-stranded DNA genomes, were compared. Negative contrast electron microscopy showed that PCV and PBFDV particles were 30% smaller than CAA particles and lacked the surface structure of CAA.